Relative Isotopic Abundances of the Elements (1950)

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20 BAINBRIDGE AND NIER POTASSIUM, Z = 19 Measurement 1 2 3 4 5 6 7 8 Method M. S. 180-deg 180-deg 180-deg 180-deg 180-deg 127-deg El. Molecula! Mag. S. Mag. S. Mag. S. Mag. S. Mag. S. and Mag. S. beam Ion source Graphite El. impact Thermionic Thermionic El. impact Thermionic Thermionic K vapor and salt Vapor Leucite Vapor Year | 1921 1921 1931 1934 1935 1935 1935 1936 Observer Aston Dempster Bainbridge Brewer, Nier Brewer Bondy, Johann- Manley Kueck sen, Popper Reference A-19 D-6 B-6 B-7 N-12, N-13 B-27 B-28 M-12 Ratio Abundance* Kk? Ku 17.85 13.88+ 0.4 13.96% 0.1 14.25+ 0.08 16.2 13.4 + 0.5 kK” /K* >300 8600 8300 + 100 K* /K”” <1/1500 <1/150,000 K* /k*? <1/600 <1/150,000 *Abundances, in atom, of the following isotopes were obtained: K™®, 93.08 + 0.04; K®, 0.0119 + 0.0001; K®, 6.91 + 0.04. tAdopted value.

12 7-deg El. and Mag. 8S. Thermionic 1936 Bondy, Vanicek B-11 14 10 180-deg Mag. S. Thermionic 1936 Sampson, Bleakney 8-5 RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS POTASSIUM, Z = 19 11 12 180-deg M. 8S. Mag. S. Dempster Thermionic Thermionic 1936 1943 Brewer Cook B-29 B-29 B-29 C-4 Abundance* Ashes Sea water Minerals Kelp Minerals 12.63 to 14.32 14.2 14.11 to 14.6 14.12 + 0.28 -— constant —— B-30 13 60-deg Mag. S. El. impact K-Al chloride 1946 White, Cameron w-4 13.66 + 0.1 21 14 60-deg Mag. S. El. impact K metal 1950 Nier N-20 13.48 + 0.07T 578 + 6t (K“ /K*)

22 C. W. Sherwin and A. J. Dempster (S-16) measured the relative abundance of Ca® and Ca*® using ions produced by a variety of methods. Variations by a fac- Measurement Method Ion source Year Observer Reference Abundance of Sc“, atom% Measure- ment Method Ion source Year Observer Reference Isotope Ca* Ca@ Ca® Ca* Ca* Ca* BAINBRIDGE AND NIER 180-deg Mag. S. El. impact Vapor 1922 Dempster D-6 ~1.4 CALCIUM, Z = 20 Graphite and salt 1934 Aston A-20, A-21 180-deg Mag. S. El. impact vapor 1938 Nier N-9 Abundance, atom % 96.76 0.77 0.17 2.30 96.971 0.64T 0.145T 2.06T 0.0033 T 0.185T tor of 10 observed in the ratio of Ca®/Ca® were at- tributed to fluctuations in the rate of combination of the isotopes with copper. 60-deg Mag. S. Thermionic 96.92 + 0.03* 0.64 + 0.01 0.132 + 0.004 2.13 +0.04 0.0082 0.179 + 0.001 *Average deviation, ‘‘at least 15 ratio determinations.”’ tAdopted value. SCANDIUM, Z = 21 1 2 M. S. 60-deg Mag. S. Isotope Anode of Thermionic Sct ScF, Sc,0, Sc@ 1932 1950 Sc* Sc“ Aston* Leland Sc A-5 L-14 Sc“ « 100 100 a *Aston could detect no other isotope above 3 per cent. Upper Limits as Set by Leland Abundance, per cent 0.001 0.0002 0.0002 0.0005 0.002 0.01 0.0002 0.0002

RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS 23 Measurement Method Ion source Year Observer Reference Isotope Ti* Ti* Ti* Ti* Ti? TITANIUM, Z = 22 1 Titanium fluo- ride vapor 1935 Aston A-20, A-21 180-deg Mag. S. El. impact Vapor, TiF, 1938 Nier* N-9 Abundance, atom % 8.5 7.8 71.3 5.9 6.9 7.95T 7.751 73.451 §.51T 5.341 *Nier also showed that, if other isotopes existed, their abun- dances relative to Ti* would be below limits given as follows: Ti™, 1/100,000; Ti**, 1/10,000; Ti* and Ti*®, 1/50,000; Ti®', Ti®*, and Ti®, 1/100,000; Ti, 1/25,000. t Adopted value. VANADIUM, Z = 23 Measure- ment 1 2 Method M.S. 60 -deg Mag. S. Ion source Anode of vana- El. impact dium chloride vocl, and lithium Thermionic iodide V,0, Year 1924 1949 Observer Aston Hess, Inghram Reference A-24 H-16 Isotope Abundance, atom % v™" 0.25 ye 100 99.75 tAdopted values. 3 4 60 -deg Mag. 8. El. impact V metal 1949 Leland L-13 H-16, L-13 0.23 0.24T 99.77 99.761

