Röntgenfotoelektronszámlálás

Röntgenfotoelektronszámlálás, often abbreviated as XPS (X-ray Photoelectron Spectroscopy) or ESCA (Electron Spectroscopy for Chemical Analysis), is a surface-sensitive quantitative spectroscopic technique that measures the elemental composition and chemical state of a material. It works by irradiating a sample with X-rays, which causes electrons to be ejected from the atoms of the material. The kinetic energy of these ejected electrons is then measured. Since the binding energy of an electron in an atom is unique to that element and its chemical environment, analyzing the kinetic energy of the emitted photoelectrons allows for the identification of the elements present on the sample surface and their chemical states.

The fundamental principle behind röntgenfotoelektronszámlálás is the photoelectric effect. When X-rays strike a material, they transfer energy to the core electrons. If this energy exceeds the electron's binding energy, the electron is emitted from the atom. The kinetic energy of the emitted photoelectron is given by the equation KE = hν - BE, where KE is the kinetic energy, hν is the energy of the incident X-ray photon, and BE is the binding energy of the electron. By measuring the kinetic energy of the emitted electrons and knowing the energy of the X-rays, the binding energy can be determined. This binding energy is characteristic of the element and its electronic configuration, enabling elemental identification. Furthermore, slight shifts in binding energy, known as chemical shifts, reveal information about the oxidation state and bonding environment of the elements. XPS is particularly useful for analyzing thin films and surfaces because the emitted photoelectrons have a short mean free path, meaning only electrons originating from the top few nanometers of the sample can escape and be detected.