Hyperfine-to-rotational energy transfer in ultracold atom-molecule collisions

• DOI: 10.48550/arxiv.2407.08891
• Publication Date: 2024-07-11
• Authors: Yi-Xiang Liu; Lingbang Zhu; Jeshurun Luke; Mark Babin; Timur V. Tscherbul; Marcin Gronowski; Hela Ladjimi; Michał Tomza; John L. Bohn; Kang-Kuen Ni
• Keywords: Ultracold atom; Rotational energy

Energy transfer between different mechanical degrees of freedom in atom-molecule collisions has been widely studied and largely understood. However, systems involving spins remain less explored, especially with a state-to-state precision. Here, we directly observed the energy from atomic hyperfine to molecular rotation $^{87}$Rb ($|F_a,M_{F_a}\rangle = |2,2\rangle$) + $^{40}$K$^{87}$Rb (in rovibronic ground state $N=0$) $\longrightarrow$ Rb ($ |1,1\rangle$) KRb ($N=0,1,2$) exothermic collision. We probed quantum states collision products using resonance-enhanced multi-photon ionization followed by time-of-flight mass spectrometry. also carried out state-of-the-art scattering calculations, which rigorously take into account coupling spin rotational at short range, assume that monomer can be treated as rigid rotor moving on single potential surface. The calculated product distribution deviates observations even after extensive tuning surface, suggesting vibrational conical intersections play an important part ultracold collisions. Additionally, our ab initio calculations indicate spin-rotation is dramatically enhanced near intersection, energetically accessible range. confirm coupled range establish benchmark for future theoretical studies.