The Influence Of The Internuclear Distances On The Ionization Of Hydrogen Molecule Irradiated By The Strong Laser Pulse

Ultrashort pulse laser has become an important research tool in atomic and molecular physics.High order harmonic emission,above-threshold ionization and non-sequential multi-electron ionization can be observed by the interaction of this light source with atomic and molecular systems.Among them,non-sequential multi-electron ionization has become one of the topics of widespread concern because it contains the correlation information between electrons and the real-time parent ion structure information carried by ionized electron recollision.Compared with atoms,molecules have more degrees of freedom,which makes the non-sequential ionization process more complex.The change of molecular nucleus distance not only affects the density distribution of electron states,but also causes the difference of ionization energy between different states.The influence of these changes on the ionization mechanism of non-sequence ionization is still needed to be further studied.In this paper,the double ionization of hydrogen molecules under different driving lasers is studied using a three-dimensional full classical ensemble model,with emphasis on the effect of nuclear distance on the double ionization mechanism.Main work contents:(1)The double ionization of hydrogen molecules under a single pulse(including linearly polarized,circularly polarized and including chirp)driven laser is studied.It is found that with the increase of molecular nuclear distance,the double ionization probability is very small at small nuclear distance,then increases rapidly,and then decreases slowly after reaching the peak value.The sequence and non-sequence processes are distinguished by the track tracking of ionized electrons.It is found that sequence ionization plays a dominant role in the nuclear distance of the structures producing peak double ionization yield.Under the condition of small nuclear distance,when the laser pulse is driven by linear polarization,the non-sequential ionization mechanism plays a major role.When the laser pulse is driven by circular polarization,the sequential ionization mechanism plays a decisive role.(2)The double ionization of hydrogen molecules by fundamental and double frequency circular polarization combined pulses is studied.It is found that when the electric field rotation direction of the two pulses is the same,the double ionization probability also presents a peak structure with the change of the nuclear distance.The analysis shows that the ionization mechanism of the two pulses is completely transformed from non-sequence ionization to sequence ionization with the increase of the nuclear distance.When the polarization rotation direction of the two laser pulses is opposite,although the double ionization characteristics are similar with the change of nuclear distance,the effect of non-sequential double ionization can not be ignored by tracking the particle trajectory under all the studied nuclear distance conditions.