Optimal selection of photo-ionization and electric field ionization

Abstract

In this paper, the dynamic characteristics of the two approaches of atomic ionization, photo-excitation plus photo-ionization (PE+PI) and the photo-excitation plus electric field ionization (PE+EFI) are investigated systematically. For the PE+PI process, two different schemes (I and II), with and without overlapping pulse duration, are designed and specified. The rate equations for both PE+PI and PE+EFI processes are established, numerical solutions of which provide profound characteristics. A detailed analysis of the theoretical results is carried out to observe the impacts on their overall ionization efficiency made by several factors, either atomic or laser parameters. Not only the ionization efficiency of both approaches is given, but also the optimal selection under some specific conditions is discussed. If the pulse widths of lasers are fixed, then the PE+EFI approach is superior to the PE+PI approach when laser powers are small, while the PE+PI approach is better otherwise.