DETERMINATION OF TWO-DIMENSIONAL CRYSTAL STRUCTURES BY IR SPECTROSCOPY

Author Institution: Department of Chemistry, Indiana UniversityWe have studied the infrared spectra of molecular monolayers on single crystals of sodium chloride. The unprecedented resolution of our experiments has revealed spectroscopic features which are due to dynamic coupling within the adsorbate array. Thanks to the relative passivity of the substrate, it is appropriate to describe the structure and vibrational motion of the monolayer as if it were a two-dimensional molecular crystal. The corresponding branch of symmetry theory involves 80 ``plane groups''. Plane group analysis has been instrumental to our determination of nontrivial monolayer structures. Examples from recent work will be discussed