Small Difference Between the Nonlinear Refractions of Normal and Deuterated Solvents Measurable by Nonlinear Ellipse Rotation

In this work, we have measured the nonlinear refractions of six different normal and deuterated solvents: water, DMSO, methanol, acetone, toluene, and chloroform using a nonlinear ellipse rotation (NER) signal with femtosecond laser pulses. High-precision, self-referenced NER measurements could detect small differences between the refractive nonlinearities of normal and deuterated solvents. We observed that the replacement of hydrogen with deuterium atoms slightly reduces the magnitude of the nonlinearity. Basically, the reduction is related to the amount of hydrogen and the replacement by deuterium atoms in the molecules; in this way, toluene (chloroform) presents the major (minor) difference. By measuring the nonlinear refraction as a function of the pulse width, we also could observe that the refractive nonlinearity increases as the pulse gets longer. Using a simple empirical model, we could discriminate the ultrafast electronic and delayed orientational refractive nonlinearities of these six pairs of solvents.