Deleng sumberé Dubnium

{{Elementbox_header | number=105 | symbol=Db | name=dubnium | left=[[rutherfordium]] | right=[[seaborgium]] | above=[[tantalum|Ta]] | below=(Upp) | color1=#ffc0c0 | color2=black }}
{{Elementbox_series | [[transition metal]]s }}
{{Elementbox_groupperiodblock | group=5 | period=7 | block=d }}
{{Elementbox_appearance | unknown, probably silvery<br />white or metallic gray }}
{{Elementbox_atomicmass_gpm | [268] }}
{{Elementbox_econfig | &#91;[[radon|Rn]]&#93; 5f<sup>14</sup> 6d<sup>3</sup> 7s<sup>2</sup><br />}}
{{Elementbox_epershell | 2, 8, 18, 32, 32, 11, 2 }}
{{Elementbox_section_physicalprop | color1=#ffc0c0 | color2=black }}
{{Elementbox_phase | presumably a [[solid]] }}
{{Elementbox_density_gpcm3nrt | unknown }}
{{Elementbox_section_atomicprop | color1=#ffc0c0 | color2=black }}
{{Elementbox_crystalstruct | unknown }}
{{Elementbox_oxistates | 5}}
{{Elementbox_atomicradiuscalc_pm | unknown }}
{{Elementbox_covalentradius_pm | unknown}}
{{Elementbox_section_miscellaneous | color1=#ffc0c0 | color2=black }}
{{Elementbox_cas_number | 53850-35-4 }}
{{Elementbox_isotopes_begin | color1=#ffc0c0 | color2=black }}
{{Elementbox_isotopes_decay2 | mn=268 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=29 h{{Fact|date=April 2008}} | dm1=SF | de1= | pn1= | ps1= | dm2 = [[electron capture|ε]] ? |de2 = |pn2 =268 |ps2=Rf  }}
{{Elementbox_isotopes_decay | mn=267 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=1.2 h | dm=SF | de= | pn= | ps=  }}
{{Elementbox_isotopes_decay | mn=266 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=22 m | dm=ε | de= | pn=266 | ps=Rf  }}
{{Elementbox_isotopes_decay3 | mn=263 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=27 s | dm1=56% SF | de1= | pn1= | ps1= | dm2=41% α | de2=8.36 | pn2=259 | ps2=Lr | dm3=3% ε | de3= | pn3=263m | ps3=Rf }}
{{Elementbox_isotopes_decay2 | mn=262 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=34 s| dm1=67% α | de1=8.66,8.45 | pn1=258 | ps1=Lr | dm2 =33% SF |de2 = |pn2 = |ps2=  }}
{{Elementbox_isotopes_decay | mn=261 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=1.8 s | dm=α | de=8.93 | pn=257 | ps=Lr  }}
{{Elementbox_isotopes_decay | mn=260 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=1.5 s | dm=α | de=9.13,9.08,9.05 | pn=256 | ps=Lr  }}
{{Elementbox_isotopes_decay | mn=259 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=0.5 s| dm=α | de=9.47 | pn=255 | ps=Lr  }}
{{Elementbox_isotopes_decay2 | mn=258 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=4.4 s| dm1=67% α| de1=9.17,9.08,9.01 | pn1=254 | ps1=Lr |dm2=33% ε| de2= | pn2=258 | ps2=Rf }}
{{Elementbox_isotopes_decay | mn=257m | sym=Db | na=[[synthetic radioisotope|syn]] | hl=0.76 s| dm= α| de=9.16| pn=253 | ps=Lr}}
{{Elementbox_isotopes_decay | mn=257g | sym=Db | na=[[synthetic radioisotope|syn]] | hl=1.50 s| dm= α| de=9.07,8.97| pn=253 | ps=Lr}}
{{Elementbox_isotopes_decay2 | mn=256 | sym=Db | na=[[synthetic radioisotope|syn]] | hl=1.6 s| dm1=70% α| de1=9.12,9.08,9.01,8.89 | pn1=253 | ps1=Lr |dm2=30% ε| de2= | pn2=256 | ps2=Rf}}
{{Elementbox_isotopes_end}}
{{Elementbox_footer | color1=#ffc0c0 | color2=black }}

'''Dubnium''' ({{pronEng|ˈduːbniəm}}) iku [[unsur kimia]] sajeroning [[tabel périodik]] kanthi simbul '''Db''' lan [[nomer atom]] 105.

