Experimentally constrained ${}^{165,166}\text{Ho}(n,{\hat{I}}^3)$ rates and implications for the $s$ process

Abstract

The ${\hat{I}}^3$-ray strength function and the nuclear level density of ${}^{167}$Ho have been extracted using the Oslo method from a ${}^{164}\text{Dy}(\hat{I}\pm ,p{\hat{I}}^3{)}^{167}$Ho experiment carried out at the Oslo Cyclotron Laboratory. The level density displays a shape that is compatible with %can be approximated with the constant temperature model in the quasicontinuum, while the strength function shows structures indicating the presence of both a scissors and a pygmy dipole resonance. Using our present results as well as data from a previous ${}^{163}\text{Dy}(\hat{I}\pm ,p{\hat{I}}^3{)}^{166}$Ho experiment, the ${}^{165}\text{Ho}(n,{\hat{I}}^3)$ and ${}^{166}\text{Ho}(n,{\hat{I}}^3)$ MACS uncertainties have been constrained. The possible influence of the low-lying, long-lived 6~keV isomer ${}^{166}$Ho in the $s$ process is investigated in the context of a 2~$M_{\odot }$, [Fe/H]=-0.5 AGB star. We show that the newly obtained ${}^{165}\text{Ho}(n,{\hat{I}}^3)$ MACS affects the final ${}^{165}$Ho abundance, while the ${}^{166}\text{Ho}(n,{\hat{I}}^3)$ MACS only impacts the enrichment of ${}^{166,167}$Er to a limited degree due to the relatively rapid ${\hat{I}}^2$ decay of the thermalized ${}^{166}$Ho at typical $s$-process temperatures.

11 pages, submitted to Physical Reviews C