110
J. D. KURBATOV
of vork necessary to \vet the solid surface. This, in turn, is inversely related t o the least possible mean vork of adhesion. REFERESCES (1) BARTELL, F. E., A X D HATCH, G. H . : J . Phys. Cheni. 39, 11 (1935). (2) D U P R: ~La thhorie nzhchanique d e la chaleur (1869). (3) NIETZ,A . €1.: J. Phys. Cheni. 32, 255 (1928). (4) YOVSG,T. : Phil. Trans. Roy. Soc. 96, 65 (1505).
h CLASSIFICATIOS O F STABLE XUCLEIl J.
Department
OJ” Physics,
I).
KURBhTOV
The Ohio State Gniverszty, Columbus 10, Ohio
Received October 81, 1944 INTRODC‘CTION
The classification of stable nuclei, that is, their division into sequences with common physical characteristics, has not been suggested for species throughout the entire range of mass numbers. Considerable work of this kind has, however, been done for nuclei of mass numbers less than 40, since the pertinent data are known mainly for light nuclei (12, 13, 70, 71). The experimental material available for the present work, accordingly, remains deficient in desired data, particularly for heavy nuclei. Such a situation indicates that this classification will be subject to a succession of changes; improvements undoubtedly will follow with the appearance of new data. Severtheless, the regularities in nuclear formation observed with the aid of this system give the whole project some justification and impetus for presentation. Several authors have proposed, from various considerations, to picture the structure of light nuclei on the basis of the alpha-particle model (20). The common characteristics, such as binding energy, Coulomb forces, the statistics, and moments to some extent justify this application of the alpha-particle model to even-even-equal nuclei. However, the attempt to present other light nuclei as (a =k 1 or 2n) ka ( a f 1 or 2 p ) or ka
+
+
has not been successful in giving a picture of property regularities. Building up nuclei by the addition of primary particles a t the rate of one to form individual species by two methods : v + H + v + H or v + v + H + H in which v is a neutron and H is a proton, did not lead to continuity of formation because of the appearance and increase with mass number of extra neutrons (5). The latter factor created a problem of the “disposal” of extra neutrons in some form, since no self-evident relation of isotopic number and mass number could be Presented in part a t the 105th and 107th Meetings of the American Chemical Society, which were held in Detroit, Michigan, April, 1943, and in Cleveland, Ohio, April, 1944, respectively.
111
4 CL;ISSIFICATIOS OF STABLE S U C L E I
traced. As a result, the possibility of considering extra neutrons as cementing material for clusters of particles has been rejected. In general, it can be said that the process of building up nuclei by the addition of one particle to the previous species does not exhibit any valuable information on the periodicity in their properties. Consequently it has been admitted that some frameu-ork of heavy particles may exist. This is mainly from the consideration that such complicated systems as iiuclei actually can be very much simplified if particle clusters are found to have ,some physical meaning (20). Therefore, the suggestion has been made to .‘dissolve” at least the unfilled part of the alpha particle n-ith some of the extra neutrons. The simplest case, the 3Li7nucleus, has been tested as an alpha-triton (H3) model (24). The last approach can be supported noJy by the fact that physical characteristics are common for large sequences of nuclei if built up of combinations of three and four mass units. Therefore, the preliminary division of all nuclei into series again became of some significance. The known stable nuclei are usually listed as isotopes of elements in the consecutive order of their charge numbers (33, 34). In some cases, the nuclei are given in sequences of their isotopic numbers. The periodicity of nuclear properties, however, cannot be visualized Jt-ell in either of the two forms, since the combination of protons and neutrons as a it-hole is the factor delineating the nuclei. Hence, the problem in the classification of the stable nuclei is to reveal, simultaneously, the periodicity of common properties and the continuity of formation of nuclei. This can be accomplished by presenting the various combinations of protons and neutrons in some aggregated form. PRIVART COIIBISATIOKS O F S E U T R O S S -4ND PROTOXS
The proton-neutron composition of all the stable nuclei can be expressed as fo1loT.i-s: A = k(p2n) Z(2p2n) q(n2p) A’ = k’(p2n) Z’(2pZn) -4’’= 6” (p2n) q”(n2p)
++
+
+
The aid of the groups of mass 3, in both their isobaric states, in addition to the group of mass 4 (ZpZn), is significant in the classification as compared to other possible primary combinations. Thus, UD to mass 4, of eight possible proton-neutron combinations ( a p bn), three combinations can build up all the k n o m species of stable nuclei, that is:
+
The notation used throughout the paper is p for proton anti n for neutron. In addition, no requirements --ere imposed t o consider the ecistence of particles as alphas or tritons in the nucleus in “space separated” groups, since the classification is based on the periodicity of physical characteristics. For this reason the group of two protons and two neutrons is noted as ( 2 p 2 n ) in order to identify such a mass 4 combination and t o distinguish i t from the helium atom nucleus Likewise, the two isobaric states of mass 3 in the nuclear structure are noted as (p2n) and ( n 2 p ) t o distinguish them from atomic nuclei of 1H3and 3He3. The mass number, charge. and mass are designated A , Z , and m , respectively. The isotopic number. t h a t is, ( A - 22) isnotedas1, distinguishingit fromthespin,Z. Thelatterisgiven in h units. The magnetic moment in nuclear magnetons is designated a s p . The quadruple electric moment Q is given in 10-*6cmz. The unconfirmed d a t a of m , I @ Q, , and abundances are given in italics.