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{{Listen|filename=dubnium.ogg|title=Dubnium|description=Common English pronunciation of dubnium|format=[[Ogg]]}}
This is a [[radioactive]] [[synthetic element]] whose most stable [[isotope]] is <sup>268</sup>Db with a [[half life]] of 29 hours. This is the longest lived transactinide isotope and is a reflection of the stability of the Z=108 and N=162 closed shells and the effect of odd particles in nuclear decay. Chemistry experiments have provided sufficient evidence confidently to place dubnium in group 5 of the [[Periodic Table]].

==Discovery profile==
Element 105 was first reported by Russian scientists in 1968-1970 at the [[Joint Institute for Nuclear Research]] in [[Dubna]], Russia. The 1968 work was based on the detection of correlated decays of element 105 to known daughter nucleui using the reaction <sup>243</sup>Am(<sup>22</sup>Ne,xn). They reported a 9.40 MeV and a 9.70 MeV alpha-activity and assigned the decays to the isotopes <sup>260</sup>105 or <sup>261</sup>105.

In 1970 they expanded their work by the application of thermal gradient chromatography and detection by spontaneous fission. They observed a 2.2 s SF activity in a fraction portraying niobium-like characteristics and assigned the activity to <sup>261</sup>DbCl<sub>5</sub>.

In late April 1970 researchers led by [[Albert Ghiorso]] working at the [[University of California, Berkeley]] published a convincing synthesis of <sup>260</sup>Db in the reaction:

:<math>\, ^{249}_{98}\mathrm{Cf} + \, ^{15}_{7}\mathrm{N} \, \to\ \, ^{260}_{105}\mathrm{Db} + 4\, ^{1}_{0}\mathrm{n}</math>

The team claimed that <sup>260</sup>Db decayed by 9.10 MeV alpha-emission with a [[half-life]] of 1.6 seconds to <sup>256</sup>Lr. Decay data for <sup>256</sup>Lr agreed with the literature values and provided strong support to their claim.

These results by the Berkeley scientists did not confirm the [[Soviet Union|Soviet]] findings regarding the 9.40 MeV or 9.70 MeV alpha-decay of <sup>260</sup>Db.

In 1971, the Russian team repeated their reaction using an improved set-up and were able to confirm the decay data for <sup>260</sup>Db using the reaction <sup>243</sup>Am(<sup>22</sup>Ne,5n)<sup>260</sup>Db.

In 1976, the Russian team continued their study of the reaction using thermal gradient chromatography and were able to identify the product <sup>260</sup>DbBr<sub>5</sub>.

In 1977, all doubt was dispelled by the L X-ray elemental detection of [[lawrencium]] isotopes from the reaction <sup>249</sup>Cf(<sup>15</sup>N,4n)<sup>260</sup>Db.

In 1992 the TWG assessed the claims of the two groups and concluded that confidence in the discovery grew from results from both laboratories and the claim of discovery should be shared.<ref>http://www.iupac.org/publications/pac/1993/pdf/6508x1757.pdf (TWG report)</ref>

==Proposed names==
Historically element 105 has been called ''[[eka-]][[tantalum]]'' using Mendeleev's terminology.

The American team proposed that the new element should be named ''hahnium'' ({{IPA|/ˈhɑːniəm/}}),Ha, in honor of the late [[Germany|German]] scientist [[Otto Hahn]]. Consequently this was the name that most American and Western European scientists used and appears in many papers published at the time.

The Russian team proposed the name ''nielsbohrium'' ({{IPA|/ˌniːlzˈbɔəriəm/}}),Ns, in honor of the Danish Nuclear Physicist [[Niels Bohr]].

