He was respected and admired by his colleagues worldwide for his research, expertise, and dedication to theoretical chemistry and has been recognized many times for his scientific achievements. In 1988 he received the first Dirac Medal from the World Association of Theoretical and Computational Chemists for being an "outstanding computational chemist in the world under the age of 40." He was an elected Fellow of the American Physical Society and of the American Association for the Advancement of Science. He was also a member of the AAS Laboratory Astrophysics Division and served on the Election Nominating Committee in 2021.
Tim lead the field in the computation of anharmonic spectra of polycyclic aromatic hydrocarbons, established highly accurate molecular line lists for stellar and exoplanetary atmosphere modeling, and both identified and quantified chemical reaction routes relevant to astrophysics. His work was substantiated and enhanced by laboratory astrophysics and continues to increase the scientific return of astrophysics and planetary science research.