| The development of laser theory and technique gives rise to influence on the traditional atomic and molecular physics in deeply, the natural radiation lifetime, Landéfactor, hyperfine structure become the focus who concern. with the help of the short intense laser pulse experiment made preparing and probing highly excited the Rydberg states in possible, and promoted, therefore, relative researches and explorations in following basic areas: the interactions between laser and particles of matter, measurement of the energy level structures, etc.Because of its unique characteristics in external field , Rydberg atoms has become an important element in atomic physics research. As a sensitive probative tool of interaction of the fields and particles, the Rydberg atoms have widely used to many fields due to the characteristics of long-lifetime, wide scattering cross section and sensitive to external fields. For example, atom-chip experiments that realize control and storage of the Rydberg states have opened the way to investigations at the frontier of solid state physics and atomic physics. Preparation of short-pulse excitation of the Rydberg state wave packet can be achieved in a number of coherent dimensions compression, to achieve the minimum uncertainty relation has become a classic study of the ideal limit. For the high-excited Rydberg atoms, molecules up to micron-scale magnitude of space, which can be used as the basic transport microcavity theoretical model; At the same time, for theoretical works the system of the Rydberg atom in strong fields is typical example demonstrating classical-quantum correspondence. Neutral tin (Sn I) is medium weight atom of carbon group element and the nuclear charge number is 50. The ground state electronic configuration of Sn I is 5s25p2 and belongs to even-parity. So far the data about energy level character of Sn I is mainly energy level values while other characteristic parameters do not have perfect research results, such as the natural radiation lifetime, Landéfactor, hyperfine structure, transition probability and oscillator strength, due to several important reasons. Firstly, the atomic beam of Sn I used in spectral measurement are difficultly produced; Secondly, low-excited levels of Sn I are quite sparse and most of the high-excited levels locate in the ultraviolet band, which brings tremendous difficulties on spectrum measurements. Since the typical excited state of Sn I is consist of an ionic core with p electron going with an excited electron outside, they possess different characteristics compared with ionic core with s electron, which is an interesting point in the theory of atomic structure.Based on the research background mentioned, in this paper, we combined the laser-atomic beam technology with the time-resolved laser-induced fluorescence spectroscopy technology, and used the two-photon two-step excitation methods to measure the natural radiative lifetime and Landéfactor in even-parity J=1 the Rydberg series of Sn I. at the same time, through analyses for the structure of energy levels, natural radiative lifetime, Landéfactor by the multichannel quantum defect theory (MQDT), their theoretical ones are obtained respectively.The laser system used in the experiment was consisted of two dye lasers pumped by two Nd:YAG lasers, respectively. The beam of neutral atoms was produced in a home-made atomic beam device. The two laser beams interacted with the atomic beam and excited the atom from the low-level to the high-levels to be studied. Then we use a grating monochromator and photomultiplier tube to detect radiation fluorescence signal, and finally we recorded the temporal electric signal by oscilloscope, stored it in a personal computer.Two-step excitation process was used in experimental study of the natural radiative lifetime and Landéfactor in even-parity J=1 the Rydberg series states of Sn I. When the pressure of vacuum chamber was 3.0×10-3 Pa and the temperature of oven was up to 1600 K, the atomic beam of Sn populated in the ground state was produced, and then the first laser beam (pump laser) was used to excite the tin atoms to the intermedial level . The second laser beam (probe laser), which was overlapped with the pump beam, was used to achieve particles distribution in even-parity J=1 level of Sn I excited states. In the direction of perpendicular to two laser beams, the radiation fluorescence signal was collected by a lens and sent into a monochromator, by which we should choose a suitable observation wavelength. The light signal was converted to electric signal and was amplified by photomultiplier tube. Finally, the signal was recorded by a oscilloscope and was stored in a personal computer.The current was recorded in time by a multimeter in experiment and we calculated the magnetic field strength B based on Current - magnetic curve. The natural radiation lifetime values in even-parity J=1 level of Sn I were obtained by fitting an exponential function to the recorded fluorescence curves. The frequency of the quantum beats was obtained by Fourier transforming and contrasting with formulaω21 =ΔE/ andΔE =2gJμBB, and then we could obtain the Landéfactors of even-parity J=1 levels. The natural radiation lifetimes of 15 levels and 14 Landéfactors had been measured in experiments. at the same time, through analyses for the structure of energy levels, natural radiative lifetime, Landéfactor by the multichannel quantum defect theory, their theoretical ones are obtained respectively, in most case, the theoretical values agree well with the experimental data.The accuracy of lifetime measurements is effected by blackbody radiation, flight-out-of-view effect, radiative trapping and so on, which were briefly described in the thesis.The results of this study will help people further understand the energy level structures of Sn I, and provide important atomic data for theoretical modeling on atomic physics and other research areas.
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