Fully quantal description of combined internal conversion and intersystem crossing processes in the smallest Criegee intermediate CHOO.

A quantal description of nuclear motion using coupled fifteen-state potential energy and spin-orbit coupling surfaces for studying the photodissociation of CHOO to HCO(XA) + OD and HCO(XA) + OP channels is presented. For the evaluation of surfaces, multireference electronic wave functions are employed. For the fully quantal description of the nuclear motion, we diabatize the PESs of the two and four lowest excited singlet and triplet states, respectively, within the three sets of vibronically coupled states, (BA', CA'), (aA', bA') and (aA'', bA''), employing the diabatization by ansatz method.

On the Fluorescence Properties and Nonradiative Transitions in Medium-Sized All-Trans Polyenes.

The nonadiabatic photodynamics of all-trans linear polyenes with = 4-8 conjugated double bonds is studied from an electronic structure perspective. Excitation energies and stationary points for the 1 and 2 singlet states have been computed by using the state-average complete active space (SA-CASSCF) method and its second-order perturbation theory variant (MS-CASPT2). The dependence of the two low-lying excited states on the "chain length" has been elucidated.

Photodissociation dynamics and UV absorption spectrum of acetone oxide (CH)COO.

The photodynamics and BA' ← XA' absorption spectrum of acetone oxide, (CH)COO, are studied theoretically from first principles. The underlying adiabatic potential energy curves (and surfaces) are computed by a second-order multireference perturbation theory method and diabatized using a diabatization by ansatz scheme. To confirm the results, for selected geometries EOM-CCSD and XMS-RS2C calculations were also performed.

Vibronic coupling in the ground and excited states of the imidazole radical cation.

Vibronic interactions in the ground and two excited states of the imidazole radical cation, XA″ (π), AA' (nσ), and BA″ (π), and the associated nuclear dynamics were studied theoretically. The results were used to interpret the recent photoelectron measurements [M. Patanen et al.

Correlated quantum treatment of the photodissociation dynamics of formaldehyde oxide CHOO.

An extended theoretical analysis of the photodissociation of the smallest Criegee intermediate CHOO following excitation to the B state is presented. It relies on explicitly correlated multireference electronic wavefunctions combined with a quantum dynamical treatment for two interacting (B-C) electronic states and three coupled nuclear degrees of freedom. The 3D model relies on PESs along the O-O and C-O stretching as well as C-O-O bending modes for the two lowest excited states with ' symmetry, and is sufficiently accurate to reproduce the experimental BA'-XA' absorption spectrum, especially at the low-energy range to unprecedented accuracy.