Theoretical Investigation Of Photoelectron Spectroscopy On KLi

The development of laser technology has made the theoretical and experimental regulation and exploration of atomic and molecular dynamics processes a key focus of scientific researchers.An increasing number of researchers by using ultrafast femtosecond laser technology to control the dynamic processes of molecular population transfer and ionization.Especially the emergence of pump-probe technology,which makes a profound significance on the study of the photoelectron spectroscopy of molecule in femtosecond laser field.In this work,based on the time-dependent quantum wavepacket method,the ionization process of the diatomic molecule KLi in femtosecond laser field is theoretically investigated.We use a pump laser and a probe laser to change the laser intensity,wavelength,pulse width and delay time to analyse the phenomenon of the Autler-Townes splitting(ATS)of the photoelectron spectroscopy in detail.Firstly,by regulating the intensity of the two laser pulses,it is found that as the pump laser intensity increases,the photoelectron spectroscopy changes from the initial single-peak structure to the double-peak structure.Meanwhile,the position of the double-peak gradually moves away.The probe laser intensity mainly affects the height of the peak,while the peak position and peak configuration are almost unchanged.Secondly,by changing the wavelength of the two lasers,we find that the peak splitting structure and peak position of the ATS have changed with the pump wavelength increases.When the pump wavelength is ?_pump<770 nm,the population of high-energy state |?>is higher than that of low-energy state |?>,and the right peak of the ATS is higher than the left peak.There is a symmetric splitting in the photoelectron spectroscopy when ?_pump=770 nm.When ?_pump>770 nm,the population of |?>is lower than that of |?>.The heigh of right peak is lower than the left peak.The probe wavelength mainly affects the peak position of the ATS.With the probe wavelength increases,the double-peak gradually move to the lower energy state.Thirdly,the pulse width of two lasers and the influence of the probe intensity on the photoelectron spectroscopy under different probe pulse widths are studied.We choose the pump and probe intensity are I_pump=6.0×1011 W/cm2 and I_probe=3.0×107 W/cm2,respectively.It can be concluded that the difference between the double-peak mainly depends on the pump pulse width,while the probe pulse width has little effect on this.Shorter pump pulse width will cause incomplete Rabi oscillation and disappearance of ATS phenomenon.The larger probe pulse width will lead to the appearance of multiple peaks in the photoelectron spectroscopy.Meanwhile,we find that when ?_probe=50 fs,as the probe intensity increases to the order of the pump pulse,the difference between the double-peak also change significantly.Finally,the delay time between the two laser pulses is changed with ?_probe=30 fs and ?_probe=50 fs,it is discovered that there are multiple peaks in the photoelectron spectroscopy at the beginning.The increase of the delay time can lead to the splitting phenomenon of peaks gradually disappear,and the peak intensity of the photoelectron spectroscopy keeps decreasing.The difference is that there is only one weak peak at 30 fs,while there are two weak peaks at 50 fs,and the two weak peaks in the middle first turn into one peak and then gradually disappear.The disappearance speed of the splitting phenomenon is slower than that at 30 fs.