J. Phys. Chem. 1981, 85, 986-989
986
TABLE IX: Hydrogen Affinities for Methyl-Substituted Amines with the D Z P Basis
theory IF
”3 CH,NH, (CH,),NH
9.44 9.93 10.24 10.40
(CH3),N
experiment
HAb aHAd
molecule
169.6 157.0 151.5 145.0
0.0 12.6 18.1 24.6
IPc
HAe
AHAd
10.16 8.97 8.24 7.82
126.1 107.8 97.4 91.5
0.0 18.3 28.7 34.6
Ionization potentials from Koopmans’ theorem in eV. Hydrogen affinity in kcal/mol. Ionization potentials Relative hydrogen affinities in kcall from ref 49 in eV. mol. e Hydrogen affinity given in kcal/mol. Relative proton affinities from ref 1 converted to absolute proton affinities by using PA(“,) = 205.6 from ref 15. a
TABLE X : Orbital Eigenvalues for N(1s) from the DZP Basis
theory (N(ls))b
A N( 1 ~ ) ~Ipd
422.81 422.70 422.80 422.87
0.0 -2.5 -0.2 1.4
-E-
molecule “3
CH,NH, (CH,),NH (CH,),N
experimen ta
405.6 405.1 404.9 404.7
AN-
( 1 ~ ) ~ 0.0 -11.5 -16.1 -20.1
Inner-shell eigena Experimental results from ref 56. Relative values for value with the DZP basis in eV. N(1s) binding energy in eV. N(1s) in kcal/mol. where IP is the appropriate ionization potential. The proton affinities are obtained from our calculations, and the ionization potentials of the amines can be calculated from Koopmans’ theorem.48 The values for the hydrogen affinity at the DZP level are summarized in Table IX together with the experimental values. The theoretical values are too large in comparison with experiment. This arises because both terms, PA(B) and IP(B), are too large in comparison with the experimental values. Although the qualitative trend of decreasing hydrogen affinity with increasing methyl substituent is reproduced by theory, the differences in methyl-substitutent effects are not repro(48) T. Koopmans, Physica, 1, 104 (1933). (49) H. M. Rosenstock, K. Draxl, B. W. Steiner, and J. T. Herron, “Energetics of Gaseous Ions”, J. Phys. Chem. Ref. Data,Suppl., 6 (1977).
Reactions of Recoil
duced quantitatively. The calculations predict a larger methyl effect for adding a third methyl group as compared to adding a second methyl group; the opposite is found experimentally. These differences, however, are not large in magnitud, and the errors in the relative values for HA are probably due to the rather crude approximation used in determining the ionization potential. There has been much recent interest in correlating ionization potentials of 1s orbitals with proton affinities.5w55 For the specific case of methyl-substituted amines, a good linear correlation between N( 1s) binding energy and the negative of the relative proton affinity is found.51 The values for the binding energy of N(1s) decrease with increasing ~ u b s t i t u t i o nwhile ~ ~ the proton affinity increases. We have tabulated N(1s) eigenvalues and their differences relative to NH3 in Table X. Very little difference in the N(1s) eigenvalues is observed with increasing methyl substitution in contrast to the experimental results. This difference could be due to our use of a single description of the core or to the fact that Koopmans’ theorem provides a very poor estimate of the ionization potential of inner shells. In summary, we find that relative proton affinities for amines can be calculated quite well with DZD and DZP basis sets if relaxed geometries for the protonated forms are employed. For molecules containing nitrogen with three substituents, it is important to use basis sets that properly describe its conformation. The DZ basis is thus inappropriate, and some caution should be taken in using this basis set to calculate molecular properties. Acknowledgment. We acknowledge grants of computing time from the University Computing Centers of Drake University and the University of Minnesota. (50) R. S. Brown and A. Tee, J. Am. Chem. SOC., 102, 5222 (1980). (51) R. L. Martin and D. A. Shirley, J . Am. Chem. Soc., 96, 5299 (1974). (52) B. E. Mills, R. L. Martin, and D. A. Shirley, J. Am. Chem. SOC., 98, 2380 (1976). (53) D. W. Davis and J. W. Rabelais, J. Am. Chem. SOC., 96, 5305 (1974). (54) R. G. Cavelland and D. A. Allison, J. Am. Chem. SOC.,99,4203 (1977). (55) A. J. Ashe, M. K. Bahl, K. D. Bomben, W.-T. Chan, J. K. Gimzewski, P. G. Sitton, and T. D. Thomas, J . Am. Chem. SOC.,101, 1764 (1979). (56) P. Finn, R. K. Pearson, J. M. Hollander, and W.L. Jolly, Inorg. Chem., 10, 378 (1971).
