Molecular dynamics in intense laser fields

We discuss recent developments in the study of the interaction of intense lasers with diatomic molecules. An overview of theory and experiment is given and particular attention is given to the energy spectra of ions resulting from photodissociative ionization. The ionization process is studied in the multiphoton regime using Floquet theory and compared with field-ionization results appropriate for the tunnelling regime. A review is given of the evidence for the existence of critical distances between the nuclei at which ionization rates are strongly enhanced. The field-ionization model is found to reproduce the main features observed by experiments. The field-ionization Coulomb explosion (FICE) model accurately reproduces the kinetic energy releases and threshold intensities of the various fragmentation channels of the iodine dimer: I-2. With the three-dimensional FICE model, threshold intensities as a function of angle between the molecular axis and the laser E-field are calculated. The angular distributions obtained are in good agreement with measurements taken for distributions of I-2 fragments. The angular distributions of the H-2 and N-2 fragments, on the other hand, are much more sharply peaked, indicating reorientation by the laser field.