A forgotten channel in the excited state dynamics of phenol-(ammonia)(n) clusters: hydrogen transfer

Small phenol-(NH3)(n) clusters have been studied through two-color two-phot on and one-photon VUV ionization, in order to disentangle the contributions of various dissociation or reaction paths in the excited and ionic states. The most striking result of the two-color experiment is that (NH4)(+)(NH3) (n=1,5) fragments are observed with large delays (up to a few hundred nanos econds) between the excitation and ionization lasers, whereas these same fr agments are not observed in the VUV one-photon ionization experiment. In or der to account for these findings, a new deactivation channel in the excite d state of phenol-(NH3)(n) clusters has to be introduced: the hydrogen atom transfer PhOH(S-1) - (NH3)(n)--> PhO. + (NH4)(NH3)(n-1). In this case, the delayed (NH4)(+)(NH3)(n-1) signals correspond to direct ionization of the (NH4)(NH3)(n-1) clusters produced in the excited state.