N VUV Linewidths and Band Oscillator Strengths
G. Stark (Physics Department, Wellesley College), P.L. Smith (CURSOAR Technologies and CfA)
Analyses of Voyager EUV occultation measurements of the N -rich atmospheres of Titan and Triton have been hampered by the lack of fundamental spectroscopic data for N -- in particular, by the lack of reliable f-values and linewidths for electronic bands of N in the 800 to 1000 Å wavelength region. In order to address this shortfall, we have studied the photoabsorption spectrum of N with a resolving power ( ) of 90,000 to 170,000. New band-integrated photoabsorption cross sections (i.e., f-values) for the region 900 and 950 Å\ will be presented. Data for linewidths -- which, in the case of the EUV bands of N , are often determined by predissociation lifetimes rather than by Doppler effects -- are as essential as f-values in calculations of the transmission of radiation through the high column densities of N (nl 10 cm ) observed by the Voyager spacecraft at Titan and Triton. We will present preliminary linewidth results for some b(v )-X(0) bands of N . We will also demonstrate that, for some bands and for high column densities, isotopically rare N N may contribute disproportionately to N absorption. This work supported in part by NASA Grants and NAGW-3607 and -5200.