Fourier-transform infrared and jet-cooled diode-laser spectra of the 867 cm~(-1) v_9 band of acetaldehyde

摘要

The spectrum of the v_9 A′ C—C stretching fundamental band of acetaldehyde (CH_3CHO) at 867 cm~(-1) has been recorded in a slit-jet nozzle expansion using a diode-laser spectrometer and in a room-temperature gas cell using a Fourier-transform infrared spectrometer. The spectrum exhibits a-type transitions which have been assigned for J′ ≤ 19 and K′_a ≤ 5 for the A state and J′ ≤ 19 and K′_a ≤ 4 for the E state. The transitions show a large tunnelling splitting of ≈0.5 cm~(-1) for K_a = 0, attributed primarily to an anharmonic interaction of the v_9 vibration with the v_(14) + v_(15) torsional combination vibration at 920 cm~(-1). Evidence is also presented for an additional interacting vibration(s) affecting the v_9 tunnelling splitting.