L8Chap4英文版原子物理.ppt

*Shanxi University Atomic Physics 4 The alkalis *Shanxi University Atomic Physics 4.1 Shell structure and the periodic table_1 The building-up principle: electrons fill up higher and higher shells as the atomic number Z increases across the periodic table. Full shells are found at atomic number Z=2,10,corresponding to helium and the other inert gases. These inert gases were originally grouped together because of their similar chemical properties, i.e. the difficulty in removing an electron from closed shells means that they do not readily undergo chemical reactions. However, inert gas atoms can be excited to higher-lying configurations by bombardment with electrons in a gas discharge, and such processes are very important in atomic and laser physics, as in the helium-neon laser. *Shanxi University Atomic Physics 4.1 Shell structure and the periodic table_2 *Shanxi University Atomic Physics 4.1 Shell structure and the periodic table_3 Each alkali metal comes next to an inert gas in the periodic table and much of the chemistry of the alkali can be explained by the simple picture of their atoms as having a single unpaired electron outside a core of closed electronic sub-shells surrounding the nucleus. The unpaired valence electron determines the chemical bonding properties; since it takes less energy to remove this outer electron than to pull an electron out of a closed sub-shell (see Table 4.1), thus the alkali can form singly- charged positive ions and are chemically reactive. However, we need more than this simple picture to explain the details of the spectra of the alkali and in the following we shall consider the wavefunctions. *Shanxi University Atomic Physics 4.1 Shell structure and the periodic table_4 Table 4.1 Ionization energies of the inert gases and alkalis ElementZIE(eV) He224.6 Li35.4 Ne1021.6 Na115.1 Ar1815.8 K194.3 Kr3614.0 Rb374.2 Xe5412.1 Cs553.9 *Shanxi University Atomic Physics 4.2 The quantum defect_1 *Shanxi University Atomic Physics (a) (b) (c) 4.2 The quantum defect_2 *Shanxi University Atomic Physics *Shanxi University Atomic Physics 4.2 The quantum defect_3 *Shanxi University Atomic Physics 4.2 The quantum defect_5 *Shanxi University Atomic Physics 4.2 The quantum defect_6 *Shanxi University Atomic Physics 4.3 The central-field approximation_1 *Shanxi University Atomic Physics 4.3 The central-field approximation_2 *Shanxi University Atomic Physics 4.3 The central-field approximation_3 *Shanxi University Atomic Physics 4.3 The central-field approximation_4 *Shanxi University Atomic Physics 4.3 The central-field approximation_5 *Shanxi University Atomic Physics 4.3 The central-field approximation_6 *Shanxi University Atomic Physics 4.3 The central-field approximation_7 *Shanxi University Atomic Physics 4.3 The central-field approximation_8 *Shanxi University Atomic Physics 4.3 The central-field approximation_1 *Shanxi University Atomic Physics 4.3 The central-field approximation_9 *Shanxi University Atomic Physics 4.3 The central-field approximation_10 *Shanxi University Atomic Physics 4.3 The central-field approximation_11 *Shanxi University Atomic Physics 4.3 The central-field approximation_12 *Shanxi University Atomic Physics Comlemrntairly: Na atom spectrum 原子外层电子能级的跃迁 2-1 光谱项 光谱项:光谱支项: 四个量子数: n主量子数； L角量子数, 0/1/2S/P/D； S总自旋量子数， , , 或0 J内量子数,2S+1(LS)个或2L+1(LS)个, J1/2/3称单/双/三重态 2-2 Na双线