Direct probe of the shape resonance mechanism in 2σg-shell photoionization of the N2 molecule -: art. no. 063003

Angular distributions of photoelectrons from a 2sigma g shell of fixed-in-space N-2 molecules have been measured for left- and right-elliptically polarized and for linearly polarized light at several photon energies in the region of sigma* shape resonance. That allowed the determination of a set of dipole matrix elements and phase shift differences characterizing the process. These data clearly show the enhancement of the f sigma(u) partial cross section in the resonance simultaneously with an abrupt increase of the corresponding phase shift by pi, which is the first experimental demonstration of the nature of the sigma* shape resonance in homonuclear diatomic molecules.