Knowledge Bank

The ground and first and second $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A\prime \prime$ surfaces of methyl mercaptan $(CH3SH)$ are calculated as a function of the C-S and S-H bond coordinates using the ab initio effective valence shell Hamiltonian $(H\nu )$ method. These computations provide the first serious tests for choosing restricted valence spaces and for computing global potential energy surfaces with the $H\nu$ methods. The global surfaces are computed with a modest basis, but larger basis set computations at selected geometries test convergence for vertical excitation energies, ionization potentials, and C-S and S-H bond energies. The calculations assist in the interpretation of $CH3SH$ photodissociation dynamics observed by Butler and $co-workers1$.