O 1s excitation and ionization processes in the CO2 molecule studied via detection of low-energy fluorescence emission

Oxygen 1s excitation and ionization processes in the CO2 molecule have been studied with dispersed and non-dispersed fluorescence spectroscopy as well as with the vacuum ultraviolet (VUV) photon?photoion coincidence technique. The intensity of the neutral O emission line at 845 nm shows particular sensitivity to core-to-Rydberg excitations and core?valence double excitations, while shape resonances are suppressed. In contrast, the partial fluorescence yield in the wavelength window 300?650 nm and the excitation functions of selected O+ and C+ emission lines in the wavelength range 400?500 nm display all of the absorption features. The relative intensity of ionic emission in the visible range increases towards higher photon energies, which is attributed to O 1s shake-off photoionization. VUV photon?photoion coincidence spectra reveal major contributions from the C+ and O+ ions and a minor contribution from C2+. No conclusive changes in the intensity ratios among the different ions are observed above the O 1s threshold. The line shape of the VUV?O+ coincidence peak in the mass spectrum carries some information on the initial core excitatio

X-ray back-lighter characterization for iron opacity measurements using laser-produced aluminium K-alpha emission

Aluminium Kα emission (1.5 keV) produced by an 8 J, 500 ps, Nd:glass laser incident at 45° onto a layered target of 0.8 µm thick aluminium (front side) and 1 µm thick iron (backside) has been used to probe the opacity of iron plasma. Source broadened spectroscopy and continuum emission analysis show that whole beam self-focusing within the aluminium plasma results in a two-temperature spatial distribution. Thermal conduction from the laser-irradiated aluminium into the iron layer, enhanced by the whole beam self-focusing, results in a temperature of ~10–150 eV in the iron layer. The iron opacity at a photon energy of 1.5 keV is shown to be strongly modified from cold values in agreement with IMP code opacities. Results presented here represent a feasibility study to seed future work using table-top laser systems for plasma opacity experiments