Nonlinear plasma spectroscopy of the hydrogen balmer-α line

The plasma line broadening of H_α fine-structure lines is investigated with Doppler-free saturation and polarization spectroscopy in He-H gas and are discharges at plasma densities of 10⁸ cm^?3 <N?1.4×10¹⁴ cm^?3. With a single-mode laser, the shift and broadening of four resolved H_α fs lines are measured in a low pressure discharge forN<10¹¹ cm^?3. With an intense, broadband multi-mode laser the plasma effects of H_α are investigated up toN=1.4×10¹⁴ cm^?3 in a hollow cathode are. Calculations in the classical phase shift and impact approximations can explain the experimental data and peculiarities of the low-density plasma effects and show that the ions are the dominant perturbers. Ion dynamical effects, perturber mass and temperature dependence, are observed and interpreted. Applications of the nonlinear techniques to other H and D lines, other atoms, and for H and D plasma diagnostics are discussed.     

Nonlinear properties of a weakly collisional plasma at low radiation intensities

In this paper we evaluate theoretically the modification of the distribution function of slow subthermal electrons heated by radiation in a completely ionized plasma. The new solution we have found to the kinetic equation under conditions typical of weak-collisional plasmas can be used to predict new nonlinear behavior arising from perturbations of the nonuniform electron density and the coefficient of nonlocal heat transfer that depend on the intensity of the radiation heating the plasma, which is absorbed via inverse bremsstrahlung. It is predicted that this new nonlinear behavior manifests itself at unexpectedly small radiation intensities. Zh. éksp. Teor. Fiz. 113, 1299–1312 (April 1998)     

Nonlinear plasma resonance in inhomogeneous relativistic plasma

We present a theoretical study of relativistic electron plasma oscillations in the plasma resonance region based on the renormalization group symmetry method. A steady-state solution to equations describing the electron dynamics in the vicinity of the plasma resonance is found and spatial-temporal and spectral characteristics of the potential electric field are discussed.     

Nonlinear interactions of surface waves with incident radiation at a narrow inhomogeneous plasma layer

The amplitudes of the waves radiating at combination frequencies from the plasma boundary due to nonlinear interaction of surface waves with radiation incident on a narrow inhomogeneous plasma layer, are determined. The method used allows for the discontinuity at the plasma boundary of the tangential components of the electric field of the wave at the combination frequencies.     

Nonlinear gravitational waves in plasma

An exact solution is obtained for the relativistic collisionless kinetic equations describing a test plasma in the field of a strong plane gravitational wave. The gravitational wave induces in the plasma a longitudinal electric current whose amplitude is maximum at temperatures Te ip m_ec². The interaction of gravitational waves with a system consisting of Boltzmann ions and degenerate electrons is also considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 20–24, July 1981.The authors thank G. G. Ivanov for a number of valuable comments.     

Nonlinear interaction of ultraintense laser pulse with relativistic thin plasma foil in the radiation pressure-dominant regime

We present a study of the effect of laser pulse temporal profile on the energy /momentum acquired by the ions as a result of the ultraintense laser pulse focussed on a thin plasma layer in the radiation pressure-dominant (RPD) regime. In the RPD regime, the plasma foil is pushed by ultraintense laser pulse when the radiation cannot propagate through the foil, while the electron and ion layers move together. The nonlinear character of laser–matter interaction is exhibited in the relativistic frequency shift, and also change in the wave amplitude as the EM wave gets reflected by the relativistically moving thin dense plasma layer. Relativistic effects in a high-energy plasma provide matching conditions that make it possible to exchange very effectively ordered kinetic energy and momentum between the EM fields and the plasma. When matter moves at relativistic velocities, the efficiency of the energy transfer from the radiation to thin plasma foil is more than 30% and in ultrarelativistic case it approaches one. The momentum /energy transfer to the ions is found to depend on the temporal profile of the laser pulse. Our numerical results show that for the same laser and plasma parameters, a Lorentzian pulse can accelerate ions upto 0.2 GeV within 10 fs which is 1.5 times larger than that a Gaussian pulse can.     

