[en] Experimental results are reported of investigations of the optical properties of the plasma produced when an Al₂O₃ target is irradiated in vacuum by a high-power neodymium-glass laser system. It is shown that a number of O VIII and O VII ion levels with principal quantum numbers n = 2, 3, 4 are inversely populated. The gain at the wavelength λ ≅ 29 nm (4 → 3 transition, OVIII) under the experimental conditions is of the order of about 0.01 cm^-1. For the helium like ions O VII, in a transition with the same principal quantum numbers (1s4p¹P₁ → 1s3s¹S₀, λ ≅ 36.9 nm), the gain is of the order of about 10^-2-10^-1 cm^-1, depending on the electron density

[en] The experimental use of a charge-exchange mechanism to form a population inversion in the levels of multiply charged ions, which may help lead to the development of sources of electromagnetic radiation in the far ultraviolet, is reported. During the expansion of a laser plasma burst containing multiply charged oxygen ions into a helium atmosphere, O VIII levels were selectively populated as a result of charge exchange of oxygen nuclei with helium ions. Results on the observed intensities of the O VIII resonant lines and on the effective cross sections for the charge exchanges are shown. 7 references

[en] Plasma parameters in the buffer space of a powerful capillary discharge are studied by measuring emission spectra of HeI (at λ=587.6, 447.1, 501.6, and 471.3 nm) and HeII (at λ=468.6 and 320.3 nm). It is found that gas-dynamic plasma expansion from this discharge space into the buffer zone is accompanied by interaction of the discharge plasma with the gas environment and population inversion between levels in HeI (n = 3,4) and HeII (n = 4,5) in a certain space-time interval. The main formation mechanism of the nonequilibrium level population is associated with resonant pumping and electronic deexcitation of the levels in a photoionized medium that is produced in the buffer space owing to the transport of resonance radiation of the capillary discharge plasma in the lines of HeII. 6 refs., 5 figs

No abstract available

[en] It has been experimentally shown that the levels of multiply charged ions may be excited in the process of recharging in the region of hot and dense plasma when a laser flame is sprayed in the gaseous atmosphere

[en] An experimental investigation was made of the optical properties of a plasma formed by irradiation of an Al₂O₃ target in vacuum with high-power neodymium-glass laser radiation. It was found that at some distance from the target surface the levels of hydrogen-like oxygen ions with the principal quantum numbers n = 2, 3, and 4 were inversely populated. The gain at the lambdaroughly-equal29 nm wavelength (4→3 transition) was approx.0.1 cm^-1