Laser technology has recently evolved to the point where tunable uv radiation can be obtained using commercially available lasers. The uv output between 217–260 nm is generated indirectly by using nonlinear optical devices such as frequency doubling and mixing crystals and/or by utilizing anti-Stokes Raman shifting techniques. For any scientist using lasers, even experts, the choices in commercial laser systems can be confusing. Because these laser systems are extremely expensive, an error in choice can result in a major scientific disaster.
Sanford A. Asher, "Some Important Considerations in the Selection of a Tunable UV Laser Excitation Source," Appl. Spectrosc. 38, 276-278 (1984)