Lawrencium
Encyclopedia
Lawrencium is a radioactive synthetic
chemical element
with the symbol Lr and atomic number
103. In the periodic table of the elements, it is a period 7
d-block
element and the last element of actinide
series. Chemistry experiments have confirmed that lawrencium behaves as the heavier homologue to lutetium and is chemically similar to other actinides.
Lawrencium was first synthesized by the nuclear-physics team led by Albert Ghiorso
on February 14, 1961, at the Lawrence Berkeley National Laboratory
of the University of California
. The first atoms of lawrencium were produced by bombarding a three-milligram target consisting of three isotopes of the element californium with boron-10 and boron-11 nuclei from the Heavy Ion Linear Accelerator. The team suggested the name lawrencium, and the symbol Lw, but Lr was officially accepted instead. It was the last element of actinide
series produced.
All isotopes of lawrencium
are radioactive; its most stable known isotope is lawrencium-262, with a half-life
of approximately 3.6 hour
s. All its isotopes, with exceptions of lawrencium-260, -261 and -262 decay with half-life less than a minute.
team of Albert Ghiorso
, Torbjørn Sikkeland, Almon Larsh, Robert M. Latimer, and their co-workers on February 14, 1961, at the Lawrence Radiation Laboratory (now called the Lawrence Berkeley National Laboratory
) at the University of California
. The first atoms of lawrencium were produced by bombarding a three-milligram target consisting of three isotopes of the element californium
with boron
-10 and boron-11 nuclei
from the Heavy Ion Linear Accelerator (HILAC). The Berkeley team reported that the isotope
257Lr was detected in this manner, and that it decayed by emitting an 8.6 MeV alpha particle
with a half-life
of about eight seconds. This identification was later corrected to be 258Lr.
In 1967, nuclear-physics researchers in Dubna
, Russia
, reported that they were not able to confirm assignment of an alpha emitter with a half-life
of eight seconds to 257Lr. This isotope was later deduced to be 258Lr. Instead, the Dubna team reported an isotope with a half-life of about 45 seconds as 256Lr.
Further experiments have demonstrated an actinide
chemistry for the new element, so by 1970 it was known that lawrencium is an actinide, and what is more, the last one. In 1971, the nuclear physics team at the University of California at Berkeley successfully performed a whole series of experiments aimed at measuring the nuclear decay properties of the lawrencium isotopes with mass numbers from 255 through 260.
In 1992, the IUPAC Trans-fermium Working Group (TWG) officially recognized the nuclear physics teams at Dubna and Berkeley as the co-discoverers of lawrencium.
, is in reference to the nuclear-physicist
Ernest O. Lawrence, of the University of California, who invented the cyclotron
particle accelerator. The symbol Lw was used originally, but the element was assigned the Lr symbol. In August 1997, the International Union of Pure and Applied Chemistry
(IUPAC) ratified the name lawrencium and the symbol Lr during a meeting in Geneva
.
. It is the first member of the 6d-block; in accordance with the Madelung rule, its electronic configuration should be [Rn]7s25f146d1. However, results from quantum mechanical research have suggested that this configuration is incorrect, and is in fact [Rn]7s25f147p1. A direct measurement of this is not possible. Though early calculations gave conflicting results, more recent studies and calculations confirm the suggestion.
A strict correlation between the periodic table blocks and the orbital-shell
configurations for neutral atoms would classify lawrencium as a transition metal
because it could be classed as a d-block
element. However, lawrencium is classified as an actinide element according to the IUPAC recommendations.
team at the Flerov Laboratory of Nuclear Reactions (FLNR) in the Soviet Union
. They used the nuclear reaction
243Am+18O to produce lawrencium nuclei, which they then exposed to a stream of chlorine
gas, and a volatile chloride product was formed. This product was deduced to be 256LrCl3, and this confirmed that lawrencium is a typical actinide element.
.
Further experiments in 1988 confirmed the formation of a trivalent lawrencium(III) ion using anion-exchange chromatography using α-hydroxyisobutyrate (α-HIB) complex. Comparison of the elution time with other actinides allowed a determination of 88.6 picometers for the ionic radius for Lr3+.
