Luminescence of He and Ne gases induced by EUV pulses from a laser plasma source

In this work helium and neon photoionization experiments, using a laser-plasma EUV (extreme ultraviolet) source were performed. The EUV radiation was focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulse. The most intense emission from the source spanned a relatively narrow spectral region centered at λ=11±1 nm, however, spectrally integrated intensity at longer wavelengths was also significant. Additionally Zr and Al filters were used to narrow the irradiation spectrum and to change the irradiation conditions. Irradiation of gases resulted in EUV luminescence, acquired by a toroidal grating spectrometer. The dominating spectral lines originate from singly charged ions, however, Ne III lines were also detected. Significant differences were observed between spectra obtained for different irradiation conditions. The differences were mainly due to various possibilities of photoexcitation of corresponding states depending on energy distribution of irradiating photons.