24 BAINBRIDGE AND NIER CHROMIUM, Z = 24 Measure - ment 1 2 3 4 Method M.S. 180-deg 60 -deg 60-deg Mag. 8S. Mag. S. Mag. S. Ion source Vapor Thermionic El. impact El. impact Hexacar- CrCl, vapor CrCl, vapor bony] Year 1931 1939 1948 1949 Observer Aston Nier* White, Hibbs Cameron Reference A-25 N-14 w-4 - ~#H-19 Isotope Abundance, atom % Cr 4.9 4.49 4.31 + 0.04T 4.41 + 0.06 Cr* 81.6 83.77 83.76 + 0.14f 83.46 + 0.11 Crés 10.4 9.43 9.55 + 0.09T 9.54 + 0.06 Cr* 3.1 2.31 2.38 + 0.02T 2.61 + 0.09 *Nier also showed that, if other isotopes existed, their abundances relative to Cr*? were below the following limits: Cr**, Cr*!, and Cr®, 1/100,000; Cr°®, 1/15,000. tAdopted value. MANGANESE, Z = 25 Measurement 1 2 Method M. S. 180-deg Mag. S. Ion source Anode of MnF, El. impact and Lil Mn vapor Year 1924 1936 Observer Aston Sampson, Bleakney * Reference A-24 S-10 Abundance of 100 100 Mn, atom *Sampson and Bleakney showed that the abundance of Mn® and Mn" could not be as much as 1/15,000 of that of Mn®*.

RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS IRON, Z = 26 Aston observed a faint line at mass 58 but was not sure that this might not be due to nickel. De Gier and Zeeman (D-7) put iron carbonyl in their parabola ap- paratus and showed that there was an isotope at mass 58 whose abundance was about 0.5 per cent. However, they did not measure the abundances of the other iso- topes. Nier looked for other isotopes and concluded that, if Measurement Methoa Ion source Year Ovserver Reference Isotope Fe* Fe Fe™ Fe™ 1 2 M. S. 180-deg Mag. S. Iron carbonyl El. impact vapor Iron vapor 1935 1939 Aston Nier A-21 N-14 6.5 6.04 90.7 91.57 2.8 2.11 0.28 TAdopted value. Sampson and Bleakney (S-10) reported a Co*” isotope 25 they existed at all, their abundances relative to Fe™ would be less than the following: Fe and Fe®', 1/50,000; Fe*>, 1/20,000; Fe®*, 1/7000; and Fe™, 1/30,000. Valley and Anderson analyzed seven different terres- trial samples and 12 meteoric samples and concluded that no variations in the relative abundance of iron iso- topes existed in the solar system. 3 4 180-deg Mag. S. 60-deg Mag. S. El. impact El. impact Iron vapor Fet in FeCL 1941 1948 Valley, White, Anderson Cameron V-3 w-4 Abundance, atom % 5.841 9.81 + 0.01 91.687 91.64 + 0.02 2.177 2.21 + 0.01 0.31T 0.34 + 0.01 COBALT, Z = 27 of such abundance that Co”/Co*® = 1/600. However, Mitchell, Brown, and Fowler (M-13) showed that Co” 3 60-deg Mag. S. El. impact Fet in FeCl, 1949 Hibbs H-19 9.903 + 0.015 91.52 + 0.02 2.245 + 0.011 0.335 + 0.003 could not exist with an abundance greater than 1/30,000 that of Co™. Measurement 1 2 Method M.S. 180-deg Mag. S. Ion source CoCL, in CoCl, vapor anode El. bomb. Year 1924 1941 Observer Aston Mitchell, Brown, Fowler Reference A-24 M-13 Abundance of 100 100 Co®®, atom %

