Wannier threshold law for two-electron escape in the presence of an external electric field
Fachbereich Physik, Philipps-Universität Marburg -
D-35032 Marburg, Germany
2 Instytut Fizyki im. Mariana Smoluchowskiego, Uniwersytet Jagielloński ul. Reymonta 4, PL-30-059 Kraków, Poland
Accepted: 20 September 2001
We consider double ionization of atoms or ions by electron impact in the presence of a static electric field. As in Wanniers analysis of the analogous situation without external field the dynamics near threshold is dominated by a saddle. With a field the saddle lies in a subspace of symmetrically escaping electrons. Near threshold the classical cross-section scales with excess energy E like , where the exponent α can be determined from the stability of the saddle and does not depend on the field strength. For example, if the remaining ion has charge Z=2, the exponent is 1.292, significantly different from the 1.056 without the field.
PACS: 34.80.Dp – Atomic excitation and ionization by electron impact / 32.60.+i – Zeeman and Stark effects / 31.25.Jf – Electron correlation calculations for atoms and ions: excited states
© EDP Sciences, 2001