Diode laser spectroscopy of the ν9 band of ethyl chloride

The vibration-rotation spectrum of the ν₉ band of C₂H₅Cl was recorded using a Nicolet 7199 Fourier Transform Infrared Spectrometer; the Q-branch, R(5)-R(6) multiplets, and P(21)-P(22) multiplets were investigated using a tunable semiconductor diode laser spectrometer. Constants derived from these assignments are (cm^?1) ν₉ = 973.8379(2), A⁹ = 1.039516(3), B⁹ = 0.183081(7), C⁹ = 0.164505(8). The line which coincides with the CO₂ laser 10R(6), which has been employed in multiphoton dissociation studies, is tentatively assigned to the 20_{3 18}-21_{3 19} transition. In addition, a very strong coincidence of transitions 19_{9 11}-19_{9 10} and 19_{9 10}-19_{9 11} with the CO₂ 10R(16) line is found, which can provide a good candidate for laser chemistry and infrared double resonance spectroscopy.