eee 26 BAINBRIDGE AND NIER NICKEL, Z = 28 Aston (A-21) found lines at masses 56 and 64 of which approximately the same abundance. Lub (L-10) re- he was not certain. De Gier and Zeeman (D-8) con- firmed mass 64 but were unable to detect mass 61. Dempster (D-9) showed that isotopes 61 and 64 have peated the parabola work of de Gier and Zeeman and found mass 61, but it was only one-tenth as intense as mass 64. Measurement 1 2 3 4 5 Method M. S. M. S. 180-deg Mag. S. M. S. 60-deg Mag. S. Ion source Ni(CO,), Faraday coll. El. bomb. Discharge El. bomb. Spark (Ni Ni vapor Ni(CO), NICL electrodes) Year 1935 1941 1941 1944 1948 Observer Aston Straus Valley Ewald White, Cameron Reference A-21 S-11 V-4 E-4 Ww-4 Isotope Abundance, atom % ni® 67.5 62.8 67.4 69.18 + 1% 67.76 + 0.22T Ni® 27.0 29.5 26.7 25.82 + 2% 26.16 + 0.66T Ni®! 1.7 1.7 1.2 0.97 + 3% 1.25 + 0.03T Ni® 3.7 4.7 3.8 3.28 + 2% 3.66 + 0.01T Ni™ ? 1.3 0.88 0.75 + 4% 1.16 + 0.20T T Adopted value. COPPER, Z = 29 Duckworth and Hogg (D-11) calibrated their photo- graphic plates using zinc lines from zinc mixed with copper. However, since they took Nier’s (N-13) old zinc -abundance values, their results may be slightly in error. The same may be said for Ewald’s (E-3) values. Brown and Inghram’s results are the average for terrestrial and meteoric copper. The Cu®/Cu® abundance ratio for the two samples was 2.235 and 2.244, respectively. They felt that this difference was within their experimental error. w Measurement 1 2 3 4 5 Method M. S. M.S. 60-degMag.S. 60-deg Mag. S. Ion source Spark (brass Spark (Cu El. impact El. impact electrode) electrode) CuCl CuCl, CuCl, Year 1944 1946 1947 1948 1947 Observer Ewald Dempster Duckworth, White, Brown, Hogg Cameron Inghram Reference E-3 D-10 D-11 W-4 B-32 Isotope Abundance, atom % Cu® 69.97 + 0.29 69.04 + 0.29 69.48 + 0.16 68.94 + 0.19 69.1T Cu 30.03 + 0.29 30.96 30.52 31.06 30.9T tAdopted value.

RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS ZINC, Z = 30 Bainbridge (B-31) showed that the traces at masses 65 and 69 observed as stronger than mass 70 by Aston were really due to hydrides of zinc isotopes 64 and 68, respectively. Aston’s figures above are corrected for hydrides. Stenvinkel and Svensson (S-12) advanced evidence from band spectra for masses 63 and 65, 27 both more abundant than mass 70. However, Nier (N-13) showed that there was no evidence for these two iso- topes or for Zn®®, He gave the following upper limits relative to Zn™: Zn®, 1/80,000; Zn®5, 1/40,000; and Zn, 1/60,000. Measurement 1 2 3 4 5 Method M. S. 180-deg Mag. S. 60 -deg Mag. S. 60-deg Mag. S. 60-deg Mag. S. Ion source Zinc methyl El. impact El. impact El. impact El. impact vapor Zinc copper ZnL, Zn Zn Year 1932 1936 1948 1948 1949 Observer Aston Nier Leland, Nier Hess, Inghram, Hibbs Hayden Reference A-25 N-13 L-2 H-15 H-19 Isotope Abundance,* atom & Zn™* 50.4 50.9 48.89 48.89T 48.901 48.87 + 0.10 zn 27.2 27.3 27.81 27.82t 27.82t 27.62 + 0.10 Zn” 4.2 3.9 4.07 4.14T 4.171 4.12 + 0.09 Zn* 17.8 17.4 18.61 18.547 18.481 18.71 + 0.10 Zn? 0.4 0.5 0.620 0.617t 0.6231 0.69 + 0.02 *The adopted values (atom 4%, obtained by averaging the values of measurements 3 and 4, are as follows: Zn™, 48.89; Zn™, 27.81; Zn”, 4.11; Zn™, 18.56; Zn”, 0.62. TElectrolytic source. tChemical source. GALLIUM, Z = 31 Measurement 1 2 3 4 Method M. S. 180-deg Mag. S. 60-deg Mag. S. 60-deg Mag. S. Ion source Anode rays Thermionic Thermionic El. impact Gallium Gallium sesqui- Gallium oxide Gal,, Galt fluoride oxide Year 1935 1936 1948 1949 Observer Aston Sampson, Inghram, Hess, Hibbs Bleakney Brown, Goldberg* Reference A-21 S-5 I-5 H-19 Isotope Abundance, atom % Ga® 61.5 61.2 60.2T 60.00 + 0.07 Ga’! 38.5 38.8 39.8T 40.00 + 0.05 *Inghram et al. (I-5) studied both terrestrial and meteoric material and were unable to detect any difference in the isotopic -abundance ratio to within 0.2 per cent. TAdopted value.

28 Measurement Method Ion source Year Observer Reference Isotope* Ge” Ge? Ge’ Ge" Ge’ 1 M. S. Discharge in volatile alkyl cpds. 1924 Aston A-24 21.2 27.3 7.9 37.1 6.5 BAINBRIDGE AND NIER GERMANIUM, Z = 32 2 3 60-deg Mag. S. 60-deg Mag. S. El. impact GeF,, Gel,, GeF}, Gelt 1947 1949 Inghram, Hibbs, Redmond, Hayden, Hess Gwinn, Harman I-12 H-13 Abundance, atom % GeFt GeIt 20.55T 20.60 + 0.06 20.65 + 0.04 27.37T 27.38 + 0.08 27.43 + 0.02 7.61T 7.83 + 0.06 7.86 + 0.04 36.741 36.40 + 0.10 36.34 + 0.05 7.671 7.78 + 0.05 7.72 + 0.01 *Bainbridge (B-33) showed that lines at masses 71, 75, and 77 observed by Aston (A-24) were really due to hydrides. The figures above are corrected to account for this. TAdopted value. Measurement Method Ion source Year Observer Reference Abundance of As, atom % ARSENIC, Z = 33 1 M. 8. Gaseous discharge AsH, 1920 Aston A-9 100 2 180-deg Mag. 8S. El. impact ° As vapor 1937 Nier* N-3 100 *Nier looked carefully for other isotopes and gave the following upper limits for their abundances: As”', As’, As’°, As”, As’®, ard As’®, 1/100,000; As, 1/20,000; and As”, 1/50,000.