An [[element naming controversy]] erupted between the two groups. The [[International Union of Pure and Applied Chemistry]] (IUPAC) thus adopted ''unnilpentium'' ({{pronEng|ˌjuːn<s>ɪ</s>lˈpɛntiəm}},  Unp) as a temporary, [[systematic element name]]. Attempting to resolve the issue, in 1994, the IUPAC proposed the name ''joliotium'' ({{IPA|/ˌdʒoʊliˈoʊtiəm/}}), Jl, after the French physicist [[Frédéric Joliot-Curie]]. The two principal claimants still disagreed about the names of elements 104-108. However in 1997 they resolved the dispute and adopted the current name, ''dubnium'' (Db), after the city that contains the Russian [[Joint Institute for Nuclear Research]]. It was argued by IUPAC that the Berkeley laboratory had already been recognised several times in the naming of elements and that the acceptance of the names ''rutherfordium'' and ''seaborgium'' for elements 104 and 106 should be offset by recognising the contributions of the Russian team to the discovery of elements 104,105 and 106.<ref>http://www.iupac.org/publications/pac/1994/pdf/6612x2419.pdf (IUPAC 1994 recomm)</ref><ref>http://www.iupac.org/publications/pac/1997/pdf/6912x2471.pdf (IUPAC 1997 recomm)</ref>

==Electronic structure==

[[Image:electron shell 105 Dubnium.svg|thumb|150px|left]]

Dubnium is element 105 in the Periodic Table. The two forms of the projected electronic structure are:

Bohr model: 2, 8, 18, 32, 32, 11, 2

Quantum mechanical model: 1s<sup>2</sup>2s<sup>2</sup>2p<sup>6</sup>3s<sup>2</sup>3p<sup>6</sup>4s<sup>2</sup>3d<sup>10</sup>
4p<sup>6</sup>5s<sup>2</sup>4d<sup>10</sup>5p<sup>6</sup>6s<sup>2</sup>4f<sup>14</sup>5d<sup>10</sup>
6p<sup>6</sup>7s<sup>2</sup>5f<sup>14</sup>6d<sup>3</sup>
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==Extrapolated chemical properties of eka-tantalum/dvi-niobium==
===Oxidation states===
Element 105 is projected to be the second member of the 6d series of transition metals and the heaviest member of group V in the Periodic Table, below [[vanadium]], [[niobium]] and [[tantalum]].
All the members of the group readily portray their oxidation state of +V and the state becomes more stable as the group is descended. Thus dubnium is expected to form a stable +V state.
For this group, +IV and +III states are also known for the heavier members and dubnium may also form these reducing oxidation states.

===Chemistry===
In an extrapolation of the chemistries from [[niobium]] and [[tantalum]], dubnium should react with oxygen to form an inert pentoxide, Db<sub>2</sub>O<sub>5</sub>. In alkali, the formation of an orthodubnate complex, DbO<sub>4</sub><sup>3-</sup>, is expected.
Reaction with the halogens should readily form the pentahalides, DbX<sub>5</sub>. The pentachlorides of niobium and tantalum exist as volatile solids or monomeric trigonal bipyramidal molecules in the vapour phase. Thus, DbCl<sub>5</sub> is expected to be a volatile solid. Similarly, the pentafluoride, DbF<sub>5</sub>, should be even more volatile.
Hydrolysis of the halides is known to readily form the oxyhalides, MOX<sub>3</sub>. Thus the halides DbX<sub>5</sub> should react with water to form DbOX<sub>3</sub>.
The reaction with fluoride ion is also well known for the lighter homologues and dubnium is expected to form a range of fluoro-complexes. In partiular, reaction of the pentafluoride with HF should form a hexafluorodubnate ion, DbF<sub>6</sub><sup>-</sup>. Excess fluoride should lead to DbF<sub>7</sub><sup>2-</sup> and DbOF<sub>5</sub><sup>2-</sup>. If eka-tantalum properties are portrayed, higher concentrations of fluoride should ultimately form DbF<sub>8</sub><sup>3-</sup> since NbF<sub>8</sub><sup>3-</sup> is not known.

==Experimental chemistry==
===Gas phase chemistry===
The chemistry of dubnium has been studied for several years using gas thermochromatography. The experiments have studied the relative adsorption characteristics of isotopes of [[niobium]], [[tantalum]] and dubnium radioisotopes. The results have indicated the formation of typical group 5 halides and oxyhalides, namely DbCl<sub>5</sub>, DbBr<sub>5</sub>, DbOCl<sub>3</sub> and DbOBr<sub>3</sub>. Reports on these early experiments usually refer to dubnium as hahnium.

