Rutherfordium Rutherfordium is a chemical element with the symbol Rf and atomic number 104, named after New Zealand-born British physicist Ernest Rutherford. As a synthetic element, it is not found in nature and can only be made in a laboratory. It is radioactiv ...

(₁₀₄Rf) 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 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. 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. 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 either ²⁵⁹Rf in 1966 or ²⁵⁷Rf in 1969. There are 16 known

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s from ²⁵³Rf to ²⁷⁰Rf (3 of which, ²⁶⁶Rf, ²⁶⁸Rf, and ²⁷⁰Rf, are unconfirmed) and 4

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 ...

s. The longest-lived isotope is ²⁶⁷Rf 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 48 minutes, and the longest-lived isomer is ^261mRf with a half-life of 81 seconds.

List of isotopes

, - , rowspan=2, ²⁵³Rf , rowspan=2 style="text-align:right" , 104 , rowspan=2 style="text-align:right" , 149 , rowspan=2, 253.10044(44)# , rowspan=2, 13(5) ms , SF , (various) , rowspan=2, (7/2)(+#) , - , α , ²⁴⁹No , - , style="text-indent:1em" , ^253mRf , colspan="3" style="text-indent:2em" , 200(150)# keV , 52(14) µs
[] , SF , (various) , (1/2)(−#) , - , rowspan=2, ²⁵⁴Rf , rowspan=2 style="text-align:right" , 104 , rowspan=2 style="text-align:right" , 150 , rowspan=2, 254.10005(30)# , rowspan=2, 23(3) µs , SF (99.7%) , (various) , rowspan=2, 0+ , - , α (.3%) , ²⁵⁰No , - , rowspan=2, ²⁵⁵Rf , rowspan=2 style="text-align:right" , 104 , rowspan=2 style="text-align:right" , 151 , rowspan=2, 255.10127(12)# , rowspan=2, 1.64(11) s , SF (52%) , (various) , rowspan=2, (9/2−)# , - , α (48%) , ²⁵¹No , - , rowspan=2, ²⁵⁶Rf , rowspan=2 style="text-align:right" , 104 , rowspan=2 style="text-align:right" , 152 , rowspan=2, 256.101152(19) , rowspan=2, 6.45(14) ms , SF (96%) , (various) , rowspan=2, 0+ , - , α (6%) , ²⁵²No , - , rowspan=3, ²⁵⁷Rf , rowspan=3 style="text-align:right" , 104 , rowspan=3 style="text-align:right" , 153 , rowspan=3, 257.102917(12) , rowspan=3, 4.7(3) s , α (79%) , ²⁵³No , rowspan=3, (1/2+) , - , β⁺ (18%) , ²⁵⁷Lr , - , SF (2.4%) , (various) , - , style="text-indent:1em" , ^257mRf , colspan="3" style="text-indent:2em" , 114(17) keV , 3.9(4) s , , , (11/2−) , - , rowspan=2, ²⁵⁸Rf , rowspan=2 style="text-align:right" , 104 , rowspan=2 style="text-align:right" , 154 , rowspan=2, 258.10343(3) , rowspan=2, 