Measurement Method Ion source Year Observer Reference Isotope B r7® Br*! RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS SELENIUM, Z = 34 Measurement 1 2 Method M. S. 60-deg Mag. S. Ion source Vapor El. impact Gas discharge Se and SeF, Year 1923 1948 Observer Aston White, Cameron Reference A-4 Ww-4 Isotope* Abundance, atom % Se”* 0.9 0.87 + 0.01T Se’é 9.5 9.02 + 0.07T Se” 8.3 7.58 + 0.07T Se’® 24.0 23.52 + 0.02T Se® 48.0 49.82 + 0.20T Se®? 9.3 9.19 + 0.20T 3 60-deg Mag. S. El. impact SeF,, SeFy 1949 Hibbs H-19 0.96 + 0.03 9.12 + 0.03 7.50 + 0.14 23.61 + 0.05 49.96 + 0.21 8.84 + 0.08 * Bainbridge (B-33) confirmed the 6 isotopes found by Aston and found no trace of masses 79 and 81 predicted by Johnson (J-7). t Adopted value. BROMINE, Z = 35 1 2 3 M. S. 180-deg Mag. S. 60-deg Mag. S. CH,Br El. impact El. impact Br, vapor Br, vapor 1920 1936 1946 Aston Blewett * Williams, Yuster f A-9, A-10 B-34 Ww-7 Abundance, atom &, 50 50.6 50.52T 30 49.4 49.48T 4 60-deg Mag. S. El. impact AgBr 1948 White, Cameron W-4 90.51 + 0.06 49.49 + 0.06 29 5 60-deg Mag. S. El. impact AgBr 1949 Hibbs H-19 90.57 * 0.07 49.43 + 0.06 *Blewett (B-34) also looked for other isotopes and set the following upper limits for their abun- dances: Br” and Br®’, 1/24,000; Br™ and Br®, 1/12,000; Br’>, Br*, and Br*®, 1/8000; Br7®, 1/6000; Br” and Br**, 1/3000; Br’® and Br®?, 1/400; and Br®, 1/2000. t Williams and Yuster concluded that Br”, Br®, and Br®* could not have an abundance greater than 1/10,000 of that of Br’, tAdopted value.

30 Measurement 1 Method M. S. Ion source El. impact Year 1930 Observer Aston Reference A-27 Isotope Kr’® 0.42 Kr” 2.45 Kr® 11.79 Kr*s 11.79 Kr™ 56.85 Kr*®* 16.70 BAINBRIDGE AND NIER KRYPTON, Z = 36 180-deg Mag. S. El. impact 1937 Nier* N-3 0.346 2.261 11.50 11.50 56.96 17.43 3 90- and 180-deg Mag. 8. El. impact 1947 Lounsbury, Epstein, Thode L-8 4 180-deg Mag. S. El. impact 1947 Dibeler, Mohler, Reese D-4 Abundance, atom % 0.342 2.228 11.500 11.480 57.020 17.430 0.36 + 0.01 2.25 * 0.02 11.57 + 0.04 11.44 * 0.03 57.14 + 0.03 17.24 + 0.05 5 60-deg Mag. S. El. impact 1950 Nier N-21 0.354 + 0.002T 2.27 +0.01T 11.56 +0.02T 11.55 +0.03T 56.90 +0.10T 17.37 +0.02T *In the original work of Nier (N-3), the Kr®/Kr®™ ratio was erroneously reported as 0.0352 instead of 0.0397. This has been corrected above and is discussed in (L-8). Nier (N-3) also looked for other iso- topes and set the following upper limits for their existence relative to Kr™: Kr", Kr™, Kr’, Kr*', and Kr*, 1/50,000; Kr** and Kr*’, 1/25,000. tAdopted value.

