[en] Numerical modelling of problems on laser radiation interaction with plane solid obstacles from different materials is considered. Problem setting is carried out, the chosen physical model is discussed. All the calculations are carried out with the help of the large particle method. The results obtained are compared with analogous data of physical experiment. The comparison has shown a very good coincidence of values of electron temperature as well as a satisfactory coincidence of density and rate values

[en] Spectra with spatial resolution and photographs of a carbon flame in the radiation of the far vacuum ultraviolet lines have been obtained for various geometries of the laser radiation focusing onto a flat target. Fine structure has been observed of the Hsub(α) transition in a CV1 ion. A profile has been measured of the electron density Nsub(e) by Stark broadening of Balmer series transitions. An expansion velocity has been measured, the electron temperature, plasma ionization state (CV2/CV1 ratio), the rate of target material evaporation and acceleration at an early stage of expansion have been estimated. Nsub(e) gradient has been evaluated in the vicinity of the critical point. Feasibility is discussed of the Nsub(e) measurement by the Stark broadening of Balmer series transitions in H-like ions in a wide density range

[en] An electron density has been measured in a thin layer of a magnesium laser plasma located along the flame axis in its central region. In this way an influence of an optical thickness on radiation of the resonance line of the Mg 11 helium-like ion is eliminated and a contribution of the flame outer regions into the radiation of this ion is strongly diminished. For the first time under these experimental conditions a correspondence has been achieved between the electron density profile measured from relative intensities of resonance and intercombination lines of the He-like ion and the profile measured from the Stark broadening of H-like ion lines. The method for measuring the electron density by relative intensities of resonance and intercombination radiation lines of helium-like ions may be used in principle for investigations of a plasma with the density up to Nsub(e) approximately 10²¹ cm^-3 containing multicharged ions with the charge of a nucleus of Z approximately 12

[en] Electron densities in laser-produced plasmas have been deduced from space-resolved spectra of oxygen-like ions CaXIII, TiXV, FeXIX, NiXXI and CuXXII in the xuv (80-170 A). The transition 2p⁶¹Ssub(o) → 2s2p⁵¹P₁ has been identified for CuXXII, the wavelength of the same transition for NiXXI has been defined more precisely. Plasma images in the light of different spectral lines have yielded the dimensions of the spacial regions in which CaXIII, FeXIX and NiXXI exist. (author)

[en] The plasma produced during laser evaporation of a solid target is formed in a stationary layer (of the Knudsen type) contiguous to the target. The boundary between this layer and the region of nonstationary flow (the jet itself) is the Jouguet point. Under these assumptions a theory of the stationary layer is proposed and the boundary condition for the jet is obtained, i.e. the relation between electron temperature and degree of ionization at the Jouguet point. The dependence of the parameters on the hydrodynamic energy flux in the jet is found. The results are compared with the experimental results

[en] The nature of the changes is studied in the Raman spectra in a crystal of Basub(x)Srsub(1-x)Nasub(2)Osub(6) (x=0.25) with the temperature range of 80 to 373 K. Normal procedure was applied with the use of an argon laser (Λ=4880 A) and a DFS-12 spectrometer. It has been established that at low temperatures the spectrum becomes more clear-cut; in the low-frequency range some sharp lines appear in the immediate vicinity of the exciting line. On heating of the crystal one observes a redistribution of the intensity in the Raman spectrum and a general displacement of the low-frequency Raman spectrum and a general displacement of the low-frequency Raman spectrum toward the exciting line. The nature of the frequency shifts some Raman maxima was investigated, and certain anomalies were observed in the vicinity of the phase transition point

[en] A method is suggested to measure the electron temperature Tsub(e) of the laser plasma with the use of relative intensities of optically thin spectral lines of Lyman or Balmer series emitted by hydrogen-like ions. The method consists in selection of the electron temperature value which corresponds to experimentally observed ratios of populations of levels in hydrogen-like ions. In this case independent measurements of the electron density and ionic composition of the plasma as well as theoretical calculations of the level populations are used. Electron temperature profiles in the laser plasma have been measured at the distances of 25-1400 μm from the NaF, NaNO₃ and C target with the use of C 6, O 8, F 9 ion spectra. The suggested method permits to measure Tsub(e) in a wide range which is determined mainly by the ionization potential of the used ion and it depends on the choice of the pair of levels. The method is practically not sensitive to errors in determining the profile of electron density and ionization state of plasma. The effect of radiation reabsorption is removed at the expense of using Layman transitions from high-excited levels or transitions of the Balmer series

[en] The electron density was measured in a thin layer of magnesium laser plasma, positioned along the axis of a jet at its center. In this way, the effect of the optical thickness on the resonance line emission of a helium-like Mg XI line was eliminated, the contribution of the outer regions of the jet to the emission of this line being considerably weakened. Agreement was achieved, for the first time under these experimental conditions, between the electron density profile determined from the intensity ratio of the resonance and intercombination lines of a helium-like ion and that deduced from Stark broadening of the lines of a hydrogen-like ion

[en] A method is proposed for determining the electron temperature of a laser plasma from the relative intensities of optically thin Lyman- or Balmer-series spectral lines of hydrogen-like ions. The method involves selecting the electron temperature corresponding to the experimentally observed ratios of the level populations of hydrogen-like ions. Independent measurements of the electron density and plasma ion composition, and also theoretical calculations of the level populations, are used. Measurements are reported of the electron temperature profiles in a laser plasma at distances of 25--1400 μ from the target using spectra of C VI, O VIII, and F IX ions

[en] Results are presented of new experimental investigations of asymmetry of spectral line profiles as a result of the self-absorption of x-ray lines of multiply charged ions in an expanding laser plasma. A theoretical interpretation is based on the solution of the one-dimensional radiation transport equation. Narrowing of the resonance line of the Mg XI ion caused by self-absorption in an inhomogeneous plasma was measured experimentally. The behavior of the profiles of trapped and optically thin spectral lines during gasdynamic expansion of a laser plasma was compared. Narrowing of the resonance line of the Mg XI ion by a factor exceeding 2 was observed