===Summary of compounds and complex ions===

{| class="wikitable"
|-
! Formula
! Names(s)
|-
| DbCl<sub>5</sub>
| dubnium pentachloride ; dubnium(V) chloride
|-
| DbBr<sub>5</sub>
| dubnium pentabromide ; dubnium(V) bromide
|-
| DbOCl<sub>3</sub>
| dubnium oxychloride ; dubnium(V) trichloride oxide ; dubnyl(V) chloride
|-
| DbOBr<sub>3</sub>
| dubnium oxybromide ; dubnium(V) tribromide oxide ; dubnyl(V) bromide
|-
|}

==History of synthesis of isotopes by cold fusion==
===<sup>209</sup>Bi(<sup>50</sup>Ti,xn)<sup>259-x</sup>Db (x=1,2,3)===
The first attempts to synthesis element 105 using cold fusion reactions were performed in 1976 by the team at FLNR, Dubna using the above reaction. They were able to detect a 5 s [[spontaneous fission]] (SF) activity which they assigned to <sup>257</sup>105. This assignment was later corrected to <sup>258</sup>105.
In 1981, the team at GSI studied this reaction using the improved technique of correlation of genetic parent-daughter decays. They were able to positively identify <sup>258</sup>Db, the product from the 1n neutron evaporation channel.<ref>[http://www.springerlink.com/content/tlx33361417u3n26/ "Identification of element 107 by α correlation chains"], '''Munzenberg et al.''', ''Z. Phys. A.'', 300, 1, 1981. Retrieved on [[2008-02-29]]</ref>
In 1983, the team at Dubna revisited the reaction using the method of identification of a descendant using chemical separation. They succeeded in measuring alpha decays from known descendants of the decay chain beginning with <sup>258</sup>105. This was taken as providing some evidence for the formation of element 105 nuclei.
The team at GSI revisited the reaction in 1985 and were able to detect 10 atoms of <sup>257</sup>Db.<ref>[http://www.springerlink.com/content/j04846712485p483/ "The new isotopes <sup>258</sup>105,<sup>257</sup>105,<sup>254</sup>Lr and <sup>253</sup>Lr"], '''Hessberger et al'''., ''Z. Phys A.'', 1985, 322, 4. Retrieved on [[2008-02-29]]</ref> 
After a significant upgrade of their facilities in 1993, in 2000 the team measured 120 decays of <sup>257</sup>Db, 16 decays of <sup>256</sup>Db and decay of <sup>258</sup>Db in the measurement of the 1n, 2n and 3n excitation functions. The data gathered for <sup>257</sup>Db allowed a first spectroscopic study of this isotope and identified an isomer, <sup>257m</sup>Db, and a first determination of a decay level structure for <sup>257</sup>Db.<ref>[http://www.edpsciences.org/articles/epja/abs/2001/09/epja1103/epja1103.html "Decay properties of neutron-deficient isotopes <sup>256,257</sup>Db, <sup>255</sup>Rf, <sup>252,253</sup>Lr"], '''Hessberger et al.''', ''Eur. Phys. J.'', A 12, 57-67 (2001). Retrieved on [[2008-02-29]]</ref>
The reaction was used in spectroscopic studies of isotopes of [[mendelevium]] and [[einsteinium]] in 2003-2004.<ref>[http://www.springerlink.com/content/7n66l7650112m776/ "Energy systematics of low-lying Nilsson levels in odd-mass einsteinium isotopes"], '''Hessberger et al'''., ''Eur. Phys. J''. A., 2005, 26, 2. Retrieved on [[2008-02-29]]</ref>

===<sup>209</sup>Bi(<sup>49</sup>Ti,xn)<sup>258-x</sup>Db (x=2?)===
This reaction was studied by Yuri Oganessian and the team at Dubna in 1983. They observed a 2.6 s SF activity tentatively assigned to <sup>256</sup>Db. Later results suggest a possible reassignment to <sup>256</sup>Rf, resulting from the ~30% EC branch in <sup>256</sup>Db.

===<sup>209</sup>Bi(<sup>48</sup>Ti,xn)<sup>257-x</sup>Db (x=1?)===
This reaction was studied by Yuri Oganessian and the team at Dubna in 1983. They observed a 1.6 s activity with a ~80% alpha branch with a ~20% SF branch. The activity was tentatively assigned to <sup>255</sup>Db. Later results suggest a reassignment to <sup>256</sup>Db.

