Circular dichroism in molecular frame photoemission

The paper reports on a comparative experimental and theoretical study of circular dichroism in electron angular distribution ( CDAD) in the molecular frame ( MF) of linear molecules photoionized by circularly or elliptically polarized light. The CDAD is derived from the analysis of the complete molecular frame angular distribution ( MFPAD) I( chi,theta(e),phi(e)), where chi is the orientation of the molecule with respect to the light propagation axis and ( theta(e),phi(e)) the electron emission direction in the MF, using the vector correlation method. The CDAD is quantified by the theta(e) dependence of the left-right emission asymmetry maximum in the plane perpendicular to the light propagation axis k, for a space fixed molecule orthogonal to k. The experimental results for selected valence shell photoionization ( PI) reactions in NO, O-2, N2O compare very well with the multichannel Schwinger configuration interaction ( MCSCI) ab initio calculations. Combined with a simple model of the ionization process, including the partial-wave composition of the initial state and phase shifts estimated from quantum defects for the various scattering partial-waves, these results provide the basis for a general discussion of the circular dichroism effect. This study enables one to disentangle the influence of the ( sp sigma, p pi...) initial valence shell ionized orbital and that of the scattering dynamics on some fingerprint properties of the CDAD. On the other hand, the CDAD for s sigma K-shell is purely assigned to a final state scattering effect. This analysis will be extended to PI of non-linear molecules where the circular dichroism characterizes recoil frame photoelectron angular distributions ( RFPADs).