XUV spectrum generated via HHG in neon, reflected by multilayer mirror

XUV spectra with spatial resolution are generated via High Harmonic Generation in neon filled cell. The conditions are optimized for high XUV yield in the spectral region of interest (bandwidth of ∼6 eV FWHM around 94.4 eV).

A laser pulse of 0.25 mJ energy, about 6 fs of duration and centered at 800 nm is focused by 50 cm focal length mirror in a gas cell of 2.5 mm length. The generated XUV beam is then focused by a multilayer Mo/Si mirror (bandwidth of ∼6 eV FWHM around 94.4 eV) into a krypton cell (1 mm long). The transmitted XUV spectra are then diffracted by a flat-field XUV concave grating with 1200 grooves per mm (Hitachi 001-0640) and acquired with a XUV camera model PI-SX:400 manufactured by Princeton Instruments. There is also a slit < 0.5 mm that is imaged by the XUV grating to the XUV camera.

• HHG_Ne is a spectrogram of XUV with the krypton cell evacuated.
• HHG_Ne_in_Kr is a spectrogram of XUV with the krypton cell filled. One can observe krypton absorption lines.
• HHG_lines is a resulting Kr absorption spectral lines with assigned shells. 5p denotes excitation to 5p, term 5/2 3/2, while 5p' denotes 5p, term 3/2 1/2.