Quantitative characteristics of pressure-induced four-wave mixing signals observed with cw laser beams

We report observation of a pressure-induced extra resonance in four-wave mixing (PIER4 signal) using single-mode continuous-wave dye lasers. The narrow laser linewidth permits for the first time a quantitative verification of the frequency, intensity, and pressure dependence of the PIER4 signal predicted by the theory of the nonlinear susceptibility ${\chi }^{\mathrm{}\left(3\right)\mathrm{}}$.