The transition dipole moment of the ν2 band of the methyl radical

By using a tunable diode laser, the decay of the absorption intensity with time, after the discharge generating the radical was switched off, was measured for a line [Q4(4)] of the CH3 ν2 fundamental band. When combined with a literature value of the CH3 recombination rate constant, the present result gave an estimate for the steady-state concentration of the CH3 radical. The steady-state absorbance of the Q4(4) line was also measured, and the two results were used to calculate the transition moment of the CH3 v2=1←0 band to be 0.280±0.049 D.