Isotopes of niobium

Naturally occurring niobium (Nb), element 41, is composed of one stable isotope (⁹³Nb). ⁹³Nb is the lightest nuclide theoretically susceptible to spontaneous fission, and although this has never been observed, it makes niobium theoretically the lightest element with no stable isotope. The first 40 elements (to zirconium) all have at least one stable nuclide which is susceptible in theory only to proton decay.

The most stable radioisotope is ⁹²Nb with a half-life of 34.7 million years. This nuclide is presently the longest-lived radionuclide of all elements that has not yet been detected in nature as primordial isotope.^[1] (The nuclide with the next longest half-life, ²⁴⁴Pu with half-life 80 million years, has been detected, and is thus primordial).

The next longest-lived niobium nuclides are ⁹⁴Nb (half-life: 20,300 years), and ⁹¹Nb with a half-life of 680 years. There is also a meta state at 31 keV whose half-life is 16.13 years. Twenty three other radioisotopes have been characterized. Most of these have half-lives that are less than two hours except ⁹⁵Nb (35 days), ⁹⁶Nb (23.4 hours) and ⁹⁰Nb (14.6 hours). The primary decay mode before the stable ⁹³Nb is electron capture and the primary mode after is beta emission with some neutron emission occurring in ^104-110Nb.

Only ⁹⁵Nb (35 days) and ⁹⁷Nb (72 minutes) and heavier isotopes (half-lives in seconds) are fission products in significant quantity, as the other isotopes are shadowed by stable or very long-lived (⁹³Zr) isotopes of the preceding element zirconium from production via beta decay of neutron-rich fission fragments. ⁹⁵Nb is the decay product of ⁹⁵Zr (64 days), so disappearance of ⁹⁵Nb in used nuclear fuel is slower than would be expected from its own 35 day halflife alone. Tiny amounts of the other isotopes may be produced as direct fission products.

Niobium's standard atomic mass is 92.90638(2) u.

