Absence Of Thermal Equilibrium Research Articles

Playing with a bulb lamp: RTL measurements and modelling

The electric, thermal and optical behaviour of an incandescent lamp was studied by a real time laboratory (RTL) apparatus, using two voltage probes and a light probe. The software STELLA was used to model the phenomena and to analyse the transient behaviour in absence of thermal equilibrium. We show how the Joule-heating effect explains the non-linear current/voltage relation and how the filament thermal capacity affects the phase lag of light peaks with respect to input power peaks.

Vibrational convection in a saturated porous medium in the absence of thermal equilibrium between the solid and liquid phases

Thermal vibrational convection in a saturated porous medium is theoretically studied on the basis of a thermal nonequilibrium model, in accordance with which the temperatures of the porous medium and the saturating liquid can be different. In the high-frequency vibration approximation the averaged equations of convection are derived. The dependence of the vibration force direction on the interphase heat transfer coefficient and the vibration frequency is established. Vibrational convection in a cylindrical layer is studied. It is shown that, depending on the interphase heat transfer coefficient, the flows of two types differing in the liquid circulation direction can exist.

Steady entanglement out of thermal equilibrium

We study two two-level atomic quantum systems (qubits) placed close to a body held at a temperature different from that of the surrounding walls. While at thermal equilibrium the two-qubit dynamics is characterized by non-entangled steady thermal states, we show that the absence of thermal equilibrium may bring to the generation of entangled steady states. Remarkably, this entanglement emerges from the two-qubit dissipative dynamic itself, without any further external action on the two qubits, suggesting a new protocol to create and protect entanglement which is intrinsically robust to environmental effects.

Exciton formation rate in quantum wells from a direct comparison between free‐carrier and exciton contributions to time resolved luminescence

We present the results of a detailed time resolved luminescence study carried on a very high quality InGaAs quantum well sample. We clearly separate the contributions to the total intensity at the energy of the exciton and at the band by performing experiments with the proper spectral resolution and sensitivity, allowing to keep the observation of these two separate contributions over a broad range of times and densities. This enables us to access to the exciton formation rate over a broad range of pair densities. We also evidence the dominant contribution of excitons to the luminescence signal even when their population is small, and the absence of thermal equilibrium between excitons and free carriers at low enough densities. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Nonadiabatic reactions in condensed phase in the absence of thermal equilibrium

Effects of nonequilibrated phonon modes on the rates of nonadiabatic reactions are analysed. A model is studied consisting of a thermal bath and a single nonequilibrated phonon mode, characterized by the microcanonical energy distribution. Generalization of the Kac formula for the frequency of zeros of a stochastic function is employed for the derivation of the expression for the averaged density of the reactive flux. The problem of evaluation of the nonadiabatic rate is reduced to quadratures. Numerical analysis of the problem for the particular case of an Ohmic thermal bath is presented. The effects of varying the energy of the nonequilibrated mode and the projection of the reactive coordinate on this mode are explored. Results are compared to the model in which a selected phonon mode is characterized by the equilibrium energy distribution, but with the temperature different from that of the thermal bath.

A study of the interference of cesium and phosphate in the low power inductively coupled radiofrequency argon plasma using spatially resolved emission and absorption measurements

The literature on interferences in the radio frequency inductively coupled atmospheric argon plasma (ICP) is reviewed. Even for the most extensively investigated interferences of aluminium, phosphate and alkali elements on calcium, the studies are mostly descriptive. Interpretation of these data is impeded by conflicting results, the absence of thermal equilibrium and the lack of radially resolved observations. The present study of a low-power ICP (0.5 kW) utilizes the Abel inversion technique for emission and absorption measurements of atom and ion lines to clarify the mechanism of interferences on calcium and magnesium due to phosphate and cesium. Under conditions of large carrier gas flow (4.5 1/min) the pronounced interferences are the result of three combined effects: volatilization interference, a change in excitation temperature and a shift in the ionization equilibrium. At lower carrier gas flow (1.4 1/min) the interferences are markedly reduced but still due to the same three effects. The relative preponderance of a particular type of interference depends upon the height of observation and upon the particular combination of analyte and interferent considered.