31 RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS *antea paydopyt "UOFEJIVA JO BBuUEI Vt OJ [9°Z 0} GG°Z GAES puv ATYBTIS AIVA 0} fA /seIH OFF81 BY) pazTOdal (GE-q) JaMaIgy "000‘'Z2/T ‘seA ‘O00'ST/T ‘gQl *O00°ZT/T ‘reA *000°09/T ‘ceF ‘000‘001/T ‘ogAU put ‘GY ‘reGY e A ‘ o g ‘ g g 0} BATJETII S B O U N P U N G R IJaYy 10; S};WIy] Jaddn BuyMol[o} ay) yas puw sadojOs] 1ayVO 10} payYooT OSTe (EI-N) I9IN, 1€0°0 + S8°LZ G°L? 8°LZ 20 +2°L2 a Le v0 + 6°LZ GZ 1g4d t€0°O + ST°SL G°SL OSL 20 + 8°CL 8° SL vO + T°SL GL ee4d % w o z ‘aouepunqy adojzos] T2-N y-d ce-d €I-N 82-a L-@ S-V 9IUdIIJOY u a s u u e y o r ‘1addog yoany J3IN [ n e g j r a M o i g + 1 3 I N ‘ A p u o g ‘ 1 a M a I g u o j s y I 3 A I I S G O O S 6 T Lv6I 8e6T 9cé6l Ge6l veel cS6T Ivax I o d v a I O d t A 1 o d e a S S B I D a } B O T I S [ V - 1 7 youduly “Tq °“quiog u0719aT1q dyuOyUTIIU, youdury *Tq J U o y U I a U , d u o y u s e a y , sAvl spouy 3dINOS UOC] *s ‘2ew pus "s ‘Sew Zep-09 ‘Ss ‘Zew Zep-09 “Ss ‘Ze Bep-ogt ‘Ss “ZEW 29P-08T "la Zap-_zt “Ss “Sew Zap-ogt ‘SW powen L 9 G y £ c T jUuseWemnstay Le = Z ‘ W n l a i a n u

32 Measurement Method Ion source Year Observer Reference Isotope 5 Sr® Sr Sr 1 M. 8S. Anode of Srl, and LiBr 1932 Aston A-5 10.0 6.6 83.3 BAINBRIDGE AND NIER STRONTIUM, Z = 38 2 180-deg Mag. S. Thermionic 1936 Blewett, Sampson* B-40 3 180-deg Mag. S. Thermionic 1936 Sampson, Bleakney* S-5 Abundance, atom % 0.5 0.5 9.6 7.5 82.4 4 180-deg Mag. S. El. impact Vapor 1938 Nier! N-15 0.56 t 9.86 T 7.02 T 82.56 t 3 60-deg Mag. S. El. impact Vapor 1948 White, Cameron w-4 0.55 + 0.01 9.75 + 0.04 6.96 + 0.01 82.74 + 0.06 *Blewett, Sampson, and Bleakney (B-40, S-5) also placed the percentage abundances of other isotopes below the following figures: Sr, 0.05; Sr®, 0.1; Sr®*, 0.05; Sr®, 0.2; Sr®, 0.05. Dempster (D-15) in 1936 confirmed the existence of Sr™. tNier (N-15) set the following upper limits of abundance for other isotopes relative to Sr: Sr, Sr®’, and Sr*, 1/200,000; Sr*? and Sr®*, 1/100,000; Sr®, 1/50,000; Sr®, Sr*, and Sr®*?, 1/300,000. tAdopted value. YTTRIUM, Z = 39 Measurement 1 Method M.S. Ion source Anode rays Fluoride Year 1924 Observer Aston Reference A-24 Abundance of 100 y®*, atom % its abundance was below 1/2000. M. 8. Hot spark Oxide 1939 Dempster* D-12 *Dempster (D-12) also showed that, if Y®*! existed,

RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS 33- Measurement Method Ion source Year Observer Reference Isotope Zr® Zr*! Zr zr” Zr® ZIRCONIUM, Z = 40 1 2 M. S. 60-deg Mag. S. Anode rays El. impact Zr and Li ZrcCl,, ZrF, fluoride 1935 1948 Aston White, Cameron* A-21 w-4 Abundance, atom % 48 51.46T 11.5 11.23 T 22 17.11T 17 17.40T 1.5 2.80T 3 Mag. S. ‘‘Nier type’’ 1949 Hintenberger H-18 91.7 10.8 17.1 17.5 2.9 *White and Cameron also showed that Zr®, Zr®*, Zr, Zr®, Zr*", Zr™®, and Zr™ are each less than 1/5000 of the total zirconium abundance. t Adopted value. NIOBIUM (COLUMBIUM), Z = 41 Measurement 1 2 3 Method M. S. 180-deg M. S. 60-deg Mag. S. Ion source Volatile penta- El. impact Thermionic fluoride Nb vapor El. mult. det. Year 1932 1936 1943 Observer Aston Sampson, Bleakney* Cohent Reference A-26 S-10 C-2 Abundance of 100 100 100 Nb® (Cb*), atom % *Sampson and Bleakney (S-10) showed that Nb*! and Nb*® could not exist with abundances greater than 1/400 of that of Nb*. tCohen (C-2) also observed that zirconium ions were emitted thermionically from his niobium wire. Therefore he was not able to set an upper limit for Nb” below 1/100. How- ever, he was able to show that Nb®, if it existed, was less than 1/4000.