in Crystalline p-Dichlorobenzenes
Klara B e r d and Hans J. Ache” Deparfment of Chemistry, Virginia Poiflechnic Institute and State University, Blacksburg, Vkginia 2406 1 (Received: September 30, 1980)
The effects of matrix structure on the chemical reactions occurring as the result of 3‘Cl(n,y)38C1in solid samples of p-dichlorobenzene were studied. No significant variations in the yields of the products formed were observed in the three phases a,6, and y of p-dichlorobenzene. These and other results suggest that the 38C1-labeled parent products are predominantly formed via hot 38C1-for-C1replacement reactions. Introduction The rapidly expanding field of solid-state chemistry information about the influence of molecprovides
ular order on chemical interactions of atoms and radicals in organic glasses and ~ ~ h dcrystals. a r There exists by now considerable evidence that radical reactions induced by photolysis1,2or ionizing radiation1p3-’ depend on the
‘Visiting scientist from Central Research Institute for Physics, Hungarian Academy of Sciences, 1525 Budapest, Hungary.
(1) Pimentel, G. C. In “Formation and Trapping of Free Radicals”; Bass A. M.; Broida H. P., Eds.; Academic Press: New York, 1960; p 69.
0022-3654/81/2085-0986$01.25/00 1981 American Chemical Society
Recoil %I Reactions in p-Dichlorobenzene
The Journal
of Physical Chemistry, Vol. 85, No. 8, 198 1 907
p , a n d y Phase of p-DCBa T A B L E I: Crystal Data for the CY, monoclinic, P2,/a, Z = 2, stable a t 0 < T < 31 " C
a = 14.664 A b = 5.740 A o = 3.925 A
p = 111.77'
v o l = 306.8 A 3
p, triclinic, P i , z = 1, stable a t T > 31 C
a = 7.302 A b = 5.873 A o = 3.882 A
(Y = 91.13" p = 112.55" y = 92.43"
vol = 153.5 A 3
y , monoclinic, P2,/c, Z = 2,
a = 8.624 A
p = 127.51"
vol = 305.4 A 3
CY,
stable at T < 0 " C
a
b = 6.021 A c = 7.414 A
Reference 18.
matrix structure. Much less is known about such influence on the primary reactions of hot atoms or radicals formed as a consequence of nuclear recoil in solid organics. In a number of early investigations on the chemical effects of nuclear transformations in polycrystalline and glassy organic systems carried out by Willard and co-workersaand later in some other laboratoriesSl3 conflicting results have been obtained considering the phase effect on the fate of recoil atoms.14 More recently, efforts were made to clarify the role of the matrix structure on the particular hot atom reactions by comparing their radiochemical yields in condensed phases exhibiting different extent of molecular order. Based on results obtained with p-bromochlorobenzene and p-dibromobenzene Halpern15 assumed a minor contribution from direct cage recombination to the a%r-for-C1 replacement process in the crystalline state with accompanying isomerization which could not be found in the liquid phase. A systematic study on replacement reactions of recoil I and Br in a number of glassy and polycrystalline hydrocarbons was carried out by Rack and co-workers.16 Especially remarkable is the high lZaI-labeling yield of the parent compound in frozen diluted aqueous solutions of monoiodo- and diiodotyrosine ascribed by the authors to the effect of the ice lattice.*6c Results obtained in our laboratories1' indicate that the behavior of recoil %C1in glassy solids resembles much more the one observed in liquid than that in crystalline systems. (2) Appel, W. K.; Greenhough, T. J.; Scheffer, J. R.; Trotter, J. J. Am. Chem. Soc. 1979, 101, 213. (3) Hamill, W. H. In "Radical Ions"; Kaiser, E. T.; Kevan L., Eds.; (4) Willard, J. E. Science 1973, 180, 553 (a review). (5) Milia, F. K.; Hadjudis, E. K. J. Phys. Chem. 1968, 72, 4707. (6) Buhler, R. E.; Funk, W. J. Phrs. Chern. 1975, 79, 2098. (7) Mivazaki, T.: Wakavama. T.: Fueki, K.: Kuri, 2. Bull. Chem. Soc. Jpn. 1969,42, 2086. (8) (a) Goldhaber. S.: Chiane, R. S. H.: Willard. J. E. J. Am. Chem. Sor. 1951,73,2271. (b) Chien, JYC. W.; Willard, J. E. Ibid.1953, 75,6160. (c) Iyer, R. M.; Willard, J. E. Ibid. 1966,88,4561. (d) Hahne, R. M. A.; Willard, J. E. J. Phys. Chem. 1964, 68, 2582. (9) Collins, K. E.; Harbottle G. Radiochim. Acta 1964, 3, 21. (10)Abedinzadeh, 2.; Grillet, S.; Stevovic, J.;Tanaka, K.; Milman, M.; Radiochim. Acta 1968, 9, 39. . -(11) Kemnitz, E. J.; Hahn, H. K. J.; Rack, E. P. Radiochim. Acta 1970, 13.
