Abstract

Strong laser field control of the methyl iodide photodissociation dynamics at the origin of the second absorption B-band has been explored [1]. It is well established that predissociation occurs with unity quantum yield into the channel yielding spin-orbit excited state iodine atoms through the crossing with a valence dissociative state belonging to the first absorption A-band [2]. The predissociation dynamics has been interrogated by femtosecond time-resolved velocity map imaging using a pump-probe scheme, with excitation at around 200 nm and where the probing step is carried out by 2+1 resonance enhanced multiphoton ionization (REMPI) of the methyl fragment in the vibrationless ground state, and found to be in the picosecond time scale (1.5±0.1 ps) [2]. A significant dynamic Stark shift of the initial quantum state in the presence of a moderately intense (<5·10¹² W cm⁻²) NIR picosecond laser pulse has been found and calibrated [3]. In addition, when the strong laser field is present, significant dump and multiphoton dissociative ionization processes occur along with the Stark shift [1]. The various processes, which appear in the presence of the strong laser field, are capable of influencing the lifetime of the initially prepared quantum state and the quantum yield of the predissociation reaction. These control strategies and their possible extension to other systems will be reviewed at the conference.

© 2013 Optical Society of America