화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.123, No.32, 6886-6896, 2019
Photodissociation of S-2 (X-3 Sigma(-)(g), a(1)Delta(g) , and b(1)Sigma(+)(g)) in the 320-205 nm Region
Photodissociation of vibrationally and electronically excited sulfur dimer molecules (S-2) has been studied in a combined experimental and computational quantum chemistry study in order to characterize boundcontinuum transitions. Ab initio quantum chemistry calculations are carried out to predict the potential energy curves, spin-orbit coupling, transition moments, and bound-continuum spectra of S-2 for comparison with the experimental data. The experiment uses velocity map imaging to measure S-atom production following S-2 photoexcitation in the ultra-violet region (320-205 nm). A pulsed electric discharge in H2S produces ground-state S-2 X-3 Sigma(-)(g)(v = 0-15) as well as electronically excited singlet sulfur and b(1)Sigma(+)(g)(v = 0, 1), and evidence is presented for the production and photodissociation of S(2)a(1)Delta(g). In a previous paper, we reported threshold photodissociation of S2X3 Sigma(-)(g)(v = 0) in the 282-266 nm region. In the present study, S(P-3(j)) fine structure branching and angular distributions for photodissociation of S-2(X-3 Sigma(-)(g)(v = 0), a(1)Delta(g) and b(1)Sigma(+)(g)) via the B ''(3)Pi(u), B-3 Sigma(-)(u) and 1(1)Pi(u) excited states are reported. In addition, photodissociation of the X-3 Sigma(-)(g)(v = 0) state of S-2 to the second dissociation limit producing S(P-3(2)) + S(D-1) is characterized. The present results on S-2 photodynamics are compared to those of the well-studied electronically isovalent O-2 molecule.