Nonorthonormal CI for molecular excited states. I. The sudden polarization effect in 90° twisted ethylene

Sudden polarization and zwitterion formation as a pseudo-Jahn–Teller effect: a new insight into the photochemistry of alkenes

We show that the intermediates of photochemical reactions—sudden polarization and zwitterion formations—are consequences of the pseudo-Jahn–Teller effect (PJTE), which facilitates a better understanding, rationalization, prediction, and manipulation of the corresponding chemical and biological processes.

Nonadiabatic photodynamics and UV absorption spectrum of all-trans-octatetraene

The short-time molecular quantum dynamics of all-trans-octatetraene after electronic excitation to the first bright valence state is theoretically investigated.

Electronic Structure and Spectroscopic Properties of the Two Structural Isomers of Donor−Acceptor Substituted Sesquifulvalene in the Gas and Solution PhasesA Case Study of Sudden Polarization

The ground state equilibrium structure and electric properties of two structural isomers of donor-acceptor substituted sesquifulvalene have been calculated at ab initio HF and MP2 levels for different conformations. The electronic properties of low lying excited singlets are calculated by using CI calculations including single excitations only. Isomer I in which the inter-ring charge transfer (CT) is reinforced in the presence of substituents shows sudden polarization in the ground and two lower lying excited states, while isomer II in which the longitudinal CT interaction is attenuated does not exhibit sudden polarization. The phenomenon of sudden polarization has been rationalized in terms of the easy polarization, smaller rotational barrier, and enhanced inter-ring CT on going from the planar to the orthogonal geometry. The appreciably large static second-order polarizability of I stems from its sudden polarized ground state. The solvent (using the conductor-like polarizable continuum model (CPCM)) plays a significant role on the modulation of ground and excited state electronic properties which, in general, predicts blue-shifts for I. However, for molecule II, the two lower energy transitions show a red-shift while the others show a weaker blue-shift at any conformation.