Theoritical Study On Photoelectron Spectra Of Nali Molecule

In recent decades, the development of femtosecond laser technology has made greatprogress, the studies of laser-matter interaction （LMI） have received the extensive attentionfrom experimentalists and theorists. Time-dependent photoelectron spectrum combinedfemtosecond pump-probe technology has been widely used in detecting the vibrationmovement of wave packet in nuclear coordinate. When atoms and molecules are subjected ina strong laser field, many interesting phenomena will present which cann’t be observed in aweak laser field, at this time the perturbation theory of quantum mechanics is no longerapplied. Time-dependent wave packet method has both the intuition of classical mechanicsand the accuracy of quantum mechanics, so it has become an effective method to research themolecular dynamics. The numerical way to solve the time-dependent Schr dinger equationsis the key of the time-dependent wave packet method. In a certain initial conditions, we cancalculate the initial wave function of the system using the suitable numerical method, andthen, through the split-operator Fourier transform method to obtain the wave functions of anytime. If we get any time wave function, we can obtain the expression of the population andphotoelectron spectra, then we can research the molecular dynamics, including thephotoelectron spectra, photodissociation and photoionization etc.In this thesis, firstly, using the three-state model and time-dependent wavepacket method,we have investigated the influence of the intense femtosecond laser wavelength on thewavepacket dynamic process of the double-minimum potential state5¹Σ⁺, as well as the laserintensity and wavelength on the population of the ground and diabatic electronic states ofNaLi. The calculation results show that, through adjusting the wavelength of laser pulse wecan control the movement of the wave packet and obtain the vibrational period of wavepacket in the potential well, however, the diabatic coupling strength between two excitedstates affects the vibrational period of wave packet. In addition, the different laser intensityand wavelength have different influence on the population of each state and the diabaticcoupling strength between two excited states. Secondly, employing the three-state model westudied the evolution of wavepacket of the double-minimum potential state4¹Σ⁺and thetime-resolved photoelectron spectra. We found that the vibrational period of wave packet isdifferent with different laser wavelength and the photoelectron spectrum is different with different pump-probe delay time. The height and position of the peak of the photoelectronspectrum is changed with the different pump-probe delay time. When λ₁=352nm and Δt=400fs, the corresponding signal in the outer well （0.5eV） is obviously larger than that in theinner well （1.35eV）. The result reveals that the time-resolved photoelectron spectrumreflects the information of the wave packet dynamic of the excited state4¹Σ⁺.