On the nature of the luminescence emitted by a polypropylene film after interaction with a cold plasma at low temperature

The light emitted by an insulating material once its surface has been submitted to a cold plasma, plasma-induced luminescence is investigated on polypropylene films at low temperature. An analysis of the integral and wavelength resolved Light is carried out. The kinetical evolution of the spectrum after plasma interaction are reported and analyzed. Investigation of the photo- and chemiluminescence spectra of the material shows that plasma-induced luminescence has three spectral components, each having different excitation mechanisms and thus different kinetics. The fastest is due to the ultraviolet irradiation during plasma contact, the second is dominated by radical chemistry producing carbonyl groups, and the third, with the slowest kinetics, is due to carrier recombination on the most conjugated chromophores which are preferentially charged by the plasma. To confirm the interpretation of plasma induced luminescence spectrum, the first results concerning short and long plasma interaction are considered. (C) 1997 American Institute of Physics.