Photo-disintegration cross section measurements on ${}^{186}$W, ${}^{187}$Re and ${}^{188}$Os: Implications for the Re-Os cosmochronology

Abstract

Cross sections of the ${}^{186}$W, ${}^{187}$Re, ${}^{188}$Os($\gamma ,n$) reactions were measured using quasi-monochromatic photon beams from laser Compton scattering (LCS) with average energies from 7.3 to 10.9 MeV. The results are compared with the predictions of Hauser-Feshbach statistical calculations using four different sets of input parameters. In addition, the inverse neutron capture cross sections were evaluated by constraining the model parameters, especially the $E1$ strength function, on the basis of the experimental data. The present experiment helps to further constrain the correction factor $F_{\sigma }$ for the neutron capture on the 9.75 keV state in ${}^{187}$Os. Implications of $F_{\sigma }$ to the Re-Os cosmochronology are discussed with a focus on the uncertainty in the estimate of the age of the Galaxy.

11 pages