===<sup>208</sup>Pb(<sup>51</sup>V,xn)<sup>259-x</sup>Db (x=1,2)===
The team at Dubna also studied this reaction in 1976 and were again able to detect the 5 s SF activity, first tentatively assigned to <sup>257</sup>Db and later to <sup>258</sup>Db.
In 2006, the team at LBNL reinvestigated this reaction as part of their odd-Z projectile program. They were able to detect <sup>258</sup>Db and <sup>257</sup>Db in their measurement of the 1n and 2n neutron evaporation channels. <ref>[http://rnc.lbl.gov/nsd/annualreport2005/contributions/Gates1_LE.pdf "Measurement of the <sup>208</sup>Pb(<sup>51</sup>V, xn)<sup>259-x</sup>Db Excitation Function"], '''Gates et al'''., ''LBNL Annual Report 2005''. Retrieved on [[2008-02-29]]</ref>

===<sup>207</sup>Pb(<sup>51</sup>V,xn)<sup>258-x</sup>Db===
The team at Dubna also studied this reaction in 1976 but this time they were unable to detect the 5 s SF activity, first tentatively assigned to <sup>257</sup>Db and later to <sup>258</sup>Db. Instead, they were able to measure a 1.5 s SF activity, tentatively assigned to <sup>255</sup>Db.

===<sup>205</sup>Tl(<sup>54</sup>Cr,xn)<sup>259-x</sup>Db (x=1?)===
The team at Dubna also studied this reaction in 1976 and were again able to detect the 5 s SF activity, first tentatively assigned to <sup>257</sup>Db and later to <sup>258</sup>Db.

==History of synthesis of isotopes by hot fusion==
===<sup>232</sup>Th(<sup>31</sup>P,xn)<sup>263-x</sup>Db (x=5)===
There are very limited reports that this rare reaction using a P-31 beam was studied in 1989 by Andreyev et al. at the FLNR. One source suggests that no atoms were detected whilst a better source from the Russians themselves indicates that <sup>258</sup>Db was synthesised in the 5n channel with a yield of 120 pb.

===<sup>238</sup>U(<sup>27</sup>Al,xn)<sup>265-x</sup>Db (x=4,5)===
In 2006, as part of their study of the use of uranium targets in superheavy element synthesis, the LBNL team led by Ken Gregorich studied the excitation functions for the 4n and 5n channels in this new reaction.<ref>http://rnc.lbl.gov/nsd/annualreport2005/contributions/Gregorich_LE.pdf (238U studies)</ref>

===<sup>236</sup>U(<sup>27</sup>Al,xn)<sup>263-x</sup>Db (x=5,6)===
This reaction was first studied by Andreyev et al. at the FLNR, Dubna in 1992. They were able to observe <sup>258</sup>Db and <sup>257</sup>Db in the 5n and 6n exit channels with yields of 450 pb and 75 pb, respectively.<ref>[http://www.springerlink.com/content/p47303w3887q36r7/ "Investigation of the fusion reaction <sup>27</sup>Al + <sup>236</sup>U → <sup>263</sup>105 at excitation energies of 57 MeV and 65 MeV"], '''Andreyev et al.''', ''Z. Phys. A.'', 1992, 344, 2. Retrieved on [[2008-02-29]]</ref>

===<sup>243</sup>Am(<sup>22</sup>Ne,xn)<sup>265-x</sup>Db (x=5)===
The first attempts to synthesis element 105 were performed in 1968 by the team at the Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna,Russia. They observed two alpha lines which they tentatively assigned to <sup>261</sup>105 and <sup>260</sup>105.
They repeated their experiment in 1970 looking for [[spontaneous fission]]. They found a 2.2 s SF activity which they assigned to <sup>261</sup>105. 
In 1970, the Dubna team began work on using gradient thermochromatography in order to detect element 105 in chemical experiments as a volatile chloride. In their first run they detected a volatile SF activity with similar adsorption properties to NbCl<sub>5</sub> and unlike HfCl<sub>4</sub>. This was taken to indicate the formation of nuclei of dvi-niobium as [105]Cl<sub>5</sub>. In 1971, they repeated the chemistry experiment using higher sensitivity and observed alpha decays from an dvi-niobium component, taken to confirm the formation of <sup>260</sup>105. The method was repeated in 1976 using the formation of bromides and obtained almost identical results, indicating the formation of a volatile, dvi-niobium-like [105]Br<sub>5</sub>.

