The (2+1) Multiphoton Ionization Spectrum Of Jet-Cooled Csp Between 54000 And 58000 Cm(-1)

The (2+1) multiphoton ionization (MPI) spectrum of jet-cooled CS2 has been recorded in the range 345-370 nm, corresponding to a two-photon frequency between 54000 and 58000 cm(-1). The origin bands of the ...2 pi(g)(3)4s sigma(g)(1)II(g) and (IIg)-I-3<--($) over tilde X(1) Sigma(g)(+) Rydberg transitions have been observed at 351.04 and 355.15 nm (vacuum 56974 and 56315 cm(-1)), respectively. A third, broader and stronger, band is observed at similar to 365 nm corresponding to a two-photon transition at similar to 54700 cm(-1), which is suggested to belong to the valence 5 sigma(u)3 pi(u)(1)II(g) state. The position of the two-photon band at 351 nm establishes it as the one-photon electric-dipole forbidden origin of the 800 cm(-1) progression observed in the ultraviolet absorption spectrum. The first-photon frequency of this transition falls at a level corresponding to the ($) over tilde a(3)A(2) valence state, so that the (2+1) MPI spectrum is supplemented by numerous transitions associated with the (1+2) MPI spectrum of the (3)A(2)<--<($)overtilde>X(1) Sigma(g)(+) transition.