The team eventually traced those results to the presence of a molecule called hydroxyl—a single hydrogen atom paired with an oxygen atom—that can also act as a reducing agent. That equally unexpected result led Katherine Walker, at the time a graduate student in Zare's lab, to wonder whether hydrogen peroxide—a molecule with two hydrogen and two oxygen atoms—was also present.

Every high school chemistry student knows that water is made up of H + OH, not H₂ + O.  I think this is a case of the testing equipment getting more proficient.