posted on 2023-11-16, 18:43authored byDo Hyung Kang, Kwang Hyun Cho, Jinwoo Kim, Han Jun Eun, Young Min Rhee, Sang Kyu Kim
The
nature of the electron-binding forces in the dipole-bound states
(DBS) of anions is interrogated through experimental and theoretical
means by investigating the autodetachment dynamics from DBS Feshbach
resonances of ortho-, meta-, and para-bromophenoxide (BrPhO–). Though the
charge-dipole electrostatic potential has been widely regarded to
be mainly responsible for the electron binding in DBS, the effect
of nonclassical electron correlation has been conceived to be quite
significant in terms of its static and/or dynamic contributions toward
the binding of the excess electron to the neutral core. State-specific
real-time autodetachment dynamics observed by picosecond time-resolved
photoelectron velocity-map imaging spectroscopy reveal that the autodetachment
processes from the DBS Feshbach resonances of BrPhO– anions cannot indeed be rationalized by the conventional charge-dipole
potential. Specifically, the autodetachment lifetime is drastically
lengthened depending on differently positioned Br-substitution, and
this rate change cannot be explained within the framework of Fermi’s
golden rule based on the charge-dipole assumption. High-level ab initio quantum chemical calculations with EOM-EA-CCSD,
which intrinsically takes into account electron correlations, generate
more reasonable predictions on the binding energies than density functional
theory (DFT) calculations, and semiclassical quantum dynamics simulations
based on the EOM-EA-CCSD data excellently predict the trend in the
autodetachment rates. These findings illustrate that static and dynamic
properties of the excess electron in the DBS are strongly influenced
by correlation interactions among electrons in the nonvalence orbital
of the dipole-bound electron and highly polarizable valence orbitals
of the bromine atom, which, in turn, dictate the interesting chemical
fate of exotic anion species.