Real-Time Autodetachment Dynamics of Vibrational Feshbach Resonances in a Dipole-Bound State
Do Hyung Kang, Sejun An, Sang Kyu Kim
Abstract
Feshbach resonances corresponding to metastable vibrational states of the dipole-bound state (DBS) have been interrogated in real time for the first time. The state-specific autodetachment rates of the DBS of the phenoxide anion in the cryogenically cooled ion trap have been directly measured, giving $\ensuremath{\tau}\ensuremath{\sim}33.5\text{ }\text{ }\mathrm{ps}$ for the lifetime of the most prominent ${11}^{\ensuremath{'}1}$ mode ($519\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$). Overall, the lifetime of the individual DBS state is strongly mode dependent to give $\ensuremath{\tau}\ensuremath{\sim}5\text{ }\text{ }\mathrm{ps}$ for the ${18}^{\ensuremath{'}1}$ mode ($632\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$) and $\ensuremath{\tau}\ensuremath{\sim}12\text{ }\text{ }\mathrm{ps}$ for the ${11}^{\ensuremath{'}2}$ mode ($1036\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$). The qualitative trend of the experiment could be successfully explained by the Fermi's golden rule. Autodetachment of the ${11}^{\ensuremath{'}1}{18}^{\ensuremath{'}1}$ combination mode is found to be much accelerated ($\ensuremath{\tau}\ensuremath{\le}1.4\text{ }\text{ }\mathrm{ps}$) than expected, and its bifurcation dynamics into either the ${11}^{1}{18}^{0}$ or ${11}^{0}{18}^{1}$ state of the neutral core radical, according to the propensity rule of $\mathrm{\ensuremath{\Delta}}v=\ensuremath{-}1$, could be distinctly differentiated through the photoelectron images to provide the unprecedented deep insights into the interaction between electronic and nuclear dynamics of the DBS, challenging the most sophisticated theoretical calculations.