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The photoionization dynamics of CS have been studied using high-resolution laser photoelectron spectroscopy. The photodissociation of CS2 at ~308 nm results in highly rotationally excited CS in its X1Σ+ singlet ground state, as well as in rotationally cold CS in the excited a3Π triplet state. The ground-state CS fragments are formed together with sulfur in its 3P, 1D, and 1S electronic states; triplet CS is produced in coincidence with ground-state sulfur (3P). In both channels the photoelectron spectra are dominated by Δv = 0 propensity, but transitions involving Δv = 1 and 2 are also observed. [ABSTRACT FROM AUTHOR]

This paper presents pulsed-field ionization, zero electron kinetic energy (ZEKE) photoelectron and threshold photoionization spectra of M-X(CH3)3 (M = Ga, In; X = P, As). The ZEKE spectra exhibit well-resolved vibrational structures. A comparison with B3LYP calculations shows that the spectrum of In-P(CH3)3 arises from the 1A1 ← 2E transition and the spectra of Ga-P(CH3)3 and Ga-As(CH3)3 arise from transitions of a Jahn–Teller distorted doublet state to the 1A1 state. The intensities of the 1A1–2E transition in the indium species are described with the Franck–Condon approximation, while the transitions in the gallium complexes are more complicated due to the dynamic Jahn–Teller effect. The adiabatic ionization potentials of Ga-P(CH3)3, In-P(CH3)3, and Ga-As(CH3)3 are 39 635, 38 930, and 40 322 cm–1, respectively, and the ionization threshold of In-As(CH3)3 is ~39 550 cm–1. The metal–ligand stretching frequencies are 143, 116, and 125 cm–1 for Ga+-P, In+-P, and Ga+-As, respectively, and 96 cm–1 for In-P. The intermolecular bending frequencies are 71, 65, and 42 cm–1 for Ga+-P-C, In+-P-C, and Ga+-As-C, respectively, and 47 cm–1 for In-P-C. In addition, ligand-based vibrational frequencies are determined for the CH3 wag, PC3 and AsC3 umbrella, and P-C stretching vibrations. [ABSTRACT FROM AUTHOR]

Rotationally resolved (1 + 1′), resonance-enhanced, two-photon ionization spectra of the C 0+u ← X 0+g transition of several isotopomers of Xe2 have been recorded. Rotational constants have been determined for the v′ = 14–26 levels of the C 0+u Rydberg state and the v′′ = 0 and 1 levels of the X 0+g ground state, and band origins have been determined with an absolute accuracy of 0.015 cm–1 for the transitions to the v′ = 14–26 levels of the C 0+u state of the 129Xe2, 129Xe–132Xe, and 131Xe–136Xe isotopomers. The equilibrium internuclear separation of the X 0+g ground state (Re = 4.3773(49) Å) was determined from the rotational constants of the v′′ = 0 and 1 levels. The analysis of the isotopic shifts of the band origins enabled the confirmation of the absolute numbering of the vibrational levels of the C 0+u state determined by Lipson et al. (R.H. Lipson, P.E. Larocque, and B.P. Stoicheff. J. Chem. Phys. 82, 4470 (1985)). A semiempirical interaction potential for the X 0+g ground state was derived in a nonlinear fitting procedure using the present spectroscopic results, the positions of the v′′ = 2–9 levels determined by Freeman et al. (D.E. Freeman, K. Yoshino, and Y. Tanaka. J. Chem. Phys. 61, 4880 (1974)) and experimental values for the second virial coefficient. The interaction potential is similar to previous semiempirical potentials but the dissociation energy (De = (196.1 ± 1.1) cm–1) differs from the value of 183.1 cm–1 determined in the latest ab initio calculation (P. Slavíček, R. Kalus, P. Paška, I. Odvárková, P. Hobza, and A. Malijevský. J. Chem. Phys. 119, 2102 (2003)). [ABSTRACT FROM AUTHOR]

We discuss the excitation of forbidden vibrational transitions accompanying photoionization of linear triatomic molecules. Excitation of a single quantum of the antisymmetric stretching vibration is observed for mole cules with inversion symmetry, as is the bending mode. Photoelectron spectra of the N2O+(A2Π), CO2+(C2Σg+), and CS2+(B2Σu+) states obtained over a range of ionization energies exhibit contrasting behavior for the relative intensities of the forbidden vibrations. These energy-dependent vibrational branching ratios are shown to result from an intrachannel vibronic coupling mechanism. Moreover, this intrachannel coupling can be further divided into two cases, one in which the photoionization cross section is sensitive to geometry changes, and a second case in which it is not. These different cases can be distinguished by comparing the experimental and theoretical results for all three molecules. [ABSTRACT FROM AUTHOR]

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