Abstract The results of investigations conducted on the valence band structure of the near-surface atoms of niobium (Nb) sample, taken from a sheet that is used for fabricating superconducting radio frequency (SRF) cavity, are presented. The valence band electronic states were excited using low energy ( ≤ 50 eV) ultraviolet radiation. It was observed that a) the valence band spectrum primarily consists of oxygen 2p-derived states, b) a typical feature expected near the Fermi edge in the valence band of Nb is conspicuously absent. Analysis of the wide band profile provides a number of electronic states peaked at ∼6.3, 7.6, 9.2, and 10.9 eV. After sputtering the surface, a small peak appeared at ∼1.4 eV near the Fermi energy edge. The Nb 4d states showed a resonance involving intra-atomic transition and also hybridization with the states of O 2p. The present study will be useful in identification of the electronic states of Nb that are accountable for superconductivity related issues in an SRF cavity.

中文翻译：

---

超导腔用铌近表面原子价带电子态的研究

摘要 介绍了对取自用于制造超导射频 (SRF) 腔的薄片的铌 (Nb) 样品的近表面原子的价带结构进行的研究结果。使用低能量 (≤ 50 eV) 紫外线辐射激发价带电子态。据观察，a) 价带光谱主要由氧 2p 衍生状态组成，b) 在 Nb 价带中的费米边缘附近预期的典型特征明显不存在。宽带分布的分析提供了许多电子态，峰值为 ~6.3、7.6、9.2 和 10.9 eV。溅射表面后，在费米能量边缘附近的~1.4 eV 处出现一个小峰。Nb 4d 态显示出共振，涉及原子内跃迁以及与 O 2p 态的杂化。