Vibrational distributions of the à 2Πu state of CO+2 and CS+2 produced by electron impact on jet‐cooled CO2 and CS2

[1 + 1] photodissociation of CS(2)(+)(X̃2Π(g)) via the vibrationally mediated B̃2Σ(u)+ state: multichannels exhibiting and mode specific dynamics

Dissociation dynamics of CS(2)(+) vibrationally mediated via its B̃(2)Σ(u)(+) state, was studied using the time-sliced velocity map imaging technique. The parent CS(2)(+) cation was prepared in its X̃(2)Π(g) ground state through a [3 + 1] resonance enhanced multiphoton ionization process, via the 4pσ(3)Π(u) intermediate Rydberg state of neutral CS(2) molecule at 483.14 nm. CS(2)(+)(X̃(2)Π(g)) was dissociated by a [1 + 1] photoexcitation mediated via the vibrationally selected B̃ state over a wavelength range of 267-283 nm. At these wavelengths the C̃(2)Σ(g)(+) and D̃(2)Σ(u)(+) states are excited, followed by numerous S(+) and CS(+) dissociation channels. The S(+) channels specified as three distinct regions were shown with vibrationally resolved structures, in contrast to the less-resolved structures being presented in the CS(+) channels. The average translational energy releases were obtained, and the S(+)∕CS(+) branching ratios with mode specificity were measured. Two types of dissociation mechanisms are proposed. One mechanism is the direct coupling of the C̃ and D̃ states with the repulsive satellite states leading to the fast photofragmentation. The other mechanism is the internal conversion of the C̃ and D̃ states to the B̃ state, followed by the slow fragmentation occurred via the coupling with the repulsive satellite states.

Should a Franck-Condon or a curve-crossing picture be applied to ion-target collisional activation? A study of keV CO2+*/He collisions by emission spectroscopy

Collision-induced photon emissions (CIE) were observed for keV CO(2)(+*)/He collisions from 190 to 1020 nm. The emissions were assigned to the Deltanu=0 band of the CO(2)(+*) B (2)Sigma(u)(+) --> X (2)Pi(g) electronic transition and the Deltanu= +3, +2, +1, 0, -1, -2, -3 vibrational transition progression in the CO(2)(+*) A (2)Pi(u) --> X (2)Pi(g) electronic transition. The other peaks arise from the emissions of excited O* fragment atoms and the target gas. The relative intensities of the CO(2)(+*) and O* emissions are independent of the ion translational energy above 3 keV, supporting the curve-crossing mechanism for collisional excitation. Investigation of the relative intensities within the A (2)Pi(u) --> X (2)Pi(g) emission of CO(2)(+*) indicates that the vibrational distribution is well described by the Franck-Condon principle at high collision energy, a consequence of short collision time but not necessarily an indication of vertical transitions. Below 3 keV ion translational energy, vibrational excitation in the A (2)Pi(u) electronic state was observed. The observation is consistent with the explanation that the reaction occurs at small impact parameters, in which short-range, repulsive interactions between the projectile and the target result in direct translational-vibrational excitation.

The molecular structure and a Renner-Teller analysis of the ground and first excited electronic states of the jet-cooled CS2+ molecular ion

The A 2Pi(u) - X 2Pi(g) electronic band system of the jet-cooled CS2 + ion has been studied by laser-induced fluorescence and wavelength-resolved emission techniques. The ions were produced in a pulsed electric discharge jet using a precursor mixture of carbon disulfide vapor in high-pressure argon. Rotational analysis of the high-resolution spectrum of the 2Pi32 component of the 0(0) 0 band gave linear-molecule molecular structures of r0" = 1.5554(10) A and r0' = 1.6172(12) A. Renner-Teller analyses of the vibronic structure in the spectra showed that the ground-state spin-orbit splitting (A = -447.0 cm(-1)) is much larger than that of the excited state (A = -177.5 cm(-1)), but that the Renner-Teller parameters are of similar magnitude and that a strong nu1 - 2nu2 Fermi resonance occurs in both states. Previous analyses of the vibronic structure in the ground and excited states of the ion from pulsed field-ionization-photoelectron data are shown to be substantially correct.