THE CH3 3PZ (2)A2''[-(X)OVER-TILDE (2)A(2)''O(0)0 BAND AT TEMPERATURES UP TO 1700-K INVESTIGATED BY REMPI SPECTROSCOPY

The 0(0)0 band of the CH3 3p(z)2A2'' <-- X2A2'' Rydberg transition has been recorded using the (2+1) resonance-enhanced multiphoton ionizati on (REMPI) of CH3 at 333 run. CH3 was generated in a discharge flow re actor at room temperature and in a hot-filament-assisted chemical vapo r deposition (HFCVD) reactor at temperatures of 820 to 1700 K. By mean s of spectral simulation the rotational constants, B0' and C0', and th e rotational state-dependent predissociation rates of the 3p(z) 2A2'' state were determined. Based on these constants and the well-known rot ational and vibrational ground-state constants, relative intensities o f the CH3 REMPI spectra were calculated for temperatures up to 2300 K. These spectra were used to evaluate relative CH3 concentrations from measured REMPI peak intensities of the dominant Q branch.