Effects of orbital angular momentum in H₂S⁺

Abstract

The vibrational and K-type rotational levels of the [Xtilde] ² B ₁ and the à ² A ₁ states of H₂S⁺ have been fitted by least squares to give a pair of Born-Oppenheimer potential curves for the combining electronic states. An accurate description of the effects of orbital angular momentum on the energy level positions has been obtained and relative transition moments for the vibronic bands of the à ² A ₁ - [Xtilde] ² B ₁ transition have been calculated. Relative transition moments for the photoelectron spectrum of H₂S(H₂S⁺, à ² A ₁ ← H₂S, [Xtilde] ¹ A ₁) have also been evaluated.

The effects of orbital angular momentum on the spin and rotational fine structure have been considered in detail. The parameters for end over end rotation are calculated directly from the bond lengths and potential curves, which were derived from the least squares fit to the vibrational and K-type structure. The erratic spin-orbit splittings and asymmetry parameters of the à ² A ₁ state have been reproduced with reasonable accuracy. Significant differences are observed between the effects of orbital angular momentum in H₂S⁺ compared to its effects in NH₂ and H₂O⁺. These differences are associated principally with the shapes of the potential curves, the size of the spin-orbit coupling and the near equality of the vibrational separation in the excited state region of H₂S⁺.