Coulomb explosion of benzene induced by an intense laser field

Coulomb explosions of benzene induced by an intense femtosecond laser field were investigated by time-of-flight (TOF) mass spectrometry at a laser intensity of 8.0x10(16) W cm(-2), with a pulse width of 120 fs. The multiply charged ions of Cq+ (q=1-4) and H+ were detected, and their energies were found to be distributed in the range of 0-160 eV. The explosions were concluded to be anisotropic because the kinetic energies of multiply charged carbon ions are highly parallel to the laser electric field. Molecular dynamics simulations, including the effects of tunnel ionization, electron recombination, and the spatial configuration of benzene for laser electric fields, were performed to elucidate the kinetic-energy distributions and the dynamics of exploded benzene ions. The results of the simulations reproduced the essential points of observation concerning the energies and distributions of the ions in the TOF experiments. The simulations suggest that the charge-hopping processes enhance ionization, finally leading to an anisotropic explosion, which events are similar to those found in the case of C-60 explosions. Furthermore, our findings have strongly suggested that time evolution of the hopping greatly depends on spatial configuration in the case of planar molecule benzene. (C) 2002 American Institute of Physics.