Solvent response to solute photo-dissociation

Phys Chem Chem Phys. 2008 Feb 21;10(7):990-5. doi: 10.1039/b711466d. Epub 2007 Dec 4.

Abstract

Ultraviolet-visible and infrared transient-absorption spectroscopy are used to investigate the transfer of energy from nitrite to water during the photo-dissociation of NO2-(aq). Nitrite is dissociated by photo-excitation at 200 nm. About 40% of the photo-fragments recombine and relax on a 3 ps timescale, while diffusive recombination accounts for another 10% of the fragments during the subsequent 50 ps. The infrared transient-absorption spectra of the photo-dissociation of nitrite solvated in H2O and D2O show no evidence of excited vibrations after 0.5 ps. Instead they reveal a sub-0.5 ps change in the infrared absorption similar to what is observed when the temperature of water is increased. Since this spectral change is associated with the weakening of the hydrogen-bond network, we infer that excess energy from the dissociation of nitrite is dissipated to the local hydrogen-bonded water network in less than 0.5 ps. The rapid change in the infrared absorption is followed by a slower (50 ps) component associated with the energy dissipation to the solvent as the photo-fragments diffusively recombine and relax.

MeSH terms

  • Deuterium Oxide / chemistry*
  • Deuterium Oxide / radiation effects*
  • Energy Transfer
  • Nitrites / chemistry*
  • Nitrites / radiation effects*
  • Photochemistry
  • Quantum Theory
  • Solubility
  • Solvents / chemistry
  • Solvents / radiation effects
  • Spectrophotometry, Infrared / methods
  • Spectrophotometry, Ultraviolet / methods
  • Time Factors
  • Ultraviolet Rays*
  • Water / chemistry

Substances

  • Nitrites
  • Solvents
  • Water
  • Deuterium Oxide