High-density phenomena in hydrogen plasma

A novel path-integral representation of the many-particle density operator is presented which makes direct Fermionic path-integral Monte Carlo simulations feasible over a wide range of parameters. The method is applied to compute the pressure, energy, and pair distribution functions of a hydrogen plasma in the region of strong coupling and strong degeneracy. Our numerical results allow one to analyze the atom and molecule formation and breakup and predict, at high density, proton ordering and pairing of electrons.     

Electron excitation of a surface by atoms from hydrogen plasma in the presence of ultraviolet radiation

The dependence describing the probability of the electron excitation of a crystal by the energy of a chemical reaction on the energy of electron transitions is derived. It is found that the probability of electron chemoexcitation grows exponentially when the energy of electron transitions falls in the solid state. The efficiency of the nonadiabatic chemo-electronic conversion of energy in structures of hydrogen energetics based on Schottky diodes is calculated.     

Nonlinear absorption of monochromatic radiation in gases

The absorption coefficient as a function of the density of monochromatic collimated radiation is discussed for an arbitrary ratio of natural to Doppler width, with allowance for the effects of collisions between molecules.We are indebted to M.A. El'yashevich for a discussion and to Ya. S. Vasilevskaya and UP. Pesotskaya in preparing the paper.     

Measurement of the absorption coefficient for the He−Ne laser radiation in a pure hydrogen plasma

The absorption coefficients for 6328 Å and 1.15 μm radiations in a pure hydrogen plasma were measured and compared with the corresponding calculated values. The absorption of these radiations were found to be in agreement with the sum of the theoretically calculated absorptions due to photoinization of the neutral atoms and the inversebremsstrahlung in the field of ions.     

The effect of a plasma microfield on hydrogen radiation near the thresholds of spectral series

The authors consider the dependence of hydrogen plasma radiation on the nonideality parameter near the thresholds of spectral series. At low electron concentrations experimental data agree well with calculations based on the principle of spectroscopic stability. At higher electron concentrations the experimental data agree better with calculations that include a decrease in the thresholds of photorecombination in the statistical plasma microfield and a change in the statistical weight of the levels which is induced by their autoionization in the plasma microfield. A. V. Luikov Heat and Mass Transfer Institute of the National Academy of Sciences of Belarus, 15, P. Brovka St., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 22–26, January–February, 1998.     

Nonlinear waves in a plasma cylinder

Nonlinear electron plasma waves in a cold plasma bounded by a cylindrical dielectric are investigated using the exact electron fluid equations. After the spatial wave structure is determined, a set of nonlinear equations governing the temporal behavior of the field quantities is solved. It is shown that finite amplitude waves and explosively unstable behavior can occur     

Population inversion in recombining hydrogen plasma

The collisional-radiative model is applied to a recombining hydrogen plasma in order to investigate plasma conditions in which a population inversion between the energy levels of hydrogen can be generated. Population inversion is expected in plasmas for which three-body recombination makes a large contribution to the recombining processes and the effective recombination rate is larger than a critical value for a given electron density and temperature. Calculated results are presented in figures and tables.     

Effect of a magnetic field on the radiation emitted by a nonequilibrium hydrogen and deuterium plasma

Radiative transfer in a nonequilibrium plasma in an external electric field is considered. The system of kinetic equations determining the populations of atomic levels is written taking into account the combination of collision and radiative processes and is solved together with the kinetic equation for photon of various frequencies, which are emitted and absorbed in the radiative transitions from the states of the continuous and discrete spectra. The shape of spectral lines is determined from the solution of the quantum-mechanical problem on the emission of an atom in the electric field of the plasma and an external magnetic field, taking the Doppler effect into consideration. The developed approach is used in the model calculation of radiative transfer under the conditions corresponding to the edge plasma in a tokamak, which is simulated by a homogeneous plane layer of a deuterium plasma. It is shown that the joint action of the external magnetic field and the electric plasma fields considerably affects the spectral and integrated characteristics of the radiation.