LAUSR

We report experimental studies of atom-ion collisions in the thermal regime (several hundred Kelvin) using trapped ytterbium (Yb$^+$) ions immersed in potassium (K) vapor. Various collisional rate coefficients of the Yb$^+$ ion per K-atom number density are measured. We find the isotopically dependent charge-exchange rate coefficients to be $\kappa_{\rm ce}=(12.7\pm0.8)\times10^{-14}$ cm$^3$s$^{-1}$ and $\kappa_{\rm ce}=(5.3\pm0.3)\times10^{-14}$ cm$^3$s$^{-1}$ for K-$^{171}$Yb$^+$ and K-$^{172}$Yb$^+$ respectively. The spin-destruction rate coefficient is $\kappa_{\rm sd}=(1.46\pm0.29)\times10^{-9}$ cm$^3$s$^{-1}$, and the spin-exchange rate coefficient is $\kappa_{\rm se}=(1.64\pm0.24)\times10^{-9}$ cm$^3$s$^{-1}$. Both spin-dependent coefficients do not show isotopic dependence. Unlike alkali-alkali atomic systems that normally have $\kappa_{\rm se}\gg\kappa_{\rm sd}$, we find this thermal atom-ion system has $\kappa_{\rm se}\sim\kappa_{\rm sd}$, which is not fully understood in theory. Similar results have also been reported previously from other cold atom-ion hybrid systems. We believe it is important to understand the collisional physics with different atom-ion combinations for developing various atomic hybrid platforms.