Measurement of the ν3 fundamental transition moment and vibrational relaxation rates of the CD3 radical

Abstract

Diode laser absorption spectroscopy was used to measure the transition dipole moment for the ν3 (degenerate asymmetric stretch) fundamental vibration of CD3 produced by the 193-nm photodissociation of acetone-d6. The time evolution of the ground state absorption was used to measure the vibrational relaxation rates from the manifold of excited vibrational states to the ground state of CD3 following collisions with various bath gases. The transition dipole moment was determined to be 0.030±0.002 D and the vibrational relaxation coefficients were determined to be (2.5±0.2)×10−13 for argon, (2.6±0.2)×10−13 for helium, (3.15±0.2)×10−13 for nitrogen, and (4.3±0.5)×10−12 for acetone-d6 in units of cm3 molecules−1 s−1. Results are compared to literature values for CH3 and the mechanism of the relaxation is discussed.