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1、H = 656.3 nm H = 486.1 nm H = 434.0 nm H = 410.2 nm :,Figure 23.1 Energy level diagram of hydrogen given by Bohr,Figure 23.2 Energy level diagram of hydrogen given by Sommerfeld and Bohr,Figure 23.3 Evolution of the n = 3 level of the hydrogen atom,Figure 23.4 Fine structure of the H line. The seven
2、 transitions in the fine structure of the n = 3 to n = 2 transition are seen in (a). Their relative intensities are illustrated in (b) along with a poor resolution(from Doppler broadening) measurement. A high resolution measurement is shown in (c),Figure 22.10 The energy levels and transitions of si
3、ngle electrons between the 3P and 3S states of sodium in a week magnetic field, Zeeman effect. (a) Energy levels and transitions in a week field,Figure 22.10 (b) D lines of sodium (no magnetic field); (c) Zeeman splitting of the D lines,Figure 22.11 Energy levels and transitions between the single-e
4、lectron states 3S and 3P in a strong magnetic field, Paschen-Back effect.,Figure 5.5 Schematic diagram of mercury energy levels,Zeeman,Einstein,Ehrenfest in Amsterdam, 1920,The Stern-Gerlach Experiment,Have we heard the last word about spin? I do not believe so. C.N. Yang (1985),Figure 4B.7 Total-bo
5、dy 0.5T superconducting MRI system,Figure 4B.8 Midline sagittal MRI view of a normal head, by using a 1.5T superconducting system, to yield a T1-weighted high-quality anatomical image,Figure 4B.9 (a) Transverse MRI through the brain of a normal volunteer at the level of the eyes with a 1.5T supercon
6、ducting system to yield a spin-density(proton-weighted) MRI image with somewhat different soft-tissue contrast in comparison with a T1-weighted image,Figure 4B.9 (b) Transverse MRI through the brain of the same subject taken at the same time and same level as Fig. 4B.9(a) except that the pulse syste
7、m was changed to spin-echo, and the soft-tissue contrast is seen to change dramatically,We must expect the 11th electron (Na) goes into 3rd orbit. Niels Bohr (1921) No reason to expect anything; you concluded it from the spectra! Wolfgang Pauli (1922),GENEVA,CERN, GENEVA,X-RAYS,Chapter 6,28 The Disc
8、overy of X-Rays and Their Wave Nature,Figure 28.2 The electromagnetic spectrum with the different wavelength(frequency) regions labelled,The Discovery of X-Rays,Cathode Ray,Sir William Crookes: Cathode rays, The 4th state of matter: radiant matter(solid,liquid and gas),In the field of observation, c
9、hance favors the one with a prepared mind. Louis Pasteur,Wilhelm Conrad Rntgen (1845 - 1923),November 8, 1895,BaPt(CN)6,Fluorescent screen Barium platinum cyanide,On the New Rays, 1895,Figure 28.1 A radiograph of the finger bones of Mrs. Roentgen,X-Ray Tube,Figure 28.3 Schematic of an x-ray tube,The
10、 Wave Nature of X-Rays,Thomas Young, Phil. Transcations, 1803,An attempt to isolate a ray by reducing the slit width fails because of diffraction, which becomes more pronounced as / approaches zero.,The Diffraction of X-Rays M.T.F. von Laue, 1912 W.Friedrich & P.Knipping,1913 Nobel, 1914 to von Laue
11、,Figure 28.5 Arrangement of the sodium ions and chloride ions in a rock salt crystal,Use the planes of atoms as natural grating (set of slits) to observe diffraction of x rays,max: = n 2 or r = n min: = m m = 1, 3, 5, ,Figure 28.6 (a) Derivation of Braggs formula,(28.1),Braggs Law Nobel, 1915,Figure
12、 28.6 (b) Parallel planes of different directions in a crystal,Figure 6.8 Single-crystal Laue film of sapphire (Al2O3),Figure 6.7 Schematic of the experiment in the Laue film method,Figure 6.9 Schematic of the polycrystalline powder method,Figure 6.10 X-ray diffraction pattern of polycrystalline mat
13、ter,(28.1),Ions in a volume of 1 cm3,Molecules of Density of 1 g of NaCl NaCl,The Polarization of X-Rays,C.G.Barkla, 1906,Wave: Transverse wave or Longitudinal wave?,The concept of polarization holds only for transverse waves, where the direction of the oscillating property is perpendicular to the p
14、ropagation direction of the wave.,If an electromagnetic wave has its electric field vector E oscillating in only one direction, that wave has linear polarization; When E moves in a circle in the plane perpendicular to the wave propagation direction: circular polarization; If the direction of E is ra
15、ndomly oriented, the wave is unpolarized.,Figure 28.4 Schematic of a double scattering experiment,If the x ray is a transverse wave,at the 1st scatterer forced oscillation can only occur in the directions of x & y,with no oscillation in z. When observed in x, a t x ray propagating in x can only osci
16、llates in y.,When the x ray which oscillates only in y strikes a 2nd scatter, the x-rays from 2nd scatter is polarized in the y direction. So we can observe strong x rays in z but not in the y direction. The 1st scatter:producer & the 2nd :detector of polarization,A Further Derivation of Braggs Relation,(28.2),(28.3),Figure 28.11 Schematic used in a more detailed derivation of Braggs formula,(28.4),(28.5),(28.6),(28.7),(28.8),(28.9),(28.10),29 Mechan
