Cross sections and transport coefficients for electrons in Zn vapour

Abstract

In this paper we present details of the following: ab initio calculations of a set of electron impact cross sections for atomic Zn; and transport coefficients and distribution functions for an electron swarm in Zn vapour, obtained from a multiterm solution of Boltzmann's equation using these cross sections, over a range of reduced fields, E/N, and gas temperatures of practical interest. Our work has been motivated, in part, by recent suggestions that zinc could be an attractive replacement for mercury in making high-pressure gas discharge lamps more environment-friendly (Born M 2001 J. Phys. D: Appl. Phys. 34 909; Born M 2002 Plasma Sources Sci. Technol. 11 A55). Current models of such lamps require a knowledge of the plasma electrical conductivity, which can be calculated from the (e, Zn) cross sections and mobility coefficients presented in this paper.

Integral Cross Sections for Electron–Zinc Scattering over a Broad Energy Range (0.01–5000 eV)

“…The situation is less clear cut, however, for the sum of the discrete inelastic ICSs. In this case, the available data are restricted to the results from our present ROP and OP computations, an earlier R-matrix result from White et al, 7 and a sum of the measured optically allowed 4 1 P and 5 1 P ICSs from Fursa et al 24 All these available data are plotted in Fig. 1(b), where the level of agreement between them is seen to be quite marginal.…”

“…As in our earlier work on Be and Mg, 1-3 those recommended integral cross section databases are as complete as we can make them and they are compiled over a broad energy range (0.01-5000 eV). As noted previously by both Tanaka et al 5 and the LXCat collaboration, 6 fulfillment of those criteria is essential if charged particle electron transport 7 or kinetic-radiative modeling 8 simulation results, for zinc vapor, are to be physical.…”

“…The latter point is particularly relevant as it has been suggested 9,10 that Zn might be an attractive replacement for mercury in making high-pressure discharge lamps more environmentally friendly. Indeed, as a consequence of the work of Born, 9,10 White et al 7 conducted an initial multiterm Boltzmann simulation study looking into the transport characteristics of a swarm of electrons drifting through a background Zn vapor under the influence of an external electric field (E). However, the energy range of the cross section database in Ref.…”

Experimental and theoretical cross sections for elastic electron scattering from zinc

“…That collisional radiative model included the RDW elastic integral cross section (ICS), as well as the ICSs for discrete inelastic processes, to ensure that the sum of their individual ICSs was consistent with the total cross section and therefore that their [7] cross-section data base was self-consistent. As a consequence of the Born [4,5] work, White et al [8] conducted an initial multiterm simulation study looking at the transport characteristics of a swarm of electrons drifting through a background Zn vapor under the influence of an external electric field. That work of White et al [8] demonstrated that anisotropic scattering, through incorporation of the elastic momentum transfer cross section [8] of Zn, was necessary for accurately describing the electron transport characteristics in Zn under the influence of such an applied (external) electric field.…”

“…As those earlier computations have been largely superseded, we do not discuss them further. More recently, a R-matrix result (incorporating 23 target states) [8], a B-spline R-matrix (BSR) approach [18] (incorporating 49 target states), and a convergent close-coupling (CCC) method [11] (incorporating 206 target states) have become available in the literature. While the CCC results were only reported in Fursa et al [11] for the 4 1 P and 5 1 P states, elastic results were also obtained as a part of that computation.…”