MID-UV SPECTROSCOPY OF PROPYNENITRILE AT LOW-TEMPERATURE - CONSEQUENCES ON EXPECTED RESULTS FROM OBSERVATIONS OF TITAN ATMOSPHERE

The interpretation of albedo spectra in the mid-UV range is critically dependent on the knowledge of the absolute absorption coefficient, at specific temperatures and with high resolution for molecular compound s likely to absorb the scattered solar radiation in this wavelength ra nge. Propynenitrile, a key molecule in prebiotic synthesis, already de tected with IR and microwave sounding in Titan's atmosphere, exhibits intense absorption bands in the 185 to 230 nm interval. This paper dea ls with the absolute absorption coefficient k of propynenitrile at low temperature and high resolution and compares it to the room temperatu re values. The consequences of the observed k variations on the interp retation of Titan's atmosphere spectra, expected in the near future, a re considered here. As an additional result, the pressure regulation s ystem of the experiment allows us to assess the determination of the t emperature dependence of the propynenitrile vapor pressure.