Editing Dubnium (section)

=== Reports ===
[[File:Transactinide chemistry apparatus Dubna.jpg|thumb|left|Apparatus at Dubna used for the chemical characterization of elements [[rutherfordium|104]], 105, and [[seaborgium|106]]<ref name="Zvara">{{cite journal|first = I. J.|last = Zvara|date = 2003|title = Dubnium|journal = Chemical and Engineering News|url = http://pubs.acs.org/cen/80th/dubnium.html|volume = 81|issue = 36|page = 182|doi = 10.1021/cen-v081n036.p182|access-date = October 9, 2017|archive-date = December 31, 2017|archive-url = https://web.archive.org/web/20171231000415/http://pubs.acs.org/cen/80th/dubnium.html|url-status = live}}</ref>]]
The first report of the [[discovery of the chemical elements|discovery of element 105]] came from the [[Joint Institute for Nuclear Research]] (JINR) in [[Dubna]], [[Moscow Oblast]], [[Soviet Union]], in April 1968. The scientists bombarded [[americium-243|<sup>243</sup>Am]] with a beam of [[neon-22|<sup>22</sup>Ne]] ions, and reported 9.4&nbsp;MeV (with a half-life of 0.1–3 seconds) and 9.7&nbsp;MeV (''t''<sub>1/2</sub>&nbsp;>&nbsp;0.05&nbsp;s) [[alpha decay|alpha activities]] followed by alpha activities similar to those of either <sup>256</sup>103 or <sup>257</sup>103. Based on prior theoretical predictions, the two activity lines were assigned to <sup>261</sup>105 and <sup>260</sup>105, respectively.<ref name="1993 report" />

:{{nuclide|americium|243}} + {{nuclide|neon|22}} → <sup>265−''x''</sup>105 + ''x'' {{SubatomicParticle|neutron}} (''x'' = 4, 5)

After observing the alpha decays of element 105, the researchers aimed to observe [[spontaneous fission]] (SF) of the element and study the resulting fission fragments. They published a paper in February 1970, reporting multiple examples of two such activities, with half-lives of 14&nbsp;ms and {{val|2.2|0.5|u=s}}. They assigned the former activity to <sup>242mf</sup>Am{{efn|This notation signifies that the nucleus is a [[nuclear isomer]] that decays via spontaneous fission.}} and ascribed the latter activity to an isotope of element 105. They suggested that it was unlikely that this activity could come from a transfer reaction instead of element 105, because the yield ratio for this reaction was significantly lower than that of the <sup>242mf</sup>Am-producing transfer reaction, in accordance with theoretical predictions. To establish that this activity was not from a (<sup>22</sup>Ne,''x''n) reaction, the researchers bombarded a <sup>243</sup>Am target with <sup>18</sup>O ions; reactions producing <sup>256</sup>103 and <sup>257</sup>103 showed very little SF activity (matching the established data), and the reaction producing heavier <sup>258</sup>103 and <sup>259</sup>103 produced no SF activity at all, in line with theoretical data. The researchers concluded that the activities observed came from SF of element 105.<ref name="1993 report" />

In April 1970, a team at [[Lawrence Berkeley National Laboratory|Lawrence Berkeley Laboratory]] (LBL), in [[Berkeley, California|Berkeley]], [[California]], United States, claimed to have synthesized element 105 by bombarding [[californium-249]] with [[nitrogen-15]] ions, with an alpha activity of 9.1&nbsp;MeV. To ensure this activity was not from a different reaction, the team attempted other reactions: bombarding <sup>249</sup>Cf with <sup>14</sup>N, Pb with <sup>15</sup>N, and Hg with <sup>15</sup>N. They stated no such activity was found in those reactions. The characteristics of the daughter nuclei matched those of <sup>256</sup>103, implying that the parent nuclei were of <sup>260</sup>105.<ref name="1993 report" />

:{{nuclide|californium|249}} + {{nuclide|nitrogen|15}} → <sup>260</sup>105 + 4 {{SubatomicParticle|neutron}}

These results did not confirm the JINR findings regarding the 9.4&nbsp;MeV or 9.7&nbsp;MeV alpha decay of <sup>260</sup>105, leaving only <sup>261</sup>105 as a possibly produced isotope.<ref name="1993 report" />

JINR then attempted another experiment to create element 105, published in a report in May 1970. They claimed that they had synthesized more nuclei of element 105 and that the experiment confirmed their previous work. According to the paper, the isotope produced by JINR was probably <sup>261</sup>105, or possibly <sup>260</sup>105.<ref name="1993 report" /> This report included an initial chemical examination: the thermal gradient version of the gas-chromatography method was applied to demonstrate that the chloride of what had formed from the SF activity nearly matched that of [[Niobium(V) chloride|niobium pentachloride]], rather than [[hafnium tetrachloride]]. The team identified a 2.2-second SF activity in a volatile chloride portraying eka-tantalum properties, and inferred that the source of the SF activity must have been element 105.<ref name="1993 report" />

In June 1970, JINR made improvements on their first experiment, using a purer target and reducing the intensity of transfer reactions by installing a [[collimator]] before the catcher. This time, they were able to find 9.1&nbsp;MeV alpha activities with daughter isotopes identifiable as either <sup>256</sup>103 or <sup>257</sup>103, implying that the original isotope was either <sup>260</sup>105 or <sup>261</sup>105.<ref name="1993 report" />