12(2) ms , SF (87%) , (various) , rowspan=2, 0+ , - , α (13%) , ²⁵⁴No , - , rowspan=3, ²⁵⁹Rf , rowspan=3 style="text-align:right" , 104 , rowspan=3 style="text-align:right" , 155 , rowspan=3, 259.10560(8)# , rowspan=3, 2.8(4) s , α (93%) , ²⁵⁵No , rowspan=3, 7/2+# , - , SF (7%) , (various) , - , β⁺ (.3%) , ²⁵⁹Lr , - , rowspan=2, ²⁶⁰Rf , rowspan=2 style="text-align:right" , 104 , rowspan=2 style="text-align:right" , 156 , rowspan=2, 260.10644(22)# , rowspan=2, 21(1) ms , SF (98%) , (various) , rowspan=2, 0+ , - , α (2%) , ²⁵⁶No , - , rowspan=3, ²⁶¹Rf , rowspan=3 style="text-align:right" , 104 , rowspan=3 style="text-align:right" , 157 , rowspan=3, 261.10877(5) , rowspan=3, 68 s , α (76%) , ²⁵⁷No , rowspan=3, 9/2+# , - , β⁺ (14%) , ²⁶¹Lr , - , SF (10%) , (various) , - , rowspan=2 style="text-indent:1em" , ^261mRf , rowspan=2 colspan="3" style="text-indent:2em" , 70(100)# keV , rowspan=2, 1.9(4) s , SF (73%) , (various) , rowspan=2, 3/2+# , - , α (27%) , ²⁵⁷No , - , rowspan=2, ²⁶²Rf , rowspan=2 style="text-align:right" , 104 , rowspan=2 style="text-align:right" , 158 , rowspan=2, 262.10993(24)# , rowspan=2, 2.3(4) s , SF (99.2%) , (various) , rowspan=2, 0+ , - , α (.8%) , ²⁵⁸No , - , style="text-indent:1em" , ^262mRf , colspan="3" style="text-indent:2em" , 600(400)# keV , 47(5) ms , SF , (various) , high , - , rowspan=2, ²⁶³Rf , rowspan=2 style="text-align:right" , 104 , rowspan=2 style="text-align:right" , 159 , rowspan=2, 263.1125(2)# , rowspan=2, 11(3) min , SF (70%) , (various) , rowspan=2, 3/2+# , - , α (30%) , ²⁵⁹No , - , ²⁶⁵RfNot directly synthesized, occurs in decay chain of ²⁸⁵Fl , style="text-align:right" , 104 , style="text-align:right" , 161 , 265.11668(39)# , , SF , (various) , , - , ²⁶⁶RfDiscovery of this isotope is unconfirmedNot directly synthesized, occurs in decay chain of ²⁸²Nh , style="text-align:right" , 104 , style="text-align:right" , 162 , 266.11817(50)# , 23 s# , SF , (various) , 0+ , - , ²⁶⁷RfNot directly synthesized, occurs in decay chain of ²⁸⁷Fl , style="text-align:right" , 104 , style="text-align:right" , 163 , 267.12179(62)# , , SF , (various) , 13/2−# , - , ²⁶⁸RfNot directly synthesized, occurs in decay chain of ²⁸⁸Mc , style="text-align:right" , 104 , style="text-align:right" , 164 , 268.12397(77)# , 1.4 s# , SF , (various) , 0+ , - , ²⁷⁰RfNot directly synthesized, occurs in decay chain of ²⁹⁴Ts , style="text-align:right" , 104 , style="text-align:right" , 166 , , 20 ms# , SF , (various) , 0+

