Hydrostatic pressure dependence of the tunneling splitting in RbCl: Ag+

We present measurements of the pressure dependence of the tunneling splitting in RbCl:Ag⁺ for hydrostatic pressures from 950 to 1850 bar. The dependence is linear above 1100 bar and appears to have a break in the curve between 1000 and 1100 bar. This data suggests that a configurational change may take place near 1000 bar.     

Absorption bands of lead in mixed KCl + KBr crystals

The absorption spectra of mixed KCl + KBr crystals with lead added were measured. The main attention was devoted to A bands and their fine structure. Measurements were made at different temperatures. The results are discussed from the point of view of the existence of lead complexes in crystals of alkali halides.     

Hydrostatic pressure and temperature dependence of correlation energy in a spherical quantum dot

The combined effects of hydrostatic pressure and temperature on the ground state binding energy of two electrons in a GaAs spherical quantum dot have been studied by using a perturbation approach within the effective-mass approximation. Our results show that an increment in temperature results in a decrease of the correlation energy while an increment in the pressure for the same temperature increases the correlation energy at a particular dot size. In all cases, it is observed that there is a decrease in the correlation energy due to an increase in the dot size with a given temperature and pressure. The combined effects of hydrostatic pressure and temperature affect the correlation energies appreciably for narrower dots only. The correlation contributes 10%–30% to the binding energy. All the calculations have been carried out with finite barriers, and good agreement is obtained with the existing literature values.     

Hydrostatic pressure and temperature dependence study of d-camphor and dl-borneole by neutron scattering

Abstract

Neutron scattering investigations have been performed down to helium temperatures under different hydrostatic pressures up to 330 MPa. Neutron diffraction (ND) and incoherent inelastic neutron scattering (IINS) spectra showed clearly the existence of a phase transition in d-camphor, which was not observed in dl-borneole. The ND spectra point to a possible cubic structure of the dl-borneole crystal down to helium temperatures. Pressure and temperature dependence of the IINS spectra assumed a glass-like transition from the dynamical to static orientational disorder of molecules in this crystal.     

Pressure and temperature dependence of the static dielectric constant of KBr

The static dielectric constant and the temperature and pressure derivatives of the static dielectric constant of KBr have been measured at several temperatures between 4·3°K and room temperature. The sample was prepared in the form of a three-terminal parallel-plate capacitor and the dielectric constant was determined from measurements of the capacitance with a high precision bridge. The dielectric constant decreases with temperature as does the magnitude of the temperature dependence and the magnitude of the pressure dependence. The data were used to calculate the fixed-volume temperature derivative of the dielectric constant. This quantity, (? ln ε/?T)_v, exhibiting lattice-anharmonicity effects, decreases slightly from its room temperature value as the temperature is lowered, rises to a maximum value at about 33°K and then decreases rapidly at lower temperatures.     

Hydrostatic pressure dependence of excitonic optical transitions in strained wurtzite GaN/AlN quantum disks

In the framework of the effective mass approximation, the effects of hydrostatic pressure on optical transitions associated with the excitons confined in strained wurtzite (WZ) GaN/AlN quantum disks (QDisks) with the confinement potential of finite depth are investigated by using a variational technique, with considering the influences of the built-in electric field (BEF) and the biaxial strain dependence of material parameters. The Schrödinger equation via the proper choice of the exciton trial wave function is solved. The behaviors of the excitonic optical transition are examined at different pressures for different QDisk sizes. In our calculations, the effective masses of electron and hole, dielectric constants, phonon frequencies, energy gaps, and piezoelectric polarizations are taken into account as functions of biaxial strain and hydrostatic pressure. Numerical results show that the hydrostatic pressure and the QDisk size have a remarkable influence on exciton states. The calculated pressure coefficient of optical transition energy shows a negative value if the QDisk height L > 3.2 nm, in contrast with the positive pressure coefficient of the GaN band gap. The peculiar pressure behavior is related to the pressure-induced increase of the built-in electric field. For a fixed pressure, the optical transition energy has a red-shift if the QDisk height and radius increase and QDisk height has a more obvious influence on E_ph than QDisk radius. Furthermore, the relationship between the radiative decay time and hydrostatic pressure (QDisk height) is also investigated. It is found that the radiative decay time increases with pressure and the increment tendency is more prominent for the large height QDisks. The radiative decay time strongly increases by three orders of magnitude reaching microsecond order if the QDisk height increases from 1 nm to 3 nm.     

