Generation of coherent VUV (vacuum ultraviolet) and soft X rays

During this reporting period three projects have been active. The first project is a study of three frequency summing in inert gases for the generation of short wavelength radiation. The authors have studied both helium and neon systems; they have concluded that the helium experiment is impractical because of the technical difficulties involved in generating the required wavelength. These difficulties are much less severe for the neon system, because of a natural near-coincidence of a neon non-allowed transition and the 16th harmonic of the Nd:YAG laser frequency. The second project resulted in the first observation of a laser induced inelastic collision. In the experiment, energy was switched from the resonant level of strontium to an excited state level of calcium by the application of a short visible laser pulse. The third project describes studies of thermal velocity charge exchange collisions as a method of selectively exciting strongly forbidden levels of singly ionized column IIA elements, leaving the ground state empty. The authors have successfully demonstrated a charge exchange collisional energy transfer from Mg(+) to the Sr(+)(4(d sup 2)D) metastable level.