In magnesium, bound‐continuum matrix elements contribute constructively to the magnitude of the third‐order nonlinear susceptibility &khgr;(3&ohgr;)(3)for sum‐frequency mixing in the region of the first continuum. Thus, continuously tunable harmonic radiation in the region 140–160 nm (9000 cm−1) can be readily obtained with two dye lasers of modest power. The onset of saturation in the vacuum ultraviolent intensity at 1436 nm was not observed until incident powers ⩾30 kW, where the measured power conversion efficiency was 0.2%.