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 compounds likely to absorb the scattered solar radiation in this wavelength range. Propynenitrile, a key molecule in prebiotic synthesis, already detected with IR and microwave sounding in Titan's atmosphere, exhibits intense absorption bands in the 185 to 230 nm interval. This paper deals with the absolute absorption coefficient k of propynenitrile at low temperature and high resolution and compares it to the room temperature values. The consequences of the observed k variations on the interpretation of Titan's atmosphere spectra, expected in the near future, are considered here. As an additional result, the pressure regulation system of the experiment allows us to assess the determination of the temperature dependence of the propynenitrile vapor pressure.