Negative luminescence in semiconductors: a retrospective view

Twenty-five years ago, we introduced the phenomenon of negative luminescence (NL) into semiconductor physics. This paper provides an overview of work conducted to develop this fundamental concept. Initially, we consider the first-principle approach to radiation interaction with basic matter and the major properties of NL. Then we describe the problems of NL direct measurements in homogeneous materials and structures. Finally, we emphasize the use of NL approach in applications involving devices for infrared (IR) wavelength (3–12 μm) high-temperature (300–400 K) optoelectronics. Our subjects will include NL IR emitting diodes, radiative coolers, IR dynamic scene simulators, light up-conversion devices, and the Stealth effect in IR.     

Status of heavy element research using a gas-filled recoil separator at RIKEN

A gas-filled type of recoil separator for heavy element research was installed at an experimental hall of RIKEN Linear Accelerator facility to realize getting higher intensity of primary beam and long beam time. Performance of the separator was studied using target recoils and various nuclear reactions. The results show the high performance of the separator for heave element research. As an application of the GARIS, production and identification of an isotope of the 110th element ²⁷¹[110] have been performed using the ²⁰⁸Pb(⁶⁴Ni,1n)²⁷¹[110] reaction. Three decay chains coincide well both in decay times and energies with the ones reported by the group of SHIP experiment at GSI, Germany. Our results provide a confirmation of the synthesis of an isotope ²⁷¹[110] of element 110.     

Strangeness saturation: Dependence on system-size, centrality and energy

The dependence of the strangeness saturation factor on the system size, centrality and energy is studied in relativistic heavy-ion collisions.     

The glow curve structure for the LiF:Mg,Cu,Na,Si TL detector with dopants concentrations and sintering temperatures

The glow curve structures for LiF:Mg,Cu,Na,Si TL detectors with various dopant concentrations and sintering temperatures were investigated for the improvement of the glow curve structure and sensitivity of the TL detector. The dopant concentrations were varied over the following ranges: Mg (0–0.25 mol%), Cu (0–0.07 mol%), Na and Si (0–1.5 mol%). With increasing Cu concentration, the intensity of the main peak was intensified and reached a maximum at a concentration of 0.05 mol%. The high-temperature peak was reduced. The dependency of the main peak intensity on the Mg concentration exhibits a sharp maximum at 0.2 mol%. The intensity of the high-temperature peak tends to rise slightly with increasing Mg concentration. It was found that the optimum concentrations of the dopants in the LiF:Mg,Cu,Na,Si TL material are Mg: 0.2 mol%, Cu: 0.05 mol%, Na and Si: 0.9 mol%. The dependency of the main peak intensity on sintering temperature exhibits a very sharp maximum at 830°C. The high-temperature peak was rapidly reduced after 825°C.     

Luminescence and lifetime characteristics of microphases in KCl:KI:Pb mixed crystals

Absorption and luminiscence measurements were performed on lead-doped KCl:KI mixed single crystals. Strong differences were found between as-grown and quenched samples. New bands were observed in the absorption spectra of unquenched samples in the spectral region between the limit positions of the A bands, corresponding to chloride or iodide lattices. The strong band at 449 nm dominates the luminescence of these samples at low temperatures. Its kinetics have a complicated form and the decay time is in the interval from ns to ms. Quenched samples have a well-known luminescence spectrum caused by octahedral lead impurity centres in KCl single crystals. The kinetics, however, also indicate mixed chlorine and iodine coordination of lead in the investigated crystals.     

Stress relaxation and viscosity of a bulk Pd<Subscript>40</Subscript>Cu<Subscript>30</Subscript>Ni<Subscript>10</Subscript>P<Subscript>20</Subscript> metallic glass under isochronous heating conditions

Isochronous relaxation of tensile stresses is measured in a bulk Pd₄₀Cu₃₀Ni₁₀P₂₀ metallic glass in the initial state and after certain thermal treatments. The results of measurements are used to find the energy spectrum of irreversible structural relaxation, from which the temperature dependence of shear viscosity is then calculated. This dependence is also found independently from measurements of creep in the same glass. The calculated viscosity is shown to agree well with the experimental data.     

