Reinvestigation of CS2 dissociation at 193 nm by means of product state-selective vacuum ultraviolet laser ionization and velocity imaging

Abstract

A branching ratio of 1.6 +/- 0.3 for S(3P)/S(1D) is obtained for the dissociation of CS2 with very low fluence 193 nm laser (less than 2 mJ/cm2), in which the S(3P) and S(1D) have been state-selectively ionized using VUV lasers at different wavelengths. The anisotropy parameters betamax(3P) = 0.8 and betamax(1D) = 1.9 indicate that these channels are preferentially populated at different geometries and the lifetime is very short.

Photoionization of the3s23p43Pand the3s2Barthel1, Flesch2, Rühl3 et al. 2015Phys. Rev. A201200View full textAdd to dashboardCite

“…The branching ratio of both species at 193 nm (6.424 eV) has been the subject of several investigations. Recently, the value of the branching ratio of 1.66 ± 0.3 for S( 3 P )/S( 1 D) was published [19]. The present work yields a similar value of 2.8 ± 0.4 (c.f.…”

“…The ratio of 2.8 ± 0.4 found in favor of of S(3s 2 3p 4 1 D) is in clear contradiction to earlier work, where S(3s 2 3p 4 3 P ) is the more abundant species. Waller et al reported a branching ratio S( 3 P J )/S( 1 S J ) = 2.8 ± 0.3 [83] and 1.6 ± 0.3 was reported by Xu et al [19], also in favor of S( 3 P ). However, the present value of 2.8 ± 0.4 in favor of the S(3s 2 3p 4 1 D) state agrees with that found by Yang et al [21,22].…”

“…Pulse energies of 1-2 mJ/cm 2 [19] may cause additional contributions of S(3s 2 3p 4 3 P ) by the dissociation of vibrationally excited CS. The pulse energy of the 193 nm (6.424 eV) excitation radiation, used in the present work, is about 0.4 mJ/cm 2 , so we safely assume that multi-photon effects play a minor role.…”

“…Recent experiments performed by Jackson and coworkers [19][20][21][22] measured the single-photon excitation spectra from the lowest 3s 2 3p 4 1 D 2 and 3s 2 3p 4 1 S 0 metastable levels of sulfur atoms recorded with a tunable vacuum ultraviolet (VUV) radiation source generated by frequency tripling in noble gases. Various new lines were observed in the spectra which have not been previously reported.…”

Time-Resolved Molecular Frame Dynamics of Fixed-in-Space CS 2 Molecules

“…The excited state bending frequency is nearly degenerate with that of the considerably weakened symmetric stretch, leading to combination bands of symmetric stretch and bend with peaks spaced by ∼400 cm −1 , each further split (∼30 cm −1 ) due to this near degeneracy (22 (24). From the peak widths in the absorption and S-atom action spectra, resonance lifetimes of less than 1 ps were estimated (23).…”