(12) (a) Sikierska, K. E.; Halpern, A. Radiochim. Acta 1966,5,51. (b) Narbutt, J.; Dancewicz, D.; Halpern, A. Ibid. 1967, 7, 55. (c) Dancewicz, D.; Halpern, A. Ibid. 1969, 12, 52. (d) Sikierska, K. E.; Halpern, A.; Maddock, A. G. J. Chem. Soc. A 1968, 1645. (13) (a) Berei, K.; Vasiros, L. Isotopenpraxis 1968,4,19. (b) Vasiros, L.; Norseyev, Yu V.; Meyer, G. J.; Berei, K.; Khalkin, V. A. Radiochim. Acta 1979, 26, 171. (14) Stocklin, G. "Hot Atom Chemistry Status Report"; IAEA: Vienna, 1975; p 174. (15) Halpern, A. Radiochirn. Acta 1971, 15, 83. (16) (a) Lambrecht, R. M.; Hahn, H. K. J.;Rack, E. P. J. Phys. Chem. 1969, 73,2779. (b) Ayres, R. L.; Rack, E. P. Radiochem. Radioanal. Lett. 1970,3, 213. (c) Arsenault, L. J.;Blotcky, A. J.; Medina, V. A.; Rack, E. P. J. Phys. Chem. 1979,83, 893. (17) (a) Kiss, I.; Berei, K.; Vaslros, L. J . Label. Comp. 1967, 3, 414. (b) Berei, K.; Ache, H. J. J. Phys. Chem. 1980, 84, 687. (c) Berei, K.; Vaslros, L.; Ache, H. J. Ibid. 1980, 84, 1063.
This is reflected in the radiochemical yields of particular replacement reactions as well as, e.g., in the fact that a considerable amount of labeled isomerization product was found in the crystalline 1,l-dichloroethanewhich could not be detected either in the liquid or in the glassy p h a ~ e . l ' ~ * ~ According to these experiments the long-range order of the matrix has a decisive influence on the course of recoil Y!1 stabilization processes. Hence, the question arose whether also finer differences in the crystalline structure could alter the course of 3aCl stabilization processes. p-Dichlorobenzene (p-DCB), which can be obtained in three polymorphic modifications by slow sublimation in different temperature intervals, offers a possibility for such cornparison. Beside the divergences in cell parameters, intermolecular forces, and molecular distortions for the three crystalline forms, the orientations of molecules in triclinic p and monoclinic a phases are quite different: the adjacent layers are translationally identical in the former, while they are related by a twofold screw axis in the latter modification. The parameters of a, P, and y p-DCB investigated by several authors have been more recently described by Wheeler and Colsonla as summarized in Table I. Experimental Section Sample Preparation and Irradiation. a, p, and y crystalline forms were prepared by vacuum sublimation of p-DCB from Aldrich Chemical Co., with 98-99% purity, in the temperature intervals of 20 to 25, 40 to 45, and 0 to -10 "C,respectively.lnJ8 To avoid phase transition the samples were frozen in liquid N2 and kept at this ternperature before and during the irradiation, until the last X-ray diffraction measurement was completed. The identification of the three different crystalline structures was accomplished by X-ray diffraction before and after the irradiation, at -150 to -160 OC, using Mo K a radiation on a DRON-20 diffractometer. Despite the experimental difficulties due to the rather microcrystalline structure of the samples, the measurements clearly showed that three different phases were prepared by sublimation at the different temperatures given above and remained unchanged during the irradiation. The X-ray diffraction data of CY p-DCB could be fitted with sufficient accuracy to those given in ASTM. Similar data for the ,f? and y phases could not be found and it cannot be excluded that they were contaminated to some, though undetermined, extent by the CY phase. Samples (0.02 g) of various crystalline forms were placed into polyethylene vials which were sealed and then irradiated while immersed in liquid NP. Irradiations were carried out both at the Virginia Polytechnic Institute and State University nuclear reactor with a neutron flux of 1.3 X 10l2n cm-2 s-l for 0.5-1 min and at the VVRS reactor of Central Research Institute for Physics in Budapest with (18) (a) Wheeler, G. L.; Colson, S. D. Acta Crystallogr.,Sect. B 1975, 31,911. (b) Wheeler, G. L.; Colson, S. D. J. Chem. Phys. 1976, 65, 1227.
