Miller's research focuses on free radicals, molecules with unpaired electrons, and their dangerous reactivity to biology.
Free radicals dominate the chemistry of higher elevations and can damage portions of the atmosphere.
His current research covers an atmospherically important transient molecule called PAD, an acetyl peroxy radical forming with an NO2 group, that has a potentially dangerous impact on the environment because of its ability to transport pollution from smoggy urban areas to pristine, rural regions. Miller relies on spectroscopy to map out the energy levels and uncover the unique structure and atomic orientation of a molecule. Using light, optical radiation, he creates a three-dimensional, global map of a molecule that can be used to study the distribution of a molecule as a function of space and time. This information is extremely useful in studying ozone concentrations and long-term atmospheric trends. He also uses spectroscopic techniques to study istopic fractionation, the different atomic masses, vibrational frequencies and rotational frequencies.