Association Reaction of Gaseous CH in Femtosecond Laser Filaments Studied by Time-of-Flight Mass Spectrometry.

Association reactions by femtosecond laser filamentation in gaseous CH were studied by time-of-flight mass spectrometry of neutral reaction products. Direct sampling from the reaction cell to a mass spectrometer via a differential pumping stage allowed the identification of various hydrocarbon molecules C H with = 3-7 and = 4-7, which includes species not observed in the previous studies. It was found that products containing three and four carbon atoms dominate the mass spectrum with smaller yields for higher-mass species, suggesting that carbon chain growth proceeds through the reaction with CH in the reaction cell. The product distribution showed a clear dependence on the laser pulse energy for filamentation.