Attempts to reduce lawrencium in the lawrencium(III) ionization state to lawrencium(I) using the potent reducing agent hydroxylamine hydrochloride were unsuccessful.
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.
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 to 256Lr 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 to 255Lr.
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 to 260Lr,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 to 257Lr.
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.
have been synthesized with 262Lr being the longest-lived and the heaviest, with a half-life
of 216 minutes. 252Lr is the lightest isotope of lawrencium to be produced to date.
) 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
and parity
of 7/2-, decaying by emission of an 8794 KeV alpha particle with a half-life
of 0.57s. 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.
Synthetic element
In chemistry, a synthetic element is a chemical element that is too unstable to occur naturally on Earth, and therefore has to be created artificially. So far 30 synthetic elements have been discovered—that is, synthesized...
chemical element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with the symbol Lr and atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
103. In the periodic table of the elements, it is a period 7
Period 7 element
A period 7 element is one of the chemical elements in the seventh row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical...
d-block
D-block
The d-block is the portion of the periodic table that contains the element groups 3-12. These groups correspond to the filling of the atomic d-orbital subshell, with electron configurations ranging from s2d1 to s2d10...
element and the last element of actinide
Actinide
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.The actinide series derives its name from the group 3 element actinium...
series. Chemistry experiments have confirmed that lawrencium behaves as the heavier homologue to lutetium and is chemically similar to other actinides.
Lawrencium was first synthesized by the nuclear-physics team led by Albert Ghiorso
Albert Ghiorso
Albert Ghiorso was an American nuclear scientist and co-discoverer of a record 12 chemical elements on the periodic table. His research career spanned five decades, from the early 1940s to the late 1990s.-Early life:...
on February 14, 1961, at the Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory
The Lawrence Berkeley National Laboratory , is a U.S. Department of Energy national laboratory conducting unclassified scientific research. It is located on the grounds of the University of California, Berkeley, in the Berkeley Hills above the central campus...
of the University of California
University of California
The University of California is a public university system in the U.S. state of California. Under the California Master Plan for Higher Education, the University of California is a part of the state's three-tier public higher education system, which also includes the California State University...
. The first atoms of lawrencium were produced by bombarding a three-milligram target consisting of three isotopes of the element californium with boron-10 and boron-11 nuclei from the Heavy Ion Linear Accelerator. The team suggested the name lawrencium, and the symbol Lw, but Lr was officially accepted instead. It was the last element of actinide
Actinide
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.The actinide series derives its name from the group 3 element actinium...
series produced.
All isotopes of lawrencium
Isotopes of lawrencium
Lawrencium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 258Lr in 1961. There are eleven known radioisotopes from 252Lr to 262Lr, and 1 isomer . The longest-lived isotope...
are radioactive; its most stable known isotope is lawrencium-262, with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of approximately 3.6 hour
Hour
The hour is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds...
s. All its isotopes, with exceptions of lawrencium-260, -261 and -262 decay with half-life less than a minute.
Discovery
Lawrencium was first synthesized by the nuclear-physicsNuclear physics
Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those...
team of Albert Ghiorso
Albert Ghiorso
Albert Ghiorso was an American nuclear scientist and co-discoverer of a record 12 chemical elements on the periodic table. His research career spanned five decades, from the early 1940s to the late 1990s.-Early life:...
, Torbjørn Sikkeland, Almon Larsh, Robert M. Latimer, and their co-workers on February 14, 1961, at the Lawrence Radiation Laboratory (now called the Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory
The Lawrence Berkeley National Laboratory , is a U.S. Department of Energy national laboratory conducting unclassified scientific research. It is located on the grounds of the University of California, Berkeley, in the Berkeley Hills above the central campus...
) at the University of California
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
. The first atoms of lawrencium were produced by bombarding a three-milligram target consisting of three isotopes of the element californium
Californium
Californium is a radioactive metallic chemical element with the symbol Cf and atomic number 98. The element was first made in the laboratory in 1950 by bombarding curium with alpha particles at the University of California, Berkeley. It is the ninth member of the actinide series and was the...
with boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
-10 and boron-11 nuclei
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...
from the Heavy Ion Linear Accelerator (HILAC). The Berkeley team reported that the isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
257Lr was detected in this manner, and that it decayed by emitting an 8.6 MeV alpha particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of about eight seconds. This identification was later corrected to be 258Lr.
