Luminescence of reaction products of mechanochemical decomposition for some gaseous hydrocarbons CxHy during tribodestruction of cerium and terbium salts

Abstract

The paper is concerned with the study of triboluminescence of lanthanide salts in an atmosphere of hydrocarbon gases (methane, its homologues, ethylene, and acetylene). The luminescence of *CH and/or *C2 appeared after mechanochemical decomposition of these gases during tribodestruction of crystals was observed in all the gases. Injection of hydrocarbon gases suppressed the glow of *N2 (a gas component in a triboluminescence spectrum of air). When heavier hydrocarbon gases were used, the triboluminescence spectra indicated that *C2 emission predominated over the luminescence of a *CH radical. The intensity of *C2 emission decreased with an increase in a hydrocarbon chain. The decomposition mechanism of hydrocarbon gases to form *CH and *C2 during triboluminescence of lanthanide salts in the atmosphere of these gases is discussed. A similar decomposition mechanism of these gases in electric discharges is also discussed. The experimental spectra of the *C2 (Swan bands) were used to calculate and to estimate some characteristics of the radiating medium. The vibrational temperatures Tvib ~ 4000–5000 K calculated for different hydrocarbon gases exceeded the rotational one Trot ˂ 3000 K. This indicates that the working medium is a nonequilibrium plasma, in which the C2 excitation occurs due to electron impact. In addition, it was assumed that the excitation could also be caused by collision with heavy particles, for example, hot gas molecules as a result of gas heating during a series of consecutive experiments.