Molecular self-assembly directed by non-covalent interactions presents a unique opportunity to create precisely engineered functional materials. Halogen bonding is a widely studied interaction in three dimensions but there is limited research in two dimensions. It can be comparable in strength to the hydrogen bond but with the potential to be more selective it appears to be an excellent candidate interaction for designing functional materials. Previous work by the Clarke group has focused on the structure of physisorbed layers on graphite but there is little experimental work on the strength of bonding within these layers. This proposed experiment, seeks to use gamma dopplerimetry to determine the atom projected vibrational density of states for iodine in three halogen bonded monolayers on graphite and, via computer models, gain a measure of the strength of halogen bonding.