R. G. Caro

Soft x‐ray pumping of metastable levels of Li+

Soft x rays from a plasma generated by a neodymium: yttrium aluminum garnet laser beam (1.06 μm) are used to photoionize neutral Li vapor to produce Li+ metastables. Maximum metastable densities of Li+ (1s2s) 1S=6×1014 ions/cm3 and Li+ (1s2s) 3S=3×1015 ions/cm3 are obtained. The effective lifetimes of these levels are measured to be approximately 5 ns. At 50 mJ of incident laser energy the inferred conversion efficiency from 1.06‐μm radiation to soft x rays is ∼14%.

Quasi-metastable quartet levels in alkalilike atoms and ions.

We describe the properties of a subclass of quartet levels of alkalilike atoms and ions that often retain metastability against autoionization and may have large radiative yields. Gain cross sections for XUV lasers with wavelengths between 20 and 100 nm are given.

Proposal for an extreme-ultraviolet Auger laser at 63.8 nm in Cs iii

A system is proposed in which Cs atoms photoionized by soft x rays from a laser-produced plasma undergo selective Auger decay, causing inversion and lasing at 63.8 nm in Cs iii. Rate-equation calculations show that lasing should occur when a small (1-J) 532-nm pump laser is used. A similar system in Rb iii is briefly discussed.

Shake-up as a mechanism for vacuum-ultraviolet lasers

We show how electron shake-up, as it occurs during core photoionization, may produce population inversion in the vacuum ultraviolet. Calculations for Li show the possibility of lasers at 165.3 and 113.2 nm.

Soft x‐ray pumping of inner‐shell excited levels for extreme ultraviolet lasers

We report the construction of a facility for investigating x‐ray pumping of extreme ultraviolet lasers. Measurements of large excited populations in Li+ and an investigation of a Li+ ‘‘shake‐up’’ laser are described.

The excitation of metastable extreme ultraviolet levels

The excitation of large densities of high energy metastable atoms and ions is described. Ionic metastable levels are produced as a result of photoionization by x‐rays emitted from a laser‐produced plasma. For the case of metastable levels in neutral atomic species, excitation is caused by a ‘‘photoionization electron source.’’ The electrons involved in this excitation are created when an ‘‘absorber’’ gas is photoionized by a burst of laser‐produced x‐rays.