resonance photo-ionization

Photo-ionization is a physics process where electromagnetic radiation interacts with matter, causing it to break apart into charged particles. A simple example is the photoelectric effect, where light striking metal ejects electrons. In other cases, covalent chemical bonds are broken, creating positively and negatively charged fragments, which is a primary step in photochemical reactions.1

Resonance-ionization spectroscopy (RIS) is a highly sensitive method that uses lasers to eject electrons from specific atoms or molecules, turning them into positive ions and free electrons. These charged particles are then detected to identify and quantify substances. RIS is used in various fields, including physics, chemistry, and biology, for applications like dating materials, studying groundwater, and detecting trace elements.2

The process typically involves at least two steps because the photon energy is not enough to ionize an atom directly from its ground state. The first step is a resonance absorption, where a photon excites an electron to a higher energy level. A second photon then completes the ionization. This method allows for the detection of almost every element.23