Theory of Nonlinear Photoconductive Sampling in Atomic Gases

Abstract

The formation and evolution of electron wave packets in the process of strong-field ionization is one of the major research topics in attosecond science. The recently developed technique of nonlinear photoconductive sampling (NPS) requires a detailed understanding of these dynamics and provides a new approach to studying them. This work is motivated by the lack of a solid theoretical foundation for NPS measurements. The analysis shows that, for NPS in atomic gases, the strong-field approximation provides an adequate description of the ionization dynamics but makes a significant error in predicting the spectral response function because the Coulomb interaction between photoelectrons and their parent ions significantly affects the motion of the electron wave packets.