High-temperature UV absorption of methyl radicals behind shock waves

The absorption of ultraviolet narrow-line laser radiation by methyl radicals (CH3) in the B2A1′←X2A2″ electronic system has been studied at high temperatures behind shock waves. Methyl radicals at high temperatures were generated by the shock heating of methyl precursors: azomethane, methyl iodide, and ethane. The spectral shape and intensity of the broadband B2A1′←X2A2″CH3 absorption feature from 211.5 to 220 nm at high temperature (1565 K) has been measured. The absorption coefficient of CH3 at 216.62 nm, the wavelength of peak absorption at high temperatures in the P+Q band, has been determined from 1200 to 2500 K. Additionally, the absorption coefficients of several interfering UV-absorbing combustion species (C2H2,C2H4, and C3H6) have been determined at 216.62 nm.