论文标题
通过单晶铜（100），通过接近阈值光发射的超低电子
Ultracold electrons via Near-Threshold Photoemission from Single-Crystal Cu(100)
论文作者
论文摘要
从基于光电的电子源发出的电子的平均横向能量或温度对于下一代和紧凑的X射线游离电子激光器以及超快电子衍射，光谱和显微镜实验至关重要。在本文中，我们证明了使用接近阈值光发射从冷冻冷却（100）表面的创纪录的低平均横向能量为5 MeV。此外，我们还表明，从这种表面获得的电子能量扩散小于11.5 meV，使其成为已知的最小能量传播电子源：比任何现有的光发射，现场发射或基于热发射的电子源小的数量级。我们的测量还阐明了电子发射的物理，并显示了在很少的MEV尺度能量下的能量如何受到状态的温度和真空密度的限制。
Achieving a low mean transverse energy or temperature of electrons emitted from the photocathode-based electron sources is critical to the development of next-generation and compact X-ray Free Electron Lasers and Ultrafast Electron Diffraction, Spectroscopy and Microscopy experiments. In this paper, we demonstrate a record low mean transverse energy of 5 meV from the cryo-cooled (100) surface of copper using near-threshold photoemission. Further, we also show that the electron energy spread obtained from such a surface is less than 11.5 meV, making it the smallest energy spread electron source known to date: more than an order of magnitude smaller than any existing photoemission, field emission or thermionic emission based electron source. Our measurements also shed light on the physics of electron emission and show how the energy spread at few meV scale energies is limited by both the temperature and the vacuum density of states.
