Time variation of optical emission lines for Hg, and other elements detected in a mercury HID lamp before and during X-ray irradiation were analyzed. Various irradiation conditions are causing differences in time dependencies of all Hg spectral line intensities (including that of 253.73 nm resonance line not completely self-absorbed). The X-ray optical depths are smaller in the case of Hg gas compared with burner wall glass. The free electrons generated during X-ray exposure (photoelectrons, Auger electrons) contribute to changes in plasma characteristics (e.g. plasma temperature, density, etc.) in transitory regime. In quasi-stable regime there are practically no differences between electron temperatures for normal and irradiated lamp. A qualitative explanation in the framework of Beer-Lambert law is given.