One facet of Dr. Miller´s research is in the area of heterogeneous environmental chemistry. His group is especially interested in the thermal and photo-induced surface chemistry important to the production and fate of tropospheric oxidants, many of which are radicals or radical precursors. Areas of research in this effort include: (1) Directly measuring the reactivity and reaction rates of ozone and NO_y compounds (HONO, PAN, MPAN, HNO₃) with a variety of natural and model surfaces under "real-world" conditions; (2) Performing direct studies of the surface reactions of those oxidants, singly and in combination; (3) Examining the effects of photochemical excitation on surface reactivity; (4) Determining what surface structural features or functional groups affect the rate of the oxidant-gas surface reactions. (5) Elucidating the mechanistic role of gas-phase or adsorbed water in these surface reactions.