Moessbauer spectrometry - ACS Publications

(10) “Physical Methods in Determinative Mineralogy,’’ J. Zussman, Ed., A m demic Press, London and New York, 1967. (11) “Advances in Materials Research,” Vol. I, H. Herman, Ed., Interscience, New York, 1967. (12) “Electron Micrographs of Limestone and Their Nannafassils,” A. G. Fischer and others, Princeton Univ. Press, Princeton, N. J., 1967. (13) “Atlas of Electron Rlicroscopy of Clav Minerals and Their Admixture.” H. Beutelspacher and H. W. Van der Marel, American Elsevier Pub. Co., Inc., New York, 1967.

(14) “An Atlas of Biological Ultrastructure,” John D. Dodge, American Elsevier, New York, 1969. (15) “The Nucleus, Vol. 3 of Ultrastructure in Biological Systems,” A. J. Dalton and F. Haguenaux, Academic Press, New York, 1968. (16) “Atlas of Human Electron hlicroscopy,” R. P. Laguena and L. A. Cesar, Mosby, Ltd., St. Louis, hlo., 1969. (1 7) “Electron Microscopy in Biology,” A. V. Grimstone, St. Martins, 1968. (18) “Electron Microscopy of Cells and Tissues,” Vol. 2, F. S. Sjostrand, Academic Press, New York 1968.

(19) “Anatomy of Paramecium Aurelia,,’ A. Jurand and G. G. Salman, MacmilIan, London, 1969. (20) “Cell Structure, An Introduction to Biological Electron hlicroscopy,” P. G. Zoner and K. E. Carr, Livingstone, Ltd., Edinburgh and London, 1968. (21) “Advances in Electronics and Electron Physics,” L. Marton, Ed., Academic Press, New York and London. 1969.

Mossbauer Spectrometry 1. R. DeVoe and 1. J. Spijkerman, National Bureau of Standards, Washington, D. C.

T

is the third one on Mossbauer Spectrometry that has appeared in the ANALYTICAL CHEMISTRY review series. The first review was devoted to the fundamentals of the technique and the second one described many of the applications. This review is essentially more of the same, except that cerhin of the problem areas that previously existed have been resolved to some ext’ent. A major problem that was indicated two years ago is the rather narrow “bandwidth” of spectral parameter change due to changes in the electronic environment a t t’he nucleus. The desire t’o see very small changes in the chemical environment has spurred improvement in the design of spectrometers to achieve higher accuracy and precision. In addit’ion, detector design such as resonant detectors, with their improved resolution, can prove to be decisive in future studies. Select,ive excitation of nuclear energy level by using polarized radiation will also enhance the discriminating power of the technique. I n addition, more attention is being paid to the mat’hematical model representing the line shape of a peak. It is evident to everyone working in the field that the use of the Lorentzian function produces significant increase in the random errors of est’imate in peak position. There is also the distinct possibility for a peak to be shifted to an apparent position which generates a systematic error if any asymmet’ryexists in the experiment,al peak and if the model is incorrect. The necessity for using standards to reference isomer shift cannot be overstated. If high precision meaningful data are going to be produced and reported, it is very necessary to report isomer shift with respect to a standard reference material. The National Bureau of Standards has available soHIS REVIEW

366R

dium nitroprusside and an iron foil will soon be certified. Dimethyl tin difluoride will also be made available. Only articles published in 1968 and 1969 are included in this review. References which appeared in the literature in late 1969 have been omitted. Certain other omissions have been made in an effort to reduce the magnitude of this task. Those references which are abstracts of manuscripts, theses, and talks have been omitted. Most often the reports also appear as regular manuscripts. -2comprehensive cornpilation of references was published four years ago by Muir et al., and i t is my understanding that a new issue will be published this year. The NBS Technical Note promised two years ago is ready after a significant delay, and it will be a bibliography of all references on chemistry including key words. This bibliography will be updated annually. Mossbauer spectrometry is still blessed with a large number of review articles and contrasted with most earlier reviews, that are not of a general nature, but are highly oriented to special disciplines or applications. The scope of interest is indeed great. I t ranges from the esoteric such as a distinction between the mass change shift and the second order Doppler shift (195) to the most surprising applications such as the use of the Mossbauer effect to investigate the movement in a group of ants (96) ! It is noteworthy that an excellent reference textbook has been published by Goldanskii and Herber (293). There are a number of reviews of special techniques that appear in the proceedings of a conference on Hyperfine Structure and Nuclear Radiations; coulomb excitation (520), nuclear properties as measured by the Mossbauer technique ( 4 l S ) , isomer shift (407), an-

ANALYTICAL CHEMISTRY, VOL. 42, NO. 5, APRIL 1970

gular correlation (481), and spin relaxation phenomenon (704). There are reviews on various disciplines, materials science (SOS), biology (58, 515), magnetic effect (31, 67, 370), metallurgy (go), minerology (132), and surface analysis (174, 369, 408). Some reviews are on special materials, organometallics (295), organotin (431), rare earths (159), tellurium (695),iodine (328, 624), neptunium (553). Finally, there are a number of general reviews, 27, 208, 258, 291, 307, 332, 380, 482, 503, 522, 592, and 614. The major emphasis in this review is placed upon the information in Table I. I n the several paragraphs to follow, only those areas that have experienced significant advance in the past two years are included. SPECTROMETRIC TECHNIQUE

Instrumentation. M a n y types of spectrometers have been described in the previous reviews (204) and several modifications of previously published spectrometers are given in (30, 110, 140, 147, 609, 625, 684, 696, 720, and 726). Recent developments have been in the areas of direct measurement of the Doppler velocity, and the “region of interest” type of spectrometers (276). The direct measurement of the Doppler velocity is achieved by a hfichelson interferometer (259) a hloirB grating (110). The use of the interferometer became practical n d h the availability of inexpensive lasers and photodetectors. The schemat’ic of the interferometer is shown in Figure la. A monochromat,ic beam of lighJ from a He-Ne laser, L (A E 6328.19 A) is divided by splitter B , and reflected from a stationary mirror S , and a moving reflector, 41. A flat mirror could be used for the reflector but W i n g of this mirror would introduce an