===<sup>241</sup>Am(<sup>22</sup>Ne,xn)<sup>263-x</sup>Db (x=4,5)===
In 2000, Chinese scientists at the Institute of Modern Physics (IMP), Lanzhou, announced the discovery of the previously unknown isotope <sup>259</sup>Db formed in the 4n neutron evaporation channel. They were also able to confirm the decay properties for <sup>258</sup>Db.<ref>[http://www.springerlink.com/content/gflp9qfdqp0l9r1u/ "A new alpha-particle-emitting isotope <sup>259</sup>Db"], '''Gan et al.''', ''Eur. Phys. J. A'', 2001, 10, 1. Retrieved on [[2008-02-29]]</ref>

===<sup>248</sup>Cm(<sup>19</sup>F,xn)<sup>267-x</sup>Db (x=4,5)===
This reaction was first studied in 1999 at the Paul Scherrer Institute (PSI) in order to produce <sup>262</sup>Db for chemical studies. Just 4 atoms were detected with a cross section of 260 pb.<ref>[http://prola.aps.org/abstract/PRC/v59/i6/p3433_1 "Production of <sup>262</sup>Db (Z=105) in the reaction <sup>248</sup>Cm(<sup>19</sup>F, 5n)"], '''Dressler et al'''., ''Phys. Rev. C'', 59, 3433 - 3436 (1999).Retrieved on [[2008-02-29]] </ref>
Japanese scientists at JAERI studied the reaction further in 2002 and determined yields for the isotope <sup>262</sup>Db during their efforts to study the aqueous chemistry of dubnium.<ref>[http://sciencelinks.jp/j-east/article/200219/000020021902A0652005.php "Production Cross Sections of <sup>261</sup>Rf and <sup>262</sup>Db in Bombardments of <sup>248</sup>Cm with <sup>18</sup>O and <sup>19</sup>F Ions"], '''Nagame et al.''', ''J. Nucl. Radiochem. Sci''., 2002, 3, 1, 85-88.Retrieved on [[2008-02-29]]</ref>

===<sup>249</sup>Bk(<sup>18</sup>O,xn)<sup>267-x</sup>Db (x=4,5)===
Following from the discovery of <sup>260</sup>Db by Albert Ghiorso in 1970 at the University of California (UC), the same team continued in 1971 with the discovery of the new isotope <sup>262</sup>Db. They also observed an unassigned 25 s SF activity, probably associated with the now-known SF branch of <sup>263</sup>Db.<ref name=71Gh01>[http://prola.aps.org/abstract/PRC/v4/i5/p1850_1 "Two New Alpha-Particle Emitting Isotopes of Element 105, <sup>261</sup>Ha and <sup>262</sup>Ha"], '''Ghiorso et al.''', ''Phys. Rev. C'', 4, 1850 - 1855 (1971). Retrieved on [[2008-02-29]]</ref>
In 1990, a team led by Kratz at LBNL definitively discovered the new isotope <sup>263</sup>Db in the 4n neutron evaporation channel.<ref>[http://prola.aps.org/abstract/PRC/v45/i3/p1064_1 "New nuclide <sup>263</sup>Ha"], '''Kratz et al.''', ''Phys. Rev. C'', 45, 1064 - 1069 (1992). Retrieved on [[2008-02-29]] </ref>
This reaction has been used by the same team on several occasions in order to attempt to confirm an electron capture (EC) branch in <sup>263</sup>Db leading to long-lived <sup>263</sup>Rf (see [[rutherfordium]]).<ref>http://www.ulrich-rieth.de/publikationen/RCA0301_059.PDF (EC of 263Db)</ref>

===<sup>249</sup>Bk(<sup>16</sup>O,xn)<sup>265-x</sup>Db (x=4)===
Following from the discovery of <sup>260</sup>Db by Albert Ghiorso in 1970 at the University of California (UC), the same team continued in 1971 with the discovery of the new isotope <sup>261</sup>Db.<ref name=71Gh01/>

===<sup>250</sup>Cf(<sup>15</sup>N,xn)<sup>265-x</sup>Db (x=4)===
Following from the discovery of <sup>260</sup>Db by Ghiorso in 1970 at LBNL, the same team continued in 1971 with the discovery of the new isotope <sup>261</sup>Db.<ref name=71Gh01/>

