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 firs ...

(₁₁₀Ds) 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 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 numb ...

to be synthesized was ²⁶⁹Ds in 1994. There are 10 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 ²⁶⁷Ds to ²⁸¹Ds (with many gaps) and 2 or 3 known

isomers 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. ...

. The longest-lived isotope is ²⁸¹Ds 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 at ...

of 14 seconds.

List of isotopes

, - , ²⁶⁷DsUnconfirmed isotope , style="text-align:right" , 110 , style="text-align:right" , 157 , 267.14377(15)# , 10(8) µs , α ? , ²⁶³Hs ? , 3/2+# , - , ²⁶⁹Ds , style="text-align:right" , 110 , style="text-align:right" , 159 , 269.14475(3) , 230(110) µs
79(+245−66) µs, α , ²⁶⁵Hs , 3/2+# , - , ²⁷⁰Ds , style="text-align:right" , 110 , style="text-align:right" , 160 , 270.14458(5) , 160(100) µs
.10(+14−4) ms, α , ²⁶⁶Hs , 0+ , - , style="text-indent:1em" , ^270mDs , colspan="3" style="text-indent:2em" , 1140(70) keV , 10(6) ms
.0(+82−22) ms, α , ²⁶⁶Hs , (10)(−#) , - , ²⁷¹Ds , style="text-align:right" , 110 , style="text-align:right" , 161 , 271.14595(10)# , 210(170) ms , α , ²⁶⁷Hs , 11/2−# , - , style="text-indent:1em" , ^271mDs , colspan="3" style="text-indent:2em" , 29(29) keV , 1.3(5) ms , α , ²⁶⁷Hs , 9/2+# , - , ²⁷³Ds , style="text-align:right" , 110 , style="text-align:right" , 163 , 273.14856(14)# , 240(100) µs , α , ²⁶⁹Hs , 13/2−# , - , ²⁷⁶DsSHE Factory Experiments
- FLNR , style="text-align:right" , 110 , style="text-align:right" , 166 , 276.15303(59)# , , α , ²⁷²Hs , 0+ , - , ²⁷⁷DsNot directly synthesized, occurs in

decay chain In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay dire ...

of ²⁸⁵Fl , style="text-align:right" , 110 , style="text-align:right" , 167 , 277.15591(41)# , , α , ²⁷³Hs , 11/2+# , - , rowspan=2, ²⁷⁹DsNot directly synthesized, occurs as decay product of ²⁸³Cn , rowspan=2 style="text-align:right" , 110 , rowspan=2 style="text-align:right" , 169 , rowspan=2, 279.16010(64)# , rowspan=2, , SF (87%) , (various) , rowspan=2, , - , α (13%) , ²⁷⁵Hs , - , ²⁸⁰DsNot directly synthesized, occurs in decay chain of ²⁸⁸Fl , style="text-align:right" , 110 , style="text-align:right" , 170 , 280.16131(89)# , , SF , (various) , 0+ , - , rowspan=2, ²⁸¹DsNot directly synthesized, occurs in decay chain of ²⁸⁹Fl , rowspan=2 style="text-align:right" , 110 , rowspan=2 style="text-align:right" , 171 , rowspan=2, 281.16451(59)# , rowspan=2, 14(3) s , SF (90%) , (various) , rowspan=2, 3/2+# , - , α (10%) , ²⁷⁷Hs

Isotopes and nuclear properties

Nucleosynthesis

Superheavy element Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, are the chemical elements with atomic number greater than 103. The superheavy elements are those beyond the actinides in the periodic table; the l ...

s such as darmstadtium 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 induce

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 darmstadtium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher atomic numbers. 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 (actinides), giving rise to compound nuclei at high excitation energy (~40–50 electronvolt, MeV) 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, 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). The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with ''Z'' = 110.

