Multi-mass velocity map imaging study of the 805 nm strong field ionization of CF3I.

Abstract

Multi-mass velocity map imaging studies of charged fragments formed by near infrared strong field ionization together with covariance map image analysis offer a new window through which to explore the dissociation dynamics of several different highly charged parent cations, simultaneously - as demonstrated here for the case of CF3IZ+ cations with charges Z ranging from 1 to at least 5. Previous reports that dissociative ionization of CF3I+ cations yields CF3+, I+ and CF2I+ fragment ions are confirmed, and some of the CF3+ fragments are deduced to undergo secondary loss of one or more neutral F atoms. Covariance map imaging confirms the dominance of CF3+ + I+ products in the photodissociation of CF3I2+ cations and, again, that some of the primary CF3+ photofragments can shed one or more F atoms. Rival charge symmetric dissociation pathways to CF2I+ + F+ and to IF+ + CF2+ products and charge asymmetric dissociations to CF3 + I2+ and CF2I2+ + F products are all also identified. The findings for parent cations with Z ≥ 3 are wholly new. In all cases, the fragment recoil velocity distributions imply dissociation dynamics in which coulombic repulsive forces play a dominant role. The major photoproducts following dissociation of CF3I3+ ions are CF3+ and I2+, with lesser contributions from the rival CF2I2+ + F+ and CF32+ + I+ channels. The CF32+ fragment ion images measured at higher incident intensities show a faster velocity sub-group consistent with their formation in tandem with I2+ fragments, from photodissociation of CF3I4+ parent ions. The measured velocity distributions of the I3+ fragment ions contain features attributable to CF3I5+ photodissociation to CF32+ + I3+ and the images of fragments with mass to charge (m/z) ratio ∼31 show formation of I4+ products that must originate from parent ions with yet higher Z.