Effect Of Ponderomotive Force On Kramers-henneberger Atoms

With the development of laser technology,strong field physics has gradually become an important research field.For example,when an atom is in a superintense laser field,electrons will oscillate with the laser fields,and the ionization rate will decrease with the increase of laser intensity.This phenomenon is called“atomic stabilization”.The problem can be simplified by using the KramersHenneberger(KH)transformation when dealing with the interaction between intense laser field and matter.The High Frequency Floquet Theory(HFFT)shows that in the high frequency approximation,the effective binding potential between electrons and the nucleus is called dressed potential,also known as KH potential.KH potential can support many bound states.These bound states are called KH states,and the corresponding atoms are called KH atoms.Since the 1970 s,there has been a lot of theoretical works about KH atoms,but experimental verifications are few.Since KH atoms can only exist in superintense laser fields,and superintense lasers are usually focused laser beams.In focused laser beams,the oscillating electrons will experience PM force.However,in previous studies of KH atoms,the effect of PM force has been neglected.In this thesis,starting from time-dependent Schr¨odinger equation,we study the effects of PM forces on structures and properties of KH atoms in focused laser beams.We hope to provide some inspiration for the experimental study of KH atoms.The works in this thesis are composed of the following two parts:1.We study the effect of PM force on the structure of ground KH state hydrogen atom in strong linearly polarized laser beams.It is well known that ground KH state hydrogen atoms in linearly polarized laser fields exhibit symmetric structure of dichotomy.However,our study shows that KH state electrons will experience PM force,which might polarize KH atoms and break the symmetry of dichotomous structure.2.We study the acceleration of KH state helium atoms in a circularly polarized laser pulse.Our study shows that helium atoms in circularly polarized laser pulses will experience both PM force and KH force.We calculate the radialvelocity gain from PM and KH forces.By analyzing the contribution of KH force to the acceleration of helium atoms,we provide means for verifying the existence of KH atoms in experiment.Furthermore,all the lasers used in this thesis are experimentally accessible.