112
J. D. KLURBATOV
(1) a = 0, b = 0 leads to the even-even-equaI series. These nuclei with their physical characteristics are given in Series 0, So. ( 2 ) a = 0, b = 1 and ( 3 ) a = 0, b = 2. These two caseslead to theeven-odd series, (2k 1)n 1(2p2n), in which k = 0,1, . . . 21, and to the even-evenunequal series, (2k 2)n 1(2p2n), in which k = 0,1,. . .21. The first terms are isotopic numbers defining the separate groups in the series. (4) a = 1, b = 0 does not form a series of stable nuclei. In the case in which Z = 0, one stable nucleus, lH1, is known. However, this combination is represented by a number of radioactive nuclei. ( 5 ) a = 1, b = 1 leads to four known odd-odd nuclei. Three of these are given as Series I , SI. ( 6 )a = 1, b = 2 leads to the odd-even series (2k l)p2n 1(2p2n),given as Series 3, Ss, where the (2k 1) term is the isotopic number k = 0 , 1 , . . . 2 1 ; and to the even-even-unequal series, (2k 2)p2n 2(2p2n), Sz, where the (2k 2) term is the isotopic number k = 0,1, . . . 2 1 . Thus the third combination above is no longer required for the formation of the even-even-unequal series, S2. ( 7 ) a = 2, b = 0 represents no stable nuclei. One radioactive nucleus, &loT = 8.8 see., is listed. (8) a = 2, b = 1 does not form a series with groups of mass number 4 (2p2n). When 2 = 0, one stable nucleus, *He3, is known. However, combination 8 together with combination 6 leads to the formation of: the odd-odd series (SI) (p2n n2p) 1(2p2n), where 1 = 0 , 1 , 2 ;and the even-odd (S4)series (p2n n2p) (2k l)p2n 1(2p2n), where the (2k 1) term is the isotopic number k = 0 , 1 , . . . 21, and combinations 2 and 5 are no longer required. The primary nuclear combinations and their characteristics are as follows :
+
+ + +
+
+
+ +
2
A
+ +
+
+
+
+
+
0
1
11
P
1 m = 1.00897 (on') -1.935 zt 0.02
p =
+
+
2
= 1.00813 (HI) = 2.790 f 0.002
2
p2n* m = 3.01708 (H3) B.E. = 0.00902 p 2.68 5
4
= 1/2
(49, 38)
Q
= 0.273
(23, 38)
Pn m = 2.01472 f 1 (H2) B.E. = 0.00237 p = 0.8569
3
I
1=1 (49) n2P = 3.01685 zt 10 (He3) = 0.00816 = - 1 84
A B . E . = 0.00086 (35, 2) I = 312 (52)
2p2n m = 4.00386 f 6 (He4) B.E. = 0.03034 p = O
z=o
(34)
* Tritium, 1H3, is radioactive with a half-life of 31 f 8 y r . , emitting electrons of 15 zt 3 kev. (47). The unstable nucleus (~211)of ,H3 is converted t o a stable nucleus (n2p) of *He3 with a loss in binding energy of = 0.00086 m.u. I t may be assumed t h a t in heavier nuclei the p2n group carries for stability the necessitated increase in binding energy. The mass given includes electrons of an atom.
