A vacuum ultraviolet laser photoionization and pulsed field ionization study of nascent S(P2,1,3) and S(D21) formed in the 193.3nm photodissociation of CS2

Abstract

The photoionization efficiency (PIE) and pulsed field ionization-photoion (PFI-PI) spectra for sulfur atoms S(3P2,1,0) and S(1D2) resulting from the 193.3 nm photodissociation of CS2 have been measured using tunable vacuum ultraviolet (vuv) laser radiation in the frequency range of 82 750-83 570 cm(-1). The PIE spectrum of S(3P2,1,0) near their ionization threshold exhibits steplike structures. On the basis of the velocity-mapped ion-imaging measurements, four strong autoionizing peaks observed in the PIE measurement in this frequency range have been identified to originate from vuv excitation of S(1D2). The PFI-PI measurement reveals over 120 previously unidentified new Rydberg lines. They have been assigned as Rydberg states [3p3(4S composite function nd3 D composite function (n=17-64)] converging to the ground ionic state S+(4S composite function) formed by vuv excitations of S(3P2,1,0). The converging limits of these Rydberg series have provided more accurate values, 82 985.43+/-0.05, 83 162.94+/-0.05, and 83 559.04+/-0.05 cm(-1) for the respective ionization energies of S(3P0), S(3P1), and S(3P2) to form S+(4S composite function). The relative intensities of the PFI-PI bands for S(3P0), S(3P1), and S(3P2) have been used to determine the branching ratios for these fine structure states, S(3P0):S(3P1):S(3P2)=1.00:1.54:3.55, produced by photodissociation of CS2 at 193.3 nm.

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

“…This structure was also observed by Pan and co-workers [23] at a wavenumber of 75 821 cm −1 (corresponding to 9.401 eV) and by Yang et al [21,22] for a wavenumber of 75 818 cm −1 (corresponding to 9.400 eV). Pan et al [23] discussed an assignment to a 1 G series, but because of ∆J = 2 this was excluded.…”

“…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]. There is no plausible explanation for the large discrepancy in the experimental values for the branching ratio of S(3s 2 3p 4 1 D) to S(3s 2 3p 4 3 P ) from the 193 nm (6.424 eV) photolysis of CS 2 .…”

“…It should be noted that the excitation of the 3s 2 3p 4 1 D state in a 3s 2 3p 4 3 D Rydberg state to the spin-selection rule in the context of one-photon processes is contrary, illustrated by the relatively low intensity. This transition was also observed by Yang and co-workers [21,22] who indicated that spin-spin and spin-orbit interactions in the case of atomic sulfur may play a role.…”

“…Pan et al [23] discussed an assignment to a 1 G series, but because of ∆J = 2 this was excluded. Yang and co-workers [21,22] suggested the transfer of excitation to a 3s 2 3p 3 ( 2 D o )3d state, without the corresponding term symbol. The energy of the photon ArF laser (6.42 eV) is insufficient to form atomic sulfur in the excited state S( 1 S), since the photodissociation energy of CS 2 is 397 kJ/mol = 4.114 eV [76] and the excitation energy of S( 1 S) is 2.7499637 eV [67] so that this electronic state is excluded as the cause of the resonance.…”

“…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.…”