Isotopes of lawrencium

Isotopes of lawrencium  (₁₀₃Lr)

Main isotopes [1] Decay abun­dance half-life (t1/2) mode pro­duct 256Lr synth 27.9 s α 252Md β+ 256No 260Lr synth 3.0 min α 256Md β+ 260No 261Lr synth 39 min SF – 262Lr synth 4 h β+ 262No 264Lr synth 4.8 h [2] SF – 266Lr synth 11 h SF –

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Lawrencium (₁₀₃Lr) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was ²⁵⁸Lr in 1961. There are fourteen known isotopes from ²⁵¹Lr to ²⁶⁶Lr, and seven isomers. The longest-lived known isotope is ²⁶⁶Lr with a half-life of 11 hours.

List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da) [n 2] [n 3]	Half-life	Decay mode [n 4]	Daughter isotope	Spin and parity [n 5] [n 6]
	Excitation energy [n 6]
251Lr [3]	103	148	251.09418(32)#	24.4+7.0 −4.5 ms	α	247Md	7/2−
					SF [4] [n 7]	(various)
251mLr [3]	117(27) keV			42+42 −14 ms	α	247Md	1/2−
252Lr [n 8] [5]	103	149	252.09526(26)#	369(75) ms [0.36+0.11 −0.07 s]	α (~98%)	248Md
					SF (~2%)	(various)
					β+?	252No
253Lr [6]	103	150	253.09509(22)#	632(46) ms [7]	α (>97%)	249Md	(7/2−)
					SF (1.0%)	(various)
					β+ (<2%)	253No
253mLr	30(100)# keV			1.32(14) s	α (>86%)	249Md	(1/2−)
					SF (12%)	(various)
					β+ (<2%)	253No
254Lr [8] [9]	103	151	254.096240(100) [10]	11.9(9) s	α (71.7%)	250Md	(4+)
					β+ (28.3%)	254No
					SF (<0.1%)	(various)
254mLr	110(6) keV [11]			20.3(4.2) s	α	250Md	(1-)
					β+	254No
					IT?	254Lr
255Lr [8]	103	152	255.096562(19)	31.1(1.1) s	α (85%)	251Md	1/2− [3]
					β+ (15%) [12]	255No
					SF (rare)	(various)
255m1Lr [8]	32(2) keV [11]			2.54(5) s	IT (~60%)	255Lr	(7/2−)
					α (~40%)	251Md
255m2Lr [8]	796(12) keV			<1 μs	IT	255m1Lr	(15/2+)
255m3Lr [8]	1465(12) keV			1.78(0.05) ms	IT	255m2Lr	(25/2+)
256Lr [13]	103	153	256.09849(9)	27.9(1.0) s	α (85%)	252Md	(0-,3-)#
					β+ (15%)	256No
					SF (<0.03%)	(various)
257Lr [14]	103	154	257.09942(5)#	1.24+0.85 −0.36 s	α	253Md	(9/2+,7/2-)
					β+ (rare)	257No
					SF (rare)	(various)
257mLr [8]	100(50)# keV			200+160 −60 ms	α	253Md	(1/2−)
					IT	257Lr
258Lr [15]	103	155	258.10176(11)#	3.54+0.46 −0.36 s	α (97.4%)	254Md
					β+ (2.6%)	258No
259Lr [16]	103	156	259.10290(8)#	6.2(3) s	α (78%)	255Md	1/2-#
					SF (22%)	(various)
					β+ (rare)	259No
260Lr [17]	103	157	260.10551(13)#	3.0(5) min	α (80%)	256Md
					β+ (20%)	260No
					SF (rare)	(various)
261Lr [18]	103	158	261.10688(22)#	39(12) min	SF	(various)	1/2-#
					α (<10%) [19]	257Md
262Lr [20]	103	159	262.10961(22)#	~4 h	β+	262No
					SF (<10%)	(various)
					α (<7.5%) [21]	258Md
264Lr [n 9]	103	161	264.11420(47)#	4.8+2.2 −1.3 h [2]	SF	(various)
266Lr [n 10]	103	163	266.11983(56)#	22(14) h [11+21 −5 h] [22]	SF	(various)
This table header & footer: view

1. ^mLr – 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:

   SF:	Spontaneous fission

5. ( ) spin value – Indicates spin with weak assignment arguments.
6. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
7. The experiment in which alpha decay of two ²⁵¹Lr states was reported did not take into account spontaneous fission branches. ^[3]
8. Not directly synthesized, occurs as a decay product of ²⁵⁶Db
9. Not directly synthesized, occurs as a decay product of ²⁸⁸Mc
10. Not directly synthesized, occurs as a decay product of ²⁹⁴Ts

Nucleosynthesis

Cold fusion

²⁰⁵Tl(⁵⁰Ti,xn)^255−xLr (x=2)

This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Evidence was provided for the formation of ²⁵³Lr in the 2n exit channel. In 2022, two states (²⁵³Lr and ^253mLr) were found.

²⁰³Tl(⁵⁰Ti,xn)^253−xLr (x=2)

This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. In 2022, two states (²⁵¹Lr and ^251mLr) were found.

