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arXiv quant-ph/0201048quant-ph
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超冷分子碰撞中的磁场效应

Magnetic field effects in ultracold molecular collisions

Alessandro Volpi, John L. Bohn

摘要:

考虑到磁场的影响,我们研究了磁囚禁超冷分子的碰撞稳定性。我们计算的弹性和自旋状态变化的非弹性碰撞的原型分子$^{17}$ O $_2$与$^3$他缓冲气体的磁场和平移碰撞能量的函数的速率常数。我们发现,自旋状态变化的碰撞抑制维格纳的阈值法律,只要渐近塞曼分裂之间的入射和最终状态不超过出口通道中的离心屏障的高度。此外,我们提出了一个有用的单参数拟合公式,该公式描述了作为场和碰撞能量的函数的非弹性速率的阈值行为。结果表明,这个公式与全量子计算的半定量协议,并建议有用的应用程序也不同的系统。作为一个例子,我们预测的低能速率常数有关的分子氧蒸发冷却。

英文摘要:

We investigate the collisional stability of magnetically trapped ultracold molecules, taking into account the influence of magnetic fields. We compute elastic and spin-state-changing inelastic rate constants for collisions of the prototype molecule $^{17}$O$_2$ with a $^3$He buffer gas as a function of the magnetic field and the translational collision energy. We find that spin-state-changing collisions are suppressed by Wigner's threshold laws as long as the asymptotic Zeeman splitting between incident and final states does not exceed the height of the centrifugal barrier in the exit channel. In addition, we propose a useful one-parameter fitting formula that describes the threshold behavior of the inelastic rates as a function of the field and collision energy. Results show a semi-quantitative agreement of this formula with the full quantum calculations, and suggest useful applications also to different systems. As an example, we predict the low-energy rate constants relevant to evaporative cooling of molecular oxygen.

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