- + → → + 5
In 1967, nuclear-physics researchers in Dubna
Dubna
Dubna is a town in Moscow Oblast, Russia. It has a status of naukograd , being home to the Joint Institute for Nuclear Research, an international nuclear physics research centre and one of the largest scientific foundations in the country. It is also home to MKB Raduga, a defence aerospace company...
, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, reported that they were not able to confirm assignment of an alpha emitter with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of eight seconds to 257Lr. This isotope was later deduced to be 258Lr. Instead, the Dubna team reported an isotope with a half-life of about 45 seconds as 256Lr.
- + → → + 5
Further experiments have demonstrated an actinide
Actinide
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.The actinide series derives its name from the group 3 element actinium...
chemistry for the new element, so by 1970 it was known that lawrencium is an actinide, and what is more, the last one. In 1971, the nuclear physics team at the University of California at Berkeley successfully performed a whole series of experiments aimed at measuring the nuclear decay properties of the lawrencium isotopes with mass numbers from 255 through 260.
In 1992, the IUPAC Trans-fermium Working Group (TWG) officially recognized the nuclear physics teams at Dubna and Berkeley as the co-discoverers of lawrencium.
Naming
The origin of the name, ratified by the American Chemical SocietyAmerican Chemical Society
The American Chemical Society is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 161,000 members at all degree-levels and in all fields of chemistry, chemical...
, is in reference to the nuclear-physicist
Nuclear physics
Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those...
Ernest O. Lawrence, of the University of California, who invented the cyclotron
Cyclotron
In technology, a cyclotron is a type of particle accelerator. In physics, the cyclotron frequency or gyrofrequency is the frequency of a charged particle moving perpendicularly to the direction of a uniform magnetic field, i.e. a magnetic field of constant magnitude and direction...
particle accelerator. The symbol Lw was used originally, but the element was assigned the Lr symbol. In August 1997, the International Union of Pure and Applied Chemistry
International Union of Pure and Applied Chemistry
The International Union of Pure and Applied Chemistry is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Council for Science . The international headquarters of IUPAC is located in Zürich,...
(IUPAC) ratified the name lawrencium and the symbol Lr during a meeting in Geneva
Geneva
Geneva In the national languages of Switzerland the city is known as Genf , Ginevra and Genevra is the second-most-populous city in Switzerland and is the most populous city of Romandie, the French-speaking part of Switzerland...
.
Electronic structure
Lawrencium is element 103 in the periodic tablePeriodic table
The periodic table of the chemical elements is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom's atomic nucleus...
. It is the first member of the 6d-block; in accordance with the Madelung rule, its electronic configuration should be [Rn]7s25f146d1. However, results from quantum mechanical research have suggested that this configuration is incorrect, and is in fact [Rn]7s25f147p1. A direct measurement of this is not possible. Though early calculations gave conflicting results, more recent studies and calculations confirm the suggestion.
A strict correlation between the periodic table blocks and the orbital-shell
Electron shell
An electron shell may be thought of as an orbit followed by electrons around an atom's nucleus. The closest shell to the nucleus is called the "1 shell" , followed by the "2 shell" , then the "3 shell" , and so on further and further from the nucleus. The shell letters K,L,M,.....
configurations for neutral atoms would classify lawrencium as a transition metal
Transition metal
The term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...
because it could be classed as a d-block
D-block
The d-block is the portion of the periodic table that contains the element groups 3-12. These groups correspond to the filling of the atomic d-orbital subshell, with electron configurations ranging from s2d1 to s2d10...
element. However, lawrencium is classified as an actinide element according to the IUPAC recommendations.
Gaseous phase
The first gaseous-phase studies of lawrencium were reported in 1969 by a nuclear-physicsNuclear physics
Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those...
team at the Flerov Laboratory of Nuclear Reactions (FLNR) in the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
. They used the nuclear reaction
Nuclear reaction
In nuclear physics and nuclear chemistry, a nuclear reaction is semantically considered to be the process in which two nuclei, or else a nucleus of an atom and a subatomic particle from outside the atom, collide to produce products different from the initial particles...
