Lawrencium Lawrencium is a synthetic chemical element with the symbol Lr (formerly Lw) and atomic number 103. It is named in honor of Ernest Lawrence, inventor of the cyclotron, a device that was used to discover many artificial radioactive elements. A radi ...

(₁₀₃Lr) is a

synthetic element A synthetic element is one of 24 known chemical elements that do not occur naturally on Earth: they have been created by human manipulation of fundamental particles in a nuclear reactor, a particle accelerator, or the explosion of an atomic bomb; ...

, and thus a

standard atomic weight The standard atomic weight of a chemical element (symbol ''A''r°(E) for element "E") is the weighted arithmetic mean of the relative isotopic masses of all isotopes of that element weighted by each isotope's abundance on Earth. For example, is ...

cannot be given. Like all synthetic elements, it has no

stable isotope The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundanc ...

s. The first

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...

to be synthesized was ²⁵⁸Lr in 1961. There are fourteen known isotopes from ²⁵¹Lr to ²⁶⁶Lr, and 1

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

(^253mLr). The longest-lived known isotope is ²⁶⁶Lr with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

of 11 hours.

List of isotopes

, - , rowspan=2, ²⁵¹Lr , rowspan=2 style="text-align:right" , 103 , rowspan=2 style="text-align:right" , 148 , rowspan=2, 251.09418(32)# , rowspan=2, , α , ²⁴⁷Md , rowspan=2, 7/2− , - , SF , (various) , - , style="text-indent:1em" , ^251mLr , colspan="3" style="text-indent:2em" , 117(27) keV , , α , ²⁴⁷Md , 1/2− , - , rowspan=3, ²⁵²LrNot directly synthesized, occurs as a

decay product In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps ( ...

of ²⁵⁶Db , rowspan=3 style="text-align:right" , 103 , rowspan=3 style="text-align:right" , 149 , rowspan=3, 252.09526(26)# , rowspan=3, 390(90) ms
[] , α (90%) , ²⁴⁸Md , rowspan=3, , - , beta decay, β⁺ (10%) , ²⁵²No , - , SF (1%) , (various) , - , rowspan=3, ²⁵³Lr , rowspan=3 style="text-align:right" , 103 , rowspan=3 style="text-align:right" , 150 , rowspan=3, 253.09509(22)# , rowspan=3, 580(70) ms
[] , α (90%) , ²⁴⁹Md , rowspan=3, (7/2−) , - , SF (9%) , (various) , - , β⁺ (1%) , ²⁵³No , - , style="text-indent:1em" , ^253mLr , colspan="3" style="text-indent:2em" , 30(100)# keV , 2.46(32) s , , , (1/2−) , - , rowspan=3, ²⁵⁴LrNot directly synthesized, occurs as a decay product of ²⁵⁸Db , rowspan=3 style="text-align:right" , 103 , rowspan=3 style="text-align:right" , 151 , rowspan=3, 254.09648(32)# , rowspan=3, 13(3) s , α (78%) , ²⁵⁰Md , rowspan=3, , - , β⁺ (22%) , ²⁵⁴No , - , SF (.1%) , (various) , - , rowspan=3, ²⁵⁵Lr , rowspan=3 style="text-align:right" , 103 , rowspan=3 style="text-align:right" , 152 , rowspan=3, 255.096562(19) , rowspan=3, 22(4) s , α (69%) , ²⁵¹Md , rowspan=3, 1/2− , - , β⁺ (30%) , ²⁵⁵No , - , SF (1%) , (various) , - , rowspan=3, ²⁵⁶Lr , rowspan=3 style="text-align:right" , 103 , rowspan=3 style="text-align:right" , 153 , rowspan=3, 256.09849(9) , rowspan=3, 27(3) s , α (80%) , ²⁵²Md , rowspan=3, , - , β⁺ (20%) , ²⁵⁶No , - , SF (.01%) , (various) , - , rowspan=3, ²⁵⁷Lr , rowspan=3 style="text-align:right" , 103 , rowspan=3 style="text-align:right" , 154 , rowspan=3, 257.09942(5)# , rowspan=3, 646(25) ms , α (99.99%) , ²⁵³Md , rowspan=3, 9/2+# , - , β⁺ (.01%) , ²⁵⁷No , - , SF (.001%) , (various) , - , rowspan=2, ²⁵⁸Lr , rowspan=2 style="text-align:right" , 103 , rowspan=2 style="text-align:right" , 155 , rowspan=2, 258.10176(11)# , rowspan=2, 4.1(3) s , α (95%) , ²⁵⁴Md , rowspan=2, , - , β⁺ (5%) , ²⁵⁸No , - , rowspan=3, ²⁵⁹Lr , rowspan=3 style="text-align:right" , 103 , rowspan=3 style="text-align:right" , 156 , rowspan=3, 259.10290(8)# , rowspan=3, 6.2(3) s , α (77%) , ²⁵⁵Md , rowspan=3, 9/2+# , - , SF (23%) , (various) , - , β⁺ (.5%) , ²⁵⁹No , - , rowspan=3, ²⁶⁰Lr , rowspan=3 style="text-align:right" , 103 , rowspan=3 style="text-align:right" , 157 , rowspan=3, 260.10551(13)# , rowspan=3, 2.7 min , α (75%) , ²⁵⁶Md , rowspan=3, , - , β⁺ (15%) , ²⁶⁰No , - , SF (10%) , (various) , - , rowspan=2, ²⁶¹Lr , rowspan=2 style="text-align:right" , 103 , rowspan=2 style="text-align:right" , 158 , rowspan=2, 261.10688(22)# , rowspan=2, 44 min , SF , (various) , rowspan=2, , - , α (rare) , ²⁵⁷Md , - , rowspan=2, ²⁶²Lr , rowspan=2 style="text-align:right" , 103 , rowspan=2 style="text-align:right" , 159 , rowspan=2, 262.10961(22)# , rowspan=2, 216 min , β⁺ , ²⁶²No , rowspan=2, , - , α (rare) , ²⁵⁸Md , - , ²⁶⁴LrNot directly synthesized, occurs as a decay product of ²⁸⁸Mc , style="text-align:right" , 103 , style="text-align:right" , 161 , 264.11420(47)# , h , SF , (various) , , - , ²⁶⁶LrNot directly synthesized, occurs as a decay product of ²⁹⁴Ts , style="text-align:right" , 103 , style="text-align:right" , 163 , 266.11983(56)# , 11 h , SF , (various) , , -

