Fri·Jul 22, 2011Friday·July 22, 2011

1. 01*

   Solar Influence on Nuclear Decay Rates: Constraints from the MESSENGER Mission

   Ephraim Fischbach🇺🇸 · K. Joseph Chen · Robert E. Gold · John O. Goldsten · David J. Lawrence🇺🇸 · Ralph J. McNutt Jr. · Edgar A. Rhodes · Jere H. Jenkins🇺🇸 · James M. Longuski

   We have analyzed Cs-137 decay data, obtained from a small sample onboard the MESSENGER spacecraft en route to Mercury, with the aim of setting limits on a possible correlation between nuclear decay rates and solar activity. Such a correlation has been suggested recently on the basis of data from Mn-54 decay during the solar flare of 13 December 2006, and by indications of an annual and other periodic variations in the decay rates of Si-32, Cl-36, and Ra-226. Data from five measurements of the Cs-137 count rate over a period of approximately 5.4 years have been fit to a formula which accounts for the usual exponential decrease in count rate over time, along with the addition of a theoretical solar contribution varying with MESSENGER-Sun separation. The indication of solar influence is then characterized by a non-zero value of the calculated parameter \xi, and we find \xi=(2.8+/-8.1)x10^{-3} for Cs-137. A simulation of the increased data that can hypothetically be expected following Mercury orbit insertion on 18 March 2011 suggests that the anticipated improvement in the determination of \xi could reveal a non-zero value of \xi if present at a level consistent with other data.

   ↳ astro-ph.SRnucl-exAstrophys.Space Sci.(2012)·3 citations
2. 02*

   Effects of density dependence of the effective pairing interaction on the first $2^{+}$ excitations and quadrupole moments of odd nuclei

   S. V. Tolokonnikov🇷🇺 · S. Kamerdzhiev🇷🇺 · D. Voytenkov🇷🇺 · S. Krewald🇩🇪 · E. E. Saperstein🇷🇺

   Excitation energies and transition probabilities of the first $2^{+}$ excitations in even tin and lead isotopes as well as the quadrupole moments of odd neighbors of these isotopes are calculated within the self-consistent Theory of Finite Fermi Systems based on the Energy Density Functional by Fayans et al. The effect of the density dependence of the effective pairing interaction is analyzed in detail by comparing results obtained with volume and surface pairing. The effect is found to be noticeable. For example, the $2^{+}$-energies are systematically higher at 200-300 keV for the volume paring as compared with the surface pairing case. But on the average both models reasonably agree with the data. Quadrupole moments of odd-neutron nuclei are very sensitive to the single-particle energy of the state $\lambda$ under consideration due to the Bogolyubov factor ($u_{\lambda }^2-v_{\lambda }^2$). A reasonable agreement with experiment for the quadrupole moments has been obtained for the most part of odd nuclei considered. The method used gives a reliable possibility to predict quadrupole moments of unstable odd nuclei including very neutron rich ones.

   ↳ nucl-thnucl-exPRC(2011)·46 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.