A Step Towards Imaging Angle Resolved Photoelectrons with X-Ray Radiation for Applications in Gas Phase

Abstract: Photoionisation dynamics occurring in Ar and N2O upon the absorption of soft X-ray radiation, have been studied through the extraction of the beta parameter from the angular distributions of Ar 2p 3/2 and N2O Nt 1s photoelectrons by a means of Velocity Map Imaging Spectroscopy. The results of beta determined in the dipole approximation for N2O at different photon energies, coincided with pre-documented values but this was not so in the case of Argon. The determination of the asymmetry parameter was effected by image distortions and background signal that were present in all of the velocity map images in varying degrees. The photon energy and the energy separation between photoelectron distributions also affected the determination of beta. Possible non-dipole effects in the angular distributions of the Nt 1s state in N2O were also investigated via the determination of the non dipole asymmetry parameters delta and gamma. Unlike beta, these parameters could not be determined through inversions of the velocity map images due the symmetry along the spectrometer axis being broken in the non-dipole regime. For an accurate description of the photoionisation process in this instance, such effects should be accounted for, but with the current method it is not possible to observe them. One aim was to study photoionisation dynamics in gas phase FePc. As a result of inhomogeneous heating of the original solid sample, no data was obtained.