Kinetic model of an He—Ne—Ar—H₂laser pumped by hard ionising radiation

Abstract

In this detailed study we have reported on single-crystal and polycrystalline phases of V 1+x S 2 ; 0.10 < x < 0.25, prepared using excess sulfur in a sealed quartz tube and investigated their structural, transport and magnetic properties. The crystal flakes have trigonal symmetry with 2c and incommensurate >2( √ 3)a superlattice ordering in the a-b plane. As-grown flakes showed complex irreversible behaviour in resistivity on cycling to low temperatures, related to the metastability of the structure. The annealing of the crystal flakes and addition of 5-10% Al stabilizes the superstructure. We observe an anomalous contribution to the resistance of these crystal flakes with a maximum around 100-150 K. The contribution is more pronounced for betterordered phases. The magnetic susceptibility and thermopower values of these compounds are large and vary smoothly on cooling around this temperature interval. The polycrystalline phase, obtained at a higher temperature, on the other hand, showed absence of superlattice distortions and gave a smooth behaviour in its resistance, but with a large T 2 -contribution. The structural and electronic properties of different phases are discussed in terms of disorder among the interstitial V atoms and the effect of in-plane vacancies on the chargedensity-wave instability in these and similar compounds.

Mechanisms of level population in gas lasers pumped by ionizing radiation

“…1) (Voinov et al, 1990;Hebner, 1993). Processes in the active media of lasers at 3p-3s transitions of NeI are considered to be well studied (Shon et al, 1993a;Karelin & Yakovlenko, 1995): population of the upper laser level is due mainly to dissociative recombination of Ne 2 + and HeNe + molecular ions. Under comparatively weak pumping, the HeNe + ions also form Ne 2 + ions in the substitution reaction HeNe + + Ne Ne + 2 + He.…”

Nuclear-Induced Plasmas of Gas Mixtures and Nuclear-Pumped Lasers

“…Kinetic equations are supplemented by the equations of electron energy balance. In some kinetic models, the number of plasma chemical reactions reaches several hundred (see, for example, [29,39]). Typically, the relevant description of plasma and laser parameters' calculation suffices it to include 10-15 basic reactions.…”

“…Report [90] on NPL lasing in 3 He-Ne-H 2 mixture with a lasing threshold of 10 14 n/cm 2 s is doubtful, as hydrogen at a pressure of 0.57 bars must be considerably quenching the upper laser level. Unlike lasers operating on IR transitions of Xe, Kr, Ar, the lasing mechanism in lasers on 3p-3s transitions of neon was considered reliably established [39,87,94]. Already the first works on neon lasers pumped by an electron beam or nuclear radiation contain roughly the same ideas about the lasing mechanism.…”

Optical Emission of the Nuclear-Induced Plasmas of Gas Mixtures

“…The lasing threshold was not achieved. Further theoretical research [19,20] and experiments conducted by other organisations [21][22][23] indicated that the lasing threshold for the line at 585 nm exceeds 10 14 n/cm 2 s. The processes involved in the active media of lasers at the 3p-3s transitions of NeI are considered to be well studied [19,24]: the population of the upper laser level occurs primarily because of the dissociative recombination of Ne 2 + and HeNe + molecular ions. Under relatively weak pumping, HeNe + ions also form Ne 2 + ions through the following substitution reaction:…”