The photoelectron spectrum of the ethoxide anion: Conical intersections,the spin-orbit interaction, and sequence bands

摘要

The negative ion photoelectron spectrum of the ethoxide anion (ethoxide-h5) and that of its fullydeuterated analog, ethoxide-d5, are calculated using the multimode vibronic coupling approach. Atwo state quasidiabatic Hamiltonian Hd is constructed which includes all terms through second orderin the full 18 dimensional internal coordinate space. Hd is centered at the ab initio determinedminimum energy crossing (MEX) point on the symmetry-allowed 2A"-2A' accidental seam ofconical intersection and determined from ab initio energy gradients and derivative couplings. Itreproduces the local topography of the 2A"-2A' MEX, in addition to accurately representing thegeometries, energetics, and harmonic frequencies of equilibrium and saddle point structures locatedon the ground electronic state potential energy surface in the vicinity of the MEX. Spin-orbit effectsare included. The results for ethoxy-h5 are compared to photoelectron and slow electronvelocity-map imaging (SEVI) spectra. By comparing the measured and predicted photoelectronspectrum, the accuracy of the electronic structure treatment is inferred. The existence of sequencebands in the SEVI spectrum is established.