Experimental Study On Ionization And Dissociation Of Co In Strong Laser Field

The interaction between the intense laser and atoms and molecules has also become one of the research hotspots with the development of ultra-strong and ultra-short pulsed laser technology.Molecules show many novel physical phenomena in strong laser field,such as multiphoton ionization?MPI?,tunneling ionization?TI?,over barrier ionization?OTBI?,non-sequential double ionization?NDSI?and threshold ionization?ATI?.A molecule will be ionized in a strong laser field,and the generated molecular ion dissociates into multiple fragment ions under the action of the Coulomb force,which is known as the Coulomb Explosion?CE?.By measuring the kinetic energy of fragment ions,the information,such as ionization and dissociation of molecules in strong laser field,can be obtained,providing important experimental data for studying the dynamic of molecules in strong laser fields.In this thesis,we study the ionization and dissociation of CO molecules in a femtosecond laser field by applying an ultra-high vacuum time-of-flight mass spectrometer.The main works are as follows:Firstly,we have optimized the related programs.The simulation of the flight time of a large number of charged particles is realized with a higher accuracy.The data acquisition and on-line processing procedures are optimized to get a more accurate peak search and the ratio of much peaks and none peaks and the bad points in the data can be detected in time.A set of focus-seeking programs is written to directly obtain the effect of the movement of the focal spot on the number of collected ions.Secondly,we complete the relevant research.?i?By measuring the yield of Ar⁺with the laser energy and comparing with the calculated results of ADK theory,the accurate laser intensity is obtained.?ii?The counts and the changes of KER of the dissociation channels of CO molecules at different laser intensity are studied.The experiment shows that when the laser intensity vary from3.5×10¹⁴ W/cm² to 1.35×10¹⁵ W/cm²,the KERs of different dissociation channels are basically unchanged;the main dissociation channels of CO³⁺and CO⁵⁺are?2,1?channel and?3,2?channel respectively.?iii?The angular distributions of different dissociation channels of CO molecules are studied with the laser intensity of 1.0×10¹55 W/cm².It is found that the?1,1?channel dissociates mainly through ³??¹?and ³?⁺states;?2,1?and?2,2?channels have significantly lower counts at?=0°,?2,1?channel may dissociates through B²?and A²?states and?2,2?channel may dissociates through ³?and ³?^-states;the full width at half maximum?FWHM?of the angular distribution of each channel gradually decreases as the valence of ions increases.