A means of express gas analysis is developed that meets all necessary requirements for determining the partial composition of natural gas and derivatives of gas mixtures using a portable Raman spectrometer with an excitation wavelength of 532 nm, rigidly coupled to a hollow crystalline light guide and equipped with a gas inlet system.

New lines are observed in the photoluminescence spectrum of a two-dimensional electron gas in a quantizing magnetic field at a filling factor of ν = 2 upon the photoexcitation of a nonequilibrium ensemble of cyclotron magnetoexcitons. Their energies lie in the region forbidden for single-particle optical transitions and allowed for inner transitions from excited states of three-particle translationally invariant complexes called magnetotrions. It is suggested that the new lines are associated with the complicated spectrum of internal motion in the magnetotrion, composed of an electron at the first Landau level and two identical holes at the zeroth Landau level.

Resonance reflection of light from a two-dimensional electron system in a strong magnetic field has been investigated in an ultraquantum limit. A line associated with the formation of a Laughlin liquid in the electron system has been discovered. Similar features have been observed in neither photoluminescence nor resonance Rayleigh scattering spectra.

The behavior of the main edge magnetoplasmon mode in the quantum Hall effect (QHE) regime has been analyzed by the method of optical detection of resonance microwave absorption. Near a filling factor of 2 at a temperature of about 0.3 K, the main edge mode splits into two modes seemingly due to broadening of the incompressible strip at the edge of the two-dimensional electron gas under such conditions.

New low-frequency modes corresponding to acoustic edge magnetoplasma excitations have been observed in the resonance microwave absorption spectra of a two-dimensional electron system in a transverse magnetic field. The additional excitation modes have been shown to appear only in the quantum-Hall-effect regime (in narrow magnetic-field regions near the integer values of the filling factor), when the resonance microwave absorption lines exhibit sharp narrowing. The absolute values of the resonance absorption frequencies and their dependence on the parameters of the electron system coincide (without any fitting parameters) with the respective theoretical predictions of the formula describing the properties of the acoustic modes of edge magnetoplasma excitations.

The magnetic field dependence of the cyclotron mass of heavy holes in asymmetric GaAs(100) quantum wells is measured by optical detection of resonant microwave absorption for various concentrations of quasi-two-dimensional holes. The effect of spin-orbit splitting on the cyclotron masses of heavy holes is discovered and investigated. The energy spectrum of holes is calculated on the basis of experimental data. The energy range in which spin-plasmon oscillations are observed in hole systems with various concentrations is predicted.

The dependence of the heavy-hole cyclotron mass in GaAs(001) quantum wells on the 2D-hole density has been measured by the optical detection method for resonance microwave by-absorption. A significant increase (almost doubling) has been observed in the cyclotron mass of heavy holes with an increase in the charge carrier density from 1.2 × 1010 cm−2 to 1.3 × 1011 cm−2.

The spectra of resonant microwave absorption in single strips of two-dimensional electrons with a large length-to-width ratio have been analyzed using the optical detection method. Deviations from the linear behavior in the region of low quasimomenta have been observed in the measured wavenumber dependences of the plasma-excitation frequencies. These deviations are caused by the effect of the logarithmic term on the dispersion law of a one-dimensional plasmon. Comparison of the experimental results with theoretical calculations confirms the applicability of the logarithmic term to the description of the one-dimensional plasmon for wavenumbers that are tens and hundreds times lower than the inverse strip width.

The spectra of edge magnetoplasma excitations in two-dimensional (2D) electron disks have been analyzed by the method of optical detection of resonant microwave absorption. The magnetic dispersion of an edge magnetoplasmon in samples with a high 2D electron density is found to be poorly reproduced by existing theoretical models. Analysis of the magnetic-field dependence of the linewidth of resonant microwave absorption for samples with various 2D electron densities shows that the inverse width of the main mode of resonant microwave absorption is universally proportional to the Hall resistance of 2D electrons.

The spectra of magnetoplasma excitations in two-dimensional electron disks and rings are studied by optical detection of resonance microwave absorption. For ring-shaped structures, two types of edge magnetoplasma modes localized along the inner and outer boundaries of the ring are observed. It is shown that the interaction between these modes leads to a strong modification of their magnetic-field dependences as compared to disks. In addition to the longitudinal edge magnetoplasma excitations, transverse plasma modes associated with the electron density oscillations along the ring radius are revealed. The spectra of magnetoplasma excitations are calculated in terms of the electrodynamic theory for both ring-shaped and disk-shaped structures. The classification of all modes of collective magnetoplasma excitations observed in the experiment is performed on the basis of the comparison between experimental and theoretical results.