Spectroscopy of radicals in condensed phase

Take it or leave it, but real chemistry does happen in condensed phases! In particular, aqueous radicals are implicated in atmospheric chemistry (HOO, ClO, NO3), radiation chemistry (water coolant in nuclear reactors), and enzymatic processes (Tyr).

Journal of Physical Chemistry A, April 13 Cover

Experiments in Bradforth lab utilize ultrafast laser techniques to investigate the coupling between the solvent and solute in ICN photodissociation. The interpretation of the data heavily depends on the spectral assignment of transient species present of the solution. Of special interest is the CN radical, for which conflicting spectral assignments appeared in literature.

Electronic structure of open-shell species in water is a theoretically difficult problem due to (i) large size of the system, (ii) high level of theory required for their proper description. The avenue to progress lead via a combination of classical molecular dynamics and electrostatic treatment of water. The study revealed an expected blue shift of the B2Σ+←X2Σ+ transition.

Electronic spectrum of CN radical in water

Electronic specrum of the A2Π←X2Σ+ transition of the CN radical in water
Maximum at 1.44 eV.
The interaction with solvent results in the blue-shifted and widened absorption lineshape (by 0.12 and 0.19 eV, respectively).

Related Publications

44. P. A. Pieniazek, S. E. Bradforth, and A. I. Krylov
Spectroscopy of the cyano radical in an aqueous environment
J. Phys. Chem. A 110, 4854 – 4865 (2006) Abstract  PDF (914 kB)