Molecular spectroscopy is the most powerful method to study properties and dynamics of molecules. We carry out a wide range of experiments throughout the entire electromagnetic spectrum. Studies of van der Waals molecules formed in supersonic beam expansions provide great insight into intermolecular interactions. The upper left panel in the figure shows a portion of the ratio frequency spectrum of acetylene dimer. Experimental results are combined with theoretical calculations to generate accurate intermolecular potential surfaces, with one example for (HCCH)2 shown in the lower left panel of the figure.

The two panels in the center of the figure relate to a series of experiments designed to study properties of highly excited vibrational states of molecules. The top center panel is a schematic diagram of a laser-microwave double resonance spectrometer. An infrared or visible laser is used to excite molecules into a high energy state. While the molecules are in these normally inaccessible energy levels, a second transition in the radio frequency or microwave portion of the spectrum is observed. The bottom center portion of the figure shows a microwave transition in ammonia obtained in an excited N-H stretching state. These transitions are observed in an electric field, to measure electric dipole moments in excited vibrational states.

The right most portion of the figure moves to the ultraviolet portion of the spectrum, and these two sketches describe an experiment used to measure dipole moments in excited electronic states. The upper right panel outlines a Stark quantum beat spectrometer. A frequency doubled pulsed dye laser electronically excites a molecular beam. The Stark effect splits up the energy levels and the laser excites a coherent superposition of these "Stark components". The lower right panel shows fluorescence from SO2 exhibiting Stark quantum beats that come from this coherent excitation.