Cold fusion

Before the first successful synthesis of darmstadtium in 1994 by the Gesellschaft für Schwerionenforschung, GSI team, scientists at GSI also tried to synthesize darmstadtium by bombarding lead-208 with nickel-64 in 1985. No darmstadtium atoms were identified. After an upgrade of their facilities, the team at GSI successfully detected 9 atoms of ²⁷¹Ds in two runs of their discovery experiment in 1994. This reaction was successfully repeated in 2000 by GSI (4 atoms), in 2000 (preprint) and 2004 by the Lawrence Berkeley National Laboratory (LBNL) (9 atoms in total) and in 2002 by RIKEN (14 atoms). The GSI team studied the analogous reaction with nickel-62 instead of nickel-64 in 1994 as part of their discovery experiment. Three atoms of ²⁶⁹Ds were detected. A fourth decay chain was measured but was subsequently retracted. In addition to the official discovery reactions, in October–November 2000, the team at GSI also studied the analogous reaction using a lead-207 target in order to synthesize the new isotope ²⁷⁰Ds. They succeeded in synthesising eight atoms of ²⁷⁰Ds, relating to a ground state isomer, ²⁷⁰Ds, and a high-spin (physics), spin metastable state, ^270mDs. In 1986, a team at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, studied the reaction: :Bi + Co → Ds + n They were unable to detect any darmstadtium atoms. In 1995, the team at LBNL reported that they had succeeded in detecting a single atom of ²⁶⁷Ds using this reaction. However, several decays were not measured and further research is required to confirm this discovery.

Hot fusion

In the late 1980s, the GSI team attempted to synthesize element 110 by bombarding a target consisting of various uranium isotopes—²³³U, ²³⁵U, and ²³⁸U—with accelerated argon-40 ions. No atoms were detected; a limiting cross section of 21 pb was reported. In September 1994, the team at Dubna detected a single atom of ²⁷³Ds by bombarding a plutonium-244 target with accelerated sulfur-34 ions. Experiments were done in 2004 at the Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna studying the fission characteristics of the compound nucleus ²⁸⁰Ds, produced in the reaction: :Th + Ca → Ds* → fission The result revealed how compound nuclei such as this fission predominantly by expelling magic number (physics), magic and doubly magic nuclei such as ¹³²Sn (''atomic number, Z'' = 50, ''neutron number, N'' = 82). No darmstadtium atoms were obtained.Flerov lab annual report 2004
/ref> A compound nucleus is a loose combination of nucleons that have not arranged themselves into nuclear shells yet. It has no internal structure and is held together only by the collision forces between the target and projectile nuclei. It is estimated that it requires around 10⁻¹⁴ s for the nucleons to arrange themselves into nuclear shells, at which point the compound nucleus becomes a nuclide, and this number is used by IUPAC as the minimum

a claimed isotope must have in order to be recognized as being discovered. The ²³²Th+⁴⁸Ca reaction was tried again at the FLNR in 2022. One atom of ²⁷⁶Ds was reported. The cross-section is reported to be small. Further details are not yet available.

As decay product

Darmstadtium has been observed as a decay product of copernicium. Copernicium currently has seven known isotopes, four of which have been shown to alpha decay into darmstadtium, with mass numbers 273, 277, and 279–281. To date, all of these bar ²⁷³Ds have only been produced by decay of copernicium. Parent copernicium nuclei can be themselves decay products of flerovium or livermorium. Darmstadtium may also have been produced in the electron capture decay of roentgenium nuclei which are themselves daughters of nihonium and moscovium. To date, no other elements have been known to decay to darmstadtium. For example, in 2004, the Dubna team (Joint Institute for Nuclear Research, JINR) identified darmstadtium-281 as a product in the decay of livermorium via an alpha decay sequence: : → + : → + : → +