===<sup>249</sup>Cf(<sup>15</sup>N,xn)<sup>264-x</sup>Db (x=4)===
In 1970, the team at the Lawrence Berkeley National Laboratory (LBNL) studied this reaction and identified the isotope <sup>260</sup>105 in their discovery experiment. They used the modern technique of correlation of genetic parent-daughter decays to confirm their assignment.<ref>[http://prola.aps.org/abstract/PRL/v24/i26/p1498_1 "New Element Hahnium, Atomic Number 105"], '''Ghiorso et al'''., ''Phys. Rev. Lett.'' 24, 1498 - 1503 (1970). Retrieved on [[2008-02-29]]</ref>
In 1977, the team at Oak Ridge repeated the experiment and were able to confirm the discovery by the identification of K X-rays from the daughter [[lawrencium]].<ref>[http://prola.aps.org/abstract/PRC/v16/i3/p1146_1 "Production, L x-ray identification, and decay of the nuclide <sup>260</sup>105"], '''Bemis et al'''., ''Phys. Rev. C'', 16, 1146 - 1158 (1977).Retrieved on [[2008-02-29]]</ref>

===<sup>254</sup>Es(<sup>13</sup>C,xn)<sup>267-x</sup>Db===
In 1988, scientists as the Lawrence Livermore National Laboratory (LLNL) used the asymmetric hot fusion reaction with an einsteinium-254 target to search for the new nuclides <sup>264</sup>Db and <sup>263</sup>Db. Due to the low sensitivity of the experiment caused by the small Es-254 target,they were unable to detect any evaporation residues (ER).

==Synthesis of isotopes as decay products==
Isotopes of dubnium have also been identified in the decay of heavier elements. Observations to date are summarised in the table below:

{| class="wikitable"
|-
! Evaporation Residue
! Observed Db isotope
|-
| <sup>288</sup>115 
| <sup>268</sup>Db
|-
| <sup>287</sup>115 
| <sup>267</sup>Db
|-
| <sup>282</sup>113 
| <sup>266</sup>Db
|-
| <sup>267</sup>Bh  
| <sup>263</sup>Db
|-
| <sup>278</sup>113, <sup>266</sup>Bh  
| <sup>262</sup>Db
|-
| <sup>265</sup>Bh 
| <sup>261</sup>Db
|-
| <sup>272</sup>Rg 
| <sup>260</sup>Db
|-
| <sup>266</sup>Mt, <sup>262</sup>Bh 
| <sup>258</sup>Db
|-
| <sup>261</sup>Bh 
| <sup>257</sup>Db
|-
| <sup>260</sup>Bh 
| <sup>256</sup>Db
|}

==Chronology of isotope discovery==

{| class="wikitable"
|-
! Isotope
! Year discovered
! discovery reaction
|-
| <sup>256</sup>Db
| 1983?, 2000
| <sup>209</sup>Bi(<sup>50</sup>Ti,3n)
|-
| <sup>257</sup>Db<sup>g</sup>
| 1985
| <sup>209</sup>Bi(<sup>50</sup>Ti,2n)
|-
| <sup>257</sup>Db<sup>m</sup>
| 2000
| <sup>209</sup>Bi(<sup>50</sup>Ti,2n)
|-
| <sup>258</sup>Db
| 1976?, 1981
| <sup>209</sup>Bi(<sup>50</sup>Ti,n)
|-
| <sup>259</sup>Db
| 2001
| <sup>241</sup>Am(<sup>22</sup>Ne,4n)
|-
| <sup>260</sup>Db
| 1970
| <sup>249</sup>Cf(<sup>15</sup>N,4n)
|-
| <sup>261</sup>Db
| 1971
| <sup>249</sup>Bk(<sup>16</sup>O,4n)
|-
| <sup>262</sup>Db
| 1971
| <sup>249</sup>Bk(<sup>18</sup>O,5n)
|-
| <sup>263</sup>Db
| 1971?, 1990
| <sup>249</sup>Bk(<sup>18</sup>O,4n)
|-
| <sup>264</sup>Db
| unknown
| 
|-
| <sup>265</sup>Db
| unknown
| 
|-
| <sup>266</sup>Db
| 2006
| <sup>237</sup>Np(<sup>48</sup>Ca,3n)
|-
| <sup>267</sup>Db
| 2003
| <sup>243</sup>Am(<sup>48Ca</sup>Ca,4n)
|-
| <sup>268</sup>Db
| 2003
| <sup>243</sup>Am(<sup>48</sup>Ca,3n)
|}

==Isomerism in dubnium nuclides==
===<sup>260</sup>Db===
Recent data on the decay of <sup>272</sup>Rg has revealed that some decay chains continue through <sup>260</sup>Db with extraordinary longer life-times than expected. These decays have been linked to an isomeric level decaying by alpha decay with a half-life of ~19 s. Further research is required to allow a definite assignment.

