Photoemission in the molecular frame using the vector correlation approach: from valence to inner-valence shell ionization

Abstract

The ( V A + , V e, e ˆ ) vector correlation method, combining imaging and time-of-flight resolved electron-ion coincidence techniques, is used to probe dissociative photoionization (DPI) of simple molecules induced by VUV polarized synchrotron radiation, to obtain the I( θ e, ϕ e) molecular frame photoelectron angular distributions (MFPADs). We focus on examples where DPI is induced by valence shell and inner-valence shell excitation. For valence shell ionisation, we report the results of a complete experiment for DPI of O 2 via the O 2 +(3 2Π u) ionic state, performed with a single circular polarization of the light at a photon excitation energy h ν = 24.4 eV. A significant circular dichroism effect characterizes electron emission in the molecular frame. Inner-valence shell ionization induced by linearly polarized light is reported for the CO 2 and N 2O isoelectronic molecules selecting two specific satellite lines using light with h ν ≃ 35 eV . For both valence and inner-valence ionization, the measured MFPADs are compared with multichannel configuration interaction calculations, as well as with the prediction of a simple theoretical model of photoionization dynamics that probe the role of the initial state molecular orbital and which is presented in this special issue.