Proton radius data update microscopic measurement without end

Although the current highest resolution microscope can only distinguish a single atom, for the researcher, direct observation does not mean that there is no way to study, nor does it mean that it cannot be measured. Just as the microscope could not observe the atom at the beginning of the 20th century, the proton discoverer Rutherford studied the internal structure of the atom by accelerating the alpha particle impinging on the nitrogen atom. Measuring the proton radius also requires an indirect method. In general, there are two methods for measuring proton radius: hydrogen spectroscopy and electron scattering experiments.

The principle of hydrogen spectroscopy experiments is the quantum shift of hydrogen atoms. When a electron of a hydrogen atom transitions from a high-energy orbit to a low-energy orbit, it emits a spectrum of photons that constitute a hydrogen atom. At this point, the energy level of the hydrogen atom can be calculated from the spectrum to calculate the proton radius. In the electron scattering experiment, the electron beam is struck against a proton, and the radius of the proton is calculated according to the scattering of the electron after contact with the proton.

Historically, physicists have measured the radius of protons using the above two methods, and obtained an approximation of 0.877 femto (1 femto = 1 x 10^-15 m), which also becomes the proton radius data for a long time. However, in 2010, a new study questioned this data. At the Simple Atomic Accurate Measurement Conference in France, physicist Randolf Pohl presented the data he measured using the new method. When the hydrogen atom in the traditional hydrogen spectroscopy experiment was replaced by muon hydrogen (the artificial hydrogen atom replaced by a negatively charged muon), the measurement accuracy of the proton radius was increased by 10 times, and the final measurement was 0.842±0.001. Meter, 4% smaller than before, the value deviation is very large. On the same day, the results of the electron scattering experiment by the complementary group of the Randolf Pohl team are still close to the traditional values. The difference between the two experimental results caused an uproar in the scientific community. There was no evidence at the time to prove that one of the data was wrong, so the proton radius became an unsolved mystery of physics.

In the past ten years, the measurement of proton radius has not stopped, and the papers that try to explain the mystery of proton radius are also emerging. The results of several research published this year have finally uncovered the mystery of the "mystery of proton radius." The research team at York University in Toronto, UK, developed a frequency-separated oscillating field technique that further improved the measurement accuracy and resulted in a result of 0.833 femtometres, similar to the 2010 muon hydrogen spectroscopy experiment. This means that the cause of the "mystery of proton radius" may be just experimental error. The research data was published in the September issue of Science, and two months later, in the latest issue of Nature, American scientists published data they measured using the new electron scattering method. 0.831 flying rice, which is consistent with the previous result.

The mystery that has plagued physicists for nearly a decade has finally been solved. Although the possibility of unknown physical interaction between muons and protons is negated, the re-determination of the proton radius is still a happy thing. However, the study of the proton radius has not stopped, and some researchers are trying to further improve the measurement accuracy. Just as the depth of the microscope to the microscopic world will not stop, the measurement of the microscopic world will not end. Instruments are constantly evolving, and technology is constantly evolving. We may find that there are also large errors in the current values, but only by constantly seeking to get closer to the truth of the world.

Editor's comment: Over the years, the scientific community has always wanted to explore the radius of protons after discovering protons. However, the results of hydrogen spectrometry experiments and electron scattering experiments used in the past have not been fully convinced after the further development of technology. . For the past decade or so, the measurement of the proton radius has continued. Recently, the research team at York University in Toronto, UK developed a frequency-separated oscillating field technology that effectively solves the mystery of researchers. In the future, I believe that more sophisticated technologies will be developed and scientific puzzles will be completely solved.