Cold collisions of an open-shell S-state atom with a 2? molecule: N(4S) colliding with OH in a magnetic field.
Cold collisions of an open-shell S-state atom with a 2? molecule: N(4S) colliding with OH in a magnetic field.
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开壳层 S 态原子与 2? 的冷碰撞
DOI：
10.1039/c1cp21200a
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Skomorowski W
中科院分区：
文献类型：
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作者：
Skomorowski W
我们提出了在磁场存在下开壳s态原子和2Π-state分子之间碰撞的量子理论研究。我们分析了碰撞哈密顿量，并讨论了这种系统中非弹性碰撞的可能机制。该理论应用于氮原子（4S）与OH分子的碰撞，假设相互作用只发生在两个高自旋（五重）势能表面上，碰撞伙伴最初都处于完全自旋拉伸（磁捕获）状态。五态的表面由单、双、非迭代三重激励下的不受自旋限制的耦合簇计算得到。我们发现由于相互作用势的各向异性和自旋-自旋偶极相互作用的各向异性而引起的强耦合引起了大量的非弹性。当磁场强度较小、碰撞能量较低时，以偶极相互作用机制为主，而当磁场强度较大（100g以上）或碰撞能量较大（1mk以上）时，以势各向异性机制为主。数值结果表明，在较高的温度下，通过与超冷的N原子碰撞对磁捕获的氢氧根进行共感冷却是不成功的。
We present quantum-theoretical studies of collisions between an open-shell S-state atom and a 2Π-state molecule in the presence of a magnetic field. We analyze the collisional Hamiltonian and discuss possible mechanisms for inelastic collisions in such systems. The theory is applied to the collisions of the nitrogen atom (4S) with the OH molecule, with both collision partners initially in fully spin-stretched (magnetically trappable) states, assuming that the interaction takes place exclusively on the two high-spin (quintet) potential energy surfaces. The surfaces for the quintet states are obtained from spin-unrestricted coupled-cluster calculations with single, double, and noniterative triple excitations. We find substantial inelasticity, arising from strong couplings due to the anisotropy of the interaction potential and the anisotropic spin–spin dipolar interaction. The mechanism involving the dipolar interaction dominates for small magnetic field strengths and ultralow collision energies, while the mechanism involving the potential anisotropy prevails when the field strength is larger (above 100 G) or the collision energy is higher (above 1 mK). The numerical results suggest that sympathetic cooling of magnetically trapped OH by collisions with ultracold N atoms will not be successful at higher temperatures.