error in the velocity measurement. A corner cube (-11)(retro-reflector) would help to eliminate alinement problems. The beam splitter recombines the two light beams, and interference produces a sinusoidal output a t the photodiode, D ,with a frequency f = 2 v / X , where v is the Doppler velocity. The Moire grating technique is simpler, and requires virtually no alinement, b u t has almost an order of magnitude less precision. The moving grating acts as a light shutter for an incoming and reflected light beam, L, as shown in Figure l b , and modulates the intensity into a triangular wave form from which the velocity is obtained. I n (110) a moving table spectrometer is described, using air bearings and a hydraulic piston to control the motion. Very low velocities (6) could be measured with the Moir6 grating. The oscillations that can be produced in flyback type spectrometers have been reduced by Chase (147), and this spectrometer is programmable for velocity region of interest. The region of interest spectrometer uses a trapezoidal velocity wave form. It accelerates rapidly to the desired velocity, and then slowly scans the velocity region of interest. This reduces the number of channels required for desired velocity resolution and great'ly decreases the time required to accumulate a spectrum. This is particularly useful for magnetic hyperfine interaction measurements. Utilization of all channels in a MCA is described in (609). Only half of the triangular wareform is used. Although the circuitry is simple, the data accumulation efficiency is only 50y0 and no net increase in detect,ioii efficiency results. For small Nossbauer effects an instrumental smoothing of data is achieved (155) by integration of the counts (rate meter principle) and using the analog-to-digital converter of the aiialyzer. This method is also capable of handling very high counting rates. Detectors. Although the Kr-C02 proportional and h'aI(T1) scint'illation couiit'ers are generally used, several new detect'ors have been described. For temperature studies over the range of 100 to 340'K the C s I ( N a ) sciiitillation detector (733) can be mounted in the cryostat. The time resolution 0.6 nsec is also superior to the nlaI(T1) detector. The energy resolution of NaI(T1) scintillation detector for "98n Mossbauer spectroscopy can be improved by using a 0.25mm thick cryst,al. A t'echnique for fabrication of these cryst,als is described in (607). For 119Sn spectroscopy an X-ray film with a SnOz suspension (93) was successfully used. The photographic emulsion det,ected the 19-keV conversion electrons. A CdS semiconductor (93) also gave satisfactory results for Il9Sn. This detector has been used for dosime-

S

Figure 1.

( a ) Michelson interferometer, (b) Moire grating

ters, and is very suitable for high counting rates. Time resolution at present is very poor for this material. In (97) the energy distribution of conversion electrons from 118Sn was analyzed with an iron-free beta particle spectrometer. The range of the conversion electrons was approximately 24,000 A. This technique presents a very sensitive tool for surface analysis of tin bearing materials. The design of a resonant detector for 5?Fe, using an enriched stainless steel foil is given in (255). The counter was used to study inorganic 57C0sources. Variable Temperature. T h e many entries in Table I show the extensive use of variable temperature spectrometers to determine the temperature dependence of the Mossbauer parameters. Several designs are presented (123,397,400, and 648),for temperatures in the range of 2'K to room temperature. Very small isomer shifts (400) can be measured a t these temperatures with 3 source-absorber pairs simultaneously. The application of longitudinal magnetic fields for variable temperature source and/or absorber experiments is described by Gwartzendruber (648). Wiggins et al. (710) have used a closed cycle H e refrigerator for cooling targets used in coulomb excitation experiments. This refrigerator is very economical for low temperature iron-57 studies, (155), but care must be taken to isolate the vibration associated with the refrigerator. A aHe/4He dilution refrigerator for experiments a t 0.05 OK and above was designed by Ehnholm (232). Precise temperature control is reviewed by Steyert et al. (636) and several thermometers are described covering a wide temperature range. Pressure. Drickamer (225, 224) has described a high pressure apparatus up to 150 kbars for 57Festudies. Pressure can be applied to sources or absorbers over a wide temperature range.

EXPERIMENTAL METHODS

Mossbauer Sources. A most thorough investigation in the preparation and determination of experimental linewidth of 57C0source matrices has been made by &aim et al. (662). The sources were prepared by electroplating cobalt-57. The narrowest lines were obtained for face-centered cubic or body-centered cubic structure. The diffusion rates and annealing times are also critical for producing a narrow line source. The properties of CaSnOa as a tin-119 source were studied by Kalyamin et al. (404). Linewidth observed was 0.9 mm/sec, f = 0.58 =t0.06. Since Ca has a much lower absorption coefficient for the tin radiation, this source has a much higher efficiency than most others commonly used. A narrow line width was also found for a Naz119mSn033H20 by Irkaev et al. (379). The development of polarized cobalt57 sources received much attention. A general review is presented by Gonser (304). Polarized sources can be made by applying an external magnetic field to a ferromagnetic material. A novel approach was used by Housley (363). This linearly polarized source consists of 57C0in a single crystal of Be, and it produces a "quadrupole-split" doublet. A stationary (NH&Fe(S04)2.6H20 absorber is used to filter out the unwanted radiation. Using a polarized sourc'e, the Faraday effect (364) was observed in 1LlgFez04, and polarization and coherence effects were observed in single crystal absorbers (366). Using two moving absorbers and a stationary scatterer, Xrtemev et al. (33) observed polarization effects in Fe metal. A general discussion of Faraday effect is given by Blume and Kistner (84). Sources prepared by coulomb excitation and implantation have increased the number of isotopes exhibiting the Mossbauer effect. Iron-57 sources ob-


-

* 367R

Table 1.

Application of 'Mossbauer Spectrometry to Chemistry Compilation of Publications for 1968 and 1969

El, EZ = Energy of Mossbauer gamma ray 1 and 2, respectively, in keV ff = Internal conversion coefficient K = K,,g X-ray energy in keV pic, plP = Magnetic moment of excited and ground state producing Mossbauer gamma ray 1, respective1 in nuclear magnetons (nm) Qls,Qlg = Electric quazupole moment of excited and ground state producing Mossbauer gamma cmz). ray 1, respectively, in barns (b = (Nuclear data taken from A. H. Muir, Jr., K. J. Ando, H. M. Coogan, "Mossbauer Effect Data Index (1958-1965)," Interscience, New York, 1966)

Abbreviations: EFG = electric field gradient AE = electric quadrupole splitting q = asymmetry parameter IS = isomer shift OD = Debye temperature AR/R = fractional nuclear radius change where excited to ground state = ( A R ) and radius of ground state = R = effective magnetic field at the nucleus H AH = applied magnetic field = fraction of effect = temperature TliZ = half-life

.'T

Mossbauer nuclides 67Fe ( -

E

l/z)

14.4 keV ( - a / ~ ) ff =9 K = 6.5 keV pc = -0.154nm pg = +0.09024nm Q. = +0.285b

Subject or material studied Nuclear parameters

=

a-FezOs iron

Source study Alloys

FeSiF6. 6Hz0 FeCL ' 4 H ~ 0 KFeFz coo Fe-Be Fe-Cr Fe-Ge Fe-Ga AurV Fe-Pd Au-Fe Hf in Fe U6Fe,PucFe FesSnz Fe-Sn, Ni-Sn Fe-Te Stainless steel 310 stainless steel Aging of steel Invar Fe-Ah-N FeMn Zr-Nb-Fe FelB, FezZr TiFeCo allow Fe-Xi

FeAl Fe-Pt Fe-Ni-A1 Cu-Ni Cu-Fe Cu-Yi-Fe Fe-Cu-Co-Be-Zn Metal

Remarks

Types

Martensitic structure

+

QL= $0.283 0.035 b Q. = 0.300 f 0.035 b p e / p g = 1.701 f 0.008 H = 329.4 f 1.2 KOe A H us. T QB= f0.18 b A R I R = -5.2 x 10-4 Single line, high'effect AE us. % Fe IS, H us. concentration of Cr, 0, 1, and 2 nearest neighbors H , AE, IS us. T

...

