N tex2html_wrap_inline24 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 tex2html_wrap_inline24 -rich atmospheres of Titan and Triton have been hampered by the lack of fundamental spectroscopic data for N tex2html_wrap_inline24 -- in particular, by the lack of reliable f-values and linewidths for electronic bands of N tex2html_wrap_inline24 in the 800 to 1000 Å wavelength region. In order to address this shortfall, we have studied the photoabsorption spectrum of N tex2html_wrap_inline24 with a resolving power ( tex2html_wrap_inline34 ) 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 tex2html_wrap_inline24 , 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 tex2html_wrap_inline24 (nl tex2html_wrap_inline40 10 tex2html_wrap_inline42  cm tex2html_wrap_inline44 ) observed by the Voyager spacecraft at Titan and Triton. We will present preliminary linewidth results for some b(v tex2html_wrap_inline46 )-X(0) bands of N tex2html_wrap_inline24 . We will also demonstrate that, for some bands and for high column densities, isotopically rare tex2html_wrap_inline50 N tex2html_wrap_inline52 N may contribute disproportionately to N tex2html_wrap_inline24 absorption. This work supported in part by NASA Grants and NAGW-3607 and -5200.