Excitation and decay of the C2Σ+u state of N+2 following collisions of He+ ions with N2 isotopes

Isotope Effects in the Predissociation of Excited States of N2+ Produced by Photoionization of 14N2 and 15N2 at Energies Between 24.2 and 25.6 eV

“…As a result, only upper limits to the 14 N 2 + branching ratios are listed for v′ = 5–8. The branching ratios in line 4 are those obtained from the fluorescence spectra observed in the ion-impact experiments (Govers et al, 1975); they are somewhat more precise than the closely similar electron-impact results (van de Runstraat et al, 1974). They are obtained by dividing the measured fluorescence intensities, relative to that of the un-predissociated v′ = 2 level (line 3), by the theoretical excitation ratios obtained by assuming a Franck-Condon excitation with configuration interaction (line 2).…”

“…The uncertainty limits are obtained after propagation of the original Poisson distribution of the photoelectron image pixel counts. Lines 2 to 4 summarize the data of Govers et al (1975). Line 5 lists the branching ratios obtained by Ehresmann et al (2006).…”

“…The competition between C-state predissociation and C → X fluorescence has previously been quantified by comparing measured C → X fluorescence cross sections with those expected in the absence of predissociation. For this purpose, vibrationally resolved fluorescence intensities were measured upon impact of electrons (van de Runstraat et al, 1974) or ions (Govers et al, 1975) on a static room-temperature target of N 2 , at impact speeds high enough for the excitation to the various C-state vibrational levels to be considered as a “vertical” Franck-Condon process. Summing fluorescence from a particular (C, v′) level to all vibrational levels v″ of the N 2 + ground-state, one obtains the vibrational fluorescence cross sections, σ em (v′), and one can write:…”

“…The excitation ratios were obtained from the N 2 + (C, v′)←N 2 (v = 0) Franck-Condon factors, (“FCF”) including configuration interaction (“CI”) (see van de Runstraat et al, 1974; Govers et al, 1975 for details).…”

“…The competition between C-state predissociation and fluorescence has first been experimentally quantified by the analysis of the vibrationally resolved C → X emission spectrum. In the work by van de Runstraat et al (1974) and Govers et al (1975), the C (v′) levels were populated under conditions where their relative populations should reflect a “vertical” ionization process, so that the vibrational fluorescence intensities could be predicted in the absence of predissociation. Comparison with the relative intensities that were actually observed made it possible to determine the ratio between the predissociation- and fluorescence probabilities, A pred (v′)/A em (v′), for each of the C-state vibrational levels v′ = 3–8.…”