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The absorption spectrum of jet-cooled CS2 has been photographed between 50 500 and 65 500 cm-1 at a resolution limit of 0.008 Å. Ab initio calculations are carried out to estimate the energy of the lower Rydberg states of ionic cores ...2π3g, ...2π3u, and ...5σu, as well as those belonging to the doubly excited configuration ...2π2g3π2u. Assigned electronic states include the ...2π3g4s 1Πg (with vibronic bands 201 and 2n0, n=1,3,5,7, observed thanks to a concurrent of Herzberg–Teller intensity borrowing and Renner–Teller intensity redistribution) and ...2π3g4p 1,3Πu, and 3Σu- (observed bands being the electronic origin, 110 and 220 bands). Model calculations of Renner–Teller interaction in the 1Π states are performed leading to ε and ω2 parameter values. In the case of the 4p 1Πu state, Fermi resonance between the v1′=1 level and the v2′=2 RT-split levels of Πu vibronic symmetry, is also taken into account. The rotational band contours of the origin bands of the whole set of the ...2π3g4p Rydberg transitions excited by one or three photons are calculated using a model based on Hund’s case (e) representation. The calculated band contours, wave numbers, and relative intensities are in excellent agreement with the observations of the present vuv absorption spectrum, and the multiphoton (3+1) ionization spectrum of Baker et al. [J. Chem. Phys. 103, 2436 (1995)] provided that in the latter, the 1Σ+u state is reassigned as 3Σu-. Fitted values of the 4p quantum defects and of the 4pπ(1Σ+u)/4pσ(1Πu) transition moment ratio are found to be perfectly consistent with the ab initio calculation results. Possible assignments of 3d transitions in the present and previous vuv absorption spectra as well as in recent multiphoton ((1+1′)+1) ionization spectra of CS2 below 65 500 cm-1 are also discussed in the light of... [ABSTRACT FROM AUTHOR]

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 54 000 and 58 000 cm-1. The origin bands of the ...2π3g4sσg 1Πg and 3Πg←X 1Σ+g Rydberg transitions have been observed at 351.04 and 355.15 nm (vacuum 56 974 and 56 315 cm-1), respectively. A third, broader and stronger, band is observed at ∼365 nm corresponding to a two-photon transition at ∼54 700 cm-1, which is suggested to belong to the valence 5σu3πu 1Πg 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 a 3A2 valence state, so that the (2+1) MPI spectrum is supplemented by numerous transitions associated with the (1+2) MPI spectrum of the 3A2←X 1Σ+g transition. [ABSTRACT FROM AUTHOR]