Retracted isotopes

;²⁸⁰Ds The first synthesis of Flerovium, element 114 resulted in two atoms assigned to ²⁸⁸Fl, decaying to the ²⁸⁰Ds, which underwent spontaneous fission. The assignment was later changed to ²⁸⁹Fl and the darmstadtium isotope to ²⁸¹Ds. Hence, ²⁸⁰Ds remained unknown until 2016, when it was populated by the hitherto unknown alpha decay of ²⁸⁴Cn (previously, that nucleus was only known to undergo spontaneous fission). The discovery of ²⁸⁰Ds in this decay chain was confirmed in 2021; it undergoes spontaneous fission with a half-life of 360 µs. ;²⁷⁷Ds In the claimed synthesis of ²⁹³Og in 1999, the isotope ²⁷⁷Ds was identified as decaying by 10.18 MeV alpha emission with a half-life of 3.0 ms. This claim was retracted in 2001. This isotope was finally created in 2010 and its decay data supported the fabrication of previous data.see Oganesson ;^273mDs In the synthesis of ²⁷⁷Cn in 1996 by GSI (see copernicium), one decay chain proceeded ''via'' ²⁷³Ds, which decayed by emission of a 9.73 MeV alpha particle with a lifetime of 170 ms. This would have been assigned to an isomeric level. This data could not be confirmed and thus this isotope is currently unknown or unconfirmed. ;²⁷²Ds In the first attempt to synthesize darmstadtium, a 10 ms SF activity was assigned to ²⁷²Ds in the reaction ²³²Th(⁴⁴Ca,4n). Given current understanding regarding stability, this isotope has been retracted from the table of isotopes.

Nuclear isomerism

;²⁸¹Ds The production of ²⁸¹Ds by the decay of ²⁸⁹Fl or ²⁹³Lv has produced two very different decay modes. The most common and readily confirmed mode is spontaneous fission with a half-life of 11 s. A much rarer and as yet unconfirmed mode is alpha decay by emission of an alpha particle with energy 8.77 MeV with an observed half-life of around 3.7 min. This decay is associated with a unique decay pathway from the parent nuclides and must be assigned to an isomeric level. The half-life suggests that it must be assigned to an isomeric state but further research is required to confirm these reports. It was suggested in 2016 that this unknown activity might be due to ²⁸²Mt, the great-granddaughter of ²⁹⁰Fl via electron capture and two consecutive alpha decays. ;²⁷¹Ds Decay data from the direct synthesis of ²⁷¹Ds clearly indicates the presence of two nuclear isomers. The first emits alpha particles with energies 10.74 and 10.69 MeV and has a half-life of 1.63 ms. The other only emits alpha particles with an energy of 10.71 MeV and has a half-life of 69 ms. The first has been assigned to the ground state and the latter to an isomeric level. It has been suggested that the closeness of the alpha decay energies indicates that the isomeric level may decay primarily by delayed isomeric transition to the ground state, resulting in an identical measured alpha energy and a combined half-life for the two processes. ;²⁷⁰Ds The direct production of ²⁷⁰Ds has clearly identified two nuclear isomers. The ground state decays by alpha emission into the ground state of ²⁶⁶Hs by emitting an alpha particle with energy 11.03 MeV and has a half-life of 0.10 ms. The metastable state decays by alpha emission, emitting alpha particles with energies of 12.15, 11.15, and 10.95 MeV, and has a half-life of 6 ms. When the metastable state emits an alpha particle of energy 12.15 MeV, it decays into the ground state of ²⁶⁶Hs, indicating that it has 1.12 MeV of excess energy.

Chemical yields of isotopes

Cold fusion

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

Fission of compound nuclei with Z = 110

Experiments have been performed in 2004 at the Flerov Laboratory of Nuclear Reactions in Dubna studying the fission characteristics of the compound nucleus ²⁸⁰Ds. The nuclear reaction used is ²³²Th+⁴⁸Ca. The result revealed how nuclei such as this fission predominantly by expelling closed shell nuclei such as ¹³²Sn (''Z'' = 50, ''N'' = 82).se
Flerov lab annual report 2004
/ref>

Theoretical calculations

Decay characteristics

Theoretical calculation in a quantum tunneling model reproduces the experimental alpha decay half live data. It also predicts that the isotope ²⁹⁴Ds would have alpha decay half-life of the order of 311 years.

Evaporation residue cross sections

The below table contains various targets-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given. DNS = Di-nuclear system; σ = cross section

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 Isotopes of darmstadtium, Darmstadtium Lists of isotopes by element, Darmstadtium