Magnetic moment measured H us. T IS us. concn. of Fe and hydrogen content H , AE, IS us. T and concentration atomic volume, explains IS H us. T I S . AE us. T H , ' A E , IS us. T Resistivity us. IS H us. T Field produced by.~ plastic deformation Pseudomartensitic

Ref. (34) (508) (732) 6991,

(616)

bo4 j

(389, 613) (599) (12, 698)

(693) (is7j (680) (472) (578)

(635) (82) (104, 377) (371)

(6441 (428, 445)

*,.

Plastic deformation H 7... 1s. T .~ H us. T H us. concn. of Zr, Nb ~

H compared with NMR H H us. concn. of Ni H us. T , particles

Diffusion of F e ' k t o Xi produced two H at grain boundaries Preferred orientation on rolling IS Corrections to phase diagrams H us. T and composition A H . v s . T , spectra of magnetic orig1n Data compared to magnetic susceptibility and NMR H , IS H us. T small Xi-Fe clusters H , AE 4 components from nearest neighbors, H , IS, AE

(11 j '

(650, 651 ) (603) (302)

(513) (715) (284, 378) (490)

(Continued)

368R


~

~~

Table I.

Application of Mossbauer Spectrometry to Chemistry Compilation of Publications for 1968 and Subject or Mossbauer nuclides material studied Types Remarks Austenitic carbon AE us. T limit of 0 at 195 “C C impurities in iron H us. T H us. T phase transition, anomalous IS H , IS us. pressure A H , H , polarization H , IS, AE vs. pressure Thin films Magnetic anisotropy Diffusion in Cu High f, diffusion line broadening Doped materials AgCl, NaCl Water is involved, AE, IS us. T Ice Pseudo melting at 65 OK Au-Ni alloy Phase boundary Ni metal H us. single crystal orientation Ge, Y, Hf, Lu, Ti, Zr, T1, ... Re, Zn, Cd, I n Intermetallic compound H us. T AFez, A = rare earths Doped Cu, Pd, Pt f and binding measured Te IS, AE, two sites Cu, V, Ti f vs. pressure Fe, Pd Sign of H using polarization Effect of absorbed hydrogen Effect of quenching VnOs IS, AE, us. T two sites CrOz H us. T . A H , spin antiparallel to CrOz MgO AE us. T , Qg +0.216 b QB = f0.21 =k 0.03 b

... ...

A1203

Inorganic

SrTiOa Sic 6 7 Cin~ZnSe, ZnTe, CdTe Coo04 InAs, GaP Intercalation compound of boron nitride and FeC13 Anh drous iron halides FeCe FeCL, FeSO4 FeClz FeC12.4H~o FeClz, FeBrz FeI2 FeBrz, FeIz FeX2. nHzO Halides Fe(II), (111) halides FeC13 Fe 111, halides, sulfides Fe (C104)~ Fe(NH3j5N0.C1z Cyclopentadienyl iron [(CH3)4NlzFeC14 (FeX4)+ CsFeFl FeF3

A H , AE AE, H AE, IS us. T IS us. pressure Two sites, IS us. T

f

1969 (Confinued) Ref. (463) (605)

(432) (500) (586) (487, 626) (563)

(416) (346, 347) (216)

(367) (143) (561 )

(105,414) (519) (253)

(499) (6741 (552)

(199) (1, 2) (613)

(145) (146)

(453) (7t5) (308)

(741

(681 )

(367)

(440) (52) ($70)

AE large

(550)

Fe3 to Fez with pressure (225, 361) IS, AE, os. T (131, 691) AE is linear with isomer shift (339) H (14) Low temperature studies (627) (“Spin-flop” ) transition (617 ) IS, AE us. T (40,550) AE (541 AE, IS compared with electronic (125) spectra Frozen aqueous solvent (686 ) Frozen methanol and formamide (687) IS, AE us. pressure (462) IS us. T , phase transition (230) Nephelauxetic effects (130) Frozen aqueous solution (211, 212) Fe is $3 (4911 Nonequivalent iron (141) Asymmetric intensities due to im- ( 4 6 ) purity of Fe3+, compound air oxidizes Halide bridge groups (77) H , AE us. T (639) H us. T (640, 7 0 2 ) No conclusive evidence for spin(676) flip model Collective spin flips near Curie (456) point Crystal field splittings AE vs. T (279) +

+

FeFz Fluorides ... FezP AE, IS us. T , H Li(Fe,Mn)POa H us. T hlixed crystal Fe(P,As)04, AE, IS, us. concn. of As (Fe,AI)P04.2H20 CozFeS(CO) ... FeP04 A H vs. T Carbonyls AE Large IS vs. pressure Fe& AH Fe& H , IS, AE vs. T Sulfides Fe3+,Fez+, AE, IS CuFezS3 cubanite AE, IS, H us. T

(703)

(596)

(610) (656)

(127) (57) (426) (461) (457 ) (473) (103) (317, 474)

(Continued )


