“…Over the past twenty years, many spectroscopic techniques have been utilized to investigate the average molecular orientation at the interface, such as second-harmonic generation, [8][9][10][11] fluorescence, 12 attenuated total internal reflection, 12,13 linear dichroism, 12,14,15 and photoacoustic spectroscopy. 11 Recently, cavity ring-down spectroscopy (CRDS) has also been used to carry out molecular orientation studies.…”