Two-color resonant four-wave mixing spectroscopy of ammonia Original Research Article

We demonstrate the use of two-color resonant four-wave mixing (TC-RFWM) spectroscopy to detect gas-phase ammonia molecules. Appropriate choice of the two different excitation frequencies is shown to cause substantial enhancement in the third-order susceptibility, χ(3), and a consequent increase both in spectral sensitivity and in selectivity as compared with the corresponding one-color degenerate four-wave mixing (DFWM) technique.