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Beyond Born-Oppenheimer treatment on spectroscopic and scattering processes
摘要： We review the formulation of beyond Born-Oppenheimer (BBO) theory based on first principle for the construction of diabatic potential energy surfaces (PESs) both for few important spectroscopic systems, viz., Na3 cluster, NO2 radical as well as scattering process like D+ + H2. The essential theoretical development leading to the BBO equations are thoroughly discussed. It has been found that the above molecular systems posses numerous nonadiabatic interactions that range from Jahn-Teller, Renner-Teller types of conical intersections along with strong pseudo Jahn-Teller couplings between various electronic states. We have calculated the adiabatic PESs and nonadiabatic coupling terms for those systems and subsequently performed adiabatic-to-diabatic transformation to construct smooth, symmetric and continuous diabatic potential energy matrix. Nuclear dynamics has been performed on the diabatic PESs of Na3 and NO2 to simulate the photoelectron spectra that match quite well with the experimentally measured ones. Moreover, we have carried out reactive scattering dynamics on the adiabatic and diabatic surfaces of H+3 system to reproduce experimental cross sections for reactive charge and non-charge transfer processes.
关键词： Beyond Born-Oppenheimer theory,nuclear dynamics,photoelectron spectra,reactive scattering dynamics,conical intersections,Jahn-Teller,diabatic potential energy surfaces,Renner-Teller,nonadiabatic interactions,pseudo Jahn-Teller couplings
更新于2025-09-09 09:28:46
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Coulomb Explosion Imaging for the Visualization of a Conical Intersection
摘要： Coulomb explosion imaging is proposed as a method to directly map the presence of conical intersections encountered by a propagating wave packet in a molecular system. The case of choice is the non-adiabatic coupling between two dissociative surfaces in the methyl iodide molecule, probed by Coulomb explosion with short, intense near-infrared pulses causing multiple ionization. On-the-fly multidimensional trajectory calculations with surface hopping using perturbation theory and including spin-orbit coupling are performed to visualize the dynamics through the conical intersection and compare with experimental results. The possibilities and limitations of the technique are examined and discussed.
关键词： ultrafast dynamics,strong laser fields,methyl halides,Nonadiabatic processes,surface hopping
更新于2025-09-04 15:30:14