34 BAINBRIDGE AND NIER Measurement 1 2 Method M. 8. M. S. Ion source Discharge Carbonyl! Year 1931 1939 Observer Aston Mattauch, Lichtblau Reference A-25 M-16 Isotope* Mo* 14.2 (15.5) Mo" 10.0 (8.7) Mo” 15.5 (16.3) Mo* 17.8 (16.8) Mo” 9.6 (8.7) Mo* 23.0 (25.4) Mo 9.8 (8.6) MOLYBDENUM, Z = 42 3 4 5 6 180-deg Mag. S. M.S. 60-deg Mag. S. 60-deg Mag. S. El. impact El. impact El. impact Mo vapor Mo(CO,), Mo Oxychlo- ride Mot 1940 1941 1946 1949 Valley Lichtblau, Williams, Hibbs Mattauch Yuster V-5 L-16 W-' H-19 Abundance, atom % 14.9 15.1 15.861 15.05 + 0.01 9.40 9.3 9.12T 9.35 + 0.01 16.1 16.1 15.70T 15.78 + 0.04 16.6 16.6 16.50T 16.56 + 0.04 9.65 9.5 9.45T 9.60 + 0.01 24.1 23.9 23.751 24.00 + 0.03 9.25 9.5 9.62T 9.68 + 0.01 *De Gier and Zeeman (D-16) with the carbonyl in a parabola apparatus claimed Mo'’™ was present with an abundance of 2 to 3 per cent. Mattauch and Lichtblau (M-16) showed that mass 102 could not have an abundance greater than 1 per cent of that claimed by de Gier and Zeeman. tAdopted value. Measurement Method Ion source Year Observer Reference Isotope Ru® Ru® Ru® Ru!© Ry?! Ryo Ru'™ RUTHENIUM, Z = 44 1 2 M.S. M. S. RuO, Spark. Ru electrode 1931 1944 Aston Ewald* - A-10 E-3 Abundance, atom % 5 (5.68)T ? (2.22)T 12 (12.81)T 14 (12.70)T 22 (16.98)T 30 (31.34)T 17 (18.27)T *Ewald (E-3) calibrated his photographic plates using Nier’s old Cd abundances (N-13). Since better values for Cd are now available (L-9), the E-3 values should be corrected, but insufficient data are avail- able to do this from published accounts. tTentatively adopted value.

RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS - 38 RHODIUM, Z = 45 Sampson and Bleakney (S-10) reported that Rh’! topes: Rh’, 1/60,000; Rh’, 1/6000; and Rh!, with an abundance of 1/1300 existed. However, Cohen 1/5000. It is interesting to note that this was the first (C-2) showed that it could not exist with an abundance work done in which an electron multiplier was used as greater than 1/30,000, if at all. Cohen also set ‘he the ion detector in a mass spectrometer. following upper limits on the abundance of other iso- Measurement 1 2 3 Method M.S. M. S. 60-deg Mag. S. Ion source Anode rays Spark El. mult. coll. Rhodium — sodium Metal Thermionic chloride anode Year 1935 1935 1943 Observer Aston Dempster Cohen Reference A-21 D-12 C-2 Abundance of 100 100 100 Rh'S, atom % PALLADIUM, Z = 46 Measurement 1 2 Method M. S. 180-deg Mag. S. Ion source Spark. Pd El. impact electrode Pd vapor Year 1935 1936 Observer Dempster Sampson, Bleakney Reference D-22 S-10 Isotope* Abundance, atom & Pqic 0.8 Pa 9.3 Pais 22.6 Pai 27.2 Pa 26.8 Pqile 13.5 *The six isotopes were discovered by Dempster (D-22) using his spark-source technique. However, no measure- ments were made of relative abundances.

36 BAINBRIDGE AND NIER SILVER, Z = 47 Measurement 1 Method M. S. Ion source Anode rays AgCl, Lil Year 1935 Observer Aston Reference A-2l Isotope Ag” 52.5 Ag’ 47.5 Tt Adopted value. CADMIUM, Z = 48 Bainbridge and Jordan (B-36) showed that Cd'!5 could other isotopes: Cd’ and Cd’, 1/2350; Cd 20t have an abundance as great as one-eighth of that claimed for it by Aston (A-21), Accordingly, Aston revised his original abundance figures to those given above. Nier (N-13) set the following upper limits on Measurement . 1 2 Method M. S. 180-deg Mag. S. Ion source Discharge El. impact Volatile Metal vapor methyl Year 1935 1936 Observer Aston Nier Reference A-29 N-13 Isotope Cais 1.5 1.4 cae 1.0 1.0 Cd? 15.6 12.8 Cd! 15.2 13.0 Cqi!2 22.0 24.2 Cd's 14.7 12.3 Cai"* 24.0 28.0 Cais 6.0 7.3 t Adopted value. 2 3 60 -deg Mag. S. 60-deg Mag. S. El. impact AgC] vapor 1943 1948 Paul White, Cameron P-3 w-4 NX Abundance, atom % ‘\. 51.92 + 0.14 51.35 + 0.091 48.08 + 0.14 48.65 + 0.07 Tt 4 ‘ \ Ca!*, 1/14,700. This investigation showed tH Cd'"® reported by Stenvinkel and Svennson (S not real. Dempster (D-14) also verified that C ported by Aston, could not exist. 3 4 5 60-deg Mag. S. 60-deg Mag. S. 60-deg Mag. S. El. impact El. impact El. impact ‘ Cdl, vapor CdCl, vapor CdL, vapor Cdlz, CdI*, Cat Cat CdI* 1948 1948 1949 Leland, Nier White, Cameron Hibbs L-9 w-4 H-19 Abundance, atom % 1.215T 1.22 + 0.01 1.22 + 0.01 0.875T 0.98 + 0.01 0.89 + 0.02 12.39T 12.35 + 0.04 12.43 + 0.04 12.751 12.78 + 0.04 12.86 + 0.04 24.07T 24.00 + 0.10 23.79 + 0.06 12.26T 12.30 + 0.04 12.34 + 0.05 28.861 28.75 + 0.20 28.81 + 0.07 7.58T 7.63 + 0.04 7.66 + 0.03

RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS 37 Measure- ment Method Ion source Year Observer Reference Isotope In2}5* In!5 In(CH,), 1935 Aston A-21 4.5 95.5 INDIUM, Z = 49 2 3 180 -deg 60-deg Mag. S. Mag. §S. Thermionic El. impact Oxide InCl, 1936 1948 Sampson, White, Bleakney Cameron S-5 Ww-4 Abundance, atom % 45 4.23 + 0.03t 95.5 95.77 + 0.03t 60-deg Mag. S. El. impact InCl, 1949 Hibbs H-19 4.16 + 0.01 95.84 + 0.01 *In'!S was discovered originally in band spectra by Wehrli (W-8) who estimated the In!!5/In'!5 ratio to be 1 to 11. Sampson and Bleakney (S-5) set the following upper limits (in per cent abun- dance) on other isotopes: In??° and In!2!, 0.01; In'!?, In™!6, and In"!”, 0.02; In?"*, 0.5; In!"*, 0.012; In?’°, 0.003. tAdopted value.

38 BAINBRIDGE AND NIER TIN, Z = 50 Bainbridge and Jordan (B-36) were unable to detect the Sn?! line originally reported by Aston (A-16), and it was concluded that hydrides must have been present in Aston’s spectra. Correction for these was made Measurement Method Ion source Year Observer Reference Isotope Sn'22 Sn? 14 Sn} 1s Sn!* Sn! 17 Sni* Sn? 19 Sn! Sn!?? Sn!**4 in A-29, Hintenberger et al. (H-22) concluded that if isotopes having masses 110, 111, 113, 121, 123, or 125 existed, their abundances would be below 0.01 per cent. 3 60-deg Mag. S. El. impact SnCL, vapor 1948 Hintenberger, Mattauch, Seelmann-Eggebert H-22 Abundance, atom % 1 2 M. 8. 60-deg Mag. S. Gas discharge El. impact tetramethyl SnCL, vapor 1936 1948 Aston White, Cameron A-29 w-4 1.1 0.90 + 0.003 0.8 0.61 + 0.01 0.4 0.35 + 0.006 15.5 14.07 + 0.08 9.1 7.54 + 0.03 22.5 23.98 + 0.03 9.8 8.62 + 0.003 28.5 33.03 $0.12 5.9 4.78 + 0.01 6.8 6.11 + 0.006 0.94 + 2% 0.65 + % 0.33 + 6% 14.36 + 0.3% 7.51 + 0.5% 24.21 + 0.3% 8.45 + 0.5% 33.11 + 0.3% 4.61 + 1.0% 5.83 + 0.9% tAdopted value, obtained by averaging the values of measurements 2, 3, and 4. ANTIMONY, Z = 51 Measurement 1 Method M. 8. Ion source Discharge Antimony methyl! Year 1923 Observer Aston Reference A-4 Isotope Sb!?2 56 Sb!23 44 2 180-deg Mag. S. El. impact SbCl, 1937 Kusch, Hustrulid, T K-5 ate* Abundance, atom % 97.1 + 0.1 42.9 + 0.1 4 5 60-deg Mag. S. El. impact, Sn* SnCL vapor 1949 Hibbs H-19 1.01 + 0.03 0.95T 0.68 + 0.01 0.65 Tf 0.35 + 0.03 0.34T 14.28 + 0.01 14.24f 7.67 + 0.05 7.571 23.84 + 0.08 24.01T 8.68 + 0.01 8.58 T 32.75 + 0.03 32.97 T 4.74 + 0.04 4.71T 6.01 + 0.09 5.981 3 60-deg Mag. S. El. impact Sb metal vapor 1948 “ White, Cameron w-4 57.25 + 0.03T 42.75 + 0.03T *Kusch, Hustrulid, and Tate also showed that no other isotopes between masses 119 and 125 existed with abundance above 1/1000. T Adopted value. — —- —_—=—s oo

