excimer lamp

Non-coherent source of ultravioletradiation capable of producing quasi-monochromatic radiation from the near UV ( $λ = 354 nm$ ) to the vacuum UV ( $λ = 126 nm$ ). The operation of the excimer lamps relies on the radiative decomposition of excimers or exciplexes created by various types of discharges.

Notes:

Using noble gas, halogen, or noble gas / halogen mixtures with fill pressure $∼ 30 kPa$ , the radiative decomposition of the excimer or the exciplex produces nearly monochromatic radiation. Some of the commercially available wavelengths for the particular excimers or exciplexes are $126 nm$ with Ar₂, $146 nm$ with Kr₂, $172 nm$ with Xe₂, $222 nm$ with KrCl, and $308 nm$ with XeCl, obtained with efficiencies of 5 - 15 %. Pulsed Xe-excimer (Xe₂) lamps may have up to 40 % efficiency. Good efficiencies are also obtained with XeBr at $291 nm$ and with XeI at $253 nm$ . Other wavelengths produced with much less efficiency are $207 nm$ (KrBr), $253 nm$ (XeI), $259 nm$ (Cl₂), and $341 nm$ (I₂) (see Table 1).

Table 1: Peak wavelengths ( $nm$ ) obtained in dielectric-barrier discharges with mixtures of noble gas (Ng) and halogen (X₂). Wavelengths of commercially available lamps are shown in boldface type. The molecular species indicated are excimers or exciplexes.
	X₂	Ne	Ar	Kr	Xe
Ng₂			126	146	172
F	157	108	193	249	354
Cl	259		175	222	308
Br	291		165	207	283
I	341			190	253

Phosphors are used to transform the UV radiation into visible radiation. This is the basis of mercury-free fluorescent lamps and of flat plasma-display panels with a large screen.

Source:

PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 335