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)