DC-FIELD TUNNELING OF POLYELECTRONIC ATOMS AND OF NEGATIVE-IONS - COMPUTATIONS BASED ON MODELS AND ON AB-INITIO THEORY

We have computed the dc-field-induced tunneling rates for H-, He, Li, and Li- by applying two methods. The first used ab initio theory, whic h not only produces reliable results but also allows the systematic an alysis of the effects of electronic structure, of the multichannel con tinuum, and of field-induced mixings. The second used previously publi shed formulas derived from semiclassical models. Comparison shows larg e quantitative differences, especially for strong fields and for He, w here the electrons are equivalent. However, for H-, Li, and Li-, the p lots of the widths on a logarithmic scale as a function of the field s trength yield similar shapes.