Observation of Hydrogen Migration in Cyclohexane under an Intense Femtosecond Laser Field

We experimentally demonstrate hydrogen migration in photoionization and photofragmentation processes of cyclohexane (C6H12) under a near-infrared (800 nm) intense femtosecond laser field by the dc-slice imaging technique, and the observation of fragment ions CH3+, C2H5+, and C3H7+ can be regarded as direct evidence that chemical bond rearrangement processes associated with hydrogen migration occur in the dissociative ionization process of cyclohexane. We measure the sliced images of fragment ions CH3+, C2H5+, and C3H7+ and calculate their corresponding kinetic energy release (KER) and angular distributions, and it is confirmed that high-KER components of these fragment ions result from two-body Coulomb explosion of the doubly charged parent ion C6H122+ whereas low-KER components result from dissociative ionization of the singly charged parent ion C6H12+. Moreover, we measure the maximally attainable relative yields of fragment ions CH3+, C2H5+, and C3H7+, which approach 4.5%, 4.0%, and 3.0%, respectively.