Helium atoms in the metastable $2{}^{3}S_1$ state (${\mathrm{He}}^{*}$) have unique advantages for ultracold atomic experiments. However, there is no known accessible Feshbach resonance in ${\mathrm{He}}^{*}$ which could be used to manipulate the scattering length and hence unlock several new experimental possibilities. Previous experimental and theoretical studies for ${\mathrm{He}}^{*}$ have produced contradictory results. We aimed to resolve this discrepancy with a theoretical search for Feshbach resonances, using a close-coupled model of ${\mathrm{He}}^{*}$ collisions in the presence of an external magnetic field. Several resonances were detected and the existing literature discrepancy was resolved. Although none of the resonances identified are readily experimentally usable, an interesting non-Feshbach scattering length variation with magnetic field was observed in heteronuclear collisions, at field strengths that are experimentally accessible.

中文翻译：

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超冷He*3和He*4原子碰撞中Feshbach共振的紧密耦合模型

亚稳态中的氦原子 $2{}^3秒_1$ 状态 （${他}^{*}$) 在超冷原子实验中具有独特的优势。然而，没有已知的可访问 Feshbach 共振${他}^{*}$这可用于操纵散射长度，从而解锁几种新的实验可能性。以前的实验和理论研究${他}^{*}$产生了矛盾的结果。我们旨在通过对 Feshbach 共振的理论搜索来解决这种差异，使用的是${他}^{*}$在存在外部磁场的情况下发生碰撞。检测到几个共振并解决了现有的文献差异。尽管所确定的共振都不是很容易在实验上使用的，但在异核碰撞中观察到了一个有趣的非费什巴赫散射长度随磁场的变化，场强可通过实验获得。