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

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.