EXPERIMENTAL-DETERMINATION OF THE SIGN OF MOLECULAR DIPOLE-MOMENT DERIVATIVES - AN INFRARED VISIBLE SUM FREQUENCY GENERATION ABSOLUTE PHASE MEASUREMENT STUDY

We show that the measurement of the absolute phase of the infrared-visible sum frequency susceptibility of a monolayer of molecules of known orientation determines the relative sign of the dipole moment derivative and the polarizability derivative with respect to the normal mode. With the sign of the polarizability derivative well established, we determine the sign of the CH bond dipole moment derivative with respect to the CH stretch for the methyl group of an alkane and for methoxy. © 1990.