Tunable Diode Laser Spectra and Assignment of the 748 cm⁻¹ Band of Propane

The rotational structure of the 748 cm -1 c-type CH 2 -rocking fundamental of propane was analysed using tunable diode laser (TDL) techniques. On grounds of a low-resolution Fourier transform (FTIR) spectrum and of the known ground-state rotational and centrifugal-distortion constants, some 700 transitions were measured and assigned in several regions of the band. The upper-state constants determined in this way allow the prediction of rovibrational frequencies to within 0.003 cm -1 , covering quantum states up to J = 50 and K a = 20. The band appears unperturbed.