Isotopes of manganese

Naturally occurring manganese (Mn) is composed of 1 stable isotope, ⁵⁵Mn. 25 radioisotopes have been characterized with the most stable being ⁵³Mn with a half-life of 3.7 million years, ⁵⁴Mn with a half-life of 312.3 days, and ⁵²Mn with a half-life of 5.591 days. All of the remaining radioactive isotopes have half-lives that are less than 3 hours and the majority of these have half-lives that are less than 1 minute, but only ⁴⁵Mn has an unknown half-life. The least stable is ⁴⁴Mn with a half-life shorter than 105 nanoseconds. This element also has 3 meta states.

Manganese is part of the iron group of elements, which are thought to be synthesized in large stars shortly before supernova explosion. ⁵³Mn decays to ⁵³Cr with a half-life of 3.7 million years. Because of its relatively short half-life, ⁵³Mn occurs only in tiny amounts due to the action of cosmic rays on iron in rocks. Manganese isotopic contents are typically combined with chromium isotopic contents and have found application in isotope geology and radiometric dating. Mn−Cr isotopic ratios reinforce the evidence from ²⁶Al and ¹⁰⁷Pd for the early history of the solar system. Variations in ⁵³Cr/⁵²Cr and Mn/Cr ratios from several meteorites indicate an initial ⁵³Mn/⁵⁵Mn ratio that suggests Mn−Cr isotopic systematics must result from in-situ decay of ⁵³Mn in differentiated planetary bodies. Hence ⁵³Mn provides additional evidence for nucleosynthetic processes immediately before coalescence of the solar system.

The isotopes of manganese range in atomic weight from 46 u (⁴⁶Mn) to 65 u (⁶⁵Mn). The primary decay mode before the most abundant stable isotope, ⁵⁵Mn, is electron capture and the primary mode after is beta decay.

Relative atomic mass: 54.938045(5).

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
44Mn	25	19	44.00687(54)#	<105 ns	p	43Cr	(2−)#
45Mn	25	20	44.99451(32)#	unknown	p	44Cr	(7/2−)#
46Mn	25	21	45.98672(12)#	37(3) ms	β+ (78%)	46Cr	(4+)
					β+, p (22%)	45V
					β+, α (<1%)	42Ti
					β+, 2p (<1%)	44Ti
46mMn	150(100)# keV			1# ms	β+	46Cr	1-#
47Mn	25	22	46.97610(17)#	100(50) ms	β+ (96.6%)	47Cr	5/2−#
					β+, p (3.4%)	46V
48Mn	25	23	47.96852(12)	158.1(22) ms	β+ (99.71%)	48Cr	4+
					β+, p (.027%)	47V
					β+, α (6×10−4%)	44Ti
49Mn	25	24	48.959618(26)	382(7) ms	β+	49Cr	5/2−
50Mn	25	25	49.9542382(11)	283.29(8) ms	β+	50Cr	0+
50mMn	229(7) keV			1.75(3) min	β+	50Cr	5+
51Mn	25	26	50.9482108(11)	46.2(1) min	β+	51Cr	5/2−
52Mn	25	27	51.9455655(21)	5.591(3) d	β+	52Cr	6+
52mMn	377.749(5) keV			21.1(2) min	β+ (98.25%)	52Cr	2+
					IT (1.75%)	52Mn
53Mn	25	28	52.9412901(9)	3.7(4)×106 y	EC	53Cr	7/2−	trace
54Mn	25	29	53.9403589(14)	312.03(3) d	EC 99.99%	54Cr	3+
					β− (2.9×10−4%)	54Fe
					β+ (5.76×10−7%)	54Cr
55Mn	25	30	54.9380451(7)	Stable			5/2−	1.0000
56Mn	25	31	55.9389049(7)	2.5789(1) h	β−	56Fe	3+
57Mn	25	32	56.9382854(20)	85.4(18) s	β−	57Fe	5/2−
58Mn	25	33	57.93998(3)	3.0(1) s	β−	58Fe	1+
58mMn	71.78(5) keV			65.2(5) s	β− (>99.9%)	58Fe	(4)+
					IT (<.1%)	58Mn
59Mn	25	34	58.94044(3)	4.59(5) s	β−	59Fe	(5/2)−
60Mn	25	35	59.94291(9)	51(6) s	β−	60Fe	0+
60mMn	271.90(10) keV			1.77(2) s	β− (88.5%)	60Fe	3+
					IT (11.5%)	60Mn
61Mn	25	36	60.94465(24)	0.67(4) s	β−	61Fe	(5/2)−
62Mn	25	37	61.94843(24)	671(5) ms	β− (>99.9%)	62Fe	(3+)
					β−, n (<.1%)	61Fe
62mMn	0(150)# keV			92(13) ms			(1+)
63Mn	25	38	62.95024(28)	275(4) ms	β−	63Fe	5/2−#
64Mn	25	39	63.95425(29)	88.8(25) ms	β− (>99.9%)	64Fe	(1+)
					β−, n (<.1%)	63Fe
64mMn	135(3) keV			>100 µs
65Mn	25	40	64.95634(58)	92(1) ms	β− (>99.9%)	65Fe	5/2−#
					β−, n (<.1%)	64Fe
66Mn	25	41	65.96108(43)#	64.4(18) ms	β− (>99.9%)	66Fe
					β−, n (<.1%)	65Fe
67Mn	25	42	66.96414(54)#	45(3) ms	β−	67Fe	5/2−#
68Mn	25	43	67.96930(64)#	28(4) ms
69Mn	25	44	68.97284(86)#	14(4) ms			5/2−#

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.
• Nuclide masses are given by IUPAP Commission on Symbols, Units, Nomenclature, Atomic Masses and Fundamental Constants (SUNAMCO)
• Isotope abundances are given by IUPAC Commission on Isotopic Abundances and Atomic Weights

References

• Isotope masses from:
• Isotopic compositions and standard atomic masses from:
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.

Isotopes of chromium	Isotopes of manganese	Isotopes of iron
Table of nuclides