Two-photon dissociation dynamics of the mercapto radical

Abstract

Two-photon dissociation dynamics of the SH/SD radicals are investigated using the high-n Rydberg atom time-of-flight (HRTOF) technique. The H/D(²S) + S(¹D) and H/D(²S) + S(¹S) products are observed in the dissociation of the SH/SD radicals on the 2²Π and B²Σ⁺ repulsive states, from sequential two-photon excitation via the A²Σ⁺ (v′ = 0, J′ = 0.5–2.5) state. The angular distributions of both H/D(²S) + S(¹D) and H/D(²S) + S(¹S) product channels are anisotropic. The anisotropy parameter (β) of the H(²S) + S(¹D) products is ∼−0.8 ± 0.1 (−0.9 ± 0.05 for SD), and that of the H(²S) + S(¹S) products is ∼1.3 ± 0.3 (1.2 for SD). The anisotropic angular distributions indicate that the SH/SD radicals promptly dissociate on the repulsive 2²Π and B²Σ⁺ potential energy curves (PECs) along with some non-adiabatic crossings, leading to the H/D(²S) + S(¹D) and H/D(²S) + S(¹S) products, respectively. The bond dissociation energy of the ground-state X²Π_3/2 SH/SD to the ground-state H/D(²S) + S(³P₂) products is measured to be D₀(S–H) = 29 253 ± 20 cm⁻¹ and D₀(S–D) = 29 650 ± 20 cm⁻¹, respectively. The dissociation energy of the A²Σ⁺ state SH/SD to the H/D(²S) + S(¹D) products is derived to be D₀[S–H(A)] = 7659 ± 20 cm⁻¹ and D₀[S–D(A)] = 7940 ± 20 cm⁻¹.