Study of the diffraction scattering 12C + 12C with the excitation of the 12C exotic state 0 2 + (the Hoyle state)

New results from a series of experiments dedicated to the study of the ¹²C exotic state (the so-called Hoyle state) are presented. In spite of the many investigations that have been carried out, the structure of this state (which lies above the threshold for breaking up into three alpha particles) is still unknown. The different models assume that the nucleus has an abnormally large size in this excited state. However, until recently, methods for measuring the radii of unbound states have not been suggested. The best way to solve this problem seems to be by measuring the angular distributions of elastic and inelastic scattering of ¹²C on different target nuclei, and the determination of the radii is based on the fact that, at small scattering angles, the cross sections for direct reactions at high enough energies behave like Frauenhofer diffraction on a black ball. Accordingly, an experiment was performed aimed at measuring the elastic and inelastic angular distributions of ¹²C with an energy of (121.5 ± 0.5) MeV on a ¹²C target. The elastic scattering was measured in the angular range from 18° to 50° in the c.m. system with uncertainty in the angle of measurement equal to Δθ = ± 0.6°. The inelastic cross section was measured for the ¹²C excited state 2⁺ (4.44 MeV) and 0⁺ (7.65 MeV). Estimates were made for the diffraction radii for the ground and excited states. An increase was observed in the radius of the state at 7.65 MeV compared to those of the ground and first excited states.     

Frequency Dependence of an Electromagnetic Absorption Coefficient in Magnetic Fluid

Technical Physics - The samples of water-based magnetic fluid, which contain Fe3O4–SiO2 particles with a spherical shape and sizes less than 100 nm, have been obtained. The method based on...     

An analog of the fundamental theorem of arithmetic in ordered groupoids

In the note we consider ordered groupoids with the Riesz interpolation property, that is, ifa _i ≤b _j (i, j=1,2), then there exists ac such thata _i ≤c≤b _j (i, j=1,2). For such groupoids possessing the descending chain condition for the positive cone and the property

Photoelectron characteristics of diode structures based on quantum-well GaAs/InGaAs heteronanostructures with a Mn δ-doped layer

A GaAs layer over Mn is found to acquire p-type conductivity in Au(Ni)/n-GaAs/InGaAs diode heteronanostructures due to laser δ-doping of Mn with a density of 0.15–1.5 monolayers, yielding the formation of a p-n junction in the Schottky barrier. The effect of the shunting of diode structures by the ohmic resistance of the Mn δ-doped layer and a p-n junction outside the Schottky electrode is revealed. This effect is found to disappear after the formation of mesadiodes. The current-voltage characteristics of the mesadiodes with Mn cannot be described by the mechanism of thermionic emission through the barrier, and the current in these mesadiodes flows with the participation of thermal-field and field emission. A compensated region in the n-GaAs buffer layer, adjacent to the δ-doped layer, formed due to the laser deposition of a coating layer is found. The length of this region decreases with reduction in the layer-production temperature. A substantial increase in the effective surface potential barrier in the semiconductor (up to 1.05 V) in structures with Mn was revealed, and the photoelectric activity and depth of Mn layer occurrence in the forbidden band of GaAs energies is revealed.     

Low-lying states of ~(92,93)Nb excited in the reactions induced by the weakly-bound nucleus ~6Li near the Coulomb barrier

Excited states of odd-odd nucleus ~(92)Nb and odd-A nucleus ~(93)Nb were populated in the 6 Li+ 89 Y reaction with an incident energy of 34 MeV. The processes that produce 92,~(93)Nb and can be measured by a combination of light charged particle and gamma ray measurements are discussed. Twenty new transitions are observed and eight new levels are constructed in ~(92)Nb, and in addition two new transitions are added to the level scheme of ~(93)Nb. Using shell2 model calculations, the low-lying structure of 9 Nb is investigated and compared with the experimental results.     

Pressure dynamics during shock loading of aqueous foams

The interaction of shock waves with aqueous foams has been numerically modeling on the basis of a gas-drop model. A modified Godunov scheme of second-order accuracy has been used to solve the gas-dynamics equations. The measured density distributions of the foam over height and the results of calculational modeling of the foam structure were used as starting data. The results of the pressure calculations are compared with experimental oscilloscope traces. Zh. Tekh. Fiz. 68, 19–23 (July 1998)     

Field effect as a method for controlling the quality of i-InP-based heteronanostructures with two-dimensional electron gases

The field effect in i-InP-based heteronanostructures has been studied in InP and In_0.52Al_0.48As layers with an In _x Ga_1?x As quantum well with a high Hall electron mobility in the frequency range of (20?2) × 10⁶ Hz and temperature range of 77?C450 K. It is shown that mobility in the field effect depends on the location of Si ??-doped areas with respect to the quantum well and on the doping level. The ??-doping level and the configurations of nanostructures have been determined for the case in which the values of the electron mobility in the field and Hall effects are close to each other and correspond to high values of mobility in the quantum well.     

Shock wave ignition in N2O-CO(N2)-He mixtures

The behavior of the pressure behind shock waves in N₂O-CO-He mixtures is investigated. The pressure can be relatively easily measured and, at the same time, reflects the general influence of the experimental conditions on flow formation in the shock tube. Shock-wave mixture ignition effects and, moreover, hydrogen combustion in the contact zone are analyzed from the standpoint of their influence on the stagnation parameters and the optical properties of the flow in the shock tube nozzle. The correctness of modeling the conditions behind the reflected wave by means of mixtures similar in composition to the equilibrium products of the N₂O-CO reaction [1] is discussed in the same context.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 164–170, September–October, 1989.The authors wish to thank G. D. Smekhov for calculating the equilibrium compositions of the mixtures behind the shock waves and A. P. Zuev for stimulating discussions.     

Obtaining monochromatic beams of radioactive nuclei with energies near the Coulomb barrier on joint institute of nuclear research accelerator complex DRIBs

Two methods for obtaining monochromatic beams of radioactive nuclei with energies near the Coulomb barrier on Joint Institute of Nuclear Research accelerator complex DRIBs are described. In the first method, an MSP-144 magnetic spectrometer was used as the monochromator of low-energy ⁶He beam obtained after passing through an energy degrader. In the second method, a specially developed probe was used for experiments with the internal beam of the DRIBs complex post-accelerator (the U-400 cyclotron).