369 R

~~

~

~~

~

~

~~~

Table I.

Application of Mossbauer Spectrometry to Chemistry Compilation of Publications for 1968 and Subject or Remarks Mossbauer nuclides material studied Types Magnetically induced quadrupole FeCrzS4 interaction No H Walker, Wertheim, Jaccarino plot holds for these tetrahedral configurations AE, IS us. T Fe(MSO4)1.6H20 M = NH4+, K+, Rb+,

1969 (Continued) Ref. (369)

(278) (567)

cs +

7,

(144)

EFG

H , relaxation calculation Fez+,Fe3 + H , IS, AE, high pressure

(134, 700) (2891

(410)

* .

AE, IS

E

Sign EFG IS, AE us. T , hydrogen bonding f us. T

(538)

(280) (340)

crystal Fe(CN)2L4,L = isocyanide IS us. T Cr, Mn, Fe, and Co as Prussian blue analogs Prussian and Turnbulls AE, IS us. T , high spin Fe3+,low (382) blue spin [Fe(II)] Sodium nitroprusside AE in frozen aqueous solution has (506) slightly higher value than solid EFG, mean square displacement (312) Fe(CS)jNO, Fe(CN)sNOH HoFe03 H us. T for insuiitor H us. T CeFeOs H us. x, H us. T Mnl-,Zn,Fe~04 CaFelOl Relaxation H us. T Faraday effect Spinei, MgFet04 (505) Small particles, superparamagnetism AE us. T Mn3-zFe,04 Mn-ZnFez04 IS, AE, H us. T" ' Cu-ZnFezOa H , AE Cu,Mnl-.Fe~04 H , AE, IS us. concn. of Cu, Sc Cu and Sc in Mg-Mn ferrite NiFe2Oc A H produces 500 kOe Ki-Ge-Fe2O4 AE, H us. T , sign EFG, 7, orientaSpinel tion of H AE, H SrFelz- .Ga,019-' LiAls- =FezOs Ca2FenO5, CanFeAlOs FeAlzOa CazFenOs Ca9eA105 coo Cos04 BaFel2Ols BaFeOz Corrosion products Oxide FeOOH FesO4

Magnetite Oxide

...

H us. x A E , H us. T Z axis of EFG, parallel to crystal b axis IS, AE H . neutron diffraction studies H'vs. T AE, H us. T two sites Two forms observed

f

Single f anisotropy, 6 sites

Fe203, y and a-FeOOH Pressure effects review H , single crystal H us. T . Ne61 t'emperature particle size dependent Linewidths of two sites Three sites Particles exhibit superparamagnetism H , AE us. T Phase transition A H , two sites, electron hopping A H , two types Quantitative measure of corrosion product, Fe20a.2Hz0 Small particles

Fe(OHh NaPOs-FezO3, KPO3-Fe203 Glasses, AE

...

( Continued)

370 R


Application of Mossbauer Spectrometry to Chemistry Compilation of Publications for 1968 and 1969 (Continued) Subject or Remarks Mossbauer nuclides material studied Types Or-FeZO3on silica gel 457 "C produced Fe+2in activated oxide Review of quantitative analyses on silica H us. T Fen03 catalyst for CO-COZ P Z O ~ - S ~ ~ O ~ - - F ~ ~ O ~Glass transformation Relaxation, H us. T CrzOa-Fe~Oa Gallium-iron garnet H us. T Relaxation times Sm-Y-Fe garnet Iron(II1) garnets ... V-Y-Ca-garnet ... Ga in yttrium iron garnet ... In-G a-garnet 4 sites Eu-Fe-garnet EFG, two sites Anisotropic exchange field UFeOa H us. T KvFeOA H us. T Radiolysis products measured AE, IS thermal decomposition similar t o -pFez03 Two sites AE, H us. T , particle size 6'Co doped CoaO4 AE, IS us. T single crystal, A H , FeC03 (siderite) sign of H is COCO3 Hot atom AE, H us. T , relaxation times SnOz FeMo04 3 forms High spin Fe2+,IS, AE us. T

Table 1.

+

NazO 3 Si02 glass Many oxides, e g . , NaFeSn04, LiFeTiO4 FeSbzOa

IS, AE us. pressure Fe3+ to Fez+ AE us. T crystal field splitting H us. T AE, IS, H us. T

...

Meteorites meteorites iron Stony Fe-Mn nodules Nodules Fe-&In deep sea nodules

+

...

Minerals

Ilmenite Biotites, amphiboles Ilmenite Spinel, FezTiO4 Chalcogenides Chalcopyrite Limonite Siderite Siderite, FeC03 Mica

IS, AE us. T Scattering geometry AE, IS, H Particles measured FeOOH present H us. T Iron bound olivine to pyroxime quantitative ratios Weathering produces Fe3+

...

Quantitative applications Two Fez+sites, AE, H us. T

...

H us. T IS, AE, H us. T two types Fez + H , IS, AE us. T AE, IS Calculation of anisotropy in f Single crystal, f anisotropy Quantitative analysis of Fez+ and 8 0 3+

Biological

Orthoclase, Fe3+ Wustite Perovskite La-Fe-Al-0 Sn-Fe-Cr-0 Illite, montmorillonite Many silicate minerals Orthopyroxeme Phosphates, vivianite Howeite, deerite and sapphirines Pyrochlores, AzFeSbO7,A = rare earths Ferberite, wolframite Tripuhyite Ilvaite, CaF2, Fe(SiO4)zOH Peroxidase and derivatives Putidaredoxin Hemoglobin Hemoglobin fluoride Cytochrome C Bacterial cytochromes Gluconate

A~,"IS

AE, IS AE, two sites Phase deviation, AE, IS us. T

...

Ion exchange process with Fe3+ Correlations IS, AE H IS us. T uantitative analysis of Fe3+/FeZ+ &, AE, area under peaks allows quantitative analysis IS, AE, H us. T High spin Fe(I1) FeSb04 AE, IS us. T , ferrous high spin Frozen solvent, relaxation effect

Problems between theory and exment AE us. T Different from c types IS, AE us. T (Continued) ~~~~~

~


~

371 R

Table 1.

Application of Massbauer Spectrometry to Chemistry Compilation of Publications for 1968 and 1969 (Continued) Subject or Remarks Ref. Mossbauer nuclides material studied Types Iron porphyrin AE, I S , A H us. T Ferritin-polymer ... FeaOs(OH)4.1.5H20 ... Deuterohemins Chloro and methoxohemins ... Hemerythrin Fe-02-Fe bridge (525) Non-heme proteins AE, IS us. T (493) Horseradish peroxidase Fe(1V) produced upon oxidation, (495) frozen solvent Ferredoxin AE,A H Spinach ferredoxin ... Enzymes (171) Metallocene MO calculation,' crystal field, AE (196) Leaves ... (468) Organic Phthalocyanine No H I AE us. TIapplied H (188, 209, 496,669) Iron (I11) p yrrolidyl dithio- H us. TI relaxation effects (245, 268, 676) carbamate N,N-dialkyl dithiocarAE us. TI IS, A H , EFG (577, 688) bamate (707) Halide, low temperature data Carbamates Relaxation effects ( 708) Iron(II1) diethyldithiocar- H , thermal equiv. of high and low (688, 690) spin state bamate Nitrosyliron bis(N,N-di(396) AE, IS, A H us. T ethyldithiocarbamate) Iron acetylacetonate chlo- IS, AE us. T , intramolecular re(177) ride laxation Iron carbonyl complexes AE (185) with fluorocyclobutene Carbonyls AE, IS (426) Polynuclear carbonyls Coordination number (1288) Cyclobutadiene tricarbonyl A H gives sign of EFG (170) Complex carbonyls (102, 429) Schiff brtse Some with binudlear and some with (675) two sites Fe(II1) Schiff