113
A CLASSIFICATION OF STABLE S U C L E I
PRINCIPLE O F CLASSIFICATION
The physical characteristics of nuclei, such as spin and magnetic moments, were taken as criteria for identification of the ~ e r i e s . ~The isotopic numbers of nuclei belonging to the same series are a continuous odd or even sequence. The nuclei of the same isotopic number of a series form a group which differ by and are built up by the addition of 2p2n. The following requirements, in addition, have been imposed in classification of nuclei: The first is that the mass number of the last nucleus of the group will not be higher than that of the first member of the follorring group. The second is that the differences in isotopic numbers betn-een groups are equal and remain constant in a series. To fulfill the requirement in regard to the isotopic numbers and mass numbers it is necessary to separate Series 2 into four periods with AI = 8 between adjoining groups of each period. The following division of nuclei results : Protons and neutrons equal
Protons-neutrons even
I 1
h single group with
I
SERIES
0 (So)
I=O,I=O
SERIES 1
Protons-neutrons odd
.1 single group with I=O,I=l p is positive
1
p = O
(SI)
Protons and neutrons zinequal SERIES
2
(S2)
I
SERIES
3
(sd)
, Protons-neutrons even-even
22 groups of consecutive isotopic numbers I = (2n 2) I t = 0,1, ... 21 I = integer or 0
+
SERIES
Proton-neu trons odd-even
1
1
n = 0,1, ... 21 I is fractional p mostly positive*
Four periods: P2, P4, P6, P8 1 One period
4
(sc)
even-odd
isotopic numbers
I
* 4,Ag107 and
I
I
isotopic numbers
' I = (2nf1) 12 = 0,1, ... 21 I is fractional
~
p
negative and positive
I
1 One period
47Ag1Og are listed with negative magnetic moments (26).
3 The d a t a on quadrupole electric moments remain insufficient in number t o be used for identification of series.
114
J. D. KURBATOV
Series 0 Characteristics: even and equal number of protons and neutrons; consists of one group of eight nuclei; are most abundant species of respective elements with the exception of ls.436; spin and magnetic moment are zero ~~
XASS NUXBERS
NUCLEI
ISOTOPIC ..BUN-
CHARACTEBISTICS OF KUCLEI
DANCE
p e r cent
p e r ccfll
12
BEPERENCE
98.9
m = 12.00386 f 2 B.E. = 0.0987 4B.E. = 0.0381
6 loo
~
I
I
99.76
16
99.80
i
8
m = 16.00000
8
I
B . E . = 0.1368 4 B . E . = 0.0354
I
J
20
90.24 I
90.00
10
m = 19.99881
10
B . E . = 0.1722 AB.E. = 0.0411 24
77.4
1
8T.5
28
89.6
,
95.5
iI
I
14
m = 23.99189 B . E . = 0.2133 4 B . E . = 0.0397
12
12
1i
l4 ~
I 32
95.1
I
95.7
1
I
I
36
0.31
I
I 0.31
,
18
18
20
20
I ~
'lo
:
96.97 z°Ca40
* hlasses
1
97.11
11
I
m = 27.98639 B.E. = 0.2530 4 B . E . = 0.0375 m = 31.98306 B . E . = 0.2905 AB.E. = 0.0388 m = 35.97852 B.E. = 0.3293 4B.E. = 0.0382 m = 39.9745 B.E. = 0.3675
obtained by mass-spectrograph measurements are designated by letters in parentheses to signify the authors: (A) Aston, (U) Bainbridge, (D) Dempster, and (N) Kier. Otherwise the data are from transmutations. Isotopic abundances according t o F. W. Aston (4). All known stable nuclei, up to July, 1944, are included in the classification. However, since the purpose of the classification is to observe general regularities of properties and t o note the deviation of species which do not fit the classification, there was no tendency t o discard nuclei not fitting or t o predict new ones to fill the gaps in groups.
% .
