Ionization and dissociation of acetonitrile by intense femtosecond laser pulse

Photoionization and photodissociation of CH,CN were studied by a linear tim e of flight mass spectrometer coupled with 800 nm, 50 fs laser pulses at in tensities of 6.3x10(13)-1.2x10(14) W/cm(2). The laser power dependences for principal ions CH3CN+, CH2CN+, CHCN+ and CCN+ were measured, which are con sistent with the numbers of photons required to produce the ions via multip hoton ionization and dissociation. The results show that eight-photon non-r esonant multiphoton ionization is the main photoionization mechanism of the parent ion CH3CN+, while the fragment ions were produced through the disso ciation of the molecules in the super-excited states.