detachment function: I. The classical-dynamic study

Abstract

We investigate the process e + H − → H + 2e at low impact energies. A (quasi)classical model for the hydrogen negative ion has been used, and the system potential function which describes the three-body force has been employed. Using the classical trajectory method we calculate the detachment function from the (classical) threshold up to 20 eV of the impact energy. The cross section evaluated within the plane two-dimensional model follows roughly the shape of the recent experimental data, but appears lower than the experimental cross section close to the threshold and lies between the latest and some of the earlier measured values at higher energies. The mechanism of the detachment process close to the threshold has been investigated in detail and some particular features of the energy, mutual angle and angular momenta distributions are discussed.

Over-the-barrier electron detachment in the hydrogen negative ion

“…Such a configuration suggests a very useful one-electron picture where the outer electron is weakly (loosely) bound in a short-range attractive potential well. To a good approximation the potential acting on the outer electron due to the neutral atom is a sum of a short-range potential and the polarization term falling off as r 1 4 (see a short overview of the potentials of this type in the appendix of [13]). Moreover, since the outer electron spends much of the time beyond the potential well, it may be treated even as a free particle subject to boundary conditions imposed at the nucleus position.…”

Single-electron description of the strong-field electron detachment of hydrogen negative ion

“…An alternative is the model-potential consisting of a single term which provides both the correct binding energy and the correct asymptotics. Several model-potentials of these two types, used by different authors, are given in a short overview by Grujić and Simonović (1998).…”

“…Another, more approximate but simpler model-potential which belongs to the secondtype is the so-called Buckingham polarization potential (Buckingham, 1938, see also Mittleman and Watson, 1960, Grujić and Simonović, 1998…”

Threshold Detachment of Negative Ions by Electron Impact

“…Storage ring based experiments on threshold detachment from the deuteron (D − ) and the oxygen (O − ) negative ions by electron impact [1,2,3], and recently also from B − [4], have stimulated the theoretical interest in the mechanism and the quantitative description of this process [5,6,7,8,9]. It is a fundamental question how threshold detachment proceeds since for very low energies the impacting electron does not even reach the atom because it is repelled by the loosely bound electron.…”

“…Without a full calculation of all electrons, one cannot avoid to use parameters in one or another way, either directly in the simpler models [1,2], or indirectly in the more involved calculations modeling polarization potentials for the loosely bound electron [5,6,7,8,9].…”