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[2][n 1]	daughter isotope(s)[n 2]	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
81Nb	41	40	80.94903(161)#	<44 ns	β+, p	80Y	3/2-#
					p	80Zr
					β+	81Zr
82Nb	41	41	81.94313(32)#	51(5) ms	β+	82Zr	0+
83Nb	41	42	82.93671(34)	4.1(3) s	β+	83Zr	(5/2+)
84Nb	41	43	83.93357(32)#	9.8(9) s	β+ (>99.9%)	84Zr	3+
					β+, p (<.1%)	83Y
84mNb	338(10) keV			103(19) ns			(5-)
85Nb	41	44	84.92791(24)	20.9(7) s	β+	85Zr	(9/2+)
85mNb	759.0(10) keV			12(5) s			(1/2-)
86Nb	41	45	85.92504(9)	88(1) s	β+	86Zr	(6+)
86mNb	250(160)# keV			56(8) s	β+	86Zr	high
87Nb	41	46	86.92036(7)	3.75(9) min	β+	87Zr	(1/2-)
87mNb	3.84(14) keV			2.6(1) min	β+	87Zr	(9/2+)#
88Nb	41	47	87.91833(11)	14.55(6) min	β+	88Zr	(8+)
88mNb	40(140) keV			7.8(1) min	β+	88Zr	(4-)
89Nb	41	48	88.913418(29)	2.03(7) h	β+	89Zr	(9/2+)
89mNb	0(30)# keV			1.10(3) h	β+	89Zr	(1/2)-
90Nb	41	49	89.911265(5)	14.60(5) h	β+	90Zr	8+
90m1Nb	122.370(22) keV			63(2) µs			6+
90m2Nb	124.67(25) keV			18.81(6) s	IT	90Nb	4-
90m3Nb	171.10(10) keV			<1 µs			7+
90m4Nb	382.01(25) keV			6.19(8) ms			1+
90m5Nb	1880.21(20) keV			472(13) ns			(11-)
91Nb	41	50	90.906996(4)	680(130) a	EC (99.98%)	91Zr	9/2+
					β+ (.013%)	91Zr
91m1Nb	104.60(5) keV			60.86(22) d	IT (93%)	91Nb	1/2-
					EC (7%)	91Zr
					β+ (.0028%)	91Zr
91m2Nb	2034.35(19) keV			3.76(12) µs			(17/2-)
92Nb	41	51	91.907194(3)	3.47(24)×107 a[n 3]	β+ (99.95%)	92Zr	(7)+
					β- (.05%)	92Mo
92m1Nb	135.5(4) keV			10.15(2) d	β+	92Zr	(2)+
92m2Nb	225.7(4) keV			5.9(2) µs			(2)-
92m3Nb	2203.3(4) keV			167(4) ns			(11-)
93Nb	41	52	92.9063781(26)	Observationally Stable[n 4]			9/2+	1.0000
93mNb	30.77(2) keV			16.13(14) a	IT	93Nb	1/2-
94Nb	41	53	93.9072839(26)	2.03(16)×104 a	β-	94Mo	(6)+
94mNb	40.902(12) keV			6.263(4) min	IT (99.5%)	94Nb	3+
					β- (.5%)	94Mo
95Nb	41	54	94.9068358(21)	34.991(6) d	β-	95Mo	9/2+
95mNb	235.690(20) keV			3.61(3) d	IT (94.4%)	95Nb	1/2-
					β- (5.6%)	95Mo
96Nb	41	55	95.908101(4)	23.35(5) h	β-	96Mo	6+
97Nb	41	56	96.9080986(27)	72.1(7) min	β-	97Mo	9/2+
97mNb	743.35(3) keV			52.7(18) s	IT	97Nb	1/2-
98Nb	41	57	97.910328(6)	2.86(6) s	β-	98Mo	1+
98mNb	84(4) keV			51.3(4) min	β- (99.9%)	98Mo	(5+)
					IT (.1%)	98Nb
99Nb	41	58	98.911618(14)	15.0(2) s	β-	99Mo	9/2+
99mNb	365.29(14) keV			2.6(2) min	β- (96.2%)	99Mo	1/2-
					IT (3.8%)	99Nb
100Nb	41	59	99.914182(28)	1.5(2) s	β-	100Mo	1+
100mNb	470(40) keV			2.99(11) s	β-	100Mo	(4+,5+)
101Nb	41	60	100.915252(20)	7.1(3) s	β-	101Mo	(5/2#)+
102Nb	41	61	101.91804(4)	1.3(2) s	β-	102Mo	1+
102mNb	130(50) keV			4.3(4) s	β-	102Mo	high
103Nb	41	62	102.91914(7)	1.5(2) s	β-	103Mo	(5/2+)
104Nb	41	63	103.92246(11)	4.9(3) s	β- (99.94%)	104Mo	(1+)
					β-, n (.06%)	103Mo
104mNb	220(120) keV			940(40) ms	β- (99.95%)	104Mo	high
					β-, n (.05%)	103Mo
105Nb	41	64	104.92394(11)	2.95(6) s	β- (98.3%)	105Mo	(5/2+)#
					β-, n (1.7%)	104Mo
106Nb	41	65	105.92797(21)#	920(40) ms	β- (95.5%)	106Mo	2+#
					β-, n (4.5%)	105Mo
107Nb	41	66	106.93031(43)#	300(9) ms	β- (94%)	107Mo	5/2+#
					β-, n (6%)	106Mo
108Nb	41	67	107.93484(32)#	0.193(17) s	β- (93.8%)	108Mo	(2+)
					β-, n (6.2%)	107Mo
109Nb	41	68	108.93763(54)#	190(30) ms	β- (69%)	109Mo	5/2+#
					β-, n (69%)	108Mo
110Nb	41	69	109.94244(54)#	170(20) ms	β- (60%)	110Mo	2+#
					β-, n (40%)	109Mo
111Nb	41	70	110.94565(54)#	80# ms [>300 ns]			5/2+#
112Nb	41	71	111.95083(75)#	60# ms [>300 ns]			2+#
113Nb	41	72	112.95470(86)#	30# ms [>300 ns]			5/2+#

1. ^ Abbreviations:
   EC: Electron capture
   IT: Isomeric transition
2. ^ Bold for stable isotopes, bold italic for near-stable isotopes (half-life longer than the age of the universe)
3. ^ Longest half-life of all non-primordial radionuclides
4. ^ Theoretically capable of spontaneous fission, lightest nuclide so capable

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.

References

1. ^ There are many shorter-lived radioisotopes in nature, but they are all cosmogenic or radiogenic
2. ^ http://www.nucleonica.net/unc.aspx

• Isotope masses from:
  • G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729: 3–128. Bibcode 2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf. 
• Isotopic compositions and standard atomic masses from:
  • J. R. de Laeter, J. K. Böhlke, P. De Bièvre, H. Hidaka, H. S. Peiser, K. J. R. Rosman and P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683. http://www.iupac.org/publications/pac/75/6/0683/pdf/. 
  • M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051. http://iupac.org/publications/pac/78/11/2051/pdf/. Lay summary. 
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
  • G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729: 3–128. Bibcode 2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf. 
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. http://www.nndc.bnl.gov/nudat2/. Retrieved September 2005. 
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0849304859. 

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