HIGH-RESOLUTION ABSORPTION-SPECTRUM OF JET-COOLED CS2 BETWEEN 70500 AND 81550 CM(-1) - NP AND NF RYDBERG SERIES CONVERGING TO THE FIRST IONIZATION-POTENTIAL

The absorption spectrum of jet-cooled CS2 was photographed between 70 500 and 81 550 cm(-1) at a resolution limit of 0.0008 nm, i.e., 0.4 to 0.5 cm(-1). Wave numbers of over 200 features an reported and assigne d in terms of ...2 pi(g)(3)np (n = 5 - 25) nf (n = 4 - 17) allowed tra nsitions-electronic origin bands and vibronic 1(0)(1) bands correspond ing to excitation of the totally symmetric stretching vibrational mode in the excited electronic states-as well as forbidden ...2 pi(g)(3)ns sigma (n = 5-7), nd sigma (n = 4 and 5), and nd delta (n = 3-5) g-g t ransitions-2(0)(1) and 2(1)(2) bands involving excitation of the bendi ng vibrational mode in the corresponding excited (1,3)Pi(g) states-, a nd the (...2 pi(u)(3)(A) over tilde(2)Pi(u)) 4s sigma(g )(1)Pi(u) allo wed transition, first term of a series converging to the second ioniza tion limit. Ab initio calculations of the electronic energies and tran sition moments for effective principal quantum numbers about 4 and 5 a re carried out for all the observed series. Rotational band contours a re calculated using Hund's case (e) representation for one- and three- photon excitation of the ...2 pi(g)(3)np and nf Rydberg complexes for every observed n value. An approximate Rydberg formula is obtained whi ch allows the calculation of the principal peak wave numbers for n > 1 2 to within 1 cm(-1). This work completes the study of CS2 Rydberg ser ies converging to the first ionization limit initiated previously with the ...2 pi(g)(3)4s and 4p complexes [C. Cossart-Magos et al., J. Che m. Phys. 104, 7412 (1996)] and the ...2 pi(g)(3)3d, 5s supercomplex [C . Cossart-Magos et al., J. Chem. Phys. 107, 1308 (1997)]. Systematic c omparison with the (3+1) resonance enhanced multiphoton ionization (RE MPI) spectra recorded by Morgan er nl. [J. Chem. Phys. 104, 6117 (1996 )] and by Berger et al. [J. Chem. Phys. 107, 8866 (1997)] reveals that only exceptionally the same transition is observed both in the absorp tion and the REMPI experiments: the two techniques give complementary information, with the absorption providing a much greater volume of da ta. Previous tentative assignments of the REMPI spectra by Morgan ct a l, and by Berger et nl, are completed, with a few reassignments being necessary. Detailed comparison of the present absorption spectrum with the vacuum-ultraviolet laser and synchrotron radiation photoionizatio n recorded by Huang et al. [J. Chem. Phys. 106, 863 (1996)], shows tha t, in the common Dart (n = 14-25), the same transitions are observed, and that, for the electric field intensities used (up to 1070 V/cm), t he Stark shifts are less than 1 cm-(1). (C) 1998 American Institute of Physics. [S0021-9606(98)01740-1].