bases Fe-0-Fe bond (47) Diary1 ethylenediamine AE, IS (4411 complexes Fe(sa1en)Cl (N,N'-ethylene- Dimer, AE us. T (116) bissalicylaldiminate ) EDTA Aquo ion is seven coordinate, AE, (628) IS Poly(1-pyrazolyl) borate AE, IS, H us. TI crossover ~ T+ z (390) 'AI FeLX2, L = 2,2',2"-ter... (573) pyridine. X = halide (Fepyrims) x, 2-(2-pyrid 1- IS, AE us. T (228) imidizole) 5 = sod; 512; Sz03etc. Tris(hydroxamato) Fe(II1) Relaxation effects (244) Iron(II1)-B-diketones AE compared with magnetic sus- (478) ceptibility and electronic spectra Iron(I1) [FeX(QP)] Coordination numbers determined (262) X = halide QP = tris(o-dipheny!phosphinophenyl) phosphin ( RzXCS2)2FeX ... (84.49) FeL2X2, L = quinolines, Tetrahedral (126) X = halides H used as probe of s density AE, (231) RFeXI-, R = EtdN IS, H us. T , A H sign EFG Stilbene-halide H , AE (7351 (R)a-.NHnFeC14 AE (157, 479) . . . (689) Salicaldehydoxime 1,2-di(salicylideneamino) IS, AE (78) ethene 1,lO-phenanthroline, etc. Salicylidenimine (685) 1,Zdithiolene complexes AE affected by kgands but not IS ( 7 8 ) ... (427) Diisopropyl-dithiophosphate Iron chelates H I IS us. T (692) A H sign EFG (483) Fe(L)e(CIO+ AE, IS (670) L = organic ... (420) [Fe(bipy)31(NCSeh Hot atom effect Trisdipyridyl W o ( I I I ) per- Evidence of some Fez+ (480) ... (514) chlorate Bispyridinocobalt(I1) ( 693 ) dichloride (Continued) +

372 R


~~

Application of Mossbauer Spectrometry to Chemistry Compilation of Publications for 1968 and 1969 (Continued)

Table 1.

Mossbauer nuclides

Subject or material studied

CoCrzO4, coCr~S4,Spinel CoFz K6’CoFa Cobalt compounds W o ( I I I ) ( l ,10-phenanthroline) (C104)32H20 Iron metal AI-Fe alloy Recoil implantation coulomb excitation Cu, All Au, Fe, Ge,.Si, FezOa, (Fe,Mg)2, Si04 Fe-Ni n, y in FeCnO4 FeSOa, (NH4)2Fe(SO&, FeCz04.2H20 Halides on organic ion exchangers Ion exchange resins

-

Radiation damage

Miscellaneous

61Ni (-a/~) E = 67.4 keV ( - S / Z ) a = 0.12 K = 7.6 keV pees = 3~0.35nm p,

=

f0.746nm

E, ‘= 6 4 6 (-E/*) Ez = 95.3 (- */2) K = 64.5 keV

lSS,184,188W lS3W (- 1/2) El = 46.5 keV (-8/2) E 2 = 99.1 keV ( - 6 / ~ ) a1 = 9.0 a 2 = 4.3 K = 60.7 keV po = f0.117nm Qir = 1.61 b 1911r ( + 8 / 2 ) El = 129.4 keV (+‘/z) E2 = 82.4 keV ( + l / ~ ) a1 =

Remarks Peg+ and Fe3+ Fez+ some Fea+ Fea+ stabilized Relaxation study, local lattice heating Fez+, a+, and 4 + Fez+ and Fe3+ Fez+, Fe3+ Existence of Fez+ may be due to “effective Fea+ lattice pressure” Auger effect observed on AE, IS

W u in copper metal

Nuclear parameters

Metal

Ni-Fe Oxide

...

...

Nuclear parameters ... Observation of effect Coulomb excitation, 3 MeV protons Inorganic Metal

Nuclear parameters

...

Nuclear parameters

...

I

No recoil effect, IS observed No effect on iron temperature, show two lines, f reduced Neutron radiation Produces oxidation Fez+to Fea+ upon gamma radiation, high spin compounds (666)

AE, line broadening Fez+, Fe3+ H vs. T relaxation effect Solvation seems necessary to exZeolite, organic ion exchangers change Superparamagnetism Fez08 in zeolite Quantitative analysis Aluminum, potassium, iron oxide catalyst for NH3 synthesis Frozen gels Oxide gels Only one iron structure Iron chloride in graphites Cotton Fe, 2+, 3+ adsorbed Composition gradually changed to PuFe2 in Perspex ferrous methyl methacrylate Pottery Observation of effect Cqulomb-excitation with 0 Compared with radioisotopic ion pe/po = -0.563 f 0.082 A R I R = -2.5 x 10-4 Nuclear parameters Ni-Cr

Source study Metal Alloy Inorganic

Ref

Can produce 100 mCi of W u

f

H us. concentration

(199, 391) (645, 646) (101,101,489)

(28) (668)

(246)

H = 98 kOe at 4 OK pe = 0.977 f 0.014 nm Q. = -0.72 & 0.11 b 69.6, T1/z 2 1.8 f 0.2 X 1O-O sec pa = 0.988 f 0.01 nm 95.3 T1/2> 0.2 X 10-9 sec 69.6 Tl/2= 2.55 f 0.06 X 10-9 sec 69.6 p e = 0.965 f 0.02 nm Ratio of quadrupole moment

... f

(2L7) (436) I

,

,

(547) (313)

(546) (334) (566, 586)

3

K = 66.4 keV plg = +0.18nm Qio = +1.3 b W r Ir (+8/~) El = 73 keV ( + l / ~ ) E2 = 139 keV ( - k 6 / 2 ) a = 6 K = 66.4 keV p , = 0.56nm p, = +1.17nm Qo = 1.5b

Inorganic Hot atom effect

IrFs, Ir-Fe alloy Beta decay from loaos

T ~= /115~

3

x

10-9 s

(634)

Orbital contribution to H assessed (544) Very fast recombination (687)

(Continued)


373 R

Table I. Application of Miissbauer Spectrometry to Chemistry Compilation of Publications for 1968 and 1969 (Continued) Mossbauer nuclides 1 0 7 A(+ ~ "2) E = 77.3 keV ( . _ LY

=

K

=

pa

=

pg Qp

3.7

70.4keV +0.37nm = +0.145nm = +O.56b

El '= Qg.9keV (-a/*) E Z = 129.7 keV ( - 6 / 2 ) ai = 7.2 MI, = -0.65 nm PI, = $0.61 nm "Ru (+6/z) E = 90 keV (+a/,) K = 19.6 keV p6 = -0.285 nm lr, = -0.625nm &e -0.15 b W a ( 7/z) E = 6.3 keV (- 9 / 2 ) K = 56.3 keV fi0 = t 2 . 3 n m 9 9 T E (+Q/~) E = 140keV ( +'/2) a = 30 K = 18.2 keV un = 5.7nm

+

LY

K

= 5.5 = 25.8 keV

pr = pp = &e =

Subject or material studied Nuclear parameters

+0.76nm -1.046nm -0.07 b

Doped metals Alloy

Catalysts Demonstration of effect for E2

Remarks T I ~=Z 2.73 =k 2 X 10-9 sec = 2.72 X 10-9 sec IS us. pressure, AR/R = +l.5 X Metal 10-4 Pd, Ag, Zn, Cu, Sn, Mg, Pb, IS, line width f In Au2Mn HI AE with pressure, spiral spin structure ps = $0.419 =k 0.005 nm, H Au-Fe H us. concn. MgO, AlzOasubstrate C1, CN complexes

...

...

IS, AE +2 to +S oxidation states Observation of effect Many compounds RuOZ,KzRuCla, KaRu(CN)6 AR/R = +IS, AE Inorganic

Demonstration of effect Nuclear parameters

1*1Win T a and W metal

...

Nuclear parameters

Nuclear parameters Source study Metal

Alloy

NazSnOa ' 3H20 BaSn01 Cobalt Gadolinium Doped Pb, In, Cd, Cu, Ag Doped Vz05 Pd-Sn MgSnz Fe-Sn Pd2MnSn XbaSn Ca-Sn Y-Sn Cu-Ag-Sn

Inorganic

Doped a-brass Do ed Cu8Au, CuAu ce8n3 SnTe Doped Cu-Ni, Co-Ni, Fe-Ni alloys Cu-Sn Sn(I1) compounds Semiconductors Metal

... T112= 55 =t 3 X sec ps = 5.14 It 0.15 nm Tllz = 2.28 X 10-9 sec

