Photoion imaging spectrometry in intense laser fields

Abstract

We describe a photoion imaging spectrometer that makes use of a position sensitive detector (PSD) incorporating a delay-line anode system. We have used this spectrometer to probe the spatial alignment of molecules in moderately intense laser fields (~2×10¹² W cm^-2). The system is used to image the angular distributions as well as to probe the kinetic energy of ions formed in the process of ionization (fragmentation) of atoms (molecules) in intense laser fields. We have imaged Xe⁺ in order to characterize the spatial and temporal properties of our spectrometer. The light-field-induced breakup of I₂ into I⁺+I has also been imaged and the kinetic energy release determined for different laser polarization directions. We discuss the merits and limitations of delay line detector systems in imaging studies of molecular ionization and fragmentation in intense laser fields.