Nucleosynthesis

Super-heavy elements such as rutherfordium are produced by bombarding lighter elements in

particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams. Large accelerators are used for fundamental research in particle ...

s that induces

fusion reaction Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the reactants and products is manifeste ...

s. Whereas most of the isotopes of rutherfordium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher

atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...

s. Depending on the energies involved, the former are separated into "hot" and "cold". In hot fusion reactions, very light, high-energy projectiles are accelerated toward very heavy targets (

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 first element in the series, actinium. The inform ...

s), giving rise to compound nuclei at high excitation energy (~40–50

MeV In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an Voltage, electric potential difference of one volt i ...

) that may either fission or evaporate several (3 to 5) neutrons. In cold fusion reactions, the produced fused nuclei have a relatively low excitation energy (~10–20 MeV), which decreases the probability that these products will undergo fission reactions. As the fused nuclei cool to the

ground state The ground state of a quantum-mechanical system is its stationary state of lowest energy; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state. ...

, they require emission of only one or two neutrons, and thus, allows for the generation of more neutron-rich products. The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion).

Hot fusion studies

The synthesis of rutherfordium was first attempted in 1964 by the team at Dubna using the hot fusion reaction of

neon Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...

-22 projectiles with

plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...

-242 targets: : + → + 3 or 5 . The first study produced evidence for a

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 ...

with a 0.3 second

and another one at 8 seconds. While the former observation was eventually retracted, the latter eventually became associated with the ²⁵⁹Rf isotope."Discovery of the transneptunium elements"
IUPAC/IUPAP Technical Report, ''Pure Appl. Chem.'', Vol. 65, No. 8, pp. 1757-1814,1993. Retrieved on 2008-03-04 In 1966, the Soviet team repeated the experiment using a chemical study of volatile chloride products. They identified a volatile chloride with eka-hafnium properties that decayed fast through spontaneous fission. This gave strong evidence for the formation of RfCl₄, and although a half-life was not accurately measured, later evidence suggested that the product was most likely ²⁵⁹Rf. The team repeated the experiment several times over the next few years, and in 1971, they revised the spontaneous fission half-life for the isotope at 4.5 seconds. In 1969, researchers at the

University of California The University of California (UC) is a public land-grant research university system in the U.S. state of California. The system is composed of the campuses at Berkeley, Davis, Irvine, Los Angeles, Merced, Riverside, San Diego, San Francisco, ...

led by Albert Ghiorso, tried to confirm the original results reported at Dubna. In a reaction of

curium Curium is a transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inte ...

-248 with

oxygen-16 Oxygen-16 (16O) is a stable isotope of oxygen, having 8 neutrons and 8 protons in its nucleus. It has a mass of . Oxygen-16 is the most abundant isotope of oxygen and accounts for 99.762% of oxygen's natural abundance. The relative and absolute ...

, they were unable to confirm the result of the Soviet team, but managed to observe the spontaneous fission of ²⁶⁰Rf with a very short half-life of 10–30 ms: : + → + 4 . In 1970, the American team also studied the same reaction with oxygen-18 and identified ²⁶¹Rf with a half-life of 65 seconds (later refined to 75 seconds). Later experiments at the

Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory (LBNL), commonly referred to as the Berkeley Lab, is a United States Department of Energy National Labs, United States national laboratory that is owned by, and conducts scientific research on behalf of, t ...

in California also revealed the formation of a short-lived isomer of ²⁶²Rf (which undergoes spontaneous fission with a half-life of 47 ms), and spontaneous fission activities with long lifetimes tentatively assigned to ²⁶³Rf. Rutherfordium experimental setup

The reaction of

californium Californium is a radioactive chemical element with the symbol Cf and atomic number 98. The element was first synthesized in 1950 at Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory), by bombarding ...

-249 with carbon-13 was also investigated by the Ghiorso team, which indicated the formation of the short-lived ²⁵⁸Rf (which undergoes spontaneous fission in 11 ms): : + → + 4 . In trying to confirm these results by using

carbon-12 Carbon-12 (12C) is the most abundant of the two stable isotopes of carbon (carbon-13 being the other), amounting to 98.93% of element carbon on Earth; its abundance is due to the triple-alpha process by which it is created in stars. Carbon-12 i ...

instead, they also observed the first

alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atom ...

s from ²⁵⁷Rf. The reaction of

berkelium Berkelium is a transuranic radioactive chemical element with the symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berke ...

-249 with

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

-14 was first studied in Dubna in 1977, and in 1985, researchers there confirmed the formation of the ²⁶⁰Rf isotope which quickly undergoes spontaneous fission in 28 ms: : + → + 3 . In 1996 the isotope ²⁶²Rf was observed in LBNL from the fusion of plutonium-244 with neon-22: : + → + 4 or 5 . The team determined a half-life of 2.1 seconds, in contrast to earlier reports of 47 ms and suggested that the two half-lives might be due to different isomeric states of ²⁶²Rf. Studies on the same reaction by a team at Dubna, lead to the observation in 2000 of alpha decays from ²⁶¹Rf and spontaneous fissions of ^261mRf. The hot fusion reaction using a uranium target was first reported at Dubna in 2000: : + → + x (x = 3, 4, 5, 6). They observed decays from ²⁶⁰Rf and ²⁵⁹Rf, and later for ²⁵⁹Rf. In 2006, as part of their program on the study of uranium targets in hot fusion reactions, the team at LBNL also observed ²⁶¹Rf.

