Quantum enhancement in laser-assisted photoionization and a method for the measurement of an attosecond xuv pulse

摘要

Quantitative investigations are made into the quantum enhancements achieved in laser-assisted photoionizations for attosecond extreme-ultraviolet ( xuv ) pulses with different chip properties. An improved pulse reconstruction scheme is presented based on the analysis of two photoelectron energy spectra (PESs) measured with different laser intensities. A direct procedure is developed to completely reconstruct the intensity and chirp of an isolated pulse (within one-half the laser period) with high precision. Results show root-mean-square frequency (time) differences less than 0.8 eV (2 as, except for a few data points near the start and/ or end of the pulse ). A stereo measurement ( recording PESs from two opposite directions along the direction of laser polarization ) is needed to reconstruct a broad bandwidth xuv pulse with a nonmonotonous instantaneous frequency.