Mid-infrared diode laser spectroscopy of (X)over-tilde(1)A' (HCCl)-Cl-35

The observation of the C-Cl stretching fundamental of (HCCl)-Cl-35 in its ground (X) over tilde(1)A' state is reported. HCCl was formed in a continuous flow system by the excimer laser photolysis of CHBr2Cl at 193 nm and the transient absorption recorded by infrared diode laser spectroscopy. The band has a-type character and the fundamental vibrational frequency is found to be 811.5963 cm(-1). No evidence was found for perturbations in either the ground or vibrationally excited states, implying that the excited triplet (a) over tilde(3)A '' states lies above the C-Cl stretching level in HCCl. The observed rotation-vibration transitions were well fit by a standard asymmetric rotor Hamiltonian. There is a decrease in the A rotational constant on vibrational excitation, suggesting that some bend-C-Cl stretch coupling is present. (C) 1997 Academic Press.