Cold fusion studies

The first cold fusion experiments involving element 104 were done in 1974 at Dubna, by using light

titanium-50 Naturally occurring titanium (22Ti) is composed of five stable isotopes; 46Ti, 47Ti, 48Ti, 49Ti and 50Ti with 48Ti being the most abundant (73.8% natural abundance). Twenty-one radioisotopes have been characterized, with the most stable being 44Ti ...

nuclei aimed at lead-208 isotope targets: : + → + x (x = 1, 2, or 3). The measurement of a spontaneous fission activity was assigned to ²⁵⁶Rf, while later studies done at the Gesellschaft für Schwerionenforschung Institute (GSI), also measured decay properties for the isotopes ²⁵⁷Rf, and ²⁵⁵Rf. In 1974 researchers at Dubna investigated the reaction of

lead-207 Lead (82Pb) has four stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium ...

with titanium-50 to produce the isotope ²⁵⁵Rf. In a 1994 study at GSI using the lead-206 isotope, ²⁵⁵Rf as well as ²⁵⁴Rf were detected. ²⁵³Rf was similarly detected that year when lead-204 was used instead.

Decay studies

Most isotopes with an

atomic mass The atomic mass (''m''a or ''m'') is the mass of an atom. Although the SI unit of mass is the kilogram (symbol: kg), atomic mass is often expressed in the non-SI unit dalton (symbol: Da) – equivalently, unified atomic mass unit (u). 1&nbs ...

below 262 have also observed as decay products of elements with a higher

, allowing for refinement of their previously measured properties. Heavier isotopes of rutherfordium have only been observed as decay products. For example, a few alpha decay events terminating in ²⁶⁷Rf were observed in the decay chain of

darmstadtium Darmstadtium is a chemical element with the symbol Ds and atomic number 110. It is an extremely radioactive synthetic element. The most stable known isotope, darmstadtium-281, has a half-life of approximately 12.7 seconds. Darmstadtium was first ...

-279 since 2004: : → + → + → + . This further underwent spontaneous fission with a half-life of about 1.3 h. Investigations on the synthesis of the dubnium-263 isotope in 1999 at the

University of Bern The University of Bern (german: Universität Bern, french: Université de Berne, la, Universitas Bernensis) is a university in the Switzerland, Swiss capital of Bern and was founded in 1834. It is regulated and financed by the Canton of Bern. It ...

revealed events consistent with

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 ...

to form ²⁶³Rf. A rutherfordium fraction was separated, and several spontaneous fission events with long half-lives of about 15 minutes were observed, as well as alpha decays with half-lives of about 10 minutes. Reports on the decay chain of

flerovium Flerovium is a superheavy chemical element with symbol Fl and atomic number 114. It is an extremely radioactive synthetic element. It is named after the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Dubn ...

-285 in 2010 showed five sequential alpha decays that terminate in ²⁶⁵Rf, which further undergoes spontaneous fission with a half-life of 152 seconds. Some experimental evidence was obtained in 2004 for an even heavier isotope, ²⁶⁸Rf, in the decay chain of an isotope of moscovium: : → + → + → + → + → + ? → + . However, the last step in this chain was uncertain. After observing the five alpha decay events that generate dubnium-268, spontaneous fission events were observed with a long half-life. It is unclear whether these events were due to direct spontaneous fission of ²⁶⁸Db, or ²⁶⁸Db produced

