2021-07-14

Chinese scientists use all-optical excitation to achieve single-atom detection of krypton-81

By yqqlm yqqlm

Recently, the research team of University of Science and Technology of China used all-optical excitation to achieve the The single-atom detection of -81, an important advancement in quantum precision measurement methods, will help the exploration of earth and environmental sciences. Related results were recently published in the international academic journal”Physics Review Letters.

Krypton is a trace amount of inert gas, the content in the air is one part per million. It is composed of a variety of isotopes, including a radioisotope with a half-life of 230,000 years, krypton-81, The content in the air is only one part in tens of billions (10-18). In the 1960s, krypton-81 was discovered in the air. Researchers dreamed of using krypton-81, a natural tracer, to help understand the water and ice cycles in the environment, and to date millions of years old ancient groundwater and glaciers.

The scientific research team invented the single-atom sensitive detection method”atom trap trace analysis”, which can count the krypton-81 atoms contained in environmental samples one by one. To capture krypton-81 with an atom trap requires first exciting the atom to a metastable quantum state /span>Up. At present, the gas discharge method is used internationally to prepare metastable krypton atoms. The method is simple and feasible, but there are problems such as low excitation efficiency, sample loss, and cross-contamination.

In the experiment, the scientific research team developed a high-brightness resonance vacuumUltraviolet lamp and apply it to all-optical excitation of krypton atoms, thereby avoiding Various problems caused by gas discharge. The study proposed a new mechanism to explain the presence of vacuum ultraviolet photons in Krypton The phenomenon of”self-absorption” during propagation-the photon is not lost after being scattered in krypton for many times, but its frequency is shifted. While maintaining the high-brightness characteristics of the light source, the researchers reduced the optical frequency shift, built a krypton trap based on all-optical excitation, and achieved a detection rate of 1,800 krypton-81 atoms per hour. This research result is of great significance to scientific issues such as the study of ancient groundwater and the search for ice cores formed millions of years ago. (Receptionist Shuai Junquan)