V. R. Marathe

Excited states of XH2+ (X=C, N, O, S) ions: a combined experimental and theoretical study

Excited electronic states of doubly charged molecular ions of the diatomic hydrides CH2+, NH2+, OH2+ and SH2+ are investigated by means of high-resolution translational energy spectrometry. Long-lived states of CH2+, NH2+ and SH2+ (but not OH2+) are observed. Potential energy functions are calculated using a semi-empirical molecular-orbital technique as well as a high-level ab initio method using large basis sets of at least double zeta plus polarisation quality. Translational energy spectra of singly charged hydride ions are also presented.

Formation of doubly charged Co2+ ions: a combined experimental and theoretical study

The formation of doubly charged molecular ions of carbon monoxide is studied by means of ion translational energy spectrometry of products resulting from electron loss collisions of CO+ and He and double electron capture collisions of H+ and CO. Theoretical calculations of potential energy functions of several low-lying states of CO2+ have been carried out using a high level, all-electron ab initio technique using large Gaussian basis sets. Vertical double ionisation energies of CO are measured to be 40.21+or-0.35 eV and 39.45+or-0.20 eV. The former value pertains to a metastable CO2+ state whereas the latter is ascribed to a dissociative state. The energy difference of 0.76 eV is a measure of the splitting between the lowest 3 Pi and 1 Pi states.

Translational energy spectrometric and quantum chemical study of CSq+ (q=1, 2) radicals: charge stripping and dissociation

A combined experimental and theoretical investigation has been carried out on CS+ and CS2+ radical ions. Ion translational energy spectrometry has been applied to study charge stripping of CS+ ions to yield metastable CS2+ ions and to study the energetics of spontaneous and collision-induced dissociation of these metastable doubly charged ions of CS. All-electron ab initio molecular orbital calculations, inclusive of fairly large-scale configuration interaction procedures, have been carried out to compute the potential energy functions of the different ionic systems involved in the collision processes studied experimentally.

Negative ion formation from CH3I by electron impact

Abstract The formation of fragment negative ions from CH3I on low energy electron collision (0–50 eV) has been measured using a pulsed electron beam and pulsed ion extraction setup in a crossed-beam geometry. In addition to I− we have observed H− and CH− at specific resonant energies due to dissociative electron attachment to CH3I. The cross-sections were put on an absolute scale using the relative flow technique. We have also carried out ab initio molecular orbital calculations to derive information on the ground state potential energy surfaces of CH3I, CH3I− and their various dissociation products.

The CS2 dication

The energies of CS2+2 formation is investigated experimentally using a crossed electron-beam molecular-beam apparatus incorporating nearly monoenergetic electrons and a quadrupole mass spectrometer, as well as theoretically using an ab initio quantum-chemical method with Gaussian basis sets of double zeta plus polarisation quality.

On the quantal identification of low-lying electronic states of CO2+

A value of 39.6 eV is measured for the lowest double ionisation energy of CO by means of a new ion translational energy loss spectrum of H- products from 3 keV double electron capture collisions between H+ and CO measured with enhanced resolution. New ab initio molecular orbital calculations with configuration interaction indicate that the lowest energy state of CO2+ accessible in such collisions possesses 1 Sigma + symmetry.

Dissociation dynamics of in intense laser fields: directional specificity of and fragments

The dissociation dynamics of bent molecules in an intense polarized light field produced by 35 ps wide laser pulses at 532 nm has been investigated by measuring the angular distributions of and ions emanating from dissociative ionization of . These angular distributions show a remarkable directional specificity: ions are preferentially formed in a direction which is parallel to the polarization vector of the applied laser field whereas, in contrast, ions are formed in a perpendicular direction.