²⁰⁸Pb(⁴⁸Ti,pxn)^255−xLr (x=1?)

This reaction was reported in 1984 by Yuri Oganessian at the FLNR. The team was able to detect decays of ²⁴⁶Cf, a descendant of ²⁵⁴Lr.

²⁰⁸Pb(⁴⁵Sc,xn)^253−xLr

This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Results are not readily available.

²⁰⁹Bi(⁴⁸Ca,xn)^257−xLr (x=2)

This reaction has been used to study the spectroscopic properties of ²⁵⁵Lr. The team at GANIL used the reaction in 2003 and the team at the FLNR used it between 2004–2006 to provide further information for the decay scheme of ²⁵⁵Lr. The work provided evidence for an isomeric level in ²⁵⁵Lr.

Hot fusion

²⁴³Am(¹⁸O,xn)^261−xLr (x=5)

This reaction was first studied in 1965 by the team at the FLNR. They were able to detect activity with a characteristic decay of 45 seconds, which was assigned to²⁵⁶Lr or ²⁵⁷Lr. Later work suggests an assignment to ²⁵⁶Lr. Further studies in 1968 produced an 8.35–8.60 MeV alpha activity with a half-life of 35 seconds. This activity was also initially assigned to ²⁵⁶Lr or ²⁵⁷Lr and later to solely ²⁵⁶Lr.

²⁴³Am(¹⁶O,xn)^259−xLr (x=4)

This reaction was studied in 1970 by the team at the FLNR. They were able to detect an 8.38 MeV alpha activity with a half-life of 20s. This was assigned to²⁵⁵Lr.

²⁴⁸Cm(¹⁵N,xn)^263−xLr (x=3,4,5)

This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to assign alpha activities to²⁶⁰Lr,²⁵⁹Lr and ²⁵⁸Lr from the 3-5n exit channels.

²⁴⁸Cm(¹⁸O,pxn)^265−xLr (x=3,4)

This reaction was studied in 1988 at the LBNL in order to assess the possibility of producing ²⁶²Lr and ²⁶¹Lr without using the exotic ²⁵⁴Es target. It was also used to attempt to measure an electron capture (EC) branch in ^261mRf from the 5n exit channel. After extraction of the Lr(III) component, they were able to measure the spontaneous fission of ²⁶¹Lr with an improved half-life of 44 minutes. The production cross-section was 700 pb. On this basis, a 14% electron capture branch was calculated if this isotope was produced via the 5n channel rather than the p4n channel. A lower bombarding energy (93 MeV c.f. 97 MeV) was then used to measure the production of ²⁶²Lr in the p3n channel. The isotope was successfully detected and a yield of 240 pb was measured. The yield was lower than expected compared to the p4n channel. However, the results were judged to indicate that the ²⁶¹Lr was most likely produced by a p3n channel and an upper limit of 14% for the electron capture branch of ^261mRf was therefore suggested.

²⁴⁶Cm(¹⁴N,xn)^260−xLr (x=3?)

This reaction was studied briefly in 1958 at the LBNL using an enriched ²⁴⁴Cm target (5% ²⁴⁶Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25 seconds. Later results suggest a tentative assignment to ²⁵⁷Lr from the 3n channel

²⁴⁴Cm(¹⁴N,xn)^258−xLr

This reaction was studied briefly in 1958 at the LBNL using an enriched ²⁴⁴Cm target (5% ²⁴⁶Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25s. Later results suggest a tentative assignment to ²⁵⁷Lr from the 3n channel with the ²⁴⁶Cm component. No activities assigned to reaction with the ²⁴⁴Cm component have been reported.

²⁴⁹Bk(¹⁸O,αxn)^263−xLr (x=3)

This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to detect an activity assigned to ²⁶⁰Lr. The reaction was further studied in 1988 to study the aqueous chemistry of lawrencium. A total of 23 alpha decays were measured for ²⁶⁰Lr, with a mean energy of 8.03 MeV and an improved half-life of 2.7 minutes. The calculated cross-section was 8.7 nb.

²⁵²Cf(¹¹B,xn)^263−xLr (x=5,7??)

This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% ²⁵²Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to ²⁵⁷Lr. Later results suggest a reassignment to ²⁵⁸Lr, resulting from the 5n exit channel. The 8.4 MeV activity was also assigned to ²⁵⁷Lr. Later results suggest a reassignment to ²⁵⁶Lr. This is most likely from the 33% ²⁵⁰Cf component in the target rather than from the 7n channel. The 8.2 MeV was subsequently associated with nobelium.

²⁵²Cf(¹⁰B,xn)^262−xLr (x=4,6)

This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% ²⁵²Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to ²⁵⁷Lr. Later results suggest a reassignment to ²⁵⁸Lr. The 8.4 MeV activity was also assigned to ²⁵⁷Lr. Later results suggest a reassignment to ²⁵⁶Lr. The 8.2 MeV was subsequently associated with nobelium.

