It was impossible at that time in his laboratory. However, for detecting the 13C signal in the graphite, Wang Yiqiu had estimated that the sensitivity of his instruments would need to be raised at least more than one order of magnitude. Nevertheless, he had improved the sensitivity of his homemade NMR spectrograph and finally detected the fluorine signals in LiF solid powder with a good signal-to-noise ratio. So, Wang Yiqiu suspected that he could detect the 13C NMR signal. Furthermore, the NMR frequency of the 13C isotope in the same magnetic field is about 1/4 compared with the 19F (its abundance is 100%), according to the general rule, the intensity of the NMR signals is proportional to the cubic of frequency, in this regards the sensitivity of the 19F signals is more than 5000 times to that of 13C. This is because the natural abundance of the 13C isotope is only about 1.1% (usual 12C isotope nuclei have no magnet moment and no NMR signals). Apparently, its layer structure indicates that the chemical bond of the carbon atoms within the same layer should be different than that between layers, so the anisotropy would appear in the chemical shifts of the 13C isotope NMR signals if the experiments were conducted when the graphite layers were parallel to the magnet field or perpendicular to that. That was to find the anisotropy in the chemical shift of NMR signals in solids. Scripov suggested that he did a more difficult task. The results were published in a journal of structural chemistry. Thereafter Wang Yiqiu measured the chemical shifts of fluorine NMR signals in aqueous solution systems of some fluorides. Scripov sent the research study to the most authoritative scientific journal in the Soviet Union, ДАН CCCP (report of Soviet Academy of Sciences). By systematically measuring the concentration effect of aqueous solution of KHF 2–H 2O, Wang definitively determined the chemical shift value of the HF molecule and the discrepancy was eliminated. This is of certain significance because there were differences in this value in the scientific literature of the Soviet Union at that time, which is related to the explanation of the properties of chemical bonds in HF molecules. Scripov suggested that Wang Yiqiu measured the chemical shifts of fluorine NMR signals in some fluoride solutions, especially to determine the chemical shifts of HF molecules. This device can be used to measure NMR signals of liquids and solids. With the help of laboratory experience, Wang Yiqiu made an electromagnet with a magnetic field controlled at about 4000 G (0.4 T) and an electronic circuit with higher sensitivity at the end of 1959. The most important thing was to build a high uniformity electromagnet with a stable magnetic field. In the first year, he suggested that Wang Yiqiu prepared some experimental instruments while passing all radio science course examinations. He also invented a radio-frequency quantum oscillator (perhaps it could be called “Raser”), which can accurately measure the strength of the earth’s magnetic field. He first invented the Fourier transform with nuclear magnetic resonance free induction signal to solve the problem of the high-resolution spectrum. Scripov was a young and innovative scientist. Scripov’s group of radio-frequency spectroscopy. In 1958, he transferred to Leningrad University and became a graduate student in the Prof. In 1957, Wang Yiqiu entered the Physics Department of Moscow State University to study radio and microwave spectroscopy. Wang’s scientific career and contributions, in honor of his academic legacy, as well as in celebration to his upcoming 90th birthday. Wang provided valuable insights and inspiration for the research of optical atomic clocks. During his research on atomic clocks, his experience with laser frequency stabilization allowed him to pioneer China’s earliest studies on the laser cooling of atoms, Bose–Einstein condensates and optical tweezers. After his return from the Soviet Union, he turned his expertise toward China’s development of microwave atomic clock, establishing China’s first cesium beam atomic clock, as well as systematically explaining the Majorana shift in cesium beam atomic clocks. Early on in his career, he studied nuclear magnetic resonance as a graduate student at Leningrad University and independently made several important discoveries. Wang Yiqiu, born on September 1932, has been a prominent figure in China’s research on quantum precision measurement and cold atom physics.
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