https://doi.org/10.1351/goldbook.ET07372
Non-coherent source of ultraviolet radiation capable of producing quasi-monochromatic radiation from the near UV (\(\lambda = 354\ \rm{nm}\)) to the vacuum UV (\(\lambda = 126\ \rm{nm}\)). 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 \(\sim 30\ \rm{kPa}\), 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 \(126\ \rm{nm}\) with $\ce{Ar2}$, \(146\ \rm{nm}\) with $\ce{Kr2}$, \(172\ \rm{nm}\) with $\ce{Xe2}$, \(222\ \rm{nm}\) with $\ce{KrCl}$, and \(308\ \rm{nm}\) with $\ce{XeCl}$, obtained with efficiencies of \(5{-}15\,\%\). Pulsed Xe-excimer ($\ce{Xe2}$) lamps may have up to 40 % efficiency. Good efficiencies are also obtained with XeBr at \(291\ \rm{nm}\) and with XeI at \(253\ \rm{nm}\). Other wavelengths produced with much less efficiency are \(207\ \rm{nm}\) ($\ce{KrBr}$), \(253\ \rm{nm}\) ($\ce{XeI}$), \(259\ \rm{nm}\) ($\ce{Cl2}$), and \(341\ \rm{nm}\) ($\ce{I2}$) (see Table 1).
Table 1: Peak wavelengths (\(\rm{nm}\)) obtained in dielectric-barrier discharges with mixtures of noble gas ($\ce{Ng}$) and halogen ($\ce{X2}$). Wavelengths of commercially available lamps are shown in boldface type. The molecular species indicated are excimers or exciplexes.
$\ce{X2}$ $\ce{Ne}$ $\ce{Ar}$ $\ce{Kr}$ $\ce{Xe}$ $\ce{Ng2}$ 126 146 172 $\ce{F}$ 157 108 193 249 354 $\ce{Cl}$ 259 175 222 308 $\ce{Br}$ 291 165 207 283 $\ce{I}$ 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.