Photoionization Dynamics in the Intense Femtosecond Laser Field by Analyzing Massand Photoelectron Spectrum

The photoionization dynamics of ammonia and benzene was studied by home-built femtosecond laser and TOF mass/photoelectron spectrometer.Beam intensities of 1012W/cm2 were used with laser pulse width of 100fs and wavelength of 407.5nm.In the PE spectra of NH3,three(2+2)REMPI and (2+2)+1 ATI,(2+2)+2 ATI were shown,within each peak a progression of stretchin gvibrations v1 were found.The vibrational distribution of ATI peaks are inverted compared to normal(2+2)REMPI.High laser power has also caused band broadening and shifting effect,which are given rise to by the pondromotive potential of intense laser.Differ-ent from that of nanosecond,benzene phtoionization using femtosecond laser has predominent molecular ion peak with very small percentage of fragments.