The Influence Of Doppler Effect On Dynamics Process Of Resonance Multiphoton Ionization

Resonance Enhanced Multiphoton Ionization(REMPI) technology is one of the significant means of studying the interaction of light and matter. The research of the characteristic of its dynamic behavior has important theoretical significance and huge potential application. This thesis establishes the theoretical model of single-resonance multiphoton ionization system firstly, and then, based on the density-matrix equations theory of Quantum mechanics, we studied the the influence of Doppler effect on resonance enhanced multiphoton ionization process middle resonance absorption,dispersion characteristics and the particle count population change by MATLAB numerical simulation.In the case of not considering Doppler effect, at the initial time of laser effect, there appeared a strong absorption peak at the center frequency, after a period of time, absorption curve appeared transparent electromagnetic induction phenomenon, and transparent depth increased with the increasing of ionization rate and Rabi frequency, and decreased with the increase of the longitudinal relaxation; we found that, with the delay of laser effect time, each level population share the characteristics of periodic change.When considering the influence of the Doppler effect that effected on multiphoton ionization process, we set up that molecule is with Maxwell speed distribution, Doppler effect broaded absorption curve, caused the absorption curve overlapping, made the electromagnetic induction phenomenon of transparent disappear, but the curve center did not happen translation and dispersion characteristics is abate, but the impact of the Doppler effect on particle number cloth is little.Based on the molecular beam jet, and according to the particularity of the actual situation, no longer consider the direction of the particles of thermal motion speed, so we think that the particle thermal motion is Maxwell velocity distribution. At the initial moment of Laser effect, Doppler effect made the absorption spectral lines broadened, and the center of the line move to the location of corresponding frequency of most probable rate; after a period of time, absorption and dispersion curves translate, and as a result of inhomogeneity of Maxwell speed distribution,there appears asymmetric phenomenon.Considering the influence of Doppler Effect, the results could provide more valuable reference information for the theoretical study and practical application of the technique of REMPI.