EXTRATERRESTRIAL SPECTROSCOPY - FOREIGN-GAS BROADENING OF PROPANE AS IT APPLIES TO THE ATMOSPHERE OF TITAN

Propane spectra in the upsilon21 band near 748 cm-1 were observed with an instrumental resolution of 0.0025 cm-1. These data were obtained at the National Optical Astronomy Observatory, Tucson, AZ using the FTS spectrometer at the National Solar Observatory McMath telescope facility. The spectra included foreign-gas broadening due to He, H-2 and N2. All of these measurements were carried out at a temperature of 175 K. The following broadening coefficients (in cm-1 atm-1) are obtained at 175 K:0.128(19) for C3H8-He, 0.146(15) for C3H8-N2, and 0.241(19) for C3Hg-H2. These results are consistent with previous room-temperature measurements when a T-1/2 scaling law is invoked.