Experimentally constrained 165,166Ho(n, & gamma;) rates and implications for the s process

The & gamma;-ray strength function and the nuclear level density of 167Ho have been extracted using the Oslo method from a 164Dy(& alpha;, p & gamma; )167Ho experiment carried out at the Oslo Cyclotron Laboratory. The level density displays a shape that is compatible with the constant temperature model in the quasicontinuum, while the strength function shows structures indicating the presence of both a scissors resonance and a pygmy dipole resonance. Using our present results as well as data from a previous 163Dy(& alpha;, p & gamma;)166Ho experiment, the 165Ho(n, & gamma;) and 166Ho(n, & gamma;) eellian-averaged cross section (MACS) uncertainties have been constrained. The possible influence of the low-lying, long-lived 6 keV isomer 166Ho in the s process is investigated in the context of a 2M0, [Fe/H] = -0.5 asymptotic giant branch star. We show that the newly obtained 165Ho(n, & gamma;) MACS affects the final 165Ho abundance, while the 166Ho(n, & gamma;) MACS only impacts the enrichment of 166,167Er to a limited degree due to the relatively rapid & beta; decay of the thermalized 166Ho at typical s-process temperatures.