GENERATION OF TUNABLE COHERENT EXTREME-ULTRAVIOLET RADIATION BEYOND 19 EV BY RESONANT 4-WAVE-MIXING IN ARGON

The upper energy limit of broadly tunable coherent radiation sources b ased on resonant four-wave mixing is investigated. An argon resonance [the two-photon (3p)(5)4p[5/2](J = 2)<--(3p)(6) resonance at 10 5617 c m(-1)] has been used in resonant four-wave mixing to generate tunable coherent narrow-bandwidth extreme ultraviolet radiation. With this res onance, spectroscopically useful laser intensities (up to 5 x 10(6) ph otons per laser pulse) can be produced beyond 19 eV with a bandwidth a s low as 0.1 cm(-1). The light source is used to record a pulsed-field -ionization zero-kinetic-energy photoelectron spectrum of the b (4)Sig ma(g)(-)(v(+) = 1)<--X (3)Sigma(g)(-)(v = 0) photoelectronic transitio n of O-2. (C) 1998 American Institute of Physics.