Generation of extreme ultraviolet radiation at 79 nm by sum frequency mixing

High brightness tunable coherent extreme ultraviolet (XUV) radiation at 79 nm with a peak power of ∼200 mW has been generated in H
2
gas by sum frequency mixing of two quanta from a high spectral brightness ArF* (193 nm) source with one quantum from a tunable dye laser (∼436 nm). Spectroscopic application of this radiation has been demonstrated by observation of a broad (∼160 cm
^-1
) autoionizing structure in Ar and narrow (∼2 cm
^-1
) autoionizing features in D
2
. An analysis is given which identifies the dominant molecular states involved in the nonlinear susceptibility of the medium (H
2
). The frequency independent tuning behavior of the 79 nm output power observed over ∼300 cm
^-1
is related to the molecular structure and response of the nonlinear medium in the intense optical field.