Dissociative ionization of benzene in intense laser fields of picosecond duration

Mass spectrometry experiments have been performed to probe the morphology o f dissociative ionization of a ring molecule benzene when it is immersed in a laser field of 35-ps duration whose intensity is in the range 10(13) W c m(-2). The field-induced fragmentation pattern is grossly different from th at obtained by electron impact. The intense laser field clearly gives rise to much more fragmentation. Covariance mapping has been applied to study fi eld-induced formation of highly charged molecular ions. Results indicate th at the overall fragmentation dynamics is complex and is likely to involve b oth fast ladder switching as well as multiple ionization of fragment molecu les at some intermediate steps in the ladder. Angular distributions of frag ment ions have been measured. Anisotropic distributions indicate that some fragments an produced From precursors that are strongly aligned along the d irection of the laser polarization vector while at least one fragment is fo rmed from a precursor whose angular distribution is markedly isotropic. The nature of the precursors remains to be discovered. [S1050-2947(99)04202-X] .