Pauli blocking of spontaneous emission is responsible for the stability of atoms. Electrons cannot decay to lower-lying internal states that are already occupied. Pauli blocking also occurs when free atoms scatter light elastically (Rayleigh scattering) and the final external momentum states are already populated. This was predicted more than 30 years ago but is challenging to realize experimentally. Here, we report on Pauli blocking of light scattering in a dense quantum-degenerate Fermi gas of ultracold lithium atoms. When the Fermi momentum is larger than the photon recoil, most final momentum states are within the Fermi surface. At low temperature, we find that light scattered even at large angles is suppressed by 37% compared with higher temperatures, where atoms scatter at the single-atom Rayleigh scattering rate.

中文翻译：

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简并费米子中光散射的泡利阻挡

自发发射的泡利阻塞是原子稳定性的原因。电子不能衰减到已经被占据的较低的内部状态。当自由原子弹性散射光（瑞利散射）并且最终的外部动量状态已经填充时，也会发生泡利阻塞。这是 30 多年前预测的，但要通过实验实现具有挑战性。在这里，我们报告了超冷锂原子致密量子简并费米气体中光散射的泡利阻挡。当费米动量大于光子反冲时，大多数最终动量状态都在费米表面内。在低温下，我们发现即使在大角度散射的光也被抑制了 37%，而在高温下，原子以单原子瑞利散射率散射。