Rotational side bands in 160Dy

The ¹⁵⁸Gd(α, 2n)¹⁶⁰Dy reaction has been used to study rotational side bands in ¹⁶⁰Dy. Several negative-parity bands are observed, with several members of K^π = 1⁻, 2⁻ and 4⁻ bands and of a K^π = 8⁻ band only the bandhead. A pronounced odd-even staggering of moments of inertia is found for members of the K^π = 2⁻ band. Of the positive-parity bands the K^π = 2⁺ (γ) band, which is seen up to a possible spin of 12 and low-spin members of K^π = (0⁺), (S), and 4⁺ bands are observed. The mixing between most of the γ-band and S-band members is observed to be smaller than 2% and no evidence for possible anti-alignment of low-spin S-band members with rotation is found.     

Temperature dependence of the Cs colloids absorption bands

Temperature dependence of the absorption bands due to Cs colloidal particles has been measured for colloids of different radii in additively colored CsBr and CsI. Large reversible shifts in the peak positions of the colloid bands are detected when we measure them at temperatures ranging between RT and LNT. The results are discussed and a tentative explanation based on the thermal change of Cs metal dielectric constants is proposed.     

Properties of side bands observed in180Os

Bands in ¹⁸⁰ Os have been studied with in-beam spectroscopy methods. Four side bands were established. Configurations have been assigned to them considering the features of similar bands in neighbouring nuclei. New aspects result from an interpretation in the framework of the cranked shell model.     

Hydrostatic pressure dependence of negative-donor-ion singlet and singlet-like bound magnetoplasmon transitions in doped GaAs/AlGaAs quantum wells

Applied hydrostatic pressure modifies the Coulomb bound states of a quasi-two-dimensional electron gas in quantum wells by increasing the effective mass and by tuning the free electron density. Here, we explore these mechanisms by measuring the effects of pressure on the cyclotron resonance, the D⁰ 1s → 2p⁺ transition, and the D⁻-singlet and singlet-like transitions in low-and high-density, modulation-doped GaAs quantum wells. For low doping density, detailed calculations employing a pressure-dependent electron mass agree well with the observed magnetic field and pressure dependencies. For high doping density and low fields, the blue-shift of the D⁻-singlet-like transition at fields below 8 T decreases with applied pressure as anticipated, due to loss of free electrons via the Γ–X crossover. However, near 7.5 T, this singlet-like transition exhibits an anomalous branching for pressures above 4 kbar, which indicates the presence of a resonant level and obscures the blue-shift at high fields.     

On the temperature dependence of the visible emission in thallium doped KCl and KBr crystals

The visible emission of KBr : Tl and KCl : Tl crystals was measured in the temperature range 10–300 K, on excitation in the low-energy tails of the corresponding A-bands. The peculiar temperature dependence of the visible emission is explained in terms of absorption changes due to thermal broadening of the A₁-side band itself and due to the growing overlap of A₁-band with the A-band on warming. A quantitative analysis is given which enables the computation of some parameters of the A₁-side band.     

Magnetic side bands induced by zero point motion

In this letter we show that zero point motion can cause magnetic side bands on optical transitions in insulating magnetic crystals. This mechanism should be dominant when the optical excited state is non-magnetic.     

Spatial elimination of side bands associated with acoustooptical pulse-picking

Under certain conditions the leading and trailing members of an acoustically deflected train can be spatially separated from the intermediate pulses. This is shown to be a simple and useful experimental technique for temporally cleaning up the output of a pulse-picked, mode-locked laser or cavity-dumped cw laser. In addition a physical model is described that explains the phenomenon.     

Investigation of the parameters of the vibrational absorption bands of impurity CNO− ions in KCl and KBr crystals

Journal of Applied Spectroscopy -     

Hydrostatic pressure and hexagonal magnetic anisotropy of hematite

The effect of hydrostatic pressure on the hexagonal basal magnetic anisotropy of a rhombohedral easy-plane weak ferromagnet is investigated in terms of the thermodynamic theory. It is shown that the contribution to the hexagonal anisotropy is determined by the effective constants of the uniaxial and cubic anisotropy, which include the additions proportional to the hydrostatic pressure. The hydrostatic pressure, which leads to the basal anisotropy observed in experiments for stressed samples, is determined for hematite.