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Title: Survival of nature's rarest isotope {sup 180}Ta under stellar conditions

Abstract

The nucleosynthesis of nature's rarest isotope {sup 180}Ta depends sensitively on the temperature of the astrophysical environment because of depopulation of the long-living isomeric state via intermediate states to the short-living ground state by thermal photons. Reaction rates for this transition have been measured in the laboratory. These ground state rates underestimate the stellar rates dramatically because under stellar conditions intermediate states are mainly populated by excitations from thermally excited states in {sup 180m}Ta. Full thermalization of {sup 180}Ta is already achieved for typical s-process temperatures around kT=25 keV. Consequently, for the survival of {sup 180}Ta in the s-process fast convective mixing is required which has to transport freshly synthesized {sup 180}Ta to cooler regions. In supernova explosions {sup 180}Ta is synthesized by photon- or neutrino-induced reactions at temperatures above T{sub 9}=1 in thermal equilibrium; independent of the production mechanism, freeze-out from thermal equilibrium occurs at kT{approx_equal}40 keV, and only 35{+-}4% of the synthesized {sup 180}Ta survive in the isomeric state.

Authors:
 [1];  [2];  [3]
  1. Diakoniekrankenhaus Schwaebisch Hall, D-74523 Schwaebisch Hall (Germany)
  2. Forschungszentrum Karlsruhe, Institut fuer Kernphysik, P.O. Box 3640, D-76021 Karlsruhe (Germany)
  3. Dipartimento di Fisica Generale, Universita di Torino, Via P. Giuria 1, I-10125 Torino (Italy)
Publication Date:
OSTI Identifier:
20990928
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevC.75.012802; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; EXCITATION; EXCITED STATES; FREEZING OUT; GROUND STATES; KEV RANGE 10-100; MASS NUMBER; NEUTRINO-NUCLEON INTERACTIONS; NEUTRINOS; NUCLEOSYNTHESIS; PHOTON-NUCLEON INTERACTIONS; PHOTONS; PHOTONUCLEAR REACTIONS; REACTION KINETICS; S PROCESS; SUPERNOVAE; TANTALUM 180; THERMAL EQUILIBRIUM; THERMALIZATION

Citation Formats

Mohr, P., Kaeppeler, F., and Gallino, R. Survival of nature's rarest isotope {sup 180}Ta under stellar conditions. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.012802.
Mohr, P., Kaeppeler, F., & Gallino, R. Survival of nature's rarest isotope {sup 180}Ta under stellar conditions. United States. doi:10.1103/PHYSREVC.75.012802.
Mohr, P., Kaeppeler, F., and Gallino, R. Mon . "Survival of nature's rarest isotope {sup 180}Ta under stellar conditions". United States. doi:10.1103/PHYSREVC.75.012802.
@article{osti_20990928,
title = {Survival of nature's rarest isotope {sup 180}Ta under stellar conditions},
author = {Mohr, P. and Kaeppeler, F. and Gallino, R.},
abstractNote = {The nucleosynthesis of nature's rarest isotope {sup 180}Ta depends sensitively on the temperature of the astrophysical environment because of depopulation of the long-living isomeric state via intermediate states to the short-living ground state by thermal photons. Reaction rates for this transition have been measured in the laboratory. These ground state rates underestimate the stellar rates dramatically because under stellar conditions intermediate states are mainly populated by excitations from thermally excited states in {sup 180m}Ta. Full thermalization of {sup 180}Ta is already achieved for typical s-process temperatures around kT=25 keV. Consequently, for the survival of {sup 180}Ta in the s-process fast convective mixing is required which has to transport freshly synthesized {sup 180}Ta to cooler regions. In supernova explosions {sup 180}Ta is synthesized by photon- or neutrino-induced reactions at temperatures above T{sub 9}=1 in thermal equilibrium; independent of the production mechanism, freeze-out from thermal equilibrium occurs at kT{approx_equal}40 keV, and only 35{+-}4% of the synthesized {sup 180}Ta survive in the isomeric state.},
doi = {10.1103/PHYSREVC.75.012802},
journal = {Physical Review. C, Nuclear Physics},
number = 1,
volume = 75,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}