Diabatic potential energy curves for the ^4{Pi} states of SH

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We present a diabatic representation of the potential energy curves (PECs) for the ^4{{Pi}} states of mathrm {SH}. Multireference, configuration interaction (MRCI) calculations were used to determine high-accuracy adiabatic PECs of both mathrm {SH} and {mathrm {SH}}^+ from which the diabatic representation is constructed for mathrm {SH}. The adiabatic PECs exhibit many avoided crossings due to strong Rydberg-valence mixing. We employ the block diagonalization method, an orthonormal rotation of the adiabatic Hamiltonian, to disentangle the valence autoionizing and Rydberg ^4Pi states of mathrm {SH} by constructing a diabatic Hamiltonian. The diagonal elements of the diabatic Hamiltonian matrix at each nuclear geometry render the diabatic PECs and the off-diagonal elements are related to the state-to-state coupling. Care is taken to assure smooth variation and consistency of chemically significant molecular orbitals across the entire geometry domain.