1^ UNITED STATES ATOMIC ENERGY COMMISSION MDDC-887 ISOTOPIC MASSES AND ABUNDANCES (LADC-285) By H. A. Bethe R. F. Christy July 21, 1943 Los Alamos Scientific Laboratory Technical Information Division, ORE, Oak Ridge, Tennessee Date Declassified: March 6, igkj Issuance of this document does not constitute authority for declassification of classified copies of the same or similar content and title and by the same authors. Eeproduced direct from copy as submitted to this office. PBINTED IN USA PEICE 5 CENTS AEC, Oak Ridge, Tenn., 11-6-50-350-A23530 ISOTOPIC MASSES AND ABUNDANCES* By H. A. Bethe and R. F. Christy This table contains the isotopic mass values which we consider most reliable. As can be seen from the given probable errors, the masses up to neon are very much more accurately known than for the heavier elements. The lighter masses were calculated, taking into account all of the more accurate data from mass spectrograph as well as disintegrations, and attempting the best possible fit. Abbreviations used in the isotopic mass table: For stable isotopes, the abundance is given in per cent. Radioactive elements are indicated by the particle they emit (j3- or /3 +): (3c means that the nucleus captures an orbital electron but does not emit positrons. P means instability against disintegration into heavy nuclear particles. Mass values, in parenthesis, refer to nuclei which have not yet been produced. The errors listed are meant to be about 3 times the probable or twice the standard error. For theoretical estimates, the error is usually not given. Sources of the data are indicated as follows: I-Calculations by Betty J. Isaacs, Cornell University, Master's Thesis, 1942. W-Wigner, Memorandum No. 24, April 2, 1940. B-Barkas, Phys. Rev. 55:691 (1939). M-Mass spectrograph value (usually most reliable). D-From disintegration experiments involving heavy particles from end-point of /J-spectrum. C- Calculated value. corr -corrected in view of more recent accurate determination of the mass of a neighboring isotope, from which the mass of the given isotope is obtained through a disintegration measurement or a theoretical estimate. E -Estimate. * This is Section 19 of LA 11, Los Alamos Handbook of Nuclear Physics. MDDC - 887 [ 1 2 1 MDDC - 387 Abundance Error Z 31enient A per cent Mass x 10 5 Source N 1 (3- 1.00893 3 ID 1 H 1 99.98 1.008123 0.6 IM 1 H 2 .02 2.014708 1.1 IM 1 H 3 J- 3.01702 3.4 ID 2 He 3 !C- 5 3.C1700 4 Ifj 2 He 4 100 ^.003t-0 3 IM and D 2 He 5 P 5.0137 35 ID 2 He 6 .■: - 6.0202 50 1/3 3 Li 5 P (5.0136) (60) WC 3 Li 6 7.9 6.01697 5 ID 3 Li 7 92.1 7.0L822 6 IM and D 3 Li 8 3- 8.02502 7 D 4 Be 6 (i + 6.0219 (100) WC 4 Be 7 c 7.01916 7 ID 4 Be 8 P 8.00785 7 ID 4 Be 9 100 9.01503 6 ID 4 B" 10 0- 10.01677 8 ID 4 Ee 11 P (11.0277) - WC 5 B 9 P 9.01620 7 ID 5 B 10 18.4 10.01618 9 IM and D 5 B 11 81.6 11.01284 8 IM and D 5 B 12 (3- 12.0x90 70 ID 5 B 13 :- (13.0207) - WC 6 C 10 ,3+ 10.0210 30 ID 6 C 11 0+ 11.01495 