A b i n i t i o synthesis of the ozone ultraviolet continuum

Abstract

A b i n i t i o SCF and CI calculations of the dipole moment function of ozonePotential energy surfaces for the ground and excited electronic states responsible for the Hartley continuum of ozone are used to obtain quadratic, cubic, and quartic force constants. Vibrational dependence of rotational constants to sixth order is calculated by perturbation theory. The spectroscopic constants enable computation of rovibronic energy levels. Overlap of ground state and excited state perturbed vibrational wave functions yield Franck-Condon factors. Electric dipole allowed rovibronic transitions are generated under the I r representation. The entire set of results generate the ultraviolet absorption spectrum. It is shown that inclusion of anharmonic terms in the vibrational Hamiltonian has a small effect upon the final spectrum, whereas rotational broadening plays a greater role in achieving agreement with experiment. a Frequencies are the harmonic frequencies; the fundamentals VI' V2' and V3 are given in parentheses. bReference 5. C Imaginary frequency.

Resonance Raman Spectroscopy of Dissociative Polyatomic Molecules

“…Various attempts were made to calculate the absorption [292][293][294][295] and Raman 293,295 spectra with harmonic or slightly anharmonic models. Based upon the model of Pack 160 or the time-dependent analogue described by Heller, 17 dissociation in these calculations occurs along the antisymmetric stretch while bound motion is executed in the other modes, leading to diffuse structure in the absorption spectrum.…”

Centrifugal distortions in molecules: An ab initio approach with application to water

“…Particularly satisfying was the excellent description of both the scalar and tensor quartic coefficients, D, and D,, respectively, for the spherical tops CH, and SF,. In a second article [2] we outlined an extension of the method to asymmetric tops and gave results for a particularly important molecule, namely ozone, for which we have also made a theoretical study of the effects of anharmonicity on its ultraviolet continuum band shape [3]. [4-101 that the representation of the dependence of the rotational energy upon the angular momentum in terms of Pad6 approximants provides much better spectral fits than the conventional power series representation that is often divergent or poorly convergent.…”

“…Particularly satisfying was the excellent description of both the scalar and tensor quartic coefficients, D, and D,, respectively, for the spherical tops CH, and SF,. In a second article [2] we outlined an extension of the method to asymmetric tops and gave results for a particularly important molecule, namely ozone, for which we have also made a theoretical study of the effects of anharmonicity on its ultraviolet continuum band shape [3]. In the present article we explore two additional questions about centrifugal distortions, namely what are the effects of electron correlation on the centrifugal stabilization energies, and what is the significance of the approximately linear fall-off of effective quartic spectroscopic constants as observed in our earlier computations [ 1,2]?…”