115
CLASSIFICATIOS OF STABLE S C C L E I
Series 1 Characteristics: odd and equal number of protons and neutrons; consists of one group of three nuclei; spin is 1 and magnetic moment is positive 1
ISOTOPIC i
SL’LIBER OF PARTICLES
BCSDAYCE
;
l--___I
f
i
per cent
7.5
3
:
I
n
3
’
CH.\R.\CTERISIICS
OF NUCLEI
l
1
? r ~= 6.01654 =tz 11
B.E. = 0.0345 AB.E. = 0.0352 = 0.8215 1=1
p
10
j
jB”
5
20.0
5
m = 10.01579 f 22
B.E. = 0.0697 AB.E. = 0.0425
I
fi
= 0.5977
I = 1 99.62
1
i
772
= 14.00753 f 3
B . E . = 0.1122 0.4025 I=1
p = I
I
In Series 0, 6C1?is liqted as the first nucleu;., since lBeShas not been observed to the estent of that of 4Be9and i- unstable against alpha emission (69). In Series 1, 3Li6 is given a;. the first nucleus. Thus, these two series differ from previous lists of the same nuclear qequences in the absence of 2He4and 1H2, which are brought in here as primary comhination~. The consecutive nuclei in Series 0 and 1 are built up by the addition of the group 2p2n.: ODD-EVES d 3 D EVES-ODD S U C L E I
The physical characteristics of Series 3 and 4 are taken up here, in advance of Series 2, since the periodicity of the properties of Series 2 can be drawn up, with some advantage, on the basi. of the regularities observed in the odd mass number nuclei. In addition, a comparative and simultaneou- observation of the properties of Series 3 and 4 is found to he helpful in disclosing the deviations of some nuclei from the places n-here they are expected by the classification (see table 1). - l i s can be seen from Series 3 and 4, all consecutive mass numbers starting with 7 and ending with 209 are represented. Four stable isobars of these two series are known; therefore, the total number of >pecies is 106 and of these, 51 are oddeven and 55 are even-odd. The difference in mas,ROUP KO.
-
4
NUCLEI
I
-
4
8
8
16
12
24
16
32
20
40
12
12 4 20 -8(!)
28
8 36
AI
AA
- 8
0
8
0
8
8
8
8
8 44
-
__
-
-
-1deviation from the requirements imposed in the classification is observed in one case,-namely, in P4 between GI0 and Glc,-on account of the existence of the nucleus 62Sm144of 3 per cent abundance (3, 4 f ~ ) . ~ In two cases there are no mass number differences between the last isotope of one group and the first of the succeeding group; in one case the mass difference is negative. AI1 these may result, therefore, in the appearance of three triodes. These triodes actually esist for each of the mass numbers 96, 124, 13C1.~ A difference of four mass units between G6 and Glo results in the longest sequence of isobars. A difference of eight mass units between adjoining groups corresponds to the esistence of four single mass number species: they are 64Gd156, 70Ybli2, 760s188, and ,OHg2Oo. d difference of twelve mass units brings two consecutive single mass number species, 30Zn68 and 32Ge72. The Sub-series S2b has seven complete groups. The incomplete groups are Gq, GIO,Gu, and GW SUMMARY
It has already been indicated that the division of all k n o m stable nuclei into groups of separate series according to their physical characteristics is lacking in continuity of species formation. Hon-ever, with the aid of this division the obThis deviation is rather significant; Sml44may be looked upon as a product of the disand 60?;d1AA.However, the radioactivity of &mlA8 has been clearly integration of 6nSm148 established. but t h a t of 60Sd"' remains in question. Some authors reported beta-radiation associated with an enriched fraction of Sd,malting no definite isotopic assignment (32, i 2 ) . Thus, all four known triodes come at breaks between groups. A fifth triode, mass number 102, previously described is omitted here, since nucleus 4 ? ? r h 1 0 2 was not confirmed by recent analysis of the mass spectra. Should triode A = 102 exist, its position would not be in the location of a break between groups (9, 10).
