Research On The Strong Field Non-adiabatic Tunneling Ionization Based On The Attoclock Method

Tunneling ionization is the first step of strong field ionization of atoms and molecules.As one of the most basic and universal quantum phenomena in strong field ionization,it has been a very important and highly concerned issue in the basic research field of ultrafast optical physics.The development and maturity of the few cycle ultra-short and ultra-strong laser technology provides a powerful tool for the deep understanding of the strong field physical process on the sub-photoperiod time scale.Based on the attosecond fringe spectrum technology,the attoclock technology has a time domain measurement accuracy of several attoseconds,which provides a good way to study the ultrafast dynamic behavior of electrons in the strong field tunneling ionization process.In this paper,we study the ultra-fast dynamics of electrons in strong field tunneling ionization by focusing on the deflection angle of photoelectron momentum spectrum.The effects of the two phases of the few-cycle ultrashort laser pulse carrier envelope phase and the non-adiabatic effect in tunneling ionization on the deflection angle of photoelectron momentum are analyzed.We study the interaction of near-circularly polarized few-cycle femtosecond laser pulses with inert atoms.Using the classical trajectory Monte Carlo simulation method,we find that the deflection angle at the probability peak of the photoelectron momentum spectrum within the laser polarization plane is maximized when the carrier envelope phase of the laser pulse is ?/2.When the other laser parameters remain unchanged,the maximum deflection angle is different in the interaction of the different duration pulse with the same atom.The corresponding relationship between the carrier envelope phase of the few-cycle ultrashort laser pulse and the deflection angle at the probability peak of the photoelectron momentum spectrum within the polarization plane is obtained by changing the carrier envelope phase of the laser pulse.Therefore,we propose an innovative method and corresponding device for measuring the carrier envelope phase of the few-cycle ultrashort laser pulse.This method is simpler than the traditional stereo-ATI method on the device.When the electrons has non-adiabatic effect during tunneling ionization,the deflection angle of the photoelectron momentum spectrum also changes.We studied photoelectron spectrum characteristics after the interaction of two kinds of circulating current electrons which are the 2p orbitals of the neon atom and the near-circularly polarized few-cycle femtosecond laser pulses,and found that the non-adiabatic effect of the circulating current electrons opposite to the laser field rotation is more significant,which has the characteristics of higher ionization rate,closer tunneling position and earlier ionization time.In addition,based on the instantaneous snapshot of the spatial probability density of the circulating current electrons wave at the peak of the laser electric field,the influence of the laser frequency on the non-adiabatic effect of the circulating current electrons in the tunneling ionization process is further studied.It is found that the higher the laser frequency,the stronger the non-adiabatic effect.The work of this paper provides reference for the accurate interpretation of the angular distribution of the photoelectron momentum spectrum in the attoclock experiment with non-adiabatic tunneling effect.