Fluorescence from photofragments as an aid in identifying new molecular states: The N2 case

Synchrotron radiation has been used to measure the excitation function for producing fluorescence in the 1050–1800 Å region through photodissociative excitation of N2 in the 400–620 Å region and the photoabsorption cross section of N2 in the 600–670 Å region. From the fluorescence excitation function we have found: (i) a molecular state(s) in the 21–22.5 eV region which has not been observed in absorption and photoionization spectra, (ii) structures which correlate with known two-electron excited Rydberg states, and (iii) a decrease in fluorescence cross section at photon energies >23.8 eV, which indicates the existence of new competing processes. The observed molecular state(s) as well as the weak absorption structure in the 19–21 eV region are tentatively assigned as a Rydberg series leading to the D 2Πg of N+2. The newly observed Rydberg states in the 21–22.5 eV region may account for the unusual behavior recently reported in photoelectron spectroscopy results.