Reactorphysics

Reactorphysics is an interdisciplinary field that studies the physical mechanisms governing chemical reactivity, integrating principles from quantum mechanics, thermodynamics, and statistical mechanics to explain how and why chemical reactions occur, and how rates and products are determined. The field emphasizes energy landscapes, transition states, and dynamical pathways, aiming to connect microscopic interactions with observable reaction outcomes. It often seeks to bridge the gap between abstract physical theories and practical chemical phenomena.

Theoretical foundations in reactorphysics include quantum reaction dynamics, potential energy surface theory, and the role of environment and solvent in shaping reaction pathways. Common frameworks include transition-state theory, RRKM (Rice–Ramsperger–Kassel–Marcus) theory for unimolecular processes, and modern quantum dynamical methods such as wavepacket propagation, semiclassical approaches, and ab initio molecular dynamics. Computational tools frequently used are density functional theory, multireference methods for nonadiabatic or excited-state processes, quantum mechanics/molecular mechanics (QM/MM) hybrids, and increasingly, machine learning potentials to model complex systems with lower cost. Experimental techniques such as ultrafast spectroscopy, pump–probe measurements, and cold-molecule experiments provide time-resolved data to test dynamical models and energy flow in reactions.

Applications span catalysis, photochemistry, atmospheric chemistry, combustion, and materials synthesis, and include investigations of energy transfer, vibrational relaxation, and spin effects in reactive systems. Limitations involve high computational cost for accurate, large-scale simulations, challenges in treating condensed-phase environments, and ongoing debates about the relative merits of statistical rate theories versus full dynamical treatments. Reactorphysics remains a developing area at the interface of physical chemistry, chemical physics, and reaction dynamics.