Professors De Lucia and Herbst are supported by a grant from the Experimental Physical Chemistry Program to continue their studies of radiative and collisional preperties involving small fundamental molecular species. Using the tools of millimeter and submillimeter spectroscopy, De Lucia and Herbst are studying the collisions of gas phase species at very low temperatures (below 5 K), the mechanisms and the modeling of intermolecular rotational energy transfer, and the spectroscopy of internal rotor states in various simple molecules. %%% This collaborative experimental and theoretical program provides important basic scientific information of potential use in various diverse fields, including molecular astrophysics, quantum electronics, and atmospheric science.