Many-photon absorption, luminescence, and dissociation of ethylene molecules in the field of high-intensity CO2 laser pulses

An experimental investigation was made of the dissociation of ethylene resulting from interaction of highintensity infrared CO₂ laser pulses with the ν₇ vibration; the resonance and threshold properties of the process were determined. This dissociation produced acetylene and ethane. A study was made of the manyphoton absorption of CO₂ laser radiation by ethylene and of the influence of the laser radiation intensity on the many-photon absorption spectrum. A fine structure was observed in this spectrum and it was attributed to a multiple vibrational-rotational resonance of symmetric-top molecules. The influence of the laser radiation frequency on the resonance characteristics of the luminescence resulting from such dissociation was investigated. The influence of the presence of buffer gases (H₂, D₂, He, Ar, Xe) on the intensity of the luminescence was also studied. It was found that the infrared excitation spectra of the luminescence and dissociation and the many-photon absorption spectrum of ethylene, which were of basically similar form, exhibited a short-wavelength shift by 4 cm^–1 relative to the linear absorption maximum due to the 0→1 transition in the ν₇ vibration.