A R I R = +3.6 x 10-4 Same line width MgZSn Anisotropy in f Thermal shift below 90 "K H us. T H (0.2 atom yoSn) us. T Isign ( - ) IS us. concentration of Sn IS, AE us. T IS us. concn. of Sn and hydrogen . content H us. T, IS FeaSn, p-SnFesSn2,H produces unresolved spectrum H Phase transitions, f, anharmonic binding IS us. concentration of Sn IS, AE Plastic deformation increase FWHM IS IS, FWHM us. T,f 2 phases at 4 OK f us. T , phase transitions H IS Relationship between IS and AE

...

Surface laver on elass AE us. pressure IS, AE

-

IS, AE IS us. electronegativity

... [SnC13POCla]+,[POZC~Z] Frozen aqueous solutions SnC14 Hydrolysis in H20, D20 AE, IS ASnC12, A = donors In ice AE, IS us. T SnCL ...

Oxide

374R


Dipolar aprotic solvent study Sn4+ H us. T Phase transition AE, IS us. T No anisotropy in fraction effect AE,IS Thermal decomposition

Application of Mossbauer Spectrometry to Chemistry Compilation of Publications for 1968 and 1 969 (Continued) Subject or Mossbauer nuclides material studied Remarks Types CY-@ stannic acid jus. T Suspensions of SnOz in vis- Line broadening cous fluids NaZO-SnOz-SiO2, glass Sn(I1) and (IV) Anisotropy off “polymer effect” SnS, dioctyltin-oxide Debye temperature Chalcogenides Hydroxides NaSn(OH)s AE, IS IS us. T neutron irradiation Mg2SnO4 RzSnz07,R = rare earths AE us. T Garnets IS Spinels, e.g., SnCoz04 Sn in minerals Quantitative analysis Hot atom Oxides AE, IS us. T MgZ118SnO4 n , y recoil effects IS, AE Effect in Co, Fe, and Sn ... salts K&~z(CZO&.~HZO First evidence of Sn4+ by radiation Radiation damage Thermal neutron capture of Chemical analysis yields oor remagnesium stannate sults, quantitative anaPysis Monoxide yradiolysis Sn4 + formed SnO, tetraphenyl tin, SnClz ... Mirror experiment shows no chemn, y effects on SnOz ical transformat,ion Organic Many New explanation for AE Tin acetylenes Organotin halides Comparison with NMR AE R2SnX4 Others correlated with stereochemistry [Me2SnC1.terpyl] +, AE, IS [MeaSnClJ IS, AE (C6ClshSn R3SnX AE, IS (CHs)aSnOH, (CH313, SnF AE us. T , asymmetries observed Me3SnCl f anisotropy MezSnMo04, MezSnClz A H , sign of EFG Tetramethvl ammonium tin Octahedral IS us. electronegativity halide Tin (IV) halide with aro... matic compounds Pyridinium halides IS, AE Triethyl vinylstannane Reaction rate with butyllithium Pyridinium halides IS, AE Cyclopentadienyltin (I1) IS, AE M~zS~(SO~X)= Z , F, C1, .*. Me, Et, CF3 [CaH$e(co)~]zSnC12, CeHS Frozen solvents do not change = phenyl spectrum, 2 forms of molecules R-Sn-oxin-X various combinations, oxin = oxinate, X = halides, R = alkyl, aryl Carboxylates AE is correlated with electronegativity and inductive effect Frozen solvent Complex oxides IS, AE MezSnMOa, M = M o , W, Cr, C SnCH2-CO group Correlate IS with NQR, IR, and mass spec. AE, IS us. T related to dipole moR2Sn(NCS)2 ments R3SnCN. Frozen solvents Methyltins IS us. spin coupling constants Nuclear parameters NaSbF6, NaSb(OH)6,others IS, CY E 10 lzlSb ( + l / z ) E = 37.2 keV (+’/a) Halide A R I R =. -9.5 3 x 10-4 CY = 10.6 Inorganic Halides IS, AE,linear with electronegativK = 26.9 keV i t,v pg = +3.359nm SbCl complexes Froien HC1 RSbX,, X = halide, R = IS, AE Qa = -0.75 f 0.09 b Qg = -0.42b phenyl SbSs ... Source study lzsTe ( + l / ~ ) La and In in PbTe f us. concentration of I n and La E = 35.6 kev ( f 3 / 2 ) 2 FWHM = 6 mm/sec B-Te03 01 = 13.3 Single crystal Anisotropy in f K = 28.0 keV Metal MnTez AE, H us. T , sign EFG pa = +0.65nm Alloy Neutron irradiation in No effect observed Hot atom j~~ = -0.887nm PbTe, Te, and TeOz &. = AO.19b NaI03, NaIO4 Many sites NaSbO3, Sb203 No effect, AR/R = $2.4 X 10-s Table I.

...

*


0

375R

Table I.


Mossbauer nuclides

73Ge( + 9 / d E = 67.0 keV (+TI2) .. a = 0.23 K = 10 keV p, = -0.88nm Qg = -0.26b ..I

1271 ( $ 6 ~

E = 57.6 keV ( +7/z) a: = 3.8 K = 29.2 keV pa = 1.96nm pa = f2.809nm Qd = -0.71 b Qu = -0.79b

Subject or material studied Inorganic

Types Many compounds, oxides, halides, etc.

Remarks Can distinguish oxidation states similar to tin Isoelectronic studies show AR/R Radiation damage observed

+

Observation of effect Cqulomb excitation with 0 ions Hot atom effects observed Nuclear parameters Recoil implantation enriched target 73Ge onto T1/2 = 2.68 f 0.14 X 10-9 sec spin = ?/z for 67.03 keV state Cr, Fe, and Cu backing Ge/GeOz couple predict AR/R = t O . 9 X Chromium Coulomb excitation, AR/R = $1.12 x 10-3 Coulomb excitation recoil f7/z, Ti12 = 2.25 0.18 X lo-' implantation into Cr, Fe, sec, AR/R = 4-1 X 10-3 Cu, Ge Hot atom, nuclear AR/R = -2.8 X l27mTe source parameter FWHM = 1.2 mm/sec Source study MgTe04

H us. T AE, IS Lattice dynamics AE, IS

Doped alloy E = 27.72 keV (+6/~) Indrganic . a: = 5.0 pa = f2.84nm pu = $2.617nm Qd = -0.68 b Q, = -0.55b

1 2 0 1 (&'/P)

f us. T (anisotropy observed) AE

in hexane

Inorganic

12

Organic

Tri-iodide of benzamide, amylose Methane Pyridine iodides

1

Inequivalent I sites AE, IS

NOBLEGASES

83Kr(f9/d E = 9.3 keV (f7/d = 11 = 12.8 keV pc = -0.97 nm Q. = 0.459 f 0.006 b Qu = +0.27b

a

K

lZ9Xe(+'/$ K = 29.3 keV pp = -0.78 nm Qd -0.41 b 4'K

(-4)

E = 29.4keV(-3) a = 0.35 K = 3.35 keV pu = -1.298 nm QP = 0.09 b la3Cs(+'/z) E = 81 keV ( + J z ) CY = 1.63 K = 32.0 keV pe = +3.3nm pa = +2.579nm Q, = -0.003b

Inorganic Measurement of nuclear parameters Hot atom Organic Inorganic Nuclear parameters

Source ZnSe, W e + 83Br + Clathrate (119) *3Kr Solid pe = -0.939 f 0.002 nm (136) pe = -0.99 f 0.08 nm (314) 83Rb halides (433) Lattice dynamics show frequencies (542) Clathrates not predicted by I R Solid Kr f us. T (290) Source = KIO4; absorber pa = 0.68 f 0.30 nm (137) = clathrate AE, Tl/z = 3.5 X lo-'' sec, hot Halides (646) atom Chlorides others ... (643) Demonstrated effect, AR/R < 5 X (668) Metal halide 39K(n,~)~'K

+

Nuclear parameters

Nuclear parameters Inorganic Doped iron

Source = BaA14 Absorber = halides 133Xe implanted into Fe 133Xe implanted into iron, vanadium. chromium

ps = 3.44 f 0.04 nm pa = 3.44 f 0.02 nm H, IS At least two sites

ALKALINE E.4RTHS ls3*Ba ( + l / ~ ) E = 12.3 keV ( + 3 / d CY = 3.4 K = 31.8 keV

Demonstration of effect

Source 39-h 133Ba absorber 7.2-ylaaBa

f = 0.95% at 4 "K

(Continued)

376R


