The Experimental Investigation Of Photoelectron Imaging From Aligned Molecules

With the development of laser technology,the intensity of laser field is close to the Coulomb field between the valence electron and the parent ion in atom or molecule.The interaction between strong laser field and atomic or molecular gases will produce many nonlinear physical phenomenas,such as High Above-threshold ionization?HATI?,Nonsequential double ionization?NSDI?,High-order harmonic generation?HHG?and Coulomb explosion and so on.The behavior of electrons in atoms and molecules under the action of strong field determines the research mode of products.In order to obtain the spatial distribution information of ions or electrons yield with laser reaction and the position and momentum in the strong laser field,velocity map imaging technology is used to analyze the ionization process of atoms or molecules and the physical regulation of the action in strong laser field.Velocity map imaging?VMI?technology has great application prospect and significance in the study of molecular reaction process in strong field physics.In this paper,we investigate the velocity map imaging of nonadiabatic collimation of N₂,O₂ and CO₂ molecules by strong femtosecond laser field,and analyze the mechanism of rescattering process and the problem of molecular orbital of the photoelectron imaging of the three molecules.This thesis consists of four chapters.In the first chapter,the development and application of intense ultrashort-pulse laser technology and the main ionization mechanism of the the strong field laser interaction with atoms or molecules are introduced.Finally,we introduce the study of strong field physics anglied molecules.In the second chapter,we mainly introduce the velocity map imaging device and the principle of velocity map imaging experiment.The energy calibration of detector and image processing are completed by the interaction between the 400nm laser and Xe atom.The multiphoton ionization process of Xe atom is analyzed and from the calibrated energy spectrum.The angular distribution information of of Xe atom in different ionization processes is extracted from the experiment.The anisotropic parameter of Legendre polynomials is extracted to confirm the angular distribution information.In the third chapter,we realized the nonadiabatic collimation by pump-probe technology and investigated the photoelectron imaging of N₂,O₂ and CO₂molecular.From the view of experimental,the rescattering process of photoelectron imaging ionization is preliminarily determined by the photoelectron energy spectroscopy of N₂.In the end,by look into the ionization difference between the three moleculars photoelectron imaging cartoon,which the ratio of aligned point to antialigned point in the rescattering region.The influence of electron orbital on moleculars ionization of N₂ and O₂ and the influence of laser-induced electron diffraction of CO₂ molecules on the ionization are discussed.In the fourth chapter,we summarized the contents of this essay and foresight to future inquiry.