ã€Chinese Instrument Network Instrument Development】 Recently, the Laser Precision Measurement and Trace Detection Research Team (atta.ustc.edu.cn) of the National Experimental Center for Hefei Microscale Physics Science and Technology at the University of Science and Technology of China has transferred the æ°¦-4 atomic 2S-2P transition level. The center frequency was measured to an accuracy of 1.4 kHz with a relative accuracy of 5.1 x 10−12. The result was published online on December 28th in Phys. Rev. Lett. 119: 263002 (2017). The first author of the thesis is Zheng Zheng, Ph.D. candidate, and Corresponding author is Dr. Sun Yu and Professor Hu Shuiming. This is another important result obtained by the research group in this field after the measurement of the fine structure splitting of the 23PJ energy level of the Ge-4 atom [Phys. Rev. Lett. 118: 063001 (2017)].
Helium atom precision spectrometer
The helium atom is the most basic multi-electron atom. Quantum electrodynamics (QED) theory-based full-quantum-computation method can get its high-precision energy level structure only from basic physical constants. The fine structure of the 23PJ energy level of the 4He atom is the most sensitive to the finest structure constant α(≈1/137) of the most basic physical constant in QED. The comparison between its experimental measurements and theoretical results is very satisfactory for the verification of QED theory and α constant. . At the same time, theoretically, since the 4He atom is affected by the finite size of the germanium atomic nucleus, its energy level will shift. By accurately measuring the frequency of the 2S-2P energy level transition, the charge radius information of the helium atomic nucleus can be calculated.
The research group set up a set of germanium atom beam precision spectrometer at China University of Science and Technology. Utilizing the generated metastable helium atomic beam, combined with laser cooling atom technology to substantially increase its brightness, and preparing a single quantum state helium atom (23S1) by laser, exciting its 23S1-23PJ transition via a single-frequency laser, and finally based on the singlet The selected atom detection and the frequency of the optical frequency comb are accurately measured to obtain a high-precision transition frequency.
The center frequency of the 4He atom 2S-2P energy level transition is 276,736,495, 600.0±0.45 (stat) ±1.3 (syst) kHz, which is the most accurate measurement result in the world. Prof. K. Pachucki, one of the most famous experts in the field of precision spectroscopy theory for atomic and molecular experts in the international few-body atomic partners, believes that the experimental results can already meet the need to measure the radius of the helium core to one-thousandth accuracy. Comparing the results of the nuclear charge radii obtained with the μ-氦 atomic measurement may be used to test new physics beyond the standard model. On the other hand, regarding the difference in the charge radii of the helium-4 and helium-3 atomic nuclei, the results of several studies in the past 20 years have not been met, and the reason for this is unknown. The result of this measurement found that there is a frequency deviation of 20 times the standard deviation between the previous experiments, which is most likely the cause of the deviation of the charge radius difference of the nuclear.
Another task of the same group in the same year, on the measurement of fine structure splitting of the 4He atom, measured the splitting of 23P0-23P2 and 23P1-23P2 to 31,908, 130.98 ± 0.13 kHz and 2,291,177.56 ± 0.19 kHz, respectively, which is the most accurate measurement result to date. The reviewer of PRL gave a high rating and considered that the work “promoted the field of precision measurement†and “showed the limits that laser spectroscopy measurement can reachâ€.
This series of work has been supported by the Chinese Academy of Sciences Precision Measurement Pilot Project, the National Natural Science Foundation of China, the Collaborative Innovation Center for Quantum Information and Quantum Physics, and the Collaborative Innovation Center for Energy Chemistry.
(Original title: China University of Science and Technology continues to make important progress in the precision measurement of atomic spectroscopy