First excited state of thes-process branching nucleusZr95

Abstract

The transfer reaction 94 Zr͑d,p͒ 95 Zr has been studied to check the existence of a low-lying first excited level at 23 keV in 95 Zr. This level-if it exists-might have significant influence on the branching of the astrophysical s process at the branching nucleus 95 Zr. Our experimental spectra, measured with very good energy resolution, do not show any evidence for the existence of such a low-lying level. This is in agreement with experimental results from several reactions and contradicts the only claim for evidence of such a low-lying level which was also derived from 94 Zr͑d,p͒ 95 Zr data, however with moderate resolution, but still the best of the previous experiments.

Stellar enhancement factors in a parity dependent approach

“…The change can reach up to 5% for temperatures higher than 30 keV. However this is only due to the first excited state at a small excitation energy in 95 Zr, whose existence is questionable [7]. If we remove this state in our calculations the SEF do not change from unity.…”

The (n,γ) cross sections of short-living s-process branching points

“…Another reason for the deviation between the measured and predicted abundance patterns might be the uncertainty in the half-life T 1/2 of 95 Zr at s-process temperatures. However, as confirmed by a recent measurement [17] the first excited level is at E = 954 keV and thus, is not significantly populated at kT = 30 keV. Hence, the half-life of 95 Zr does not depend on temperature under s-process conditions and can be omitted as an error source because of its small error: T 1/2 ( 95 Zr) = (64.032 ± 0.006) d [18].…”

The 95Zr(n, γ)96Zr Cross Section from the Surrogate Ratio Method and Its Effect on s-process Nucleosynthesis

“…Thus, the stellar enhancement factor remains very close to unity, and the ground state contribution to the astrophysical rate is almost 100% (Rauscher et al 2011). A suggested candidate for a very low-lying excited state in 95 Zr at 23 keV has been definitely excluded by a high-resolution 94 Zr(d,p) 95 Zr experiment (Sonnabend et al 2003).…”