Physics:Isotopes of arsenic

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Main isotopes of Chemistry:arsenic (33As)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
73As syn 80.3 d ε 73Ge
γ –
74As syn 17.8 d ε 74Ge
β+ 74Ge
γ –
β− 74Se
75As 100% stable
Standard atomic weight Ar, standard(As)
  • 74.921595(6)[1]
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Arsenic occurs naturally as one stable isotope, 75As, so is monoisotopic and mononuclidic. Synthetic radioisotopes are known from 64As to 95As, as well as at least 11 isomers.

The most stable of these are 73As with a half-life of 80.30 days and 74As with a half-life of 17.77 days, followed by 71As (65.30 hours), 77As (38.79 hours), 76As (26.24 hours), and 72As (26.0 hours). All others outside this range of mass number 71-77 have half-lives under 100 minutes and most under one minute. The longest-lived of the isomers is 82mAs at 13.6 seconds.

Isotopes lighter than the stable one generally decay by positron emission or electron capture to germanium isotopes, while those heavier beta decay to selenium isotopes. A notable exception is that 74As decays both ways.

List of isotopes


Nuclide
[n 1] 		Z N Isotopic mass (u)
[n 2][n 3] 		Half-life
 Decay
mode
[n 4] 		Daughter
isotope
[n 5][n 6] 		Spin and
parity
[n 7][n 8] 		Physics:Natural abundance (mole fraction)
Excitation energy[n 8] Normal proportion Range of variation
64As 33 31 63.95756(22)# 1995 69.0(14) ms β+ 64Ge 0+#
β+, p? 63Ga
65As 33 32 64.949611(91) 1991 130.3(6) ms β+ 65Ge 3/2−#
β+, p? 64Ga
66As 33 33 65.9441488(61) 1978 95.77(23) ms β+ 66Ge 0+
66m1As 1356.63(17) keV 1998 1.14(4) μs IT 66As 5+
66m2As 3023.(3) keV 1998 7.98(26) μs IT 66As 9+
67As 33 34 66.93925111(48) 1980 42.5(12) s β+ 67Ge (5/2−)
68As 33 35 67.9367741(20) 1971 151.6(8) s β+ 68Ge 3+
68mAs 425.1(2) keV 1994 111(20) ns IT 68As 1+
69As 33 36 68.932246(34) 1955 15.2(2) min β+ 69Ge 5/2−
70As 33 37 69.9309346(15) 1950 52.6(3) min β+ 70Ge 4+
70mAs 32.046(23) keV 1979 96(3) μs IT 70As 2+
71As 33 38 70.9271136(45) 1939 65.30(7) h β+ 71Ge 5/2−
72As 33 39 71.9267523(44) 1947 26.0(1) h β+ 72Ge 2−
73As 33 40 72.9238291(41) 1948 80.30(6) d EC 73Ge 3/2−
73mAs 427.902(21) keV 1956 5.7(2) μs IT 73As 9/2+
74As 33 41 73.9239286(18) 1938 17.77(2) d β+ (66%) 74Ge 2−
β− (34%) 74Se
75As 33 42 74.92159456(95) 1920 Stable 3/2− 1.0000
75mAs 303.9243(8) keV 1957 17.62(23) ms IT 75As 9/2+
76As 33 43 75.92239201(95) 1934 1.0933(38) d β− 76Se 2−
76mAs 44.425(1) keV 1968 1.84(6) μs IT 76As (1)+
77As[n 9] 33 44 76.9206476(18) 1951 38.79(5) h β− 77Se 3/2−
77mAs 475.48(4) keV 1957 114.0(25) μs IT 77As 9/2+
78As 33 45 77.921828(10) 1937 90.7(2) min β− 78Se 2−
79As 33 46 78.9209484(57) 1950 9.01(15) min β− 79Se 3/2−
79mAs 772.81(6) keV 1998 1.21(1) μs IT 79As (9/2)+
80As 33 47 79.9224744(36) 1959 15.2(2) s β− 80Se 1+
81As 33 48 80.9221323(28) 1960 33.3(8) s β− 81Se 3/2−
82As 33 49 81.9247387(40) 1968 19.1(5) s β− 82Se (2−)
82mAs 131.6(5) keV 1970 13.6(4) s β− 82Se (5-)
83As 33 50 82.9252069(30) 1968 13.4(4) s β− 83Se 5/2−#
84As 33 51 83.9293033(34) 1968 3.16(58) s β− (99.72%) 84Se (2−)
β−, n (.28%) 83Se
85As 33 52 84.9321637(33) 1967 2.022(7) s β−, n (62.6%) 84Se (5/2−)
β− (37.4%) 85Se
86As 33 53 85.9367015(37) 1973 945(8) ms β− (64.5%) 86Se (1−,2−)
β−, n (35.5%) 85Se
β−, 2n? 84Se
87As 33 54 86.9402917(32) 1970 492(25) ms β− (84.6%) 87Se (5/2−,3/2−)
β−, n (15.4%) 86Se
β−, 2n? 85Se
88As 33 55 87.94584(22)# 1994 270(150) ms β− 88Se
β−, n? 87Se
89As 33 56 88.95005(32)# 1994 220# ms [>150 ns] β−? 89Se 5/2−#
β−, n? 88Se
β−, 2n? 87Se
90As 33 57 89.95600(43)# 1997 70# ms [>300 ns] β−? 90Se
β−, n? 89Se
β−, 2n? 88Se
90mAs 124.5(5) keV 2012 220(100) ns IT 90As
91As 33 58 90.96082(43)# 1997 100# ms [>300 ns] β−? 91Se 5/2−#
β−, n? 90Se
β−, 2n? 89Se
92As 33 59 91.96739(54)# 1997 45# ms [>300 ns] β−? 92Se
β−, n? 91Se
β−, 2n? 90Se
93As[2] 33 60 2024
94As[2] 33 61 2024
95As[2] 33 62 2024
  1. ↑ mAs – Excited nuclear isomer.
  2. ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. ↑ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. ↑ Modes of decay:
    EC: Electron capture


    n: Neutron emission
    p: Proton emission
  5. ↑ Bold italics symbol as daughter – Daughter product is nearly stable.
  6. ↑ Bold symbol as daughter – Daughter product is stable.
  7. ↑ ( ) spin value – Indicates spin with weak assignment arguments.
  8. ↑ 8.0 8.1 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  9. ↑ Fission product

See also

Daughter products other than arsenic

References

  1. ↑ Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry 88 (3): 265–91. doi:10.1515/pac-2015-0305. 
  2. ↑ 2.0 2.1 2.2 Shimizu, Y.; Kubo, T.; Sumikama, T.; Fukuda, N.; Takeda, H.; Suzuki, H.; Ahn, D. S.; Inabe, N. et al. (8 April 2024). "Production of new neutron-rich isotopes near the N = 60 isotones Ge 92 and As 93 by in-flight fission of a 345 MeV/nucleon U 238 beam". Physical Review C 109 (4). doi:10.1103/PhysRevC.109.044313. 
  • A.Shore, A. Fritsch, M. Heim, A. Schuh, M. Thoennessen. Discovery of the Arsenic Isotopes. arXiv:0902.4361.

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