Controlling Selective Excitation Of Vibrational States Of Diatomic Molecule By A Chirped Laser Pulse

Population transfer and coherent control of quantum states have been a important subject in many theoretical and experimental studies.It is widely used in the generation of higher harmonic,molecular spectroscopy,photolysis photoionization and control of chemical reactions.In this paper,based on the time-dependent quantum wave packet method and the chirped adiabatic channel technique,the population transfer between the electronic states of three stateNa₂ molecules and the selective excitation of the vibrational states on the target electronic state are studied.Firstly,the influence of laser parameters on the population transfer of target electronic states is studied,Compared with the single negative chirped pulse,a positive chirped pulse can achieve almost complete population transfer,and can achieve efficient population transfer in a large range of laser parameters,which is also conducive to the control of population transfer.Secondly,the effects of half-width,laser intensity,central frequency and chirp rate on the vibrational population distribution of the target electronic state are studied.It is concluded that with the increase of the half-width,the pulse bandwidth becomes smaller and the frequency involved becomes less,which results in less vibrational excitation.When the laser intensity increases,the interaction between electronic states increases,and the population transfer efficiency becomes higher.However,compared with other laser parameters,the influence on the vibrational population distribution is not obvious.With the increase of chirp rate,the vibrational population moves to the lower energy level.Finally,by choosing the appropriate half-width,laser intensity and chirp rate,we can realize the selective excitation of vibrational states by adjusting the central frequency.