XeCl

XeCl refers to a xenon chloride excimer, a short‑lived excited dimer used as a gain medium in ultraviolet lasers. The emitted radiation arises from the transition of the excited molecule XeCl* back to dissociated xenon and chlorine, producing ultraviolet light with a typical peak wavelength near 308 nanometers.

XeCl lasers are typically pumped in pulsed gas discharges using a mixture of xenon, a chlorine donor such as chlorine gas (Cl2) or hydrogen chloride (HCl), and a noble buffer gas such as neon, argon, or helium. When electrical energy excites the xenon atoms, energy transfer forms XeCl*, which rapidly decays to Xe and Cl, emitting a 308 nm photon. The optical cavity of a laser resonator provides feedback to amplify this radiation, producing pulses of UV light.

Key characteristics include short pulse durations, usually in the nanosecond range, high peak powers, and a UV output suitable for microlithography and materials processing. XeCl lasers require UV‑grade optics and clean gas handling, as impurities strongly affect performance and the lifetime of the discharge electrodes and the gain medium.

Historically, XeCl was among the first excimer laser media developed alongside KrF and ArF in the 1970s and 1980s. It has been used in early photolithography, microfabrication, and various laser‑assisted processing applications. Owing to the rise of shorter-wavelength excimer lasers (such as ArF at 193 nm) for semiconductor manufacturing, current use of XeCl is more specialized and primarily research‑oriented.