Laser excitation and emission spectroscopy of the methoxy radical in a supersonic jet

A sophisticated spin-vibronic model was developed to study electronic and nuclear dynamics in twofold degenerate electron systems. Eigenenergies and eigenfunctions of a model Hamiltonian are calculated in a basis set of products of electronic, electron spin, and vibrational functions. The X 2 E ground electronic state of the CH 3 O pyramidal (C 3v ) system has been studied with the simultaneous treatment of spin-orbit coupling, all linear and quadratic Jahn-Teller interactions including multimode couplings, and anharmonic effects up to the sixth order for the CH-stretching. The group-theoretical analysis of the spin-vibronic Hamiltonian and its eigenfunctions was performed in terms of irreducible representations (E 3/2 and E 1/2 ) of the double C 3v symmetry group. Vibronic and anharmonic model parameters of X 2 E CH 3 O were calculated with numerical differentiation using ab initio energies of the CH 3 O geometries distorted on normal coordinates. The equation-of-motion coupled cluster method with augmented core-valence basis sets of triple-quality was applied in these calculations. The value of the spin-orbit splitting in X 2 E CH 3 O was calculated using multiconfiguration quasidegenerate second-order perturbation theory with a complete active space reference wave function followed by a perturbative calculation of eigenvalues of the full Breit-Pauli spin-orbit operator.

Section: Results Of Calculations and Discussionmentioning

confidence: 99%

A model spin-vibronic Hamiltonian for twofold degenerate electron systems: A variational ab initio study of X̃ 2E CH3O•

Marenich

Boggs

2004

“…The methoxy radical is characterized by a near UV electronic transition, Ã 2 A 1 -X 2 E, which is easily observed [8][9][10][11][12][13][14][15][16][17][18] by laser induced fluorescence ͑LIF͒ and other techniques. While much work has been performed on CH 3 O, the details of the spectroscopy, particularly the assignments of the Ã state vibrational levels, are not without some controversy.…”

Section: Introductionmentioning

confidence: 99%

Vibrational mode and frequency dependence of the photofragmentation of the methoxy radical

Powers

Pushkarsky

Miller

1997

“…Various jet expansion studies [9][10][11][12]14,15,18,20 have been performed over the past 15 years and a number of the vibrational frequencies have been determined for the A excited state but there have also been some problems associated with these studies. For a considerable time, even the frequency of the origin of the electronic transition was under dispute with a variety of values reported in the literature (for more information see Foster et al 12 ).…”

Section: Introductionmentioning

confidence: 99%

“…Experimentally, the radical can be conveniently studied by a variety of optical techniques for which the strong oscillator strength of the transition from the ground state to the first excited state ( A 2 A 1 ↔ X 2 E) lends itself well to laser induced fluorescence [8][9][10][11][12][13][14][15][16][17][18] (LIF) and dispersed fluorescence (and emission) 10,12,13,16,[18][19][20][21] and more recently stimulated emission pumping (SEP) studies. 22 Such experiments have led to considerable knowledge about the vibrational frequencies in the ground and excited electronic states.…”

Section: Introductionmentioning

confidence: 99%

Rovibronic analysis of the laser induced fluorescence excitation spectrum of the jet-cooled methoxy radical

Powers

Pushkarsky

Miller

1997

The laser induced fluoresence excitation spectrum for the A 2 A 1 ↔ X 2 E transition of the methoxy radical has been reinvestigated. An extensive set of vibrational levels has been assigned with the aid of increased vibrational and rotational cooling. Many of these vibrational assignments are confirmed by rotational analysis of bands involving both the symmetric and asymmetric fundamentals of the A state as well as vibrations containing two quanta of the e modes. Although parts of the vibrational structure have been assigned previously, several discrepancies are identified and corrected. Vibrational frequencies have been obtained for all the modes in the A 2 A 1 state of the molecule. The Fermi resonance that exists between ν 3 and ν 2 has been investigated and interaction constants describing it have been obtained.