events with long half-lives to generate ²⁶⁸Rf. If the latter is produced and decays with a short half-life, the two possibilities cannot be distinguished. Given that the

of ²⁶⁸Db cannot be detected, these spontaneous fission events may be due to ²⁶⁸Rf, in which case the half-life of this isotope cannot be extracted. A similar mechanism is proposed for the formation of the even heavier isotope ²⁷⁰Rf as a short-lived daughter of ²⁷⁰Db (in the decay chain of ²⁹⁴Ts, first synthesized in 2010) which then undergoes spontaneous fission: : → + → + → + → + → + → + ? → + . According to a 2007 report on the synthesis of

nihonium Nihonium is a synthetic chemical element with the symbol Nh and atomic number 113. It is extremely radioactive; its most stable known isotope, nihonium-286, has a half-life of about 10 seconds. In the periodic table, nihonium is a transactinid ...

, the isotope ²⁸²Nh was twice observed to undergo a similar decay to form ²⁶⁶Db. In one case this underwent spontaneous fission with a half-life of 22 minutes. Given that the electron capture of ²⁶⁶Db cannot be detected, these spontaneous fission events may be due to ²⁶⁶Rf, in which case the half-life of this isotope cannot be extracted. In the other case, no spontaneous fission event was observed; it could have been missed, or ²⁶⁶Db might have undergone two more alpha decays to long-lived ²⁵⁸Md, with a half-life (51.5 d) longer than the total time of the experiment.

Nuclear isomerism

Several early studies on the synthesis of ²⁶³Rf have indicated that this nuclide decays primarily by spontaneous fission with a half-life of 10–20 minutes. More recently, a study of hassium isotopes allowed the synthesis of atoms of ²⁶³Rf decaying with a shorter half-life of 8 seconds. These two different decay modes must be associated with two isomeric states, but specific assignments are difficult due to the low number of observed events. During research on the synthesis of rutherfordium isotopes utilizing the ²⁴⁴Pu(²²Ne,5n)²⁶¹Rf reaction, the product was found to undergo exclusive 8.28 MeV alpha decay with a half-life of 78 seconds. Later studies at GSI on the synthesis of copernicium and hassium isotopes produced conflicting data, as ²⁶¹Rf produced in the decay chain was found to undergo 8.52 MeV alpha decay with a half-life of 4 seconds. Later results indicated a predominant fission branch. These contradictions led to some doubt on the discovery of copernicium. The first isomer is currently denoted ^261aRf (or simply ²⁶¹Rf) whilst the second is denoted ^261bRf (or ^261mRf). However, it is thought that the first nucleus belongs to a high-spin ground state and the latter to a low-spin metastable state. The discovery and confirmation of ^261bRf provided proof for the discovery of copernicium in 1996. A detailed spectroscopic study of the production of ²⁵⁷Rf nuclei using the reaction ²⁰⁸Pb(⁵⁰Ti,n)²⁵⁷Rf allowed the identification of an isomeric level in ²⁵⁷Rf. The work confirmed that ^257gRf has a complex spectrum with 15 alpha lines. A level structure diagram was calculated for both isomers. Similar isomers were reported for ²⁵⁶Rf also.

Chemical yields of isotopes

Cold fusion

The table below provides cross-sections and excitation energies for cold fusion reactions producing rutherfordium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

Hot fusion

The table below provides cross-sections and excitation energies for hot fusion reactions producing rutherfordium isotopes directly. Data in bold represents maxima derived from excitation function measurements. + represents an observed exit channel.

References

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

External links

*http://www.radiochemistry.org/periodictable/elements/isotopes_data/104.html *http://www-phynu.cea.fr/science_en_ligne/carte_potentiels_microscopiques/choix/isotopes/z104_eng.html *http://www.springermaterials.com/docs/info/978-3-540-70609-0_7730.html {{Navbox element isotopes Rutherfordium Rutherfordium