Depolarization rates of resonance lines of Mg, Ca, Sr and Na atoms by collisions with neutral hydrogen

Abstract

Abstract.Multipole relaxation and transfer rates due to isotropic collisions with neutral hydrogen atoms are calculated and a general expression for the hyperfine-structured levels are obtained. Evaluation of these rates has been carried out using accurate potential energy curves. The formulae given here for the depolarizing collisional rates should be useful for accurately modelling the complex linear polarization pattern of the Na  doublet in a complement to the ground state's depolarizing collisional rates which were presented in a previous paper (Kerkeni et al. 2000) hereafter referred to as Paper I. Similarly the depolarizing collisional rates of the Mg , Ca , Sr  resonance lines should be useful for polarization studies.

Depolarizing Collisions With Hydrogen: Neutral and Singly Ionized Alkaline Earths

“…For Mg i ( 1 P • ), this crossing produces a double well in the 2 Σ and 2 Π states with a rather long interaction length (Figure 2). The a i values obtained in this work are very close to those reported by Kerkeni (2002), within 1-2%, showing that the potential curves are rather similar.…”

“…In the quantum ab initio approach used here and in most previous studies (Kerkeni 2002;Kerkeni et al 2003), an adiabatic description of the electronic states is used. In this description, the states correlating to given states of the A(α, J ) + H fragments change adiabatically as they cross with others, essentially of ionic character.…”

“…The total depolarizing rate of the αJ level is defined as the term within the brackets in Equation (9), according to Kerkeni (2002), Brouard et al (2009), and Dagdigian & Alexander (2009) …”

“…However, the matrix elements of the electronic terms of the Hamiltonian, H el and H A SO , deserve some attention. For treatment of these two terms, we are considering three approximations that are commonly used in the previous quantum treatments of collisional depolarization of atoms (Kerkeni et al 2000;Kerkeni 2002). …”

“…More recently, Derouich et al (2003aDerouich et al ( , 2003bDerouich et al ( , 2004aDerouich et al ( , 2004bDerouich et al ( , 2005; Derouich & Barklem (2007) used ab initio interaction potentials and a semi-classical approach using straight line trajectories at different impact parameters. Kerkeni et al (2000); Kerkeni (2002); Kerkeni & Bommier (2002); Kerkeni et al (2003) have calculated depolarizing rates with neutral hydrogen with a fully quantum mechanical approach for the Hamiltonian interaction and dynamics. We follow a similar approach here.…”