Generation Of Isolated Attosecond Pulse And Its Application In The Laser-Dressed Bound-state Wavepacket Detection

Observing and controlling the ultrafast electrons motion in atoms and molecules experimentally has been a dream of researchers for a long time.For the ultrafast electron motion,this time scale is on the order of attoseconds(1 0^-18 s).Tracing this ultrafast process requires attosecond probe pulses.Due to the advantages of broadband spectral structure,good spatiotemporal coherence and energy tenability,high-harmonic generation has become a common method of experimentally generating attosecond light sources.High-harmonic frequency comb corresponds to the attosecond pulse train in the time domain.In recent years,many gating techniques have been proposed to make it possible to generate isolated attosecond pulse.During the laser-matter interaction,the ionized photoelectrons contain a wealth information of ultrafast dynamics.The main content of this paper focuses on the generation of isolated attosecond pulse and the ultrafast detection scheme based on the attosecond photoelectron spectroscopy,which provide experimental and theoretical basis for the subsequent study.The main research contents of this thesis are as follows:（1）An isolated attosecond pulse with duration of 252 as is produced in the laboratory.A 0.8 m J,6.7 fs pulse is applied to the double optical gating to obtain the ellipticity varing pulse.The XUV supercontinuum spectra are generated in the argon and neon targets,which correspond to the energy range of 27 51 e V and 43 70 e V respectively.The photoelectron detection system is set up and optimized,and the attosecond streaking camera experiment is performed to verify the generation of isolated attosecond pulse from argon target.The center energy of the isolated attosecond pulse is37 e V,the pulse width is 252 as,and the single pulse energy is about 560 p J.（2）We proposed a method to accurately measure the evolution of the laser-dressed bound wavepacket.By analyzing the laser assisted attosecond photoionization,the analytical expression of the attosecond photoelectron spectrum is obtained.This spectrum is different from the traditional attoseconnd streking camera,which implies the coupling process of the bound states during the laser-atom interaction.By using the self-developed reconstruction algorithm,the laser-driven bound wavepacket evolution are completely reconstructed.The ultrafast electron dynamics,including Rabi oscillation and resonance transition,are well recovered.This method expands the application field of attosecond streaking camera.（3）A detection scheme for the charge migration ofH₂⁺based on the attosecond photoelectron spectroscopy is proposed.The interference structure in the attosecond photoelectron spectrum ofH₂⁺contains the information of the molecular charge migration process.The analytical expression of the photoelectron spectrum is given under the strong-field approximation model.Combined with the double-slit interference model,the quantitative dependence of the interference structure and charge migration is given,including the internuclaser distance,the population of the two nuclei and their relative phases.This method provides a new idea for tracing the ultrafast motion of electrons in molecules.