Description
تفصیل
Bohrium is a chemical element with the symbol Bh and atomic number 107 and is the heaviest member of group 7 (VIIB).
It is a synthetic element whose most stable known isotope, 270Bh, has a half-life of 61 seconds. Chemical experiments have confirmed bohrium's predicted position as a heavier homologue to rhenium with the formation of a stable +7 oxidation state.
The first convincing synthesis was in 1981 by a German research team led by Peter Armbruster and Gottfried Münzenberg at the Gesellschaft für Schwerionenforschung (Institute for Heavy Ion Research, GSI) in Darmstadt using the Dubna reaction.
209
83Bi + 54
24Cr → 262
107Bh + n
A total of eleven isotopes of bohrium have been characterized. The proton-rich isotopes with masses 260, 261, and 262 were directly produced by cold fusion, those with mass 262 and 264 were reported in the chains of the elements 109 and 111, while the neutron-rich isotopes with masses 266, 267 were created in irradiations of actinide targets. The four most neutron-rich ones with masses 270, 271, 272, and 274 appear in decay chains of 282113, 287115, 288115, and 294117 respectively. These ten isotopes have half- lives ranging from 8 miliseconds to 0.9 minute, and all undergo alpha-decay.
References:
^ Johnson, E.; Fricke, B.; Jacob, T.; Dong, C. Z.; Fritzsche, S.; Pershina, V. (2002). "Ionization potentials and radii of neutral and ionized species of elements 107 (bohrium) and 108 (hassium) from extended multiconfiguration Dirac–Fock calculations". The Journal of Chemical Physics 116: 1862. doi:10.1063/1.1430256.
^ Oganessian, Yu. Ts.; Abdullin, F. Sh.; Bailey, P. D.; Benker, D. E.; Bennett, M. E.; Dmitriev, S. N.; Ezold, J. G.; Hamilton, J. H. et al. (2010). "Synthesis of a New Element with Atomic Number Z=117". Physical Review Letters 104. doi:10.1103/PhysRevLett.104.142502. PMID 20481935. (gives life-time of 1.3 min based on a single event; conversion to half-life is done by multiplying with ln(2).)
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^ Münzenberg, G.; Hofmann, S.; He�berger, F. P.; Reisdorf, W.; Schmidt, K. H.; Schneider, J. H. R.; Armbruster, P.; Sahm, C. C. et al. (1981). "Identification of element 107 by α correlation chains". Zeitschrift für Physik A 300: 107. Bibcode 1981ZPhyA.300..107M. doi:10.1007/BF01412623.
^ Münzenberg, G.; Armbruster, P.; Hofmann, S.; Heßberger, F. P.; Folger, H.; Keller, J. G.; Ninov, V.; Poppensieker, K. et al. (1989). "Element 107". Zeitschrift für Physik A 333 (2): 163. Bibcode 1989ZPhyA.333..163M. doi:10.1007/BF01565147.
^ "Entrance Channel Effects in the Production of 262,261Bh", Nelson et al., LBNL repositories 2005. Retrieved on 2008-03-04
^ Nelson, S.; Gregorich, K.; Dragojević, I.; Garcia, M.; Gates, J.; Sudowe, R.; Nitsche, H. (2008). "Lightest Isotope of Bh Produced via the Bi209(Cr52,n)Bh260 Reaction". Physical Review Letters 100 (2). Bibcode 2008PhRvL.100b2501N. doi:10.1103/PhysRevLett.100.022501.
^ Folden Iii, C. M. (2006). "Excitation function for the production of 262Bh (Z=107) in the odd-Z-projectile reaction 208Pb(55Mn, n)". Physical Review C 73: 014611. Bibcode 2006PhRvC..73a4611F. doi:10.1103/PhysRevC.73.014611.
^ "Excitation function for the production of 262Bh (Z=107) in the odd-Z-projectile reaction 208Pb(55Mn, n)", Folden et al., LBNL repositories, May 19, 2005. Retrieved on 2008 -02-29
^ Hot fusion studies at the BGS with light projectiles and 238U targets, J. M. Gates
^ Gan, Z.G.; Guo, J. S.; Wu, X. L.; Qin, Z.; Fan, H. M.; Lei, X. G.; Liu, H. Y.; Guo, B. et al. (2004). "New isotope 265Bh". The European Physical Journal A 20 (3): 385. Bibcode 2004EPJA...20..385G. doi:10.1140/epja/i2004-10020-2.
^ Morita, Kosuke; et al. (2009). "Decay Properties of 266Bh and 262Db Produced in the 248Cm + 23Na Reaction". Journal of the Physical Society of Japan 78 (6): 064201. arXiv:0904.1093. Bibcode 2009JPSJ...78f4201M. doi:10.1143/JPSJ.78.064201.
