X射线光电子能谱X-ray photoelectron spectroscopy

基于光电效应：E_结合 = hν − E_动 − φ（φ 为仪器功函数）。常用 Al Kα（1486.6 eV）或 Mg Kα（1253.6 eV）X 射线。每种元素内层电子结合能有特征值，可鉴定除 H、He 外的所有元素；元素的氧化态和化学环境改变会使结合能位移（化学位移，通常 0.1–10 eV），如 C 1s：C–C 284.8 eV，C–O 约 286.5 eV，C=O 约 288 eV。只有表面几纳米内的光电子能无损失逸出，所以 XPS 是表面敏感技术，需在超高真空中进行。

It rests on the photoelectric effect: E_binding = hν − E_kinetic − φ, with φ the spectrometer work function. Al Kα (1486.6 eV) or Mg Kα (1253.6 eV) X-rays are typical. Each element's core levels have characteristic binding energies, identifying all elements except H and He; oxidation state and chemical environment shift them (chemical shifts, usually 0.1–10 eV), as in C 1s at 284.8 eV for C–C, about 286.5 eV for C–O and about 288 eV for C=O. Only electrons from the top few nanometres escape without energy loss, so XPS is surface-sensitive and runs in ultra-high vacuum.

1950–1960 年代瑞典乌普萨拉大学的凯·西格巴恩发展了高分辨率电子能谱仪，发现了内层电子结合能的化学位移，并命名为 ESCA（化学分析用电子能谱），获 1981 年诺贝尔物理学奖。他的父亲曼内·西格巴恩因 X 射线光谱学获 1924 年诺贝尔物理学奖。

In the 1950s and 1960s Kai Siegbahn at Uppsala developed high-resolution electron spectrometers, discovered chemical shifts in core binding energies and named the method ESCA, electron spectroscopy for chemical analysis; he shared the 1981 Nobel Prize in Physics. His father, Manne Siegbahn, had received the 1924 Nobel Prize in Physics for X-ray spectroscopy.

XPS 用于分析催化剂表面活性组分的价态（如 Pt⁰/Pt²⁺）、腐蚀和钝化膜、半导体界面、高分子表面改性、电池电极界面膜（SEI）、薄膜和涂层成分。结合氩离子溅射可做深度剖析。紫外光电子能谱（UPS）用于测定价带和分子轨道能级。

XPS analyses the oxidation states of active catalyst components (such as Pt⁰/Pt²⁺), corrosion and passive films, semiconductor interfaces, surface-modified polymers, battery electrode interphases (SEI), and thin films and coatings. With argon-ion sputtering it gives depth profiles. Ultraviolet photoelectron spectroscopy (UPS) measures valence bands and molecular orbital energies.