Two-photon dissociation dynamics of the mercapto radical.

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( 2 S) + S( 1 D) and H/D( 2 S) + S( 1 S) products are observed in the dissociation of the SH/SD radicals on the 2 2 Π and B 2 Σ + repulsive states, from sequential two-photon excitation via the A 2 Σ + ( v ' = 0, J ' = 0.5-2.5) state. The angular distributions of both H/D( 2 S) + S( 1 D) and H/D( 2 S) + S( 1 S) product channels are anisotropic. The anisotropy parameter ( β ) of the H( 2 S) + S( 1 D) products is ∼-0.8 ± 0.1 (-0.9 ± 0.05 for SD), and that of the H( 2 S) + S( 1 S) 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 2 2 Π and B 2 Σ + potential energy curves (PECs) along with some non-adiabatic crossings, leading to the H/D( 2 S) + S( 1 D) and H/D( 2 S) + S( 1 S) products, respectively. The bond dissociation energy of the ground-state X 2 Π 3/2 SH/SD to the ground-state H/D( 2 S) + S( 3 P 2 ) products is measured to be D 0 (S-H) = 29 253 ± 20 cm -1 and D 0 (S-D) = 29 650 ± 20 cm -1 , respectively. The dissociation energy of the A 2 Σ + state SH/SD to the H/D( 2 S) + S( 1 D) products is derived to be D 0 [S-H(A)] = 7659 ± 20 cm -1 and D 0 [S-D(A)] = 7940 ± 20 cm -1 .