HIGH-RESOLUTION MASS-RESOLVED ION SPECTROSCOPY OF CORE-EXCITED STATESOF THE NITROGEN MOLECULE

Photoionization and photofragmentation processes of core excited nitro gen molecules have been studied in the 390-425 eV energy region by mea ns of mass spectroscopy at the Swedish National Synchrotron Facility M AX in Lund. Vibrationally-resolved spectra of the pi resonance and th e series of one-hole Rydberg states have been recorded for N-2(+), Nand N2+ ions with a resolution comparable to recent photoabsorption me asurements and eight times higher than the previously reported mass-re solved spectra. In general the relative intensities of the vibrational members of the pi resonance follow the Franck-Condon distribution fo r all the studied fragments. However, shake-off processes significantl y modify the cross section for the formation of N+ and N2+ fragments i n the vicinity of the 1s core electron binging energy threshold. Also, the results of the N-2(+) ion yield are discussed in view of the repo rted fluorescence yield experiment.