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. ;²⁰³Tl(⁵⁰Ti,xn)^253−xLr This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. ;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

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

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 Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Thi ...

(EC) branch in ^261mRf from the 5n exit channel. After extraction of the Lr(III) component, they were able to measure the

spontaneous fission Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56 (e.g., iron-56); spontaneous breakdo ...

of ²⁶¹Lr with an improved

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

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

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

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 Albert Ghiorso (July 15, 1915 – December 26, 2010) was an American nuclear scientist and co-discoverer of a record 12 chemical elements on the periodic table. His research career spanned six decades, from the early 1940s to the late 1990s. Biog ...

by using a californium target (52% ²⁵²Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with

half-lives Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...

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 Nobelium is a synthetic chemical element with the symbol No and atomic number 102. It is named in honor of Alfred Nobel, the inventor of dynamite and benefactor of science. A radioactive metal, it is the tenth transuranic element and is the penul ...

. ;²⁵²Cf(¹⁰B,xn)^262−xLr (x=4,6) This reaction was first studied in 1961 at the University of California by

by using a californium target (52% ²⁵²Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with

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

. ;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

(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

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:

Isotopes

Fourteen isotopes of lawrencium plus one

have been synthesized with ²⁶⁶Lr being the longest-lived and the heaviest, with a

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 Dubnium is a Synthetic element, synthetic chemical element with the Symbol (chemistry), symbol Db and atomic number 105. It is highly radioactive: the most stable known isotopes of dubnium, isotope, dubnium-268, has a half-life of about 16 ho ...

) 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 two isomeric levels in ²⁵³Lr from the decay of the corresponding isomers in ²⁵⁷Db. The ground state was assigned

spin Spin or spinning most often refers to: * Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning * Spin, the rotation of an object around a central axis * Spin (propaganda), an intentionally b ...

and

parity Parity may refer to: * Parity (computing) ** Parity bit in computing, sets the parity of data for the purpose of error detection ** Parity flag in computing, indicates if the number of set bits is odd or even in the binary representation of the r ...

of 7/2−, decaying by emission of an 8794 keV alpha particle with a

of 0.57 s. The isomeric level was assigned

and

of 1/2−, decaying by emission of an 8722 keV alpha particle with a

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

* Isotope masses from: ** ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Navbox element isotopes Lawrencium