Spin-orbit coupling in O2(v)+O2 collisions.II.Quantum scattering calculations on dimer states involving the X 3SUM_g~-,a1 DELTA_g,and b 1SUM_g~+ states of O2

摘要

The dynamics of collisional deactivation of O2(X 3SUM_g~-,v=20-32) by O2(X 3SUM_g~-,v'=0) is investigated in detail by means of quantum-mechanical calculations..The theoretical approach involves ab initio potential energy surfaces correlating to the X 3SUM_g~-,a 1DELTA_g,and b 1SUM_g~+ states of O2 and their corresponding spin-orbit couplings [F.Dayou,M.I.Hernandez,J.Campos-Martinez,and R.Hernandez-Lamoneda,J.Chem.Phys.123,074311 (2005)].Accurate Rydberg-Klein-Rees potentials are included in order to improve the description of the vibrational structure of the fragments.The calculated Boltzmann-averaged depletion probabilities display a dependence with v in good agreement with experimental measurements.The onset of the vibrational-to-electronic (V-E) depletion mechanism is noticeable for v>= 26,and it is due to energy transfer to both a 1DELTA_g~- and b 1SUM_g~+ states of the diatom.For O2(X 3SUM_g~+,v=28),a further and sharp increase in the removal probabilities is caused by a near degeneracy with the O2(b 1SUM_g~+,v = 19) vibrational state.Analysis of the temperature dependence of the Boltzmann-averaged probabilities indicates a transition from the vibrational-to-translational to the V-E energy transfer regime,which can be traced back to the behavior of the inelastic probabilities as functions of kinetic energy.Furthermore,branching ratios for outcomes through the three different electronic states show a strong propensity towards populating a unique vibrational level within each electronic state.These results provide supported evidence that spin-orbit couplings account for a large portion of the "dark channel" reported in total depletion measurements.New insight for further experimental and theoretical investigations is also given.