Research On N₂ Molecular Auger Spectra Based On Ultra-short X-ray Pump-continuous Infrared Control Technology

As an important scientific technology in atomic and molecular physics,Free electron laser(FEL)can provide short pulse radiation with tunable wavelength,high photon flux and high coherence.At present,FEL is mainly developed for ultrashort,ultraintense pulse with high coherence.Furthermore,the ultrashort and ultraintense x-ray free electron laser(XFEL)can even be used to interact with the inner shell electrons of atoms and molecules to excite the system to a specific resonant excited state by single photon absorption,thus the objective of investigating the significant resonant Auger(RA)effect in the relaxation process of the unstable states can be achieved.In this paper,we mainly focus on the study of the RA effect in certain small quantum systems exposed to ultrashort and ultraintense x-ray laser pulses.Based on a large number of relevant research at home and abroad,we proposed an ultrashort x-ray pump and strong continous-wave(CW)IR control scheme to study the dynamics of core-excited state of N2 theoretically.The structure of this paper is as follows:Firstly,the present progress of XFEL and the application on the interaction between XFEL and matter were introduced.Secondly,the general theoretical and calculation methods in this work,including Born-Oppenheimer(B-O)approximation,Franck-Condon(F-C)principle,time-dependent wave-packet propagation method for describing dynamic process and MCTDH calculating method for solving time-dependent Schrodinger equation were summarized.Finally,empolying above techniques and theoretical methods,we selected diatomic molecule N2 as the research object,and implemented ultrashort x-ray pump-CW IR control scheme to make a theoretical research on its RAS,among which a femtosecond weak x-ray pump resonantly excites the nitrogen core-excited 1s??*of N2 molecule;a strong CW IR control induces dynamic Stark shift of the core-excited level.With the pulse duration of the ultrashort pump comparable to or even shorter than the period of the IR control,the time overlapping between the pump and control pulses reduces into a subcycle of the IR pulse;the efficient pumping process strongly depends on the dynamic Stark shift and the relative phase between the two pulses.The results are numerically illustrated for the N2 molecule by a 2-fs x-ray pulse,RAS also show a strong dependence on the bond-distance-dependent Auger decay probability.The dynamics of wave packet on the core-excited state and the formation of RAS is manipulated by changing the relative phase.