Application of Mossbauer Spectrometry to Chemistry Compilation of Publications for 1968 and Subject or Remarks material studied hlossbauer nuclides Types RAREEARTHS Observation of effect Coulomb excitation 3.3 MeV 01 particles lelDy (+6/z) 74.5 keV Nuclear parameter pz6 = -0.377 i 0.012 nm El = 25.6 keV ( - "2) Qze = 1.5 i 0.2 b Ez = 74.5 keV ( - 3 / ~ ) DyFez E3 = 43.8 keV ( + 7 / ~ ) Alloy H us. T Many Inorganic 011 = 2.5 IS LYZ = 0.65 Relaxation, H us. T Metal garnet Qo/Qq = 0.56 & 0.04 03 = 3 DyCrO3 K = 47.0 keV Relaxation effect AE, I S us. T in ice pl. = +0.5nm Dy(C1Oa)a GdDyFa Single line source, FWHhl = 0.4 pzs = 3=1.6nm cm/sec pq = -0.455 nm Q1, = +1.75 b H and EFG collinear Qp = +1.8b

Table I.

161E~ (+'/z)

E 01

K po pa

Qd Qo

= = = = = = =

21.6 keV ( + 7 / ~ ) 29 42.5 keV +2.5nm +3.464nm +1.2b +0.95b

Nuclear parameters

EulOl irradiated with 16$lev deuterons 22 keV

Alloy

Eu-Y b, Eu-Ba

Source study

...

Eu-Yb Inorganic

Relaxation studies with single crystal 161Gd was separated and purified bv chemistrv . . .. .

H us. T Phase transition, H us. T Conduction electron contribution to H IS, H us. concn. of Yb IS us. interatomic distance Relaxation eff ec't; I S Electron hop between oxidation states H v s . T-phase transition H us. T Eu~+ Pseudo-melting a t -65 OK High f attributed to coupling between acoustical and optical

Organic

EusOa, EuO Garnet EuSiz, EuGez Doped ice EDTA

Alloy Inorganic

SmFe?, SmzCo17 Garnet

H , AE us. T Exchange interaction Anisotropic exchange field

Metals Alloy

H

Inorganic

Holmium metal ErCop, ErCoNi ErAl ErCrOs


79.3 keV state by coulomb excitation 3 MeV protons

T I ~=Z 0.103 i 006 X 10-9 sec

Iron alloy

H , ratio of magnetic and electric moments

1969 (Continued) Ref. (662) (419) (106) (3)

(618) (180) (2411 (810) (164) (706)

(37L) . .,

(122) li7.9)

(isSj (166) (372, 709) (3731

(71) (4661 (448) (70)

%:l

(608 j

(216) (194)

modes

. . . .. ...

I63Eu (+6/z) El = 97.4 keV ( - 6 / z ) Ez = 103.2 keV (+a/Z) 011 = 0.41 011 = 1.55 K = 42.5 keV pie = f3.2 nm ppS = $2.03 nm Qio = +2.93 b 16eEr ( + O ) E = 80.6 keV (+2) a = 7.2 K = iO2keV pe = +0.61 nm Q. = -1.6 b le7Er( + O )

E K

= = pp = Qr =

79.3 kev (+e/*) 50.2 keV -0.56nm +2.8b

17oEr ( + O ) E = 79.3 keV (+2) K = 50.2 keV 1E4Gd ls6Gd ( - 3 / ~ ) El = 60.0 keV ( -"z) EZ = 86.5 keV ( f a / z ) E3 = 105keV a1 = 7.5 CY = 0.49 K =44keV p ~ .= -0.564nm pl0 = -0.27 nm Qg = +1.3b ls6Gd E = 89 keV 167Gd E = 64 keV 178,178,180Hf 178Hf( + O ) E = 93 keV a

=1

Nuclear parameters Nuclear parameters Alloy

166Gd compared with 1ssGd Oxide halide Gdz08 GdFez

(32) (37) (38)

... ...

H us. T , spin relaxation

Qs/Qr = -0.07'2 0.21 3/z, QO/Qp = 2.89 =t0.10

Ez is H

Nuclear parameter

.. Hot atom Inorganic

Q./Q,

Oxides Coulomb excitation Hf, HfOz, (NH4)zHfFe

=

1.78 3= 0.04

Ratios of quadrupole moments Radiation damage observed f us. AE

K = 54.6 keV pg = +0.6nm (Continued)


377 R

Table I.


Mossbauer nuclides l69Tm (+ l / z ) E = 8.41 keV (+$/z) a = 325 K = 51.9 keV pa = +0.6nm fig = -0.23nm Qd = - 1 . 2 b 17OYb

E = 84.2 (+2) CY = 6.7 K = 53.6 keV fie = +0.668nm 1’lY b (- ‘/z) El = 66.7keV E2 = 75.9keV a = 10 pz6 = 1.01 f 0.01 nm fig = +0.5b

Subject or material studied Demonstration of effect, nuclear parameters Metal Alloy Inorganic Nuclear parameters Inorganic

Types TmF3, TmCla, TrnrO2

Remarks 0,IS, us. T, AR/R =

16DEr imbedded into W, WOa, TmzOa by mass se arator TmRuz, ?mRez, TmMnz Glasses

Conversion electron spectra compared with IS H us. T H us. T AE us. T Crystal field calculations

YbGe, Y bSii,‘YbSi,

Yb2+,Yba+

(5h)

243Am ( - 6 / ~ ) E = 83.9 keV ( - k 6 / d LY = 0.2 K = 102 keV fig = +1.4nm Qg = $4.9 b


243Pu

““djkev ( f 2 )


242Pu,source Coulomb excitation

Nuclear parameters

Oxide, metal

:*”

=5 = 94.7 keV Qd = $11.3 f 0.3 b 237Np E = 59.5 keV

...

...

Nuclear parameter

--f

24aAm

+

ARIR

=

8-

-9

j=3

x

10-4

(402)

a

K

CY

K

= 1.07

= pe = pg =

103.5keV +2nm &5nm

231Pa E = 84.2 keV a = 2.8 K = 104.2 keV *32Th( + O ) E = 49.8 keV (+2) K = 90 keV

Inorganic Hot atom

Oxide Oxide Thorium oxide

Inorganic

Oxide

Nuclear parameters

Metal oxide

tained b y implantation (409, 620, and 630) gave similar results as obtained by Co57 sources. 73Ge Mossbauer effects were observed (187, 610,621, and 604). Sylvester et al. (662) observed the effect in 161Dy. Wilenzick et al. (713) in I67Er and Lee et al. (461) in *W also made a systematic study of nuclear moments b y the Mossbauer effect following coulomb excitation. Goldanskii et al. (292) excited Mossbauer levels b y heavy ion bombardment. Time filtering as observed by Albrecht et al. (16) and Hamill et al. (331) using coincidence techniques can be used to reduce the observed linewidth. Debye-Waller factors (f) were measured by Singh et al. (618) for metals and b y Mahesh (470) as a function of temperature. These f measurements present a technique for detecting local vibrational modes and lattice effects in solids (477), and mean square displacements, shown for tin alloys b y Alekseev et al. (25). A novel technique using Rayleigh scattering and two absorbers developed by Kroy et al. (436) for f mea378 R

...

Metal

AR/R ratios of nuclear moments, 2 4 1 Am used as source AE,IS, H us. T Np(VI1) IS fl, N 0.01 nm Thorium matrix gives narrower line than oxide AR/R very small

NO. 5,

APRIL 1970

(227) (642) ($28) (18)

(1811

Demonstration of effect T1/2 > 0.33 (362) ns

surements is very accurate. Mossbauer et al. (497) observed self-inversion of resonant absorption for Wo(Pd) and 0.9 Fe-Pd alloy. This effect has good possibilities for f measurements. Backscattering. I n the previous review (204), resonant fluorescence scattering was briefly discussed, and the advantage of measuring bulk samples was indicated. Collins (169) made several backscattering measurements for steel and corroded surfaces. The potential of surface analysis with Mossbauer spectroscopy was shown by Terre11 et al. (661), and they calculated the backscattering amplitude as a function of penetration depth into the sample for conversion X-ray detection. This technique can be used to analyze iron bearto ing surfaces in the range of cm. Much thinner surface films can be analyzed b y using the 8 keV conversion electrons, as shown in Figure 2. By evaporating a natural F e film on a stainless steel plate, the range of the 8-keV conversion electrons could be estimated. The conversion electron detection tech-

