The optical characteristics of gas-discharge plasma are being its most important characteristics. They carry information about the physicochemical processes occurring in plasma, its parameters and characteristics, and primarily, such as the concentrations of electrons, atoms and molecules, the energy distribution of electrons and their drift velocities; characterize the efficiency of elastic and inelastic processes of electron collisions with plasma components, quenching the energy states of excited particles, and specific losses of discharge power on electronic processes. The book presents the investigation of optical characteristics of a barrier discharge plasma on mixtures of mercury dibromide vapor with gases: helium, xenon, krypton, nitrogen and sulfur hexafluoride, its parameters and the efficiency of inelastic electron collisions with the components of the mixture. The application of research results to create effective gas-discharge radiation sources (exciplex lamps) of blue-green and ultraviolet spectral ranges is proposed. The book is a monograph addressed to scientists, engineers and graduate students specializing in the field of plasma physics and quantum electronics.