Fluorescence measurements of the M-band photon emission from a laser-irradiated gold disk

Gold M-band x rays with energies above the sulfur K edge of 2.472 keV create sulfur K/sub α/ fluorescence with a quantum efficiency of 8.1%. The sulfur fluorescer was a 600 x 1500-μm rectangle about 1100 μm from the gold plate. It was 25 μm of C6H4S plastic shielded by 50 μm of beryllium. The absolute brightnesses of both the M-band spectrum and of the fluorescence line were measured by separate spectrographs. The spectrograph measuring the fluorescence did not have a direct line of sight to the hot gold. These measurements were made with 3512-A laser light irradiating the gold plate for 1 ns over a number of intensities between 2 x 1014 and 1015 W/cm2