Excimer stands for "excited dimer". Basically, this is a pair of atoms with an excited gas atom which in its ground state is usually unconnected (Xe + Xe* = Xe2* (excimer)).
Excimers can be formed by noble gases and noble gas/halogen mixtures. The excimer state is of short duration. When the excimer breaks up, UV radiation is emitted in a very narrow, quasi monochromatic spectral range. Depending on the gas selected, different narrow-band UV spectrums are emitted, mainly in a single spectral line.
There are many different excimer combinations today that can emit UV radiation in the wavelength range between 120 nm and 380 nm. As the spectral range contains no infrared portion, these lamps deliver the pure UV spectrum.
The gas discharge is caused by a radio-frequency field and this is why no electrodes are required for the gas discharge.
