Emission spectra of gaseous avalanches and their time structure

Spectroscopic measurements of the emission spectra or argon/ethane and methane/ethane spectra are presented. In addition, time-resolved measurements were performed in argon/ethane, argon/methane, and methane/ethane in the vacuum ultraviolet region of the spectrum. In argon/ethane mixtures the energy spectra present a complex pattern, not only as a result of the many dissociation processes that may take place but also due to the high sensitivity to the presence of impurity molecules. In argon/methane mixtures, the presence of impurities is no longer detected, probably because of the high cross section for the quenching of atomic excited states of argon by methane molecules, for high methane concentrations. In methane/ethane and in argon/methane the number of photons emitted per electron is of the same order of magnitude for the proportional mode, while in argon/ethane this number is much lower, even when operated in the SQS mode