SINGLE AND MULTIPLE IONIZATION OF CS2 IN INTENSE LASER FIELDS - WAVELENGTH DEPENDENCE AND ENERGETICS

Single and multiple ionization of carbon disulphide by intense picosec ond laser fields is the subject of this paper. Mass spectra were measu red at five wavelengths from the infrared to the ultraviolet In terms of the Keldysh adiabaticity parameter, we cover both the multiphoton a nd the tunnelling regimes. The dynamics of the dissociative ionization process is shown to be dependent upon the regime in which the laser-m olecule interaction occurs. Resonances, which may be possible and whic h could access electronically excited states of the molecule, appear t o play little part in the dynamics. Ion abundances have been measured as a function of laser intensity in the tunnelling regime; no correlat ion is found between measured values of saturation intensity and zero- held molecular properties such as dissociation or ionization threshold s and ionization energies. In addition, the covariance mapping techniq ue is applied to study the dissociation dynamics of multiply charged i ons at 1064 nm The measured values of kinetic energy release accompany ing formation of fragment ion-pairs are very much less than those meas ured in single-photon and electron-impact experiments. It is postulate d that this reduction may be a manifestation of the extent to which po tential energy surfaces of CS2q+ ions are 'flattened' by the action of the intense, linearly polarized laser radiation, akin to the bond-sof tening process that has been observed in the case of diatomic molecule s. Our observations indicate that distortion of molecular potential en ergy surfaces may be the dominating feature in intense laser-molecule interactions.