The lowest lying excited electronic states for HFCO including a potential energy surface for S 1 in sum-of-products form

Abstract

The vertical excitation energies to the S and T states for HFCO were determined using multi-reference (CASSCF, CASPT2, CASPT2-F12, MRCI, and MRCI-F12) and the single reference EOM-CCSD methods. The geometries, relative energies, and harmonic frequencies for the stationary points (minimum and transition state to inversion) on both the S and T potential energy surfaces (PESs) were characterised. A six-dimensional PES for the S state was constructed, in sum-of-products form using a neural network with exponential neurons, based on EOM-CCSD/aug-cc-pVTZ ab initio energies. Using the PES, the fundamental vibrational frequencies were computed using block-improved relaxation in MCTDH, and they agreed well with previous experiments (RMSE cm). A corresponding transition dipole moment surface (TDMS) was also fit to sum-of-products form. With the present PES and TDMS, along with the previous S surface, UV-vis absorption, stimulated emission pumping spectra, or optimal control of quantum dynamics via S can be explored.