High-frequency pulse enables the association of triatomic molecules in an ultracold gas

The three-body system is already a formidable mystery in classical physics, let alone the quantum-state three-body system. But what if scientists could synthesize triatomic molecules under quantum constraints? It could serve as a suitable platform to study the potential energy area of ​​three bodies, which is important but difficult to calculate.

Recently, Prof. Pan Jianwei and Prof. Zhao Bo from the University of Science and Technology of China (USTC), in collaboration with Prof. Bai Chunli from the Institute of Chemistry, Chinese Academy of Sciences, found strong evidence for the association of triatomic molecules after applying a ratio -Frequency (RF) pulses on an ultra-cold mixture ²³N / A⁴⁰K and ⁴⁰K near Feshbach resonance. The work was published innature.

Direct cooling of triatomic molecules is extremely difficult due to the complex vibrational and rotational energy levels of molecules. Therefore, the team took a different approach, combining ultracold atoms with diatomic molecules to get ultracold triatomic molecules. However, due to the weak coupling strength, an atom-diatomic-molecule Feshbach resonance should be introduced to enhance the molecular association, which is challenging due to the complexity and complexity of the Feshbach resonance.

In this work, researchers tuned the Feshbach resonance by applying external RF fields and successfully coupled the triatomic bound state and the atom-diatomic-molecule scattering state.

The association of triatomic molecules was evidenced by the HF loss spectrum: the HF spectrum showed additional loss with less ²³N / A⁴⁰K molecules in the system and the loss of ²³N / A⁴⁰K indicated the formation of triatomic molecules. Although the triatomic molecules had a short lifetime, the association signal could still be obtained, which was an advantage of the RF pulse.

By analyzing the RF spectrum, the researchers estimated the binding energy of the triatomic molecule by assuming a universal relationship near the resonance point. The result showed strong binding arising from the interaction between the scattering state and the bound state.

This work pioneered the association of triatomic molecules and paved the way for ultracold chemical physics and quantum simulation with molecules.

Provided by the University of Science and Technology of China