THE BAND OF CH3CH2D FROM 770-880 cm_1

Abstract

To extend the ethane database we recorded a 0.0028 wn resolution spectrum of chem{CH_3CH_2D} from 650 to 1500 wn using a Bruker IFS-125HR at the Jet Propulsion Laboratory. The 98% deuterium-enriched sample was contained in the 0.2038 m absorption cell; one scan was taken with the sample cryogenically cooled to 130 K and another at room temperature. From the cold data, we retrieved line positions and intensities of 8704 individual absorption features from 770 � 880 wn using a least squares curve fitting algorithm. From this set of measurements, we assigned 5041 transitions to the nub{17} fundamental at 805.3427686(234) wn; this band is a c-type vibration, with A and E components arising from internal rotation. The positions were modeled using a 22 term torsional Hamiltonian using SPFIT producing the A and E energy splitting of 5.409(25)x10$^{-3}$ wn (162.2(8) MHz) with a standard deviation of 7x10$^{-4}$ wn (21 MHz). The calculated line intensities at 130 K agree very well with retrieved intensities. To predict line intensities at different temperatures, the partition function value was determined at eight temperatures between 9.8 and 300 K by summing individual energy levels up to J = 99 and K$_{a}$ = 99 for the six states up through nub{17} at 805 wn. The resulting prediction of singly-deuterated ethane absorption at 12.5 $mu$m enables its detection in planetary atmospheres, including those of Titan and exoplanets.