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

International audienceAbstract We present a diabatic representation of the potential energy curves (PECs) for the $^4{{\Pi}} $ 4 Π states of $\mathrm {SH}$ SH . Multireference, configuration interaction (MRCI) calculations were used to determine high-accuracy adiabatic PECs of both $\mathrm {SH}$ SH and ${\mathrm {SH}}^+$ SH + from which the diabatic representation is constructed for $\mathrm {SH}$ 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 $^4\Pi $ 4 Π states of $\mathrm {SH}$ 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