KrCl

KrCl, krypton chloride, is a diatomic molecule consisting of a krypton atom bonded to a chlorine atom. In its neutral ground state, KrCl is weakly bound and tends to be a transient species, typically formed under high-energy conditions such as electrical discharges in mixtures of krypton and chlorine gas or by photolysis of suitable precursors. Because the ground-state bond is weak, KrCl is not a stable species under ordinary conditions.

In many practical contexts KrCl is discussed as an excited-state species. When formed in excited electronic states, KrCl* or KrCl excimers are short-lived due to rapid radiative decay or dissociation. The most technologically notable form is the KrCl* excimer, a bound excited-state complex that emits ultraviolet light with a peak near 222 nanometers. This emission is exploited in KrCl-based excimer lasers, which are part of the family of noble-gas halide laser systems.

Generation of KrCl excimers typically occurs in gas-discharge environments containing krypton and chlorine sources, often with inert buffer gases such as neon or helium to optimize population of the excimer state. Optical pumping or electrical discharge can achieve the necessary excitation to populate the KrCl* state.

Applications of KrCl-based systems include ultraviolet laser sources for microlithography, precision micromachining, and sterilization technologies that benefit from short-wavelength UV output. Beyond lasers, KrCl chemistry is of interest in fundamental studies of noble-gas halide interactions and excimer formation, as well as in spectroscopic investigations of short-lived species.

Safety considerations include the reactive chlorine component and the ultraviolet radiation produced by KrCl* emission, which require appropriate containment, shielding, and handling protocols.