²⁵⁰Cf(¹⁴N,αxn)^260−xLr (x=3)

This reaction was studied in 1971 at the LBNL. They were able to identify a 0.7s alpha activity with two alpha lines at 8.87 and 8.82 MeV. This was assigned to²⁵⁷Lr.

²⁴⁹Cf(¹¹B,xn)^260−xLr (x=4)

This reaction was first studied in 1970 at the LBNL in an attempt to study the aqueous chemistry of lawrencium. They were able to measure a Lr³⁺ activity. The reaction was repeated in 1976 at Oak Ridge and 26s ²⁵⁶Lr was confirmed by measurement of coincident X-rays.

²⁴⁹Cf(¹²C,pxn)^260−xLr (x=2)

This reaction was studied in 1971 by the team at the LBNL. They were able to detect an activity assigned to ²⁵⁸Lr from the p2n channel.

²⁴⁹Cf(¹⁵N,αxn)^260−xLr (x=2,3)

This reaction was studied in 1971 by the team at the LBNL. They were able to detect an activities assigned to ²⁵⁸Lr and ²⁵⁷Lr from the α2n and α3n and channels. The reaction was repeated in 1976 at Oak Ridge and the synthesis of ²⁵⁸Lr was confirmed.

²⁵⁴Es + ²²Ne – transfer

This reaction was studied in 1987 at the LLNL. They were able to detect new spontaneous fission (SF) activities assigned to ²⁶¹Lr and ²⁶²Lr, resulting from transfer from the ²²Ne nuclei to the ²⁵⁴Es target. In addition, a 5 ms SF activity was detected in delayed coincidence with nobelium K-shell X-rays and was assigned to ²⁶²No, resulting from the electron capture of ²⁶²Lr.

Decay products

Isotopes of lawrencium have also been identified in the decay of heavier elements. Observations to date are summarised in the table below:

List of lawrencium isotopes produced as other nuclei decay products

Parent nuclide	Observed lawrencium isotope
294Ts, 290Mc, 286Nh, 282Rg, 278Mt, 274Bh, 270Db	266Lr
288Mc, 284Nh, 280Rg, 276Mt, 272Bh, 268Db	264Lr
267Bh, 263Db	259Lr
278Nh, 274Rg, 270Mt, 266Bh, 262Db	258Lr
261Db	257Lr
272Rg, 268Mt, 264Bh, 260Db	256Lr
259Db	255Lr
266Mt, 262Bh, 258Db	254Lr
261Bh, 257Dbg,m	253Lrg,m
260Bh, 256Db	252Lr
255Db	251Lr

Isotopes

Summary of all lawrencium isotopes known

Isotope	Year discovered	discovery reaction
251Lrg	2005	209Bi(48Ti,2n)
251Lrm	2022	203Tl(50Ti,2n)
252Lr	2001	209Bi(50Ti,3n)
253Lrg	1985	209Bi(50Ti,2n)
253Lrm	2001	209Bi(50Ti,2n)
254Lrg	1985	209Bi(50Ti,n)
254Lrm	2019
255Lrg	1970	243Am(16O,4n)
255Lrm1	2006
255Lrm2	2009
255Lrm3	2008
256Lr	1961? 1965? 1968? 1971	252Cf(10B,6n)
257Lrg	1958? 1971	249Cf(15N,α3n)
257Lrm	2018
258Lr	1961? 1971	249Cf(15N,α2n)
259Lr	1971	248Cm(15N,4n)
260Lr	1971	248Cm(15N,3n)
261Lr	1987	254Es + 22Ne
262Lr	1987	254Es + 22Ne
264Lr	2020	243Am(48Ca,6α3n)
266Lr	2014	249Bk(48Ca,7α3n)

Fourteen isotopes of lawrencium plus seven isomers have been synthesized with ²⁶⁶Lr being the longest-lived and the heaviest, with a half-life of 11 hours. ²⁵¹Lr is the lightest isotope of lawrencium to be produced to date.

Lawrencium-253 isomers

A study of the decay properties of ²⁵⁷Db (see dubnium) in 2001 by Hessberger et al. at the GSI provided some data for the decay of ²⁵³Lr. Analysis of the data indicated the population of an isomeric level in ²⁵³Lr from the decay of the corresponding isomer in ²⁵⁷Db. The ground state was assigned spin and parity of 7/2−, decaying by emission of an 8794 keV alpha particle with a half-life of 0.57 s. The isomeric level was assigned spin and parity of 1/2−, decaying by emission of an 8722 keV alpha particle with a half-life of 1.49 s.

Lawrencium-255 isomers

Recent work on the spectroscopy of ²⁵⁵Lr formed in the reaction ²⁰⁹Bi(⁴⁸Ca,2n)²⁵⁵Lr has provided evidence for an isomeric level.

References

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• Isotopic compositions and standard atomic masses from:
  • de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry . 75 (6): 683–800. doi: 10.1351/pac200375060683 .
  • Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry . 78 (11): 2051–2066. doi: 10.1351/pac200678112051 .
• "News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
• Half-life, spin, and isomer data selected from the following sources.
  • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (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
  • National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  • Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN   978-0-8493-0485-9.