Longitudinal DC electric discharge in a supersonic air flow

A longitudinal dc electric discharge in a submerged high-pressure supersonic air jet is described. Photographs of the discharge are provided. The experimental voltage across the discharge gap and the discharge current are given for two resistances of the resistor that limits the discharge current over a certain range of the discharge channel length along the air flow. The current-voltage discharge characteristic is provided at a constant discharge length. The main discharge characteristics are obtained from a comparison of the experimental and theoretical results calculated on the basis of the simplest model.     

Measured and calculated vertical structure of a sound field in the ocean

Results of measuring the monochromatic sound field with a dipping probe in the deep ocean are presented. The sound speed profile in the region of measurements had a minimum at a depth of 1600 m. The experiment was carried out in the Atlantic Ocean with the use of two vessels separated by a distance of approximately four ray cycles (～240 km). The experimental data are compared with the calculations based on a new concept of the Brillouin waves for describing the vertical structure of the sound field produced by rays. It is shown that a satisfactory agreement between experiment and calculation can be achieved by fitting the parameters of the experiment. Such a procedure allows one to refine or even to determine the experimental conditions, which not are always known. The proposed method of calculation offers an opportunity for solving inverse problems of ocean acoustics.     

Characteristics of high-power radiating imploding discharge with cold start

A qualitative model of the dynamics of a multiterawatt radiating Z-pinch with cold start and high rate of current rise is proposed. The model is used to analyze discharges with currents I ～ 2–5 MA (with dI/dt > 10¹³ A/s) through uniform or structured plasma-producing loads, including wire arrays. The most important consequence of cold start is that spatially nonuniform plasma production is prolonged to almost the entire current rise time. Under these conditions, the Ampére force begins to play a dominant role in the plasma dynamics before the plasma-producing load is completely transformed into an accelerated plasma. The results of computations of wire-array vaporization are presented. A formula is proposed for estimating the highest attainable velocity of plasma flow into a heterogeneous liner driven by the Ampére force. It is shown that local imbalance between radial motion of the produced plasma and supply of the plasma-producing substance to be ionized leads to axially nonuniform breakthrough of magnetic flux into the liner, which precedes plasma collapse. The magnetic-flux breakthrough gives rise to a chaotic azimuthal-axial plasma structure consisting of radial plasma jets of relatively small diameter, which is called a radial plasma rainstorm. The breaking-through azimuthal magnetic flux obstructs further current flow in the breakthrough region. Analyses of Z-pinch implosion based on the theory of Rayleigh-Taylor instability or the snowplow model are incorrect under the plasma-rainstorm conditions. The processes taking place in a stagnant Z-pinch include conversion of the energy carried by the current-generated magnetic field into turbulent MHD flow of the ion component of the plasma, its convective mixing with magnetic field, heating, energy transfer from ions to electrons, and emission from the plasma. Under typical experimental conditions, emission plays a key role in the energy balance in an imploding pinch. Z-pinch is modeled by an electric-circuit component that has a time-dependent nonlinear impedance and consumes the magnetic energy supplied by a generator through a magnetically insulated transmission line (MITL). The peak power reached in the circuit is comparable to the peak soft X-ray power output emitted by the pinch in terms of magnitude and timing. Optimum matching conditions are formulated for the generator-MITL-pinch circuit.     

Electromechanical properties of Pb<Subscript>3</Subscript>Ga<Subscript>2</Subscript>Ge<Subscript>4</Subscript>O<Subscript>14</Subscript> piezoelectric crystals grown from solution in a melt

Single crystals of lead gallium germanate Pb₃Ga₂Ge₄O₁₄ are grown from their own solution melts. The propagation of bulk acoustic waves is investigated, and the elastic, piezoelectric, and dielectric constants are calculated. The temperature dependences of the dielectric constants of this compound are analyzed.