Dynamic Role of the Correlation Effect Revealed in the Exceptionally Slow Autodetachment Rates of the Vibrational Feshbach Resonances in the Dipole-Bound State

Abstract

Real-time autodetachment dynamics of the loosely-bound excess electron from the vibrational Feshbach resonances of the dipole-bound states (DBS) of 4-bromophonoxide (4-BrPhO-) and 4-chlorophenoxide (4-ClPhO-) anions have been thoroughly investigated. The state-specific autodetachment rate measurements obtained by the picosecond time-resolved pump-probe method on the cryogenically cooled anions, exhibit the exceptionally long lifetime (τ) of ~ 2.5  0.6 ns (as the upper bound) for the 11’1 vibrational mode of the 4-BrPhO- DBS. Strong mode-dependency in the wide dynamic range has also been found, giving τ ~ 5.3 ps for the 10’1 mode, for instance. Though it is nontrivial to get the state-specific rates for the 4-ClPhO- DBS, the average autodetachment lifetime of the 19’120’1/11’1 mode has been estimated to be ~ 548  108 ps. Observation of these exceptionally slow autodetachment rates of vibrational Feshbach resonances strongly indicates that the ‘correlation effect’ may play a significant role in the DBS photodetachment dynamics. The Fermi’s golden rule has been invoked so that the correlation effect is taken into account in the form of the interaction between the charge and the induced dipole where the latter is given by the polarizable counterparts of the electron-rich halogenated compound and the diffuse non-valence electron. This report suggests that one may measure, from the real-time autodetachment dynamics, the extent of the correlation effect contribution to the stabilization and/or dynamics of the excess non-valence electron among many different types of the long-range interactions of the DBS.