Andrew Orr-Ewing and co-workers, Bristol University, UK, have used transient infrared absorption spectra to observe how solvent collisions affect the energy of the products of a chemical reaction. The results were obtained with picoseconds time resolution, allowing them to follow a chemical reaction in more detail than ever before.

The team studied the reaction of CN radicals with cyclohexane in chlorinated organic solvents. The main product, HCN, exhibited one quantum of the C–H stretching mode and up to two quanta of the bending mode. In the gas phase, HCN exhibits greater excitation in both the bending and stretching modes. The HCN products were seen to relax to the ground state through coupling to the solvent bath in ~100 to 300 ps. The reduced excitation in solution is attributed to dampening by the vibrational motion of the solvent.

This data will be used to better inform computer models designed to simulate chemical reactions in liquids for use in drug design, industrial processing, and applications in bio- and atmospheric chemistry.

• Vibrationally Quantum-State–Specific Reaction Dynamics of H Atom Abstraction by CN Radical in Solution
  S. J. Greaves, R. A. Rose, T. A. A. Oliver, D. R. Glowacki, M. N. R. Ashfold, et al.,
  Science 2011.
  DOI: 10.1126/science.1197796