243Am+18O to produce lawrencium nuclei, which they then exposed to a stream of chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
gas, and a volatile chloride product was formed. This product was deduced to be 256LrCl3, and this confirmed that lawrencium is a typical actinide element.
Aqueous phase
The first aqueous-phase studies of lawrencium were reported in 1970 by a nuclear-physics team at the Lawrence Berkeley National Laboratory in California. This team used the nuclear reaction 249Cf+11B to produce lawrencium nuclei. They were able to show that lawrencium forms a trivalent ion, similar to those of the other actinide elements, but in contrast with that of nobeliumNobelium
Nobelium is a synthetic element with the symbol No and atomic number 102. It was first correctly identified in 1966 by scientists at the Flerov Laboratory of Nuclear Reactions in Dubna, Soviet Union...
.
Further experiments in 1988 confirmed the formation of a trivalent lawrencium(III) ion using anion-exchange chromatography using α-hydroxyisobutyrate (α-HIB) complex. Comparison of the elution time with other actinides allowed a determination of 88.6 picometers for the ionic radius for Lr3+.
Attempts to reduce lawrencium in the lawrencium(III) ionization state to lawrencium(I) using the potent reducing agent hydroxylamine hydrochloride were unsuccessful.
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 to 256Lr 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
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
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
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 20s. This was assigned to 255Lr.
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 to 260Lr,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
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
(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
Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...
of 261Lr with an improved half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
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
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
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
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
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
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
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
Albert Ghiorso was an American nuclear scientist and co-discoverer of a record 12 chemical elements on the periodic table. His research career spanned five decades, from the early 1940s to the late 1990s.-Early life:...
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
Nobelium
Nobelium is a synthetic element with the symbol No and atomic number 102. It was first correctly identified in 1966 by scientists at the Flerov Laboratory of Nuclear Reactions in Dubna, Soviet Union...
.
252Cf(10B,xn)262-xLr (x=4,6)
This reaction was first studied in 1961 at the University of California by Albert Ghiorso
Albert Ghiorso
Albert Ghiorso was an American nuclear scientist and co-discoverer of a record 12 chemical elements on the periodic table. His research career spanned five decades, from the early 1940s to the late 1990s.-Early life:...
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
Nobelium
Nobelium is a synthetic element with the symbol No and atomic number 102. It was first correctly identified in 1966 by scientists at the Flerov Laboratory of Nuclear Reactions in Dubna, Soviet Union...
.
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 to 257Lr.
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
Spontaneous fission
Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...
(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
Nobelium
Nobelium is a synthetic element with the symbol No and atomic number 102. It was first correctly identified in 1966 by scientists at the Flerov Laboratory of Nuclear Reactions in Dubna, Soviet Union...
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:| Parent nuclide | Observed lawrencium isotope |
|---|---|
| 267Bh, 263Db | 259Lr |
| 278Uut, 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 |
Isotopes
Eleven isotopes of lawrencium plus one isomerNuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
have been synthesized with 262Lr being the longest-lived and the heaviest, with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 216 minutes. 252Lr is the lightest isotope of lawrencium to be produced to date.
Lawrencium-253
A study of the decay properties of 257Db (see dubniumDubnium
The Soviet team proposed the name nielsbohrium in honor of the Danish nuclear physicist Niels Bohr. The American team proposed that the new element should be named hahnium , in honor of the late German chemist Otto Hahn...
) 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 (physics)
In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,...
and parity
Parity (physics)
In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...
of 7/2-, decaying by emission of an 8794 KeV alpha particle with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 0.57s. The isomeric level was assigned spin
Spin (physics)
In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,...
and parity
Parity (physics)
In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...
of 1/2-, decaying by emission of an 8722 KeV alpha particle with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 1.49 s.
Lawrencium-255
Recent work on the spectroscopy of 255Lr formed in the reaction 209Bi(48Ca,2n)255Lr has provided evidence for an isomeric level.See also
Further reading
- Los Alamos National Laboratory's Chemistry Division: Periodic Table – Lawrencium
- Guide to the Elements – Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
- Eric Scerri, The Periodic Table, Its Story and Its Significance, (Oxford University Press; 2007)