SINGLE-PHOTOIONIZATION AND DOUBLE-PHOTOIONIZATION CROSS-SECTIONS OF NITRIC-OXIDE (NO) AND IONIC FRAGMENTATION OF NO+ AND NO2+

Single- and double-photoionization processes of gaseous nitric oxide (NO) have been studied in the photon energy region 37- 100 eV by use of time-of-flight mass spectrometry and a photoion-photoion-coincidence method together with synchrotron radiation. The single- (sigma+) and double- (sigma2+) photoionization cross sections of NO are determined. Dissociation ratios of the precursors NO+ and NO2+ are determined separately at the excitation energies where the single and double photoionization are in competition. The results show that the metastable NO2+ ions amount to about 15% at higher photon energies in the double-photoionization processes. Ionic branching ratios and the partial cross sections for the individual ions produced from the precursors NO+ and NO2+ are also presented. The threshold for the dissociative double photoionization was found to be 41.0+/-0.5 eV.