Enhancement of anthracene fragmentation by circularly polarized intense femtosecond laser pulse

摘要

The authors compared circularly and linearly polarized lights in the ionization and fragmentation of anthracene, using 800 nm femtosecond laser pulses at intensities of 1013-1015 W cm-2, Singly and doubly charged intact molecular ions as well as numerous fragment ions were observed in the mass spectra, which were investigated as a function of laser intensity and polarization.At comparable intensities above the saturation threshold for complete ionization, the fragmentation pathways are enhanced with a circularly polarized field compared to a linearly polarized field.Resonant excitation of the molecular cation through the 2A_u<- 2B_g transition is proposed to be the initial step to ion fragmentation.The circularly polarized field interacts with a larger fraction of the randomly oriented molecules than the linearly polarized field, and this is considered to be the reason for the enhanced fragmentation brought about by circularly polarized light.