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.