Accurate ab initio near-equilibrium potential energy and dipole moment functions of the X 2B1 and first excited A22 electronic states of OClO and OBrO

Abstract

Using highly correlated multireference configuration interaction wave functions with large correlation consistent basis sets, three-dimensional near-equilibrium potential energy functions ͑PEFs͒ have been calculated for the X 2 B 1 and first excited 2 A 2 electronic states of the atmospherically important OClO and OBrO radicals. The analytical PEFs have been used in perturbational and variational calculations of the anharmonic spectroscopic constants and vibrational spectra of both species. Excellent agreement with the available experimental data are observed for both species and electronic states, e.g., the vibrational fundamental frequencies in the ground electronic states are reproduced to within about 5 cm Ϫ1. For the A 2 A 2 state of OClO, it is demonstrated that the anomolously strong intensity of the 3 mode in the UV absorption spectrum is due to strong anharmonic coupling between the stretching vibrations and not to a double minimum in the potential. Three-dimensional electric dipole moment functions have also been calculated for the ground electronic states of both species. These were used to calculate accurate absolute infrared absorption intensities for the fundamentals and low-lying overtones and combination bands of both species.

Global error control of the time-propagation for the Schrödinger equation with a time-dependent Hamiltonian

“…[30]) with a computational grid of size 128 × 128 × 64. Peterson [27] computed the electronic ground state and the first excited state of the ClO 2 molecule in a number of points and fitted the potential energies to a polynomial. We use these potential energies.…”

Understanding the Phase-Dependent Reactivity of Chlorine Dioxide Using Resonance Raman Spectroscopy

“…20 Ab initio results reported by Peterson and Werner were consistent with a single minimum along the asymmetric-stretch coordinate in support of the anharmonic-coupling model. 21,22 Consensus as to the nature of the 2 A 2 surface along the asymmetric-stretch coordinate has not been achieved; however, both models predict that substantial evolution along the asymmetric-stretch coordinate occurs following photoexcitation. This prediction raises the question, does evolution along the asymmetricstretch coordinate indeed occur upon photoexcitation?…”

Quadratic Corrections to Harmonic Vibrational Frequencies Outperform Linear Models

“…10 However, more extensive recent work has concluded that the negative (according to the sign convention adopted here) anharmonicity corrections arise from strong anharmonic coupling between symmetric and asymmetric stretching modes. 11 Again, a normal coordinate force constant scaling approach is ill-suited to capturing these effects. This is reflected in the residual error data illustrated in Figure 1(d).…”