Orientation of doubly excited states in N2

Abstract

We have measured the total fluorescent intensity and circular polarization of light emitted in $3p{\phantom{\rule{0.16em}{0ex}}}^{4}\phantom{\rule{-0.16em}{0ex}}{P}^{o}\ensuremath{\rightarrow}3s{\phantom{\rule{0.16em}{0ex}}}^{4}\phantom{\rule{-0.16em}{0ex}}P$ transitions of excited neutral nitrogen atoms created by the photofragmentation of the N${}_{2}$ molecule with circularly polarized light having energies between 21 and 26 eV. The intensity measurements show the effect of predissociation of the ${\text{N}}_{2}$ Rydberg series $R$($C$) ${}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Sigma}}_{u}^{+}$ states by non-Rydberg doubly excited resonances (NRDERs), while nonzero values of circular polarization allow us to unambiguously identify the presence of a directly excited NRDER with ${}^{1}\phantom{\rule{-0.16em}{0ex}}{\ensuremath{\Pi}}_{u}$ symmetry in this energy range.