Cooling-down Process Research Articles

Strain-Induced Reconstruction of Impurity States in PbTe(Ga) Films

ABSTRACTn-type PbTe(Ga) films were grown by the laser deposition and the hot wall techniques on BaF2 substrates in <111> orientation. Doping results in the appearance of a high-ohmic state with nearly intrinsic free carrier concentration at low temperatures and activation character of conductivity at T∼300 K. Persistent photoconductivity has been observed at T < 100 K. In the hot wall-grown layers a new effect of bistability during the cooling-heating-cooling cycles has been found. On the first stage of the cycle a rapid decrease of resistivity (∼3 orders of magnitude) is observed at To∼50 K. The value of To changes by ± 15 K depending on the cooling rate. After a brief heating up to 80 K the subsequent cooling results in the high-ohmic state of the layer at the low temperatures. This state seems to be unstable. Relaxation to the low ohmic state can be accelerated by the application of electric field. The effect may be understood in terms of bistability of the Ga impurity charge state under the action of strain between the film and the substrate during the cooling-down process.

Statistical Analysis of Preequilibriumα-Particle Spectra and Possible Local Heating

It is shown that energy spectra of preequilibrium $\ensuremath{\alpha}$-particle emission in $^{209}\mathrm{Bi}$+$^{14}\mathrm{N}$ reactions are reproduced well by the statistical formula of Ericson when nuclear temperature is treated as a parameter depending on the emission angle. The resultant temperature shows monotonical decrease with increasing angles, indicating the cooling-down process of the associated composite system.

Moderator Effects on the Reactions of 82Br Activated by the Isomeric Transition with Gaseous Methyl Bromide

Abstract 82Br obtained via the (I. T.) process has been reacted with methyl bromide. In the gaseous phase, only CH382Br and CH282BrBr are observed as major products, whereas in the solid phase other products, such as CH82BrBr2 and C2H582Br, have also been observed. Moderator experiments using He or Xe indicate that the formations of both CH382Br and CH282BrBr involve the reactions of the energetic 82Br atom. This is in great contrast to the early observations of the Br2-CH4 system, where the ionic as well as the energetic reactions of 82Br play a role in the formation of the C-82Br bond. Comparisons of these results with those found in the reactions of the 80Br obtained via the (n, γ) process suggest that the Br atom obtained via the (n, γ) process is more electronically excited than that from the (I. T.) process. The kinetic analysis of the present results gives the following relative α-values: αHe, 1.0; αXe, 8.8; αCH3Br, 10.3. It is suggested that, during the cooling-down process of 82Br, a high inelasticity is involved in the collision of 82Br, even with monatomic molecules.

Contribution to the theory of aerosol formation in an inert gas atmosphere. Pre-nucleation kinetics

The kinetics of aerosol formation in an inert gas atmosphere may be considered as proceeding in the following steps: prenucleation, nucleation, growth, and coagulation. In this paper the prenucleation kinetics or the cooling-down process of a hot vapor in the presence of a cooler inert gas is examined using the model that the cooling mechanism is the elastic collision process between vapor and gas atoms. Computed values of average energy loss per collision, asymptotic time constant for the cooling-down process, and the time required for cooling a vapor from 1800°K. to 900°K. and 450°K., respectively, are presented for sixteen different vapor-gas pairs. Our results are consistent with the conclusion of Kerker and co-workers that the rate of energy transfer from a body of hot NaCl vapor to a cooler helium gas is extremely rapid.