Negative absorption coefficient at indirect transitions in semiconductors

Abstract

In this paper a method for obtaining states with negative temperature in semiconductors is discussed; as shown this method requires relatively small densities of excitation.Ac present three different methods ate proposed for obtaining the states with negative temperatures in semiconductors [1--3]. The impulse method put forward in the paper [1] for obtaining such states is based on a considerable difference of the time of recombination and the slowing-down time of nonequilibrium carriers in the bands [4]. The conditions for producing the states with negative temperatures with these methods ate as follows: large lifetimes of nonequilibrium carriers, high densities of excitation and low temperatures of the sample [5]. All this strongly restricts selection of the semiconductors and creates a number of technical difficulties.The method of obtaining the states with negative temperatures in semiconductors proposed in the paper by B. LAx [2] is based on the Landau levels not being equidistant in strong magnetic fields. The comparatively short times of relaxation of the noncquilibrium carriers of these levels make ir difficult to create the states with negative temperatures using the above method.In the present paper the method for obtaining states with negative temperatures in semiconductors put forward in the paper [3] will be studied in detail. As it will be shown below, this method requires relatively small densities of excitation.

Mathematical Modeling of Gradual Ignition Process and Unsteady Erosive Burning of Gunpowder Charge at Triggered Artillery Shot

“…For this reason, blowing of the gunpowder gases, which affects mainly on the surface friction, effects slightly on the total resistance of the gunpowder grains for the incoming flow. Experimentally, this fact was confirmed in [6,7], where it is shown that since Re σ > 10 3 correction for blowing can be ignored.…”

Emission from cooled inert gases in the VUV region The xenon-dimer excimer laser

“…N. G. Basov, who proposed crystals of inert gases as a VUV-laser medium in 1966, 4 depended on the successful use of the electron-beam method 5 that he had proposed in 1961 to pump lasers based on broad-band semiconductor crystals, first implemented on cadmium sulfide crystals in 1964 at FIAN. 6 An experimental technique had already been prepared and studies had been carried out on the properties of semiconductor crystals at low temperatures: 350-58 K (liquid nitrogen), 4.2-1.08 K (liquid He4), and 3.3-0.35 K (liquid He3) by the time studies began on the electronic pumping of VUV lasers based on inert-gas crystals.…”