PRESSURE-BROADENED LINEWIDTH MEASUREMENTS IN THE NU(2) BAND OF THE CH3 RADICAL

Pressure broadening coefficients for an infrared transition of the met hyl radical have been measured for the first time. CH3 radicals, gener ated by pyrolyzing di-tert-butyl peroxide in a flow of either N-2 or A r, were probed using a tunable diode laser and a multipass absorption cell. The Lorentz half-width of the Q(6,6) line of the nu(2) band of C H3 at 607.024 cm(-1) was measured as a function of pressure at 295 K. The broadening coefficients (HWHM) are b(Ar) = 0.0310 +/- 0.0012 cm(-1 ) atm(-1) and b(N-2) = 0.0390 +/- 0.0020 cm(-1) atm(-1). These coeffic ients are lower than those for CH4-Ar, N-2 broadening. This may be due to a lower polarizability or smaller effective hard collision diamete r for CH3 relative to CH4. (C) 1996 Academic Press, Inc.