===<sup>258</sup>Db===
Evidence for an isomeric state in <sup>258</sup>Db has been gathered from the study of the decay of <sup>266</sup>Mt and <sup>262</sup>Bh. It has been noted that those decays assigned to an electron capture (EC) branch has a significantly different half-life to those decaying by alpha emission. This has been taken to suggest the existence of an isomeric state decaying by EC with a half-life of ~20 s. Further experiments are required to confirm this assignment.

===<sup>257</sup>Db===
A study of the formation and decay of <sup>257</sup>Db has proved the existence of an isomeric state. Initially, <sup>257</sup>Db was taken to decay by alpha emission with energies 9.16,9.07 and 8.97 MeV. A measurement of the correlations of these decays with those of <sup>253</sup>Lr have shown that the 9.16 MeV decay belongs to a separate isomer. Analysis of the data in conjunction with theory have assigned this activity to a meta stable state, <sup>257m</sup>Db. The ground state decays by alpha emission with energies 9.07 and 8.97 MeV. Spontaneous fission of <sup>257m,g</sup>Db was not confirmed in recent experiments.

==Spectroscopic decay level schemes for dubnium isotopes==
===<sup>257</sup>Db===

[[Image:257Db decay scheme.png|thumb|325px|none|The is the currently suggested decay level scheme for <sup>257</sup>Db<sup>g,m</sup> from the study performed in 2001 by Hessberger et al. at GSI]]

==Retracted isotopes==
===<sup>255</sup>Db===
In 1983, scientists at [[Dubna]] carried out a series of supportive experiments in their quest for the discovery of [[element 107]]. In two such experiments, they claimed they had detected a ~1.5 s [[spontaneous fission]] activity from the reactions <sup>207</sup>Pb(<sup>51</sup>V,xn) and <sup>209</sup>Bi(<sup>48</sup>Ti,xn). The activity was assigned to <sup>255</sup>Db. Later research suggested that the assignment should be changed to <sup>256</sup>Db. As such, the isotope <sup>255</sup>Db is currently not recognised on the chart of radionuclides and further research is required to confirm this isotope.

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

{| class="wikitable"
|-
! Projectile
! Target
! CN
! 1n 
! 2n
! 3n
|-
| <sup>51</sup>V
| <sup>208</sup>Pb
| <sup>259</sup>Db
| '''1.54 nb, 15.6 MeV'''
| '''1.8 nb, 23.7 MeV'''
|
|-
| <sup>50</sup>Ti 
| <sup>209</sup>Bi
| <sup>259</sup>Db
| '''4.64 nb, 16.4 MeV'''
| '''2.4 nb, 22.3 MeV'''
| 200 pb, 31.0 MeV
|-
|}

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

{| class="wikitable"
|-
! Projectile
! Target
! CN
! 3n 
! 4n
! 5n
|-
| <sup>27</sup>Al
| <sup>238</sup>U
| <sup>265</sup>Db
| 
| +
| +
|-
| <sup>22</sup>Ne 
| <sup>241</sup>Am
| <sup>263</sup>Db
| 
| 1.6 nb
| 3.6 nb
|-
| <sup>22</sup>Ne
| <sup>243</sup>Am
| <sup>265</sup>Db
| 
| +
| +
|-
| <sup>19</sup>F
| <sup>248</sup>Cm
| <sup>267</sup>Db
| 
| 
| 1.0 nb
|-
| <sup>18</sup>O
| <sup>249</sup>Bk
| <sup>267</sup>Db
| 
| 10.0 nb
| 6.0 nb
|}
 web..
-->
== Rujukan ==
{{reflist|2}}

== Pranala njaba ==
{{Commons|Dubnium}}
* [http://www.webelements.com/webelements/elements/text/Db/index.html WebElements.com - Dubnium]
{{clear}}
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