Detailed photonuclear crosssection calculations and astrophysical applications
Abstract
We have investigated the role of an isomeric state and its coupling to the ground state (g.s.) via photons and neutron inelastic scattering in a stellar environment by making detailed photonuclear and neutron crosssection calculations for (176)Lu and (210)Bi. In the case of (176)Lu, the g.s. would function as an excellent galactic slow (s) process chronometer were it not for the 3.7h isomer at 123 KeV. Our calculations predicted much larger photon cross sections for production of the isomer, as well as a lower threshold, than had been assumed based on earlier measurements. These two factors combine to indicate that an enormous correction, a factor of 10(7), must be applied to shorten the current estimate of the halflife against photoexcitation of (176)Lu as a function of temperature. This severely limits the use of (176)Lu as a stellar chronometer and indicates a significantly lower temperature at which the two states reach thermal equilibrium. For (210)Bi, our preliminary calculations of the production and destruction of the 3 times 10(6) y isomeric state by neutrons and photons suggest that the (210)Bi isomer may not be destroyed by photons as rapidly as assumed in certain stellar environments. This leads to an alternate production path of (207)Pb and significantly affects presently interpreted lead isotopic abundances.
 Publication:

Presented at the WEIN '89: International Symposium on Weak and Electromagnetic Interactions in Nuclei
 Pub Date:
 June 1989
 Bibcode:
 1989wwei.symp...15G
 Keywords:

 Astrophysics;
 Inelastic Scattering;
 Nuclei (Nuclear Physics);
 Photonuclear Reactions;
 Bismuth Isotopes;
 Computation;
 Ground State;
 Lutetium Isotopes;
 Temperature Dependence;
 Astrophysics