Electronic- and phonon-terminated laser emission from Ho<sup>3+</sup>in BaY<inf>2</inf>F<inf>8</inf>

Infrared spontaneous and stimulated emission from Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> in BaY <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</inf> is reported. In addition to the familiar <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_{7} \rightarrow</tex> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</inf> transition at 2 μ, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F_{5} \rightarrow</tex> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> emission at 2.4μ and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_{6} \rightarrow</tex> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</inf> emission at 2.9μ are discussed. There are several unusual features of the 2-μ laser emission. At room temperature, phonon-terminated laser emission is observed at 2.171 μ. At 77 K a complex CW laser output is observed in a wavelength interval lying on the shoulder of a fluorescence line. The complex output is attributed to oscillation in transverse modes of the resonator. Oscillation is not observed in the strongest emission line, despite a large terminal state splitting of 310 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . These results are explained on the basis of a theory developed earlier for transition metal ion lasers. The validity of the model is supported by demonstrating the tunability through loss modulation predicted by theory. The observation of these effects is made possible by the very low internal scattering loss in the crystals. The <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F_{5} \rightarrow</tex> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> laser lines near 2.4 μ represent relatively low gain transitions with pulse durations limited by accumulation in a longer lived terminal state. The dynamics of laser emission indicate the possible absence of thermal equilibrium in the excited state. For the 2.9-μ transition the bottleneck posed by a longer lived terminal state may be eliminated by the addition of Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> or Pr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> , but laser emission could not be obtained.

A theoretical study of the interpretation of emission-absorption intensity ratio temperature measurements in the absence of thermal equilibrium

Emission-absorption intensity ration temperature measurements of diatomic molecules under thermal non-equilibrium conditions are investigated theoretically. It is shown that the rotational population distribution must be taken into account when a small part of a vibration-rotation band is viewed in experiments for measuring a vibrational temperature. An emission-absorption intensity ratio of unity does not always mean equality of effective brightness temperature of background source and a vibrational temperature. Such an assumption could lead to errors of several per cent in experimentally deduced vibrational temperatures, particularly in situations where the ratio of rotational and vibrational temperatures is less than unity. The rotational temperature dependence is explained in terms of transitions taking place in vibration-rotation bands and this dependence decreases when a larger part of a band is viewed. Emission-absorption measurements are also investigated for cases where the vibrational population distribution deviates from Boltzmann, for polyatomic and for molecular electronic spectra. Finally it is shown that, in principle, both rotational and vibrational temperatures may be determined from two simultaneous emission-absorption measurements.

Mean diurnal variation of the topside ionosphere at mid-latitudes

About 500 ionograms obtained with the Alouette satellite have been used to construct the mean diurnal variation of the mid-latitude topside ionosphere. Since this diurnal variation is based on observations from October to December 1962, quasi-seasonal effects had to be removed. The data are presented in the form of electron-density contours at fixed altitudes for two latitude ranges, 35°N−40°N and 40°N−45°N. These ranges, which are approximately separated at the 75°W meridian by the 70° magnetic dip line, show remarkable differences in the detailed behavior of electron density as a function of time and altitude. From the scale heights of these mean distributions it is apparent that there is absence of thermal equilibrium, at least during the day, and that light ionic constituents become important in the altitude region from 500 to 1000 km, especially during the night. There is also the suggestion of latitude gradients in the electron temperature and mean ionic mass.

Non-Equilibrium States in Helium II

It is shown that second sound is thermodynamically possible only in the absence of thermal equilibrium between the superfluid and normal component of He II. The tendency of the assembly to drop back irreversibly to the state of internal equilibrium within a certain time of relaxation provides a consistent account of the observed limitations of superfluidity and heat conductivity in liquid helium. As a consequence it is to be expected that the times of relaxation calculated from heat conductivity measurements should be identical with those which can be derived from Pellam's direct attenuation measurements in second sound. This expectation is confirmed within the accuracy of available data.