Construction of an Undulator Beamline Using a Normal Incidence Monochromator for Ultra-High Resolution Photoemission and Other Studies at NSF's Synchrotron Radiation Center

9503883 Campuzano角度分辨光电子能谱（ARPES）技术是目前确定材料中电子能量-动量关系的唯一方法，即材料的完整电子结构。 最近，我们已经大大提高了ARPES的技术，从以前的典型分辨率为~30 meV的8 meV。 这一改进为理解新材料，特别是具有大晶胞的人造材料开辟了新的可能性。 这是因为在具有大晶胞的材料中，电子态在能量上间隔很近，需要极高的分辨率。 我们建议研究的例子是高温和有机超导体，量子限制在金属，磁性和半导体多层膜等，虽然我们已经取得了很大的进步，在提高能量分辨率，同样不能说动量分辨率。 新的人造大晶胞材料具有非常小的布里渊区。 幸运的是，这个问题本质上只是几何问题：通过简单地限制电子分析器的接收角，可以提高动量分辨率。 然而，由于计数率随着孔径的平方而减小，因此需要更高的光子束通量。 有了这个奖项，我们将在威斯康星大学麦迪逊分校的同步辐射中心的客座研究员计划中建造一个具有高通量高分辨率正入射单色器的基于波荡器的光束线。 该仪器不仅将为电子结构的研究开辟新的可能性，而且还将减轻SRC现有4米NIM光束线的沉重负担。 ***

9503883 Campuzano The technique of Angle-Resolved Photoemission (ARPES) is currently the only method of determining the energy - momentum relationship of electrons in materials, that is, the complete electronic structure of materials. Recently, we have dramatically improved the technique of ARPES from its previous typical resolution of ~30 meV to 8 meV. This improvement opens up new possibilities in understanding new materials, particularly the man-made ones with large unit cells. This is because in materials with large unit cells the eclectron states are closely spaced in energy, requiring extreme resolution. Examples of what we propose to study are the high temperature and organic superconductors, quantum confinement in metallic, magnetic, and semiconducting multilayers, etc. Although we have made great strides in improving the energy resolution, the same cannot be said about momentum resolution. The new man- made large unit cell materials have very small Brillouin zones. This problem is fortunately only geometrical in nature: the momentum resolution can be improved by simply restricting the acceptance angle of the electron analyzer. However, since the counting rate decreases as the square of that aperture, higher photon beam flux is required. %%% With this award we will construct an undulator-based beamline with a high throughput-high resolution normal incidence monochromator at the University of Wisconsin-Madison's Synchrotron Radiation Center;s Guest Investigator Program. The instrument will not only open new possibilities in the study of electronic structure, but will also relieve the heavy burden placed on the existing 4m NIM beamline at SRC. ***