Theoretical Study Of Ionization Of Diatomic Molecules In Strong Laser Fields

With the rapid development of laser technology, more and more researchers begin to pay attention to the reaction kinetics of the atomic and molecular in the ultrafast laser field in theory and experimental research. We used the ultrafast laser pulses to detect the kinetic process of atoms and molecules only in theory or experiment. Now we can use ultrafast laser pulses to control the photochemical reaction of atoms and molecules. Due to the high needs of the experiment, it is very significant to research the dynamic process of atomic and molecular under the ultrafast laser pulses in theory.The main content of this thesis is the time-dependent quantum wave packet method, we studying on the ionization dynamics theory of Li2 molecules in strong laser field in theory, the ionization occurs in ultrafast laser field under the pump probe technique, Li2 molecular photoelectron spectroscopy AT splitting was calculated by solving Schrodinger equation. According to the corresponding relation between the photoelectron spectrum and dressed state and analyzing of the structure and photoelectron spectrum, we got the distribution information of dressed state of Li2 molecular. By changing the intensity, the wavelength of the laser pulse, the detection delay time between pulses and pump pulse and the laser pulse envelope to control the distribution of dressed state.When the peak intensity of the laser field is 1.2 x 1011 W/cm2, The population of electronic state|1> will present a Rabi oscillation, at the same time, the photoelectron spectrum of the ionized present AT splitting. Changing the peak intensity of the laser field can control the dressed state energy.When the wavelength of the laser pulse is changed near the resonance frequency (?pump=665 nm), the photoelectron spectra of AT splitting are no longer symmetric. When the laser frequency is greater than the resonance frequency(?pump<665 nm), the population of low energy state|?>is gradually reduced, and the population of high energy state|a>is gradually increasing. When the laser frequency is smaller than the resonance frequency (?pump>665 nm), the population of low energy state|?> is gradually increasing, and the population of high energy state|a> is gradually reduced. So the population of dressed state can be controlled by changing the laser pulse frequency (i.e. wavelength).When the delay time between the pump and the probe laser changes, the peak of the AT splitting of photoelectron spectroscopy has been changed. With the delay time changing from Ofs to 30fs, the peak to the right side of the photoelectron spectrum gradually reduced or even disappeared, and the left peak is still very high, even increase.Adjusting the laser pulse envelope, to control the distribution of dressed states. When we need a large number of low energy states, we can choose the sech2 pulse, When need more total number of the population we can consider the selection of super Gauss type.