Obtaining molecular orientation from second harmonic and sum frequency scattering experiments in water: Angular distribution and polarization dependence

We present a method for determining molecular orientation from second-order nonlinear light scattering experiments. Our modeling shows that there is an optimal angular region, for which the scattering pattern is most sensitive to molecular orientation. We show that molecular orientation can be retrieved from measuring intensities at different polarization combinations, measuring the relative amplitudes of different vibrational modes of the same moiety and by analyzing the shape of the angular scattering pattern. We further show that for C(2v) and C(3v) point groups, the asymmetric stretch mode displays a higher sensitivity to molecular orientation than the corresponding symmetric mode. We have implemented the model in an interactive simulation program that may be found at http://www.mf.mpg.de/en/abteilungen/roke/simulation.html. (C) 2010 American Institute of Physics. [doi:10.1063/1.3429969]