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Nuclear Data Sheets for A = 93

Nuclear structure data pertaining to all nuclei with mass number A=93 (Se, Br, Kr, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag) have been compiled and evaluated and incorporated into the ENSDF data file. This publication for A=93 supersedes the previous publication by C.M. Baglin, Nuclear Data Sheets80, 1 (1997) (literature cutoff date November 1996) and subsequent revisions by C.M. Baglin of the ENSDF files for 93Br and {sup 93}Kr (literature cutoff 26 February 2001) and for {sup 93}Rh (literature cutoff 27 February 2001); it includes all data available prior to 15 December 2010. Significant changes since prior evaluations include the following: 2010Hw03 identified several high-spin states in {sup 93}Kr in {sup 252}Cf SF decay; in addition to the many low-spin levels already known in {sup 93}Rb from {beta}{sup -} decay, several higher-spin states have now been identified in a {sup 252}Cf SF decay study (2009Hw03); this SF decay has also been used to identify additional states in {sup 93}Sr (2003Hw01) and the {sup 238}U({sup 82}Se,X{gamma}) reaction (2007Bu35) has provided new information on {sup 93}Y. (HI,xn{gamma}) reaction studies have expanded our knowledge of the structure of {sup 93}Zr (2002Fo03, 2005Pa48), {sup 93}Nb (2007Wa45), {sup 93}Mo (2005Fu01), {sup 93}Tc (2003Ha22) and {sup 93}Pd (2004So04,2004Ru02). Considerable information on {sup 93}Nb was provided by a (p,2n{gamma}) study (2010Or01, 2006Or09, 2007Or01). The level schemes of {sup 93}Ru, {sup 93}Rh and {sup 93}Pd have undergone the most extensive revision thanks to studies of {sup 93}Rh {epsilon} decay (2004De40), {sup 94}Ag {epsilon}p decay (2004Mu30) and {sup 94}Ag p decay (2005Mu15, 2005Mu30), respectively. The half-life of the Zr member of this chain is of particular interest because of {sup 93}Zr's large contribution to long-term activity of nuclear reactor waste and also due to its potential as a supernova chronometer. During 2010, two new well-documented measurements of T{sub 1/2}({sup 93}Zr) were published (2010Ya01 and 2010Ca01); one agrees well with an earlier, undocumented measurement but, unfortunately, the other is many standard deviations lower for reasons which are not immediately apparent.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

No Evidence of Isomerism for the First Excited State of {sup 93}Rb

The 253.3–keV excited state located in {sup 93}Rb was studied at the Holifield Radioactive Ion Beam Facility in Oak Ridge. This state, described as isomeric in databases, was populated in the decay of {sup 93}Kr produced by proton–induced fission of {sup 238}U and isolated using the isotope separation on–line technique. We report that the 253.3–keV level does not reveal isomerism and the upper limit of the half-life from our measurement is 4 ns. Our findings are supported by previously reported results that were not taken into account in the latest nuclear databases.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Interstellar carbon in meteorites

The Murchison and Allende chondrites contain up to 5 parts per million carbon that is enriched in carbon-13 by up to +1100 per mil (the ratio of carbon-12 to carbon-13 is approximately 42, compared to 88 to 93 for terrestrial carbon). This 'heavy' carbon is associated with neon-22 and with anomalous krypton and xenon showing the signature of the s-process (neutron capture on a slow time scale). It apparently represents interstellar grains ejected from late-type stars. A second anomalous xenon component ('CCFXe') is associated with a distinctive, light carbon (depleted in carbon-13 by 38 per mil), which, however, falls within the terrestrial range and hence may be of either local or exotic origin.

Swart, P. K.↗

Role of angular momentum in the production of complex fragments in fusion and quasifission reactions

The influence of angular momentum on the competition between complete fusion followed by the decay of compound nucleus and quasifission channels is treated within the dinuclear system model. The charge distributions of the products in the reactions {sup 28}Si+{sup 96}Zr, {sup 4}He+{sup 130}Te, and {sup 40}Ca+{sup 82}Kr are predicted at bombarding energies above the Coulomb barrier. The results of calculations for the reactions {sup 93}Nb+{sup 9}Be,{sup 12}C,{sup 27}Al; {sup 84}Kr+{sup 27}Al; {sup 86}Kr+{sup 63}Cu; {sup 139}La+{sup 12}C,{sup 27}Al; and {sup 45}Sc+{sup 65}Cu are compared with the available experimental data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