An optical four-wave mixing (FWM) described by the nonlinear susceptib
ility chi((3)) (omega(as) = 2 omega(p)-omega(s)) is studied in a singl
e crystal of Rochelle salt (NaKC4H4O6 . H2O) In addition to the cohere
nt anti-Stokes Raman Scattering (CARS) structure, the FWM spectra cons
ist of nonvibrational (background) components. After analysis of the F
WM spectra in the range from 1100 to 1450 cm(-1), the nonresonant (ele
ctronic) susceptibility elements chi(zzzz)(el) and chi(xxxx)(el) of Ro
chelle salt single crystal are estimated.