RELATIVE ISOTOPIC ABUNDANCES OF THE ELEMENTS TELLURIUM, Z = 52 Bainbridge (B-37) discovered isotopes 122, 123, and 124 and found a faint line at mass 127. Dempster (D-15) discovered a weak line at mass 120 but was un- 39 was confirmed in 1936 by Bainbridge and Jordan (B-36). Leland (L-12) has placed an upper limit of 0.0003 able to detect one at mass 127. This latter observation Measurement Method Ion source Year Observer Reference Isotope Te’ Te!23 Te! Te'™ Te!* Te'* Te!* Te! 1 2 3 4 M. 8S. M. 8. 60-deg Mag. 8S. 60-deg Mag. S. Chloride in Discharge TeF, Te, TeF, vapor discharge Te vapor El. impact El. impact , in Ne TeFj, TeF} 1931 1932 1946 1948 Aston Bainbridge Williams, White, Yuster Cameron A-10 B-37 W-7 w-4 Abundance,* atom % 0.088 0.091 + 0.001 2.9 2.43 2.49 + 0.02 1.6 0.85 0.89 + 0.02 4.5 4.59 4.63 + 0.05 6.6 6 6.97 7.01 + 0.01 20.9 19.0 18.70 18.72 +0.04 36.1 32.8 31.85 31.72 +0.01 36.4 33.1 34.51 34.46 +0.09 per cent for Te?!*. 5 60-deg Mag. S. TeF, vapor El. impact TeF; 1949 Hibbs 0.090 + 0.01 2.47 + 0.01 0.89 + 0.01 4.74 +0.02 7.03 + 0.03 18.72 +0.05 31.75 + 0.06 34.27 + 0.05 *The following values, obtained by averaging the values of measurements 3 and 4, were adopted: Te'™*, 0.089; Te’*?, 2.46; Te!**, 0.87; Te™™, 4.61; Te'*, 6.99; Te’®, 18.71; Te!™, 31.79; Te!™, 34.49. IODINE, Z = 53 Nier (N-3) searched for rare isotopes and set the following upper limits for their abundances: 2*, P™, and I'*, 1/50,000; I'*, 1/25,000; 2, 1/15,000; 179, Measurement Method Ion source Year Observer Reference Abundance of I’? atom % 1/40,000; FP, 1/120,000; and I'*", 1/250,000. Leland (L-12) gives an upper limit of 0.000033 per cent for I'?° relative to ['?’. 1 2 M. 8. 180-deg Mag. S. Discharge El]. impact Methyl iodide I, vapor 1921 1937 Aston Nier A-28 N-3 100 100

BAINBRIDGE AND NIER XENON, Z = 54 Measurement 1 2 3 4 5 Method M.S. 180-deg Mag. S. 180-deg Mag. S. 180-deg Mag. S. 60-deg Mag. 8S. Ion source El. impact El. impact El. impact El. impact Year 1930 1937 . 1947 1947 1950 Observer Aston Nier* Lounsbury, Dibeler, Mohler, Nier Epstein, Thode Reese Reference A-27 N-3 L-8 D-4 N-21 Isotope Abundance, atom % Xe'™ 0.08 0.094 0.095 0.102 0.096 + 0.001T Xe!* 0.08 0.088 0.088 0.098 0.090 + 0.001T Xel* 2.30 1.90 1.917 1.93 1.919 + 0.004T Xel?° 27.13 26.23 _ 26.240 26.51 26.44 + 0.08T Xe'™ 4.18 4.07 4.053 3.68 4.08 +0.01T Xe'*! 20.67 21.17 21.240 21.04 21.18 + 0.05T Xe's? 26.45 26.96 26.930 27.12 26.89 +0.07T Xe'™ 10.31 10.54 10.520 10.54 10.44 +0.02T Xels 8.79 8.95 8.930 8.98 8.87 +0.01T *Nier (N-3) set the following upper limits of abundance relative to Xe'*? for possible additional iso- topes: Xe!?*, Xe'?5, and Xe'™, 1/60,000; Xe’?’, 1/30,000; Xe!*?, Xe! Xe!3”, and Xe!®, 1/15,000. | tAdopted value. CESIUM, Z = 55 Measurement 1 2 3 Method M. S. 180-deg Mag. S. 180-deg Mag. S. Ion source Anode Thermionic El. impact CsCl Pollucite Vapor Year 1921 1930 1937 Observer Aston Bainbridge* Niert Reference A-28 B-38 N-3 Abundance of 100 100 100 Cs! atom % *Bainbridge (B-38) showed that, if the packing fraction of Cs'** were —5.3, which is comparable to the measured packing fractions of the adjacent elements I and Xe, no other isotope existed to as much as 10 per cent of the amount required to account for the chem- ical atomic weight 132.81 (1930 value). tNier (N-3) showed that the following upper limits can be set for the abundances of hypothetical isotopes relative to Cs'**: Cs'*" and Cs’, 1/100,000; Cs!55, 1/50,000; Cs'™*, 1/6000; Cs'*?, 1/4000; Cs'*, 1/20,000; Cs'® and Cs!**, 1/100,000.