Raman scattering of laser radiation to the far ultraviolet by excited states of helium and neon

An investigation was made of spontaneous Raman scattering of YAG:Nd³⁺ laser radiation with the wavelength λ=1.064μ by the metastable state 2¹S of the helium atom and the 2p⁵3p[5/2]₂ state of neon, both excited in a hollow-cathode discharge. This scattering produced radiation at the wavelengths of 56.9 and 62.8 nm, respectively. The spectral brightness of the source was 1.5×10¹⁵ and 1.0×10¹⁴ photons·sec^–1·cm^–2·sr^–1·cm when the population of the He(2¹S) state was 1.4×10¹¹cm^–3 and the population of the Ne(2p⁵3p[5/2]₂) state was 3.5×10⁸cm^–3. It was found that the Raman scattering by the atomic or ionic levels excited in a gas-discharge plasma made it possible to generate strong far ultraviolet radiation and could be used for plasma diagnostics.