988
The Journal of Physical Chemistry, Vol. 85, No. 8, 1981
Berei and Ache
TABLE 11: W l Product Yields in Different Crystalline Forms of p-C,H,Cl, crystalline form
sublimation temp, C O
20-25
c!
P Y
40-4 5
0 to -10
a "C1-for C1.
radiochemical yield, % total 3aCl activity
irradn temp, " C
organic
p-C, H, C 1 3 W a
20-25 -196 - 196 -196
77.8 78.3 80.0 79.2
20.3 17.1 18.0 17.2
1,2,4-C,H3C1,3aClb
5.0 4.9 4.9 5.1
rn-C,H,C13xCl
o-C,H,Cl
0. 7
0.8 0.9 0.8 0. 7
0.8 0. 7 0.6
3*C1-for-H.
a neutron flux of 3 x W3n cm-2 s-l for 3-4 s. Samples of the e phase were also irradiated at room temperature. Sample Analysis. To determine the total induced activity and its distribution among the organic and inorganic forms we placed the solid samples into a liquid mixture consisting of C C 4 which contained adequate amounts of carriers and of 0.1 M NaOH aqueous solution with a small amount of Na2S03as a reducing agent. After extraction aliquots of the phases were subjected to radioactivity measurement. The total activity was calculated from the sum of the activities measured in the two phases. The radiochemical yields of the individual organic products were determined by radiogas chromatography. The different fractions, as indicated by the thermal conductivity detection of the added carriers or the parent compound itself, were adsorbed in charcoal tubes and subjected to radioacivity mea~urement.'~ To avoid errors caused by tailing peaks, columns separating 0-, m-, and p-DCB in different sequences were used: (a) 4 m long, 4 mm i.d. glass column packed with 20% silicone oil 6% Bentone-38 on Chromosorb W-AWDMCS 60/80 mesh at 155 "C, 80 mL He/min; (b) 4.40 m long, 4 mm i.d. glass column packed with 20% Igepal CO-880 on Chromosorb W-AW-DMCS 60/80 mesh at 125 "C, 80 mL of He/min; (c) 5.5 m long, 4 mm i.d. glass column packed with 25% Carbowax 20M on Chromosorb P 60/80 mesh at 175 "C, 60 mL of He/min. Radioactivity Assay. The radioactivity of the several fractions was measured in a well-type scintillation counter under identical conditions. The yields were calculated by making correction for the 3sCl decay. Data presented in Tables I1 and I11 represent the average values of five to six individual runs. The standard deviation does not exceed 10%.
TABLE 111: Effect of t h e Phase o n t h e Yield of 3xClReplacement Products
system p - C, H, C1, a
p-C,H,Cl, t 0.5 mol % I, o-C,H,Cl, o-C,H,Cl, + 0.5 mol % I,
O-C,H,CI-CH,OH~ ( N = 1:9)
+
Results and Discussion The radiochemical yields obtained for the three different crystalline forms of p-DCB are shown in Table 11. They are fairly identical with a slight (1520%) increase in the yields of labeled parent compound for the cy phase irradiated at room temperature as compared to irradiations at -196 " C , the yields for the other products remaining unchanged even in this case. This finding is in striking contrast with significant differences observed for radiolytic processes in cy vs. ,8 p-DCB5 or in solid aliphatic hydrocarbon~.~ Our first attempt was to explain the constancy of the yields in different crystalline forms of p-DCB by the "hot zone" model of Harbottle and SutinSz0According to this model, the recoil atom, which originated in a solid media, is taking part in chemical reactions in a "hot spot" of melted crystal which is created as the result of a microscopic temperature increase due to the slowing down processes of the recoil species. This reaction should, (19) Stocklin, G.; Tornau, W. Radiochirn. Acta 1968, 9, 95. (20) Harbottle, G.; Sutin, N. In "Advances in Inorganic Chemistry and Radiochemistry"; EmelBus, H. J.; Sharpe, A. G., Eds.; Academic Press: New York, 1959; p 267.
