Rydberg State Excitation And Ultrafast Ionic Dynamics Of CS₂ Molecule In The Intense Laser Fields

The interaction between the femtosecond intense laser field and gas-phase atoms/molecules is a hotspot in the current physical researches.The strong field physical processes of atoms and molecules include many nonlinear and non-perturbative phenomena,such as non-sequential double ionization,high-order harmonic generation,above threshold ionization and so on.In recent years,the Rydberg state excitation in the intense fields has received extensive attention from experimental and theoretical researchers.Compared with atoms and small molecules,the Rydberg state excitation of polyatomic molecules has not been reported.Therefore,this paper studied the Rydberg state excitation process of CS₂ molecules using the delayed pulsed electrostatic field ionization method.At the same time,the optical fragmentation spectrum based on the strong field ionization is an effective method to study the dynamics of excited electronic states in the molecular cations.Therefore,this dissertation studied the ultrafast dynamics of excited state in the CS₂ molecular cation with the pump-probe method.The following conclusions are obtained from the two aspects of the research:1.In the 800 nm laser fields,the neutral parent and fragment Rydberg states of the CS₂ molecule survived;the dependences of the yields on the laser parameters were measured and compared with the corresponding ions,analysis shows the formation of the Rydberg state parent CS₂ is a result of the recapture of low-energy photoelectrons,and the neutral Rydberg fragments are produced by the photoelectrons trapping of the fragment ion which came from dissociation or Coulomb explosion.2.Using the strong field ionization-photo fragmentation method,we studied the ultrafast dynamics of the CS₂ molecular cations.The stable CS₂²⁺exists in the laser field have been confirmed experimentally;the dissociation pathway of the CS₂²⁺which absorbed a single 400 nm photon to generate CS⁺+S⁺was indentified.In addition,the ultrafast transient of S⁺produced by CS₂⁺which absorbed the 400 nm photons was also observed,and the relaxation time was estimated to be 210 fs.