Investigation of resonant nonlinear molecular susceptibilities using a tunable infrared optical parametric oscillator

The results are given of an investigation of the dispersion of the cubic susceptibility of liquid chloroform in the region of the first overtone (5890 cm^–1) of the valence vibration of the C–H bond. Four-photon spectroscopy of allowed transitions based on a tunable infrared optical parametric oscillator was used. Several variants of the method, involving the use of double electron or vibrational–vibrational resonances are considered.