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Energy transfer between different mechanical degrees of freedom in atom–molecule collisions has been studied and largely understood. However, systems involving spins remain less explored. In this study, we directly observed energy transfer from atomic hyperfine to molecular rotation in the 87Rb (|Fa , MFa ⟩=|2, 2⟩) + 40K 87Rb (X1Σ + , rotational state N = 0) ⟶ Rb (|1, 1⟩) + KRb (N = 0, 1, 2) collision with state-to-state precision. We also performed quantum scattering calculations that rigorously included the coupling between spin and rotational degrees of freedom at short range under the assumption of rigid-rotor KRb monomers moving along a single potential energy surface. The calculated product rotational state distribution deviates from the observations even after extensive tuning of the atom–molecule potential energy surface. In addition, our ab initio calculations indicate that spin–rotation coupling is enhanced close to a conical intersection that is energetically accessible at short range. This, together with the deviation, suggests that vibrational degrees of freedom and conical intersections play an important part in the coupling. Our observations confirm that spin is coupled to mechanical rotation at short range and establish a benchmark for future theoretical studies.
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Collisional spin transfer in an atomic heteronuclear spinor Bose gas
We observe spin transfer within a nondegenerate heteronuclear spinor atomic gas comprising a small 7Li population admixed with a 87Rb bath, with both elements in their F = 1 hyperfine spin manifolds. Prepared in a nonequilibrium initial state, the 7Li spin distribution evolves through incoherent spin-changing collisions toward a steady-state distribution. We identify and measure the cross sections of all three types of spin-dependent heteronuclear collisions, namely the spin-exchange, spin-mixing, and quadrupole-exchange interactions, and find agreement with predictions of heteronuclear 7Li - 87Rb interactions at low energy. Moreover, we observe that the steady state of the 7Li spinor gas can be controlled by varying the composition of the 87Rb spin bath with which it interacts.
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- PAR ID:
- 10191266
- Date Published:
- Journal Name:
- Physical review research
- Volume:
- 2
- ISSN:
- 2643-1564
- Page Range / eLocation ID:
- 032054(R)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1103/PhysRevResearch.2.032054