140
J. D. KURBATOV
E
c
A CL-4SSIFICATIOS OF STABLE SVCLEI
" ' 9 O
w 30
w
y
c
2
*
m
II U CD
a
1
9
h
141
142 l
J. D. KURBATOV a
1 5
c
I 1
8
%
143
9 CLSSSIFICATIOX O F STABLE NUCLEI
D W"
I I
~
i
144
-I
J. D. KURBATOV
A C L A S S I F I C I T I O S O F ST.kBLE S C C L E I
145
146
J. D. IiURBATOV
A CLASSIFICATIOS OF STABLE SCCLEL
IsiI I
I ! i I I I
147
148
J. D. KURBSTOV
servation has been made that the groups of Series 4 aln a p precede the groups of nuclei of Series 3 with a difference of four niass units. The isotopic number of a sequence of Series 4 is aln-3ys two units lon-er than the following sequence of Series 3. With this observation it \\a5 possible t o connect stable nuclei in the order of their mass numbers while maintaining sequences of identical characteristics. Tables 5 and G are arranged in a form eo that the series appear periodically and coincide .\vith consecutive numbers of particles of three niass units. The number of particles of mass 3, except for Series 4, also represent the isotopic numbers of respective groups of nuclei. The nuniber of particles of mass 3 in Series 4 is two units higher than the isotopic number of the corresponding group. This connection of Series 4 and three species can be regarded as a change of an n2p group into a p2n. Identically the nuclei of Series 1 (SI)precede the nuclei of Series 2, Period 2. The connection likeirise, can be regarded as a change of n2p into p2n. T’ertically are given the number of particles of four mass units (2p2n). CL 4SSIFICATIOK OF STABLE S U C L E I TVITH T H E AID O F THREE A S D FOCR JIASS U S I T S (TABLES
5
ASD
6)
Series 0 remains separated fyoin the other series. However, the nucleus could be as well regarded aq the first nucleus of a sequence r i t h four particles of three mass units. described above, is The shifted position of the nucleus of mass number 39, found to be adapted to the summarized classification. The shifts described in Group 6, I = 11, of Series 3 and Group 7, I = 13, of Series 4, and in Groups 12 and 13 of Series 3 and 4, I = 23 and 25, suggest that sixty-one protons may not form a stable nucleus with any combination of neutrons. In the even-even series all charge nuinber~are represented; however, there are gaps in Periods 4, 6, and 8, due to non-observance of stable nuclei hoZrS8, &3rgo, 56Ba140, The radioactive specieq of these mass numbers are not yet established. The position of remains unique, since it is a nucleus of Series 3 located in the middle of a sequence of Series 4. Only three nuclei, odd isobars, the stability of which is debated, could not be placed in the summarized classification. These three nuclei are shown separately on the tables. On the other hand both the isobars 48Cd”? and 491n113are properly placed in the classification. Four nuclei of known even-even triodes, il = 06, 124, 130, 136, have the species dOZrg6,50Sn1?4, 62Te130,and 64Xe136 occupying positions out of line. It is reasonable to assume some future corrections of presently knon-n stable isotopes, especially in the rare earth region. REFERESCES (1) ALLISOX, S.I< : Phps. Rev. 55, 624 (1939). (2) A q ~S.JX., ~ R ~ ~I L L E~R L. , ~c , PERLOT, ~ , G J Phys. Rev. 58, 1% (1940).
, S I i A G G a , L. d , . k S D
SMITH,
1. , J R
:
I CLASSIFICATION OF STABLE NUCLEI
149
