Detecting IR and mm radiation

摘要

An atomic beam is excited by laser radiation to a state with large principal quantum number. The beam is irradiated with infrared or millimeter wave radiation which is to be detected. The atoms absorb the radiation by making transitions to higher-lying states. The transitions are sensed by applying an electric field which ionizes atoms in the final state, but not the initial state. The ions ae collected and detected by conventional pulse-counting or direct current methods.