S ID 6 C 12 98.9 12.00382 4 IM 6 C 13 1.1 13.00751 10 IM and D 6 C 14 fJ- 14.00767 5 ID and (3 6 C 15 ;3- (15.0165) - WC 7 N 12 (/3+) (12.0233) - WC 7 N 13 (3+ 13.00988 7 ID 7 N 14 99.62 14.00751 4 IM MDDC - 887 Abundance Error 13 z Element A per cent Mass x 10 5 Source 7 N 15 G.38 15.00489 21 IM 7 N 16 0- f > 16.0065"! \< 16.011 J - ID 7 N 17 0- (17.014) - WC 8 O 14 + (14.0131) - WC 8 15 + 15.0078 40 10 8 16 99.76 16.000000 - Standard 8 o 17 0.04 17.00450 6 ID 8 o 18 0.20 18.0049 40 WM 8 o 19 (0-) 19.0139) - WC 9 F 16 f3 + (16.0175) - WC 9 F 17 + 17.0075 30 ID 9 F 18 + 18.0065 60 WD 9 F 19 100 19.00450 26 IM 9 F 20 0- >20.0042 < 20.0092 - 10 ID 9 F 21 0- (21.0059) - WC 10 Ne 18 + (18.0114) - WC 10 Ne 19 ^ 19.00781 20 Wj3 10 Ne 20 90.0 19.99877 10 IM 10 Ne 21 0.27 20.99963 22 IM 1C Ne 22 9.73 21.99844 36 IM 10 Ne 23 0- (23.0013) - WC 11 Na 21 + (21.0035) - WC 11 Na 22 + 21.9999 50 10 ii Na 23 100 22.99618 31 ID n Na 24 0- 23.9975 45 ID n Na 25 0- (24.9967) - WC 12 Mg 22 + (22.0062) - WC 12 Mg 23 + 23.0002 40 W/3 1- Mg 24 77.4 23.9924 60 B£ 12 ,\ g _!5 11.5 24.9938 90 WD 12 Mg 26 11.1 25.9898 50 WD 4 J MDDC - 837 Abundance Error Z Element A per cent Mass x 10 s Source 12 Mg 27 0- 26.9928 150 W0 13 Al 25 + 24.9981 100 W/3 13 Al 26 + 25.9929 150 W/3 13 Al 27 100 26.9899 80 WD 13 Al 28 0- 27.9903 70 W0 13 Al 29 0- 28.9893 80 W/3 13 Al 30 0- (29.9954) - WC 14 Si 27 + 26.9949 90 10 14 Si 28 89.6 27.9866 60 WM 14 Si 29 6.2 28.9866 60 WM 14 Si 30 4.2 29.9832 90 WD 14 Si 31 0- 30.9862 60 W/3 14 Si 32 0- (31.9849) - WC 15 P 29 + (28.9919) (100) WC 15 P 30 + 29.9873 100 10 15 P 31 100 30.9843 50 WM 15 P 32 0- 31.9827 40 10 15 P 33 0- (32.9826) - WC 16 S 31 t> + (30.9899) - c 16 s 32 95.0 31.98089 7 IM 16 s 33 0.74 32.9800 60 W corr 16 s 34 4.2 33.97710 35 IM 16 s 35 0- 34.9788 80 W corr 16 s 36 0.016 35.978 100 W 17 CI 33 + (32.9860) - WC corr 17 CI 34 + 33.9801 - 10 17 CI 35 75.4 34.97867 21 IM 17 CI 36 0c 35.9788 100 W 17 CI 37 24.6 36.97750 14 IM 17 CI 38 0- 37.981 300 W 17 CI 39 0- (38.9794) - WC 18 A 35 + (34.9850) - C MDDC - 887 [5 Abundance Error z Element A per cent Mass x 10* Source 18 A 36 0.307 35.9780 100 W 18 A 37 3c (36.9777) - E 18 A 38 0.061 37.974 250 ID 18 A 39 p- (38.9755) WC 18 A 40 99.63 39.9756 60 IM 18 A 41 n- 40.9770 60 W 19 K 37 l3f (36.9830) - WC 19 K 38 3 + (37.9795) - WC 19 K 39 93.3 (38.9747) - WC 19 K 40 0.012 39.9760 100 w 20 Ca 40 96.96 39.9753 150 E 20 Ca 42 0.64 41.9711 - W 20 Ca 43 0.15 42.9723 - W 20 Ca 44 2.06 - - - 20 Ca 45 0- 44.968 - G 21 Sc 45 100 44.9669 - ID 22 Ti 46 - 45.9661 100 IM 22 Ti 47 - 46.9647 100 IM 22 Ti 48 - 47.9631 50 IM 22 Ti 49 - 48.9646 60 IM 22 Ti 50 - 49.9621 40 IM 22 Ti 51 - 50.9587 100 W corr 23 V 51 - 50.9577 50 - 24 Cr 51 /3c 50.958 - W corr 24 Cr 52 81.6 51.956 - W corr 24 Cr 53 10.4 52.956 - W corr 25 Mn 55 100 54.957 - E 26 Fe 54 6.04 53.957 - W corr 26 Fe 56 91.57 55.9568 170 IM 26 Fe 57 2.11 56.957 - W corr 26 Fe 58 0.28 - - - Bill? 3 1262 08909 7991 I