The photodissociation of triiodide anion ([I?]?) is a classic textbook reaction that has been extensively studied both in solution and in gas phase. However, probing the ultrafast dynamics of this reaction in the solid state was proven challenging due to partial reversibility of the reaction and its sensitivity to experimental conditions. Due to an improved sample handling a team of scientists from the MPSD at CFEL and the University of Edinburgh has currently discovered a new reaction intermediate, the tetraiodide radical anion ([I?]• ?), formed as a result of the unique ordering of [I?]? in the crystal lattice to direct the dissociating I atom - in a process reminiscent of a quantum Newton's cradle. The results have now been published in Nature Chemistry.
The full article can be found here.