Full-dimensional quantum scattering calculations on ultracold atom-molecule collisions in magnetic fields: The role of molecular vibrations
Full-dimensional quantum scattering calculations on ultracold atom-molecule collisions in magnetic fields: The role of molecular vibrations
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DOI：
10.1103/physrevresearch.2.043294
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
M. Morita;J. Kłos;T. Tscherbul
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文献类型：
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作者：
M. Morita;J. Kłos;T. Tscherbul
严格的量子散射计算在外场中的超冷分子碰撞提出了一个突出的计算问题，由于强烈的各向异性的原子-分子相互作用，依赖于碰撞伙伴的相对取向，以及对他们的振动自由度。本文采用非限制耦合团簇方法，基于宇称调整的总角动量表象和一个新的三维势能面，首次数值精确地计算了外磁场中强各向异性原子-分子（Li+CaH）碰撞的三维量子散射。双重和微扰三重激发[UCCSD（T）]和一个大的四重zeta型基组。我们发现，虽然全三维处理对于精确描述Li（$MS =1/2$）+CaH（$v=0，N= 0，MS =1/2$）碰撞作为磁场的函数是必要的，但自旋极化原子-分子碰撞的磁共振密度和统计性质不受振动自由度的强烈影响，证明了以前计算中使用的刚性转子近似的合理性.我们在超冷Li（$MS =1/2$）+CaH（$v=1，N=0，MS =1/2$）碰撞中观察到了快速的场不敏感的振动猝灭，导致了CaH振动的有效碰撞冷却。
Rigorous quantum scattering calculations on ultracold molecular collisions in external fields present an outstanding computational problem due to strongly anisotropic atom-molecule interactions that depend on the relative orientation of the collision partners, as well as on their vibrational degrees of freedom. Here, we present the first numerically exact three-dimensional quantum scattering calculations on strongly anisotropic atom-molecule (Li+CaH) collisions in an external magnetic field based on the parity-adapted total angular momentum representation and a new three-dimensional potential energy surface (PES) for the triplet Li-CaH collision complex using the unrestricted coupled cluster method with single, double and perturbative triple excitations [UCCSD(T)] and a large quadruple-zeta type basis set. We find that while the full three-dimensional treatment is necessary for the accurate description of Li ($M_S=1/2$)+CaH ($v=0,N=0,M_S=1/2$) collisions as a function of magnetic field, the magnetic resonance density and statistical properties of spin-polarized atom-molecule collisions are not strongly affected by vibrational degrees of freedom, justifying the rigid-rotor approximation used in previous calculations. We observe rapid, field-insensitive vibrational quenching in ultracold Li ($M_S=1/2$)+CaH ($v=1,N=0, M_S=1/2$) collisions, leading to efficient collisional cooling of CaH vibrations.