Rare gas halogen excimers

Although the rare gas halide lasers were discovered only about three years ago [4.1–6], they have received a great deal of attention since then and are presently the most highly developed excimer lasers. Moreover, the rare gas monohalides themselves represent an intriguing new class of molecules which (except for XeF [4.7]) have only recently been observed [4.8–12]. In spite of their recent discovery, a great deal is now understood about these molecules and lasers, and it is worth reviewing what is known.