Natural Radiative Lifetimes And Landé Factors Of Even-parity J=2 Rydberg Series Of Sn I

For more than a hundred years, the investigation of atomic internal configuration for human being have never stopped.The internal information of atom is so tempting. Recently, the rapid development of laser technique offer us a powerful tool for investigating atomic internal configuration in depth. Laser spectroscopy have been an indispensable technique in atomic and molecular physics.We can get a deeper insight into the properties of Rydberg states of atoms, and confirm atomic state from investigating radiative lifetimes and Lande g-factors, the investigation is also valuable for new laser material development.Neutral (Z= 50) tin is the second heaviest carbon-group element, has a 5s25p2 ground configuration, and its singly excited configurations include an excited electron outside of a 5p-electron ionic core. In comparison to the extensive investigation of energy levels of neutral tin, the radiative lifetimes and Lande g-factors derived experimentally are still very fragmentary. The reasons why the experimental lifetime and Lande g-factor data are so rare are as follows:(1) a high-temperature source for getting an atomic beam with sufficient vapour density is needed; (2) for even-parity levels, the intermediate resonance levels used in the two-step excitation can only be excited by UV laser and have lifetimes of only a few nanoseconds and, for odd-parity states, almost all the excitations from the ground level need vacuum ultraviolet(VUV) laser which is rather difficult to obtain.Because the lack of data in this field, we carry on the work in this paper. Utilizing time-resolved laser-induced fluorescence and Zeeman quantum-beat techniques, we measured radiative lifetimes and Lande g-factors of the even-parity J = 2 levels of neutral tin. We measured 32 lifetimes:J=25pnp (n=7,8,10-13, 15-19,27,31,32),5pnf(n= 4,5,9-19,22,23); and 30 Lande g-factors:J= 25pnp (n= 7,8,11-13,15-19,31,32),5pnf (n= 4,5,9-19,22,23), including perturbing levels of neutral tin. We validated the experimental data reliability and predicted the result of unknown levels by comparing experimental data with MQDT calculating date.A two-step excitation was used in the experiment. Two dye lasers pumped respectively by two Q-switched Nd:YAG lasers. The time delay between the two lasers was controlled by digital signal generator DG535. The atomic beam was produced by a high-temperature oven in vacuum. The air pressure was inspected by resistance manometer and ionization manometer and the temperature was inspected by thermoelectric couple. The system consist of condensing lens, monochromator, PMT was used to detect fluorescence. A 500MHz digital storage oscilloscope was used to observe fluorescence signal. The magnetic field calibrated by measuring the Lande g-factors of 6s6p3P10 level of Yb was generated by steady Helmholtz coils.We got the lifetimes by exponential fitting to the fluorescence decay signals, and got the Lande g-factors by gauss fitting to the the peak of frequency spectrum gained by Fourier transform of quantum beat signals.We considered all kinds of effect that maybe affect the lifetime results derived in the experiment, including black-body radiation effects, collisional quenching effects, flight-out-of-view effects and radiation trapping effects. We eliminated or reduced the effects by experimental technique and calculation. We obtained Sn I lifetimes at 0 K by approximatively determining BBR depopulation rates for Sn and the scaling with n. We also considered geomagnetic field effect that would disturb Lande g-factor results, and eliminated the effect by smart method. The experimental error was analysed in the round, the scattering error and systematic error of lifetimes and Lande g-factors was wholly calculated.Two unknow energy levels 5p9f (1/2,5/2)2 and 5pl3f (1/2,5/2)2 were found, their lifetimes and Lande g-factors were also measured. We named them by considering their energy and Lande g-factors. The interruption at n= 9,14 was explained by consulting resonance ionization spectroscopy in the literature. The resson why levels with high n values could not be measured was also given in the thesis, however, affectting by the 5p5f perturbing levels, the fluorescence signals of the levels J= 25pnp n= 31,32 and 5pnf n=22,23 were detected.The experimental results in this thesis are directly related with transition probability and oscillator strength of Sn I, and will be helpful for people to understand the internal configuration of Sn I, moreover, the results fill up the blank of spectrum of Sn I, and make much sense in atomic and molecular physics and astrophysics.