Abstract: Chemistry in strong laser fields is a new research field in which dissociation of molecules in the intense laser field is a current topic of interest. Our results, including the theoretical model of field-assisted dissociation (FAD) and the experimental investigations on the dissociation of CH4 and CH3COCH3 in the intense femtosecond laser field are presented. Some assumptions are made in the model. When a laser field applies to a molecule, only the change of the one bond length, which lies along with the laser field, is taken into account and the rest of the molecular geometry is fixed. In addition, only molecular ions in the ground electronic state are considered. Ab initio potential energy surfaces in the external fields indicate that chemical bond tends to dissociate. QCT (quasi-classical trajectory) calculations clearly show the processes of bond breaking. It was found that the calculations based on the theoretical model are in excellent agreement with the experiment data.

Key words: Intense femtosecond laser field, TOF-MS, Field-assisted dissociation, 　Methane, Acetone