No abstract

Abstract. The paper presents the results of studies of luminescent centers induced by irradiation of LiF crystals with flow of silver ions of a fluence varying in a range of 2×10 13 -5×10 17 ions/cm 2 and energy about of 150 keV. Two bands with maxima at 250 nm and 420 nm in the absorption spectra of the exposed crystals were observed. The former was due to the absorption of F colour centers and the latter consisted of F 2 (F 3 + ) colour centers band and a plasmon resonance band arose due to the embedded silver ions. The peak of the latter remained stable after annealing the sample at 400 0 C unlike the colour centers bands. The luminescence spectra of the crystals under excitation with a laser irradiation of 375 nm wavelength showed a band with a peak at 450 nm along with the bands with peaks at 530 and 680 nm corresponding to F 3 + and F 2 colour centers, respectively. The peak of the former reached saturation, while the peaks of the colour centers bands increased with ion fluence increasing. These results show that subnanometre sized metal clusters Ag(n+) (n=3-6) are responsible for the observed luminescence, while the Ag particles of a nanometer scale are not luminescent.

The energy spectra of a metallic ion beam extracted by a three-grid extractor from the plasma of a pulsed vacuum arc (pulse duration of 200 μs, discharge current Id of up to 100 A and ion current of up to 0.6 A) are studied by means of an electrostatic energy analyzer in a range of the extraction voltage Uext of up to 10 keV. It is found that the most probable ion energy Em/Z is markedly less than eUext, and the difference between these values as well as the width of the spectra decrease with increasing Uext or/and decreasing Id. It is found as well that the spectra contain “tails” of ions with energies significantly exceeding Em/Z. The shape of the spectra differs at various phases of the pulse, so that Em/Z in the initial transition phase is considerably more than that in the quasi-stationary phase. As possible causes of these effects, the nonmatched ion optics of the extraction gap and the action of the non-neutralized space charge of the extracted ion beam moving through the drift gap are considered.

No abstract

No abstract