The band system of ethane around 7 micron: Frequency analysis of the ν6 band

•A detailed analysis of the weak ν6 band in the 1340-1410 cm−1 region is made.•A spectrum recorded at a resolution of 0.003 cm−1 and temperature of 200 K was used.•The Hamiltonian included two couplings between ν6 and ν9 and one between ν6 and ν8.•Experimental characterization for states lying below 1400 cm−1 is made.

High quality line parameters of the band systems of ethane are required for accurate characterization of spectral features observed in the atmospheres of Jovian planets and their satellites. To date, experimental characterization of the excited vibrational states lying below 1300 cm−1 has been made. This includes the torsional bands around 35 µm, ν9 (820 cm−1), ν3 (990 cm−1), ν12−ν9 (380 cm−1) and ν9+ν4−ν4 (830 cm−1) bands. These earlier high resolution ro-vibrational analyses were made to experimental accuracy. Here, we report a detailed analysis of the weak ν6 band in the 1340-1410 cm−1 region using a spectrum recorded at a resolution of 0.003 cm−1 and temperature of 200 K. The Hamiltonian model included couplings between ν6 and ν9 (in particular with ν9+2ν4 with which it is resonantly coupled) as well as couplings between ν6 and ν8. An excellent fit to within experimental accuracy was obtained. Taking the results of this 5-state fit, together with earlier results on lower lying vibrations, we now have experimental characterization for torsion-vibration states of ethane lying below 1400 cm−1.