(3) . ~ T O S , F. I T . : Proc. Roy. SOC.(London) A146, 46 (1934). (4) .ISTOS, F. I T . : X a s s Spectra arid I s o t o p e s . Edn-ard Arnold Company, London (1942). (,5) BARKAS, W. H.: Phys. Rev. 55, 691 (1930,. (6) B ~ s s o s -1.: , ASD S . ~ ~ - Y ERR. .-4.:Phys. R e v . 49, 867 (1936). (7) BETHE,H . A . , ASD BACKER, R . F.: Rev. hIodern Phys. 8 , 8 2 (1936). (8) CRAXFORD, 31.F.. ASD BATESOS,S.: C a n J. Research 10, 693 (1934). (9) COHES,A . A , : Phys. Rev. 63, 219 (1943). 110) DEJIPSTER, A . J. : Phj-s. Rev. 49, 917 (1936). i l l ) ELLIOTT, A , : Proc. Roy. Sac. (IJonCion) 127, 638 (1930). E . , ASD PHILLIPS. 31.: Phys. Rev. 51, 597 (1937). (12) FEESBERG, E . , ASD WIGSER,E.: Phys. Rev. 51, 95 (1937). (13) FEESBERG, (14) FISHER, R . A . , AXD PE(,E;. E . R . : Phys. Rev. 55, 270 (1939). (15) GOLLSOW, H . : Z . Physili 103, 413 (1936). (16) HAMILTOX, D. R . : Phys. Rev. 56, 30 (1939). (17) HARDY,T . c.,ASD MILLMAS, S.:Phys. Rev. 61, 459 (1912). (18) H A Y ,R.H . : Phys. Rev. 58, 180 (1940); 60, 75 (1941). : ZS. ,Physik 108, 232 (1938). (19) H E Y D E N&I., , ASD I ~ O P F E R XH~.X D . R . : Phys. Rev. 60,837 (1941) ; and references given therein. (20) ISGLIS, D. R . : Phys. Rev. 60, 843 (1941). (21) IXGLIS, (22) J a c ~ s o s D. , il.,. ~ S D KL-HS.H.: Proc. Roy. SOC.(London) 158, 372 (1937). J. hI. B . , RABI.I . I . , RAJISEY, S.F., JR.,ASD Z.XCHARIAS,J. R . : Phys. Rev. (23) KELLOGG, 57, 677 (1940). (24) KITTEL,C . : Phys. Rev. 62, 109 (1942). H.: Z. Physik 83, 4 l i (1933). (25) KOPFERMANS, , H. : Kernnmnents. dkadeniische 1-erlagsgesellschaft, Leipzig (1940). , H., ASD RISDAL,E.: Z. Physik 87, 460 (1934). (28) I < O r F E R h f A N s , H., ASD WITTGE,H . : z.Physik 105, 16 (1937). (29) KL-SCH, P., ASD ~ I I L L J I A 8.: S ,Phgs. Rev. 56, 527 (1939). (30) I~L-SCH, P., MILLMAS:8..ASD RABI,I . I . : Phys. Rev. 55, 666 (1939). (31) KUSCH,P., M I L L x t s . S., ASD RABI,I . I . : Phys. Rev. 55, 1176 (1939). (32) LIBBY,W.F. : Phys. Rev. 45, S45 (1931) ; 46, 196 (1934). (33) L I ~ I S G O OJ. D ,J., ASD SEABORG. G . T . : Rev. Modern Phys. 12, 30 (1940). (34) LII-ISGSTOS, 11.S.. ASD BCTHE.H . -1.:Rev. Modern Phys. 9, 380 (1937). Rev. Modern Phys. 9, 373 (1937). (35) LIVISGSTOS,AI. S..ASD BETHE.II.-4.: (36) LYSHEDE, J. SI.,ASD RASXL-SSES: E.: Z.Physik 104, 434 (1937). (37j ~ I A R G E NH A.L , ASD - , WIGSER,E.: Phys. Rev. 58, 103 (1940). (38) >I.iT.r.%uCH,J . : Phys. Rev. 57, 1155 (194Oi. (39) 3 I c L . 4 ~ -4. B . , ASD C'RATVFORD, 31. F . : Phys. Rev. 44, 986 (1933). , S., ASD Fox, 31.:Phys. Rev. 50, 220 (1936). (41) >IILLJIAS, S., ASD IicscH. P.: Phys. Rev. 56, 303 (1939). RXBI, I . I . : Phys. Rev. 56, 165 (1939). (42) M I L L ~ I A S., S , KCSCH.P.: .\SI) (43) l I I I m r a s , S., RABI.I. I . , ASD ZACHARIAS:J. R . : Phys. Rev. 53, 384 (1939). , . : Phys. Rev. 49, 921 (1936). (44) ~ I A S L EJ.YH (45) L f o R E , K. R . : Phys. Rev. 46, 470 (1934). (46) SIER, A . 0.: Phys. Rev. 52, 933 (1937). (47) O'SEAL,R . D . , ASD GOLDHABER, 11.:Pliys. Rev. 58, 574 (1940). (48) POLLARD, E . : Phys. Rev. 57, 1186 (1940). (49) RABI,I. I . : The J1oment.s of the Light S u c l e i , Sziclear Physics. University of Pennsylvania Press (1941I . (501 RABI,I . I . , MILLMAS, P.. KL-SCH, P., ASD ZACHARIAS,J. R.: Phys. Rev. 55, 526 (1939). S , R . : Phys. Rev. 57, 570 (1940). (51) RESZETTI,K . X . ? ASD H A ~ I I L T OD. (52) SACHS, R. G., ASD SCHTVISGER. J.: Phys. Rev. 61, 732 (1942). (53) S C H ~ L EH., R , A N D JOSES, E. G . : Z. Physik 74, 631 (1932). (541 ~ H C - L E R , H . , - 4 S D KETSTOS.J. E . : Z . Physik 71, 413 (1931).
150 (55) (56) (57) (58) (59) (60) (61) (62) (63) (64) (65) (66) (67) (68) (69) (70) (71) (72) (73) (74)
E. D E B. DARWEKT AND C . A. TVINKLER
S C H ~ L EH., R , A N D I i O R S C H I S G , H . : Z.Physik 103, 434 (1936). SCHULER, H., AND KORSCHING, H.: Z . Physik 111, 386 (1939). S C H ~ ~ L H., E R ,ROIG:J., A S D I