o-c,H,c~,-c,H,oH~
( N =1 : 9 )
phase liquid (60°C) crystal (- 1 9 6 C)b liquid (60 "C) liquid crystal (-196 " C ) liquid liquid glassy (-196 "C) crystal (-196 "C) liquid glassy crystal (-196 "C)
radiochemical yield, % total activity 38~1- 38~1f o r 4 1 for-H 38.5
4.3
17.5
4.9
23.8
4.1
30.5 11.1
15.7 1.9 1.7
11.1 1.2
1.1 9.2
Average values of d a t a measured in the t w o laboratories Average of d a t a for t h e three Referdifferent crystalline forms. Reference 17b,c. ences 1 7 c and 2112.
(VPI + SU and CRIP).
therefore, not be influenced by the original crystalline order. However, data shown in Table I11 seem to contradict this interpretation. Namely, the 38C1-for-C1replacement in the crystalline form is much lower: less than half of that obtained in the neat liquid (melted) p-DCB, irradiated at 60 "C. The same is true for the labeled parent yields in crystalline and liquid o-DCB (Table 111). Furthermore, our earlier have shown that in solid glassy phases the replacement yields of recoil 38Cl atoms resemble much more those in the liquid than those observed in crystalline systems, as can be seen by using the example of the o-DCB-MeOH mixtures in Table 111. This means that the yields obtained in the three crystalline forms of p-DCB are characteristic not simply for the solid phase but for the long-range order in these media. On the other hand, comparison of the results shown in Table I11 indicates that the replacement products in the crystalline phase may be formed by purely hot reactions of recoil 38Clatoms. Being much lower than in the liquid unscavenged systems, the 38C1-for-C1replacement yields are very similar to those obtained in liquid dichlorobenzenes containing enough molecular iodine radical scavenger to suppress radical recombination processes. The fact that the 38C1-for-C1replacement remains the same in all these systems fits well into the picture, since only hot C1 atoms are able to replace H atoms in the aromatic ring. The assumption of mainly hot reactions occurring in p-DCB phases is consistent with the well-known reduced mobility of radicals in the crystalline phase, especially at
J. Phys. Chern. 1981, 85, 989-994
low temperatures.’J5 Thus, e.g., the somewhat higher yield of the labeled parent compound in a p-DCB at room temperature compared to that at the liquid Nz temperature, as can be seen from the data in Table 11, may be caused by increasing participation of radical recombination due to increased diffusion of radicals, TI TM1being about 0.90 in this case. It should be pointed out that, similarly to earlier results obtained with liquid disubstituted benzene derivatives,21 no significant isomerization could be formed for 38Clreplacement reactions in the three crystalline form of p-DCB. That is indicated by the negligible 38Cllabeled yields of m-and o-DCB in Table 11. It is, therefore, our opinion that reports on isomerization in the course of recoil replacement, in analogous systems, are caused by misevaluating the tailing peaks on the gas chromatograms. When a Silicone oil-Bentone-38 gas chromatographic column was used for separation, where m-DCB shortly follows p-DCB, the yield of m-DCB was found to be 2-2.5 times higher (21) (a) Berei, K.; Stacklin, G. Radiochirn.Acta 1971,15, 39. (b) Berei, K. “Hot Atom Chemistry Status Report”; IAEA: Vienna, 1975; p 185. (c) Vasiros, L.; Berei, K. “Proceedings of the 4th Symposium on Radiation Chemistry”; Akademiai Kiadb: Budapest, 1977; p 39.
