Isotopes of arsenic

Isotopes of arsenic (33As)
Main isotopes[1] Decay
Isotope abun­dance half-life (t1/2) mode pro­duct
73As synth 80.30 d ε 73Ge
74As synth 17.77 d β+66% 74Ge
β−34% 74Se
75As 100% stable
Standard atomic weight Ar°(As)

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 (Da)[4]
[n 2][n 3] 		Half-life[1]
 Decay
mode[1]
[n 4] 		Daughter
isotope
[n 5][n 6] 		Spin and
parity[1]
[n 7][n 8] 		Isotopic
abundance
Excitation energy[n 8]
63As 33 30
64As 33 31 63.95756(22)# 69.0(14) ms β+ 64Ge 0+#
β+, p? 63Ga
65As 33 32 64.949611(91) 130.3(6) ms β+ 65Ge 3/2−#
β+, p? 64Ga
66As 33 33 65.9441488(61) 95.77(23) ms β+ 66Ge 0+
66m1As 1356.63(17) keV 1.14(4) μs IT 66As 5+
66m2As 3023.(3) keV 7.98(26) μs IT 66As 9+
67As 33 34 66.93925111(48) 42.5(12) s β+ 67Ge (5/2−)
68As 33 35 67.9367741(20) 151.6(8) s β+ 68Ge 3+
68mAs 425.1(2) keV 111(20) ns IT 68As 1+
69As 33 36 68.932246(34) 15.2(2) min β+ 69Ge 5/2−
70As 33 37 69.9309346(15) 52.6(3) min β+ 70Ge 4+
70mAs 32.046(23) keV 96(3) μs IT 70As 2+
71As 33 38 70.9271136(45) 65.30(7) h β+ 71Ge 5/2−
72As 33 39 71.9267523(44) 26.0(1) h β+ 72Ge 2−
73As 33 40 72.9238291(41) 80.30(6) d EC 73Ge 3/2−
73mAs 427.902(21) keV 5.7(2) μs IT 73As 9/2+
74As 33 41 73.9239286(18) 17.77(2) d β+ (66%) 74Ge 2−
β− (34%) 74Se
75As 33 42 74.92159456(95) Stable 3/2− 1.0000
75mAs 303.9243(8) keV 17.62(23) ms IT 75As 9/2+
76As 33 43 75.92239201(95) 1.0933(38) d β− 76Se 2−
76mAs 44.425(1) keV 1.84(6) μs IT 76As (1)+
77As[n 9] 33 44 76.9206476(18) 38.79(5) h β− 77Se 3/2−
77mAs 475.48(4) keV 114.0(25) μs IT 77As 9/2+
78As 33 45 77.921828(10) 90.7(2) min β− 78Se 2−
79As 33 46 78.9209484(57) 9.01(15) min β− 79Se 3/2−
79mAs 772.81(6) keV 1.21(1) μs IT 79As (9/2)+
80As 33 47 79.9224744(36) 15.2(2) s β− 80Se 1+
81As 33 48 80.9221323(28) 33.3(8) s β− 81Se 3/2−
82As 33 49 81.9247387(40) 19.1(5) s β− 82Se (2−)
82mAs 131.6(5) keV 13.6(4) s β− 82Se (5-)
83As 33 50 82.9252069(30) 13.4(4) s β− 83Se 5/2−#
84As 33 51 83.9293033(34) 3.16(58) s β− (99.72%) 84Se (2−)
β−, n (.28%) 83Se
85As 33 52 84.9321637(33) 2.022(7) s β−, n (62.6%) 84Se (5/2−)
β− (37.4%) 85Se
86As 33 53 85.9367015(37) 945(8) ms β− (64.5%) 86Se (1−,2−)
β−, n (35.5%) 85Se
β−, 2n? 84Se
87As 33 54 86.9402917(32) 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)# 270(150) ms β− 88Se
β−, n? 87Se
89As 33 56 88.95005(32)# 220# ms [>150 ns] β−? 89Se 5/2−#
β−, n? 88Se
β−, 2n? 87Se
90As 33 57 89.95600(43)# 70# ms [>300 ns] β−? 90Se
β−, n? 89Se
β−, 2n? 88Se
90mAs 124.5(5) keV 220(100) ns IT 90As
91As 33 58 90.96082(43)# 100# ms [>300 ns] β−? 91Se 5/2−#
β−, n? 90Se
β−, 2n? 89Se
92As 33 59 91.96739(54)# 45# ms [>300 ns] β−? 92Se
β−, n? 91Se
β−, 2n? 90Se
93As[5] 33 60
94As[5] 33 61
95As[5] 33 62
This table header & footer:
  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. ^ a b # – 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. ^ a b c d Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3) 030001. doi:10.1088/1674-1137/abddae.
  2. ^ "Standard Atomic Weights: Arsenic". CIAAW. 2013.
  3. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. ^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3) 030003. doi:10.1088/1674-1137/abddaf.
  5. ^ a b c Shimizu, Y.; Kubo, T.; Sumikama, T.; Fukuda, N.; Takeda, H.; Suzuki, H.; Ahn, D. S.; Inabe, N.; Kusaka, K.; Ohtake, M.; Yanagisawa, Y.; Yoshida, K.; Ichikawa, Y.; Isobe, T.; Otsu, H.; Sato, H.; Sonoda, T.; Murai, D.; Iwasa, N.; Imai, N.; Hirayama, Y.; Jeong, S. C.; Kimura, S.; Miyatake, H.; Mukai, M.; Kim, D. G.; Kim, E.; Yagi, A. (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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