Tunable Coherent Vacuum-Ultraviolet Generation in Atomic Vapors

Two tunable dye lasers have been used to generate coherent radiation at a tunable sum frequency in the vacuum-ultraviolet spectral region. Spectral ranges of ∼3500 ${\mathrm{cm}}^{-1\mathrm{}}$ around 1895 Å and ∼1200 ${\mathrm{cm}}^{-1\mathrm{}}$ around 1798 Å have been covered. These ranges may easily be extended. Large (∼×${10}^4$) enhancements of $2{\nu }_1+{\nu }_2$ sum mixing are seen when $2{\nu }_1$ is tuned to a double-quantum allowed transition from the ground state in Sr vapor.