ANALYTICAL CHEMISTRY, VQC. 42,

( 19, 229, 641 )

nique makes it possible to analyze a surface thickness of 50 to 3000 A. A flow detector which uses a 90% He-100jo CH4 counting gas decreases the detection of 6.3 keV X-rays. Catalytic action and adsorption of NH3 on FezOa was investigated by Hobson (369) and Karasev et al. (408). Surface compound formation of tin in the range of 24,000 A was observed by Bonchev et al. (97) using conversion electrons as indicated above. Special Methods. Several special techniques were also reported. Zero velocity can be measured for constant acceleration spectrometers using t h e technique of Carrel1 et al. (139); nonlinearity corrections due to the “cosine effect” have been calculated by Riesenman et al. (679). Heiman et al. (346) observed selective excitation of the magnetic hyperfine levels of iron by radio frequency excitation. Gutlich et al. (S26) studied the FeSOd KCN reaction, and Champeney et al. (141) observed molecular motions in super-cooled liquids from the Mossbauer spectra.

+

COMPUTATION METHODS

The computer programs for curve fitting of Mossbauer data have greatly improved in the last two years, mainly as a result of placing theoretical constraints upon the number of variables. Least square analysis programs have been published by Agresti et al. (8), Christ et al. (154) and Kundig (4%). Nistor et al. (516) has analyzed the relationship of Mossbauer parameters to their standard errors using a least square method. Theoretical spectra can be computed b y a program of Gabriel et al. (274), which uses the Hamiltonian of the hyperfine interactions as a basis for the computation. A simple analytical method to obtain the hyperfine parameters directly from the observed spectrum is described by Williams et al. (714). These parameters can then be used as input for an interactive least square program to obtain the final parameters and their errors. The main difficulty with the least square techniques normally used resides in the use of an improper mathematical model for peak profile. Invariably a Lorentaian profile is used which is valid only for an infinitely thin source or absorber. Shimony (812) has analyzed the line profile by calculating the distribution of oscillators in a solid material] and although the mathematical formulation is given, it has not yet been incorporated into a computer program to our knowledge. Propagation of errors in the calculation of Mossbauer parameters from the least square fitting has been determined by Zemcik (732), and he used his formulas to evaluate the parameters and their errors for a metallic iron foil. The analysis of very complex spectra such as have been observed in minerals of mixed composition can be achieved by using a stripping technique developed by Muir (501). This requires reference spectra of the individual components which are often difficult to obtain. Spectrometer stability is also of extreme importance if this technique is to work well. Gavron et al. (282) have developed a similar computer program. THEORETICAL CONSIDERATIONS

Line Shape. This is of great interest, both theoretically and experimentally. Heberle et al. (344) have analyzed the transmission of a Lorentzian spectral line through a layer of Lorentzian absorbers] to study thickness broadening (348). The second major contribution to line broadening is spin relaxation. The theory of relaxation processes and its relation to line broadening has been analyzed by Levinson et al. (455), Krivoglaz et al. (434), Wickman (704), Lang et al. (447), and Van Zorge et al. (679). Gabriel et al.

t

-64

-32

00

32

64

SOURCE VELOCITY, MM SEC 4

Figure 2. Conversion-electron Mossbauer backscattering spectra for vacuum-deposited iron on stainless steel foil. Nat. Bur. Sfand. ( U . S . ) Tech. Note 501, pp. 6-19 (Feb.

1970)

(278) have computed line shapes using spin lattice relaxation theory. Temperature Dependence. Much information can be obtained from the temperature dependence of the Mossbauer parameters. Many temperature studies have been made and are shown in Table I. The identification and distribution of lattice sites almost always requires measurements a t several temperatures, Particularly in the case of substitutional and interstitial lattice sites, the f-factor dependence on temperature can be used to differentiate between these. A temperature range of 2 O K to 400 O K is adequate, and temperature control of f1 O K is sufficient. Measurements of Curie or Ne41 temperatures can be made very accurately with Mossbauer spectroscopy. This requires temperature control to (0.01 f 0.1%) O K to 1000 OK. In structural chemistry the temperature effect upon quadrupole splitting can be used to determine the contribution of axial ligands, and to obtain the axial field splitting parameter. These have been described in a very clear and concise manner by Webb (699). The quadrupole interaction arises from two major contributions to the electric field gradient p, the valence electron contribution, qval, and the lattice charge distribution, p i s t . The latter has very little temperature dependence. I n the case of an axial fieldenvironment, p = pva,,(l - R ) q ~ ( -l y) where (1 - R ) and (1 y) are thesternheimer factors and (pval )% = ( V J e ) , evaluation of (VzZ/e)$ gives

for the configurations 3d1 and spin-free 3d6 (+)i

5

= 2 (r-3)i[3Ls2

-UL

+ 111

where ( r 2 ) i refers to the expectation value of the square of the radius of the i t h d orbital. By combinations of one-electron wave functions

Moessbauer spectrometry - ACS Publications

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