Four-wave sum mixing (130–180 nm) in molecular vapors

It is demonstrated that molecular vapors such as nitric oxide, bromine, and benzene can be used for resonantly enhanced four-wave mixing into the vacuum ultraviolet. Coherent radiation in the 130–152-nm region has been generated in nitric oxide, and continuous wavelength tunability achieved by pressure broadening the rotational structure at 10 atm. Estimates of the third-order nonlinear susceptibility are shown to be consistent with the observed conversion efficiency in nitric oxide.