Electron rescattering and the dissociative ionization of alcohols in intense laser light

Abstract

The fragmentation dynamics of a series of alcohol molecules, from methanol and ethanol, through hexanol to dodecanol, has been studied by irradiating these molecules with 100 fs duration pulses of linearly and circularly polarized, infrared, intensity-selected laser light. At laser intensities of 10¹⁶W cm^-2, the yields of singly and multiply charged atomic fragments from all these molecules are suppressed when circularly polarized light is used. This dependence of the fragmentation dynamics on polarization is rationalized using a simple electron rescattering model. Circular polarization switches "off" electron rescattering and leads to suppression of multiple ionization and molecular fragmentation. The degree of suppression depends upon the amount of energy transfer from the optical field to the molecule: the larger the energy transfer that is required for a particular fragmentation channel, the more marked is its suppression when circular polarization is used. The maximum kinetic energy that is released upon fragmentation appears to be more or less independent of the polarization state of the incident light. The observation that the actual values of kinetic energy released are less than Coulombic indicates that the enhanced ionization mechanism also holds for circularly polarized light.