E. Pradhan and Alex Brown
Mol. Phys. accepted
Publication year: 2019

The vertical excitation energies to the S1 and T1 states for HFCO were deter- mined using multi-reference (CASSCF, CASPT2, CASPT2-F12, MRCI, and MRCI- F12) and the single reference EOM-CCSD methods. The geometries, relative ener- gies, and harmonic frequencies for the stationary points (minimum and transition state to inversion) on both the S1 and T1 potential energy surfaces (PESs) were characterized. A six-dimensional PES for the S1 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 = 45 cm−1). A corresponding tran- sition dipole moment surface (TDMS) was also fit to sum-of-products form. With the present PES and TDMS, along with the previous S0 surface, UV-vis absorption, stimulated emission pumping spectra, or optimal control of quantum dynamics via S1 can be explored.