Excitation Of Hydrogen Atom Irradiated By Strong Laser Field

Many nonlinear phenomena can be observed when ultrashort intense laser pulses interact with atoms and molecules,for example,high-order harmonic,high-order above threshold ionization ionization,thwarted tunneling ionization,etc.Neutral atom acceleration can be achieved by using excited atom,therefore,the study of excitation process has recently become the focus of research.In this paper,the excitation of atoms under ultrashort intense laser pulses is calculated by solving the threedimensional time-dependent Schrodinger equation numerically.First of all,the probability of excited states and its distribution on the principal quantum number and angular quantum number are studied systematically under the condition of on-line polarization laser pulses.We find that the excitation probability of the atom exhibits a “knee” structure with the increase of the intensity of the incident laser pulse.By analyzing the distribution of the excitation probability on the principal quantum number,it is found that the source of the structure is the resonant transition between the ground state and the highly excited state of the laser electric field.The distribution of atomic excitation probability in different angular quantum numbers shows the law of even and odd phase with the increase of incident laser pulse intensity.The results show that the excitation process of atoms not only satisfies the condition of energy resonance,but also satisfies the conservation of angular momentum.On this basis,we analyze the effect of polarization on the atomic excitation process.We find that the excitation probability of atoms decreases with the increase of the degree of polarization of the laser pulses at the same laser pulses energy,the excitation probability is distributed on the higher principal quantum number,and the excitation probability increases gradually.The excitation probability of laser pulse with wavelength of 800 nm increases with the increase of polarization,which is higher than that of 400 nm laser pulse at wavelength.