989
than with columns with the opposite peak sequence. This phenomenon must be a consequence of a tailing of the highly radioactive p-DCB peak which should be taken into account in evaluating the radiochemical yields of m-DCB. Summarizing, the results of this study and their comparison with those obtained for systems with lower molecular order seem to indicate that in crystalline p-DCB the W-labeled parent compound is formed predominantly via hot 38C1-for-C1replacement reactions. Their course and, hence, yield apparently is not influenced by the variations in the intermolecular packing of the CY,p, and y phases of p-DCB. Only negligible amounts of isomerization products could be found, similar to earlier results for liquid disubstituted benzene derivatives.21 Acknowledgment. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Fundamental Interactions Branch. The authors express their gratitude to I. Manninger, Institute of Isotope Production, Budapest, for X-ray diffraction measurements. The help of G. Knight and other co-workers of the Virginia Polytechnic Institute and State University research reactor in carrying out irradiations is also deeply appreciated.
Charge-Transfer Reactions of Ground 02+(X2ng, v ) and Excited 02+(a4nu,v ) State Ions with Neutral Molecules J. B. Wilcox and T. F. Moran” School of Chemistry, Georgia Institute of Technology, Atlanta, Georgia 30332 (Received: October 3 1, 1980)
Total charge-transfer cross sections have been measured for reactions of 0.8-3.0-keV ground-state O2+(X2IIg,u’) ions and long-lived, excited-state Oz+(a411,,u’)ions with Hz, N2, CO, COO,Oz, NO, and Ar. Time-of-flight techniques have been used to measure the fast neutral O2products from charge-transfer reactions. These reactions have been examined as a function of electron energy used to produce the reactant ions and cross sections have been determined for ground- and long-lived excited-state 02+reactant ions. Cross sections for charge-transfer reactions involving excited-state ions are generally larger than those for ground-state ions, a fact in harmony with energy defects and vibrational overlaps computed for these systems.
Introduction Ionization of molecular oxygen leads to the formation ions. Production of both ground- and metastable-state 02+ of Oz+in the a411umetastable state is well documented in experiments involving electron impact,’ photoionization,2 Penning ioni~ation,~ and heavy particle i m p a ~ t . ~ The appearance energy of 02+(a411u)state ions is more than 4 eV above the Oz+(X211,)ionization energy5 and, correspondingly, the 02+(a4nu)dissociation energy is 4 eV smaller than that of Oz+(X211k) ions. The presence of the a411, state in a beam of 02+ ions has been suggested6 to account for the low threshold energy for 02+dissociation measured in ion-molecule collisions. Beam attenuation (1) W. L. Borst and E. C. Zipf, Phys. Reu. A, 1, 1410 (1970). (2) 0. Edqvist, E. Lindholm, L. E. Selin, and L. Asbrink, Phys. Scr., 1, 25 (1970).
(3) W. C. Richardson and D. W. Setser, J. Chem. Phys., 58, 1809 (1973). (4) E. W. Thomas and G. D. Bent, J . Phys. B, 1, 233 (1968). (5) P. H. Krupenie, J. Phys. Chem. Ref. Data, 1, 423 (1972). (6) T. 0. Tiernan and R. E. Marcotte, J. Chem. Phys., 53,2107 (1970).
measurements7 have indicated that the fraction of excited metastable state ions is 33% when Oz+ ions are produced by 100-eV electron impact ionization. This metastable state has been accepted* as being the a411ustate which has been confirmed by high-resolution laser photodissociation experiment^.^^^ Flow drift tube measurernentsl0J1 have shown that several ion-molecule reactions occur rapidly when they involve the a411, state but very slowly or not at all for the corresponding ground X211, state. The dominant reaction channel for 02’(a411,)-AB interactions (AB = Nz,Ar, CO, COz,and 0,) in the 0.04-2-eV (7) B. R. Turner, J. A. Rutherford, and D. M. J. Compton, J. Chen. Phys., 48, 1602 (1968). (8) D. C. McGilvery, J. D. Morrison, and D. L. Smith, J. Chern. Phys., 70, 4761 (1979). (9) M. Tadjeddine, R. Abouaf, P. C. Cosby, B. A. Huber, and J. T. Moseley, J . Chem. Phys., 69, 710 (1978). (10) W. Lindinger, D. L. Albritton, and F. C. Fehsenfeld, J. Chem. Phys., 70, 2038 (1979). (11) W. Lindinger, D. L. Albritton, M. McFarland, F. C. Fehsenfeld, A. L. Schmeltekopf,and E. E. Ferguson, J. Chem. Phys., 62,4101 (1975).
0022-3654/81/2085-0989$01.25/00 1981 American Chemical Society
