Efficiency of ionic lasers with energy transfer from a buffer gas

Abstract

We propose two approaches for determining the native basins in off-lattice models of proteins. The first of them is based on exploring the saddle points on selected trajectories emerging from the native state. In the second approach, the basin size can be determined by monitoring random distortions in the shape of the protein around the native state. Both techniques yield similar results. As a byproduct, a simple method to determine the folding temperature is obtained.Chains of beads on cubic or square lattices, with some effective interactions between the beads, often serve as simple models of proteins (see for instance [1]). A more realistic modelling, however, requires considering off-lattice systems. Simple off-lattice heteropolymers have been discussed recently by Iori et al [2], Irback et al [3], Klimov and Thirumalai [4] and by the present authors [5]. The purpose in using such models is to understand the basic mechanism of folding to the native state. In lattice models, the native state is usually non-degenerate and it coincides with the ground state of the system. Delineating boundaries of the native basin in off-lattice systems, however, is difficult, especially when the number of degrees of freedom is large, yet it is essential for studies of almost all equilibrium and dynamical properties of proteins. For instance, stability of a protein is determined by estimating the equilibrium probability to stay in the native basin: the temperature at which this probability is 1 2 defines the folding temperature, T f . The native basin consists of the native state and its immediate neighbourhood, as shown schematically in figure 1, and it should not be confused with the whole folding funnel. The latter involves a much larger set of conformations which are linked kinetically to the native state.In most studies, such as in [3,4], the size of a basin is declared by adopting a reasonable but ad hoc cutoff bound. Systematic approaches, however, are needed and will be presented here. The task of delineating of the native basin is facilitated by introducing the concept of a distance between two conformations a and b, δ ab . The distance should be defined in a way that excludes effects of an overall translation or rotation. There are two definitions of δ ab , for a sequence of N monomers, that we shall use. The first one is [2, 6]:

The dominant pumping mechanism of the 441.6 nm Cd II line in a three-colour hollow-cathode discharge laser

“…It is obvious that the CDS works as an external ionizer for the NG plasma and thus that processes in the CDS are weakly connected to the NG parameters. This explains why the optimum density of metal atoms (Vainer et al 1979) and, as a result, the efficiency of pumping (Vainer et al 1986) inside the NG of a HCD are higher than those in a PC. Thus, the scenario of generation of high-speed electrons determines the sort of EDF which differs considerably from the Maxwellian distribution due to these being a large amount of highspeed electrons (Kagan et al 1972a(Kagan et al , 1972b(Kagan et al , 1973(Kagan et al , 1975a(Kagan et al , 1975b.…”

About creation of population inversion in mixture of inert noble gas and metal vapor

“…As a result of the prediction of energy parameters of lasers emitting on new transitions it is shown that these lasers may become effective sources of radiation not only in visible but also in the infrared. 10 -9 10 -11 10 16 10 14 10 12 10 10 10 13 10 11 10 15 10 -10 for the following levels of thallium ion: 7 3 P 2 (curve 1), 7 3 P 1 (2), 7 3 P 0 (3), 6 3 D 3 (4), 6 3 D 2 (5) and 6 3 D 1 (6); (b) the dependences of the gain for the IR transitions: 7 3 P 2 -6 3 D 3 (curve 1), 7 3 P 1 -6 3 D 2 (2) and 7 3 P 0 -6 3 D 1 (3). …”

“…The values of specific laser output power were found using the calculations of the energy conver sion efficiency η of discharge to output energy of laser radiation in HCD and experimental data on the specific input power entered to the discharge at the optimum value of current density j opt for each of the laser transition: (11) where is the quantum efficiency, is the pumping efficiency, i.e. serial conver sion of the discharge energy (power) into the energy of fast electrons of the NG plasma, further into the energy accumulated in ions (in atoms B m ) and transferred to metal atoms in the CT (or PI) reaction; η las -the conversion efficiency of energy which has been accumulated in excited ions of metal M + *, into laser light.…”

“…serial conver sion of the discharge energy (power) into the energy of fast electrons of the NG plasma, further into the energy accumulated in ions (in atoms B m ) and transferred to metal atoms in the CT (or PI) reaction; η las -the conversion efficiency of energy which has been accumulated in excited ions of metal M + *, into laser light. The and η las were calculated by the method described in [11].…”