High resolution laser spectroscopy beyond 18 eV: the B 2Σu+←X 1Σg+ photoelectronic transition of N2

Coherent, narrow-bandwidth laser radiation has been generated beyond 18 eV. The radiation has been used to record a rotationally resolved pulsed-field-ionization zero-kinetic-energy photoelectron spectrum of the B 2Σu+←X 1Σg+ transition of N2. Analysis of the rotational structure indicates that the removal of one of the two 2σu∗ inner-valence-shell electrons is accompanied by substantial changes in the core rotational angular momentum quantum number: Rotational branches are observed with ΔN=N+−N=±1 and ±3, where N+ and N represent the core rotational angular momentum of the ion and the neutral, respectively. These branches can be explained by the ejection of a photoelectron with dominant l=0 and l=2 character.