The spin–orbit effect on potential surfaces of NO2 photodissociation

Abstract

Potential energy surfaces for photodissociation reaction NO2→NO(2Π)+O(3P) have been studied by ab initio calculations. The effect of spin–orbit interaction on the potential surface features was studied near the product region. All the 12 potential surfaces asymptotically correlated to the NO(2Π)+O(3P) limit were obtained by the state-averaged complete-active-space-self-consistent-field (CASSCF) method. The adiabatic potential surfaces including the spin–orbit interaction were constructed using the full Breit–Pauli Hamiltonian. It was found that the lowest two states are attractive, while all the other states are repulsive. Assuming that NO2 undergoes the photodissociation on the ground state surface, we obtained the bending-rotation energy levels along the dissociation coordinate, and the transition state for each bending level was determined. The potential barriers for the vibrationally adiabatic energy curves were consistent with the recent experiments. Using a simplified model based on the infinite order sudden approximation (IOSA) and the Franck–Condon approximation, the product fine structure distribution was estimated, which is in good agreement with the experimental results.

NO Rotational Orientation Following 308 nm Photodissociation ofNO2

“…The only adjustable parameters used in the fitting were the bipolar moments of interest: the returned values are given in Table I, together with their Monte Carlo determined errors. The values reported here for the bipolar moments with even k are consistent with the somewhat more limited set determined previously by Hancock and co-workers [24] for the photolysis of NO 2 at 355 nm: excitation at both 355 and 308 nm are believed to access theÃ͑ 2 B 2 ͒ state [25], which has its transition moment polarized parallel to the terminal oxygen atoms. The greater magnitude of the translational anisotropy, 2b 2 0 ͑20͒, obtained in the present thermal measurements, however, suggests a significant reduction in dissociation time at the higher available energy employed here [24].…”

“…TheÃ͑ 2 B 2 ͒ electronic state to which NO 2 is excited around 300 nm correlates with electronically excited atomic oxygen products (a channel which is closed at the energies supplied to the parent molecule). Dissociation to the products O͑ 3 P͒ 1 NO͑ 2 P͒ is believed to occur via passage through a conical intersection with the groundX͑ 2 A 1 ͒ electronic state (see, for example, [25]). The geometry of the excited electronic state [which has a smaller equilibrium bond angle than NO 2 ͑X͒], and the predicted configuration of the conical intersection [25], are FIG.…”

Quasiclassical trajectory study of NO vibrational relaxation by collisions with atomic oxygen

“…It is interesting to note that the relaxation rate constant predicted by the statistical adiabatic channel model There is currently only limited experimental 24 and theoretical information 17 concerning the importance of multiquantum versus single quantum relaxation for O+NO(v). The ab initio electronic structure calculations, 23 which indicate that the NO vibrational relaxation occur on surfaces dominated by a strongly bound complex, would argue for efficient multiquantum relaxation. 17,32 In fact, it has been shown by It is difficult to establish whether a particular dynamical system can be described by statistical theories.…”

Photoinitiated unimolecular decomposition of NO2: Rotational dependence of the dissociation rate

“…[11][12][13][14][15] In the energy range of interest in the present study ͑i.e., less then 120 cm Ϫ1 above D 0 ) only the ground vibrational state of NO(X 2 ⌸ 1/2 ) and the lowest oxygen spin-orbit state ( 3 P 2 ) are accessible.…”