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)
	74.921595±0.000006 [2] 74.922±0.001 (abridged) [3]
view talk edit

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: view

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. # – 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

• Isotopes of selenium
• Isotopes of germanium
• Isotopes of gallium

References

1. 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. 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.