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Hypervalent dimethyloxonium radical, (CH3)2O&z.sbnd;H⋅ (1), is formed by collisional electron transfer to protonated dimethyl ether in the gas phase and dissociates rapidly by cleavage of the O&z.sbnd;H and O&z.sbnd;C bonds. Ab initio and density functional theory calculations show that these dissociations originate from different electronic states of 1. The loss of H proceeds from the repulsive ground electronic (X) state of 1 and is 131 kJ mol−1 exothermic to form vibrationally excited (CH3)2O. The loss of methyl proceeds from the first excited electronic (A) state of 1 by crossing to the repulsive part of the X state potential energy surface, yielding vibrationally excited methanol. A substantial fraction of deuterated radicals, (CH3)2O&z.sbnd;D⋅ (1-OD), are metastable on the microsecond time scale. The metastable species result from the population of the B and higher excited states of 1 that are calculated to be bound along both O&z.sbnd;H and O&z.sbnd;C coordinates. The isotope effects on the metastability of 1 are explained by less efficient vibronic coupling between the bound B and dissociative A states in the deuterated radical. [Copyright &y& Elsevier]

New experimental and analysis methods for investigating the role local environment has on photoluminescence intermittency (PI) exhibited by single luminophores are presented. Quasi-single molecule (SM) microscopy provides spatial resolution of dielectric environments within poly(vinylidene fluoride) (PVDF) films, and reveals annealing's effect on the structural phase of PVDF. New analysis methods establish that the PI exhibited by nile red (NR) SMs in PVDF are consistent with photoinduced electron transfer between NR and PVDF, where transfer rates depend on local dielectric environment. These methods should prove useful for SM studies of guest–host materials where elucidating PI contribution from the host is required. [ABSTRACT FROM AUTHOR]