Study On Atomic Ionization Characteristics Driven By Ultrafast Intense Laser Pulses

The interaction between the ultrafast intense laser pulses and the atom can produce various types of nonlinear physical processes,such as single ionization,double ionization,frustrated single ionization and frustrated double ionization,all of these processes reflect the response of atoms to intense laser field.The response of these four processes in laser field is studied in this paper.In particular,nonsequential double ionization（NSDI）has become one of the research hotspots in the field of strong field physics because of its strong electron correlation effect,which is one of the most basic phenomena in nature.In this paper,the dynamic process of electron correlation in NSDI is studied deeply and systematically,on this basis,a scheme for controlling the associated electron dynamics of NSDI of atoms is proposed.The main research contents of this paper are as follows:（1）The energy exchange during the ionization of argon atom driven by intense laser pulse is investigated.Our results show that when the laser intensity is fixed,with the increase of wavelength,the energy obtained by the two-electron system in the whole ensemble increases gradually at low intensity,and decreases first and then increases gradually at high intensity.At different wavelengths the energy obtained by two-electron systems presents two crossing points with the increase of intensity.The dependence of the energy obtained by the two-electron system in the whole ensemble on the ellipticity is as follows:the energy obtained by the two-electron system decreases first and then increases at low intensity,presents a“step type”at medium intensity,and increases first and then decreases at high intensity.The analysis shows that the dependence of the energy obtained by the two-electron system in the whole ensemble on wavelength,intensity and ellipticity is the result of the dominant role of an ionization channel.（2）The dependence of NSDI on relative frequency in different relative initial phases driven by the orthogonal two-color laser pulse is studied.The results show at the same relative initial phase the recollision time of the first electron can be controlled by adjusting the relative frequency,resulting the emission direction of Ar²⁺clearly depends on the relative frequency.The contribution of recollision excitation with subsequent ionization channel（RESI）can also be controlled by adjusting the relative frequency.The results show that the RESI channel is more sensitive to the relative initial phase at 400 nm+1200 nm than at 400 nm+800 nm.（3）The dependence of NSDI on the relative phase driven by the few-cycle counter-rotating TCCP laser pulse is explored.The results show that the probability of NSDI is obviously dependent on the relative phase.The analysis shows that the returning probability of the first electron is strongly dependent on the relative phase of the counter-rotating TCCP laser pulse,resulting in the NSDI probability dependent on the relative phase.In addition,by adjusting the relative phase of the counter-rotating TCCP laser pulse,the emission direction of Ar²⁺can be effectively regulated on the one hand,and the electrons can return to the parent ion from a relatively single direction on the other hand,which provides an effective scheme for studying the subcycle ultrafast electron dynamics.