We apply certain methods of nonlinear time series analysis to the extensive air shower clusters found earlier in the data set obtained with the EAS-1000 Prototype array. In particular, we use the Grassberger-Procaccia algorithm to compute the correlation dimension of samples in the vicinity of the clusters. The validity of the results is checked by surrogate data tests and some additional quantities. We compare our conclusions with the results of similar investigations performed by the EAS-TOP and LAAS groups.
The photoresponsivity spectra of a p-i-n diode comprising of a layer of quantum dots (QD) in the intrinsic region are measured for a wide range of wavelengths of light and applied voltages. The complex behaviour of the measured spectra is analysed taking into account different channels for electron and hole capture onto the QD and their escape dynamics. The photocurrent data are accompanied by measurements of dark conductivity which reveal both S- and Z-shaped current bistability. The phenomena are explained in terms of a QD charging effect. A model presented in this work shows that switching between the two current states of the first and second bistable regions is controlled by the charges stored in the QD.
Main properties (strength function, energy-dependent transition density, branching ratios for direct nucleon decay) of the isoscalar giant dipole resonance in several medium-heavy mass spherical nuclei are described within a continuum-RPA approach, taking into account the smearing effect. All model parameters used in the calculations are taken from independent data. Calculation results are compared with available experimental data.
An opportunity to compensate phase and polarizing distortions of the laser radiation directly in Nd:GGG active medium and also in phototropic LiF:F2- crystal is investigated. We found that an application of modified Sagnac interferometer with passive LiF:F2- Q- switcher, located inside it, allows not only to increase stability and power of laser pulses, but also to narrow the laser oscillation spectrum. The possibility is demonstrated of generating single-mode radiation with an energy in a train of laser pulses higher than 7 J, a peak power of a single pulse in a train up to 50 kW, the spatial brightness exceeding 5 x 1010 W/cm2 x sr, and the coherence length in excess of 13 m.
Based on a detailed consideration of excitation mechanisms of erbium in crystalline and amorphous matrix we present an analysis of the physical meaning of the Auger excitation cross section of Er{sup 3+} ions in semiconductor. It is demonstrated that large values of Auger excitation cross sections under optical pumping in semiconductor matrices are due to large values of band-to-band absorption coefficient exceeding by several orders of magnitude the absorption coefficient of erbium in dielectric SiO{sub 2} and Al{sub 2}O{sub 3} matrix. The Auger excitation cross section of Er{sup 3+} in semiconductor matrices is roughly given by the ratio of the matrix absorption coefficient to concentration of Er{sup 3+} ions. While the analysis of the excitation cross section is carried out for Er-doped crystalline and amorphous silicon, the results are expected to be applicable to the other rare-earth doped semiconductors. Based on low-temperature experimental results for crystalline silicon we get the Auger excitation coefficient of c{sub A}{sup cryst}{approx}7 x 10{sup -10} cm{sup 3}s{sup -1} and the effective excitation cross section {sigma}{sub eff}{sup cryst}=(2-8) x 10{sup -12} cm{sup 2}. For amorphous silicon at 100 K we obtain {sigma}{sub eff}{sup amorph}{approx}1.4 x 10{sup -14} cm{sup 2}.
We investigate possible regimes of one -- or two -- color mode superradiance of femtosecond optical pulses and accompanying parametric generation of infrared pulses, which contain a few periods of field oscillations, in quantum-well heterolasers of micrometer length under cw pumping. The effects of strong magnetic field and inhomogeneous broadening of electronic levels of dimensional quantization in quantum wells are analyzed.
Free polarization decay and photon echo were detected as heterodyne signals in the weak component of radiation, polarized at right angle to the principal part of exciting radiation. Coherent responses were generated in 13CH3F gas by Stark switching of molecular levels in a gas excited by CW CO2 laser radiation at 9P(32) line. The specific features of this technique in comparison with the conventional Stark switching method of coherent transients generation is considered.
The photovoltaic effect in the semiconductor/electrolyte junction is an effective method for investigation of the energy spectrum of InAs/GaAs heterostructures with self-assembled quantum dots. An important advantage of this method is its high sensitivity. This makes it possible to obtain photoelectric spectra from quantum dots with high barriers for the electron and hole emission from quantum dots into the matrix even if the surface density of the dots is low (∼10 9 cm −2 ). In a strong transverse electric field, broadening of the lines of optical transitions and emission of electrons and holes from quantum dots into the matrix directly from the excited states are observed. The effect of the photovoltage sign reversal was detected for a sufficiently high positive bias across the barrier within the semiconductor. This effect is related to the formation of a positive charge at the interface between the cap layer and electrolyte and of the negative charge on impurities and defects in the quantum dot layer.
The results of research on the nonequilibrium liberation of deuterium from niobium, palladium, and stainless steel under electron-beam bombardment are reported. The maximum on the deuterium gas liberation curve in the low-temperature region is shown to shift under linear heating with simultaneous electron-beam bombardment in comparison with linear heating without such bombardment. The shift reaches 130° in Nb, 100° in stainless steel, and 65° in Pd. The rate of radiation-stimulated gas liberation increases nonlinearly with the concentration of deuterium introduced and the electron-beam current.
