We have measured the nonlinear refractive index n2 of CS2 at 10.6 μm using two different techniques. We find that n2 is (2.2 ± 0.7) x 1010 esu which is over an order of magnitude larger than its value in the visible.
M. J. Soileau,
E. W. Van Stryland,
"Nonlinear Refractive Index Of CS2 At 10.6 µm", Proc. SPIE 0540, Southwest Conf on Optics '85, (20 November 1985); doi: 10.1117/12.976163; https://doi.org/10.1117/12.976163