Extended line assignments for the ν3 + ν4 band of 12CH4

Abstract The ν 3 + ν 4 absorption band of 12 CH 4 at 2.3 μm has been re-examined at 0.01-cm −1 resolution with a Fourier transform spectrometer in order to extend and review the line assignments of Bobin and Guelachvili. More than 300 new or revised excited-state energy levels have been determined by means of combination differences in ν 3 + ν 4 and corroborating lines in the spectrum of ν 3 + ν 4 − ν 4 at 3.3 μm.