Optical control of the vibrational excitation of the polyatomic ions via strong field multi-photon ionization

The dynamics of multi-photon ionization of CH3I under strong field has been studied experimentally by femtosecond photoelectron imaging. Ultrafast optical control of the vibrational excitation in a polyatomic ion by strong field multiphoton ionization is experimentally realized. The present work enhances the intensity of the ionization beam from 1.6 x 10(13) to 2.5 x 10(13) W/cm(2). In the order of this higher field, a new energy component is observed and attributed. From the photoelectron imaging, photoelectron kinetic energy distributions and the photoelectron angular distributions are obtained. The discussions of the previous letter are mostly based on the photoelectron kinetic energy information, and the present study emphasizes on the trend of the photoelectron angular anisotropy. More detailed dynamics on vibrational optical control is further explored.