Hydrogen‐release by photoexcitation, excited‐state‐hydrogen‐transfer (ESHT), is one of the important photochemical processes that occur in aromatic acids and is responsible for photoprotection of biomolecules. The mechanism is described by conversion of the initial state to a charge‐separated state along the O(N)‐H bond elongation, leading to dissociation. Thus ESHT is not a simple H‐atom transfer in which a proton and a 1s electron move together. Here we show that the electron‐transfer and the proton‐motion are decoupled in gas‐phase ESHT. We monitor electron and proton transfer independently by picosecond time‐resolved near‐infrared and infrared spectroscopy for isolated phenol–(ammonia)5, a benchmark molecular cluster. Electron transfer from phenol to ammonia occurred in less than 3 picoseconds, while the overall H‐atom transfer took 15 picoseconds. The observed electron‐proton decoupling will allow for a deeper understanding and control of of photochemistry in biomolecules. 相似文献
The equilibrium solution of a damaged zone in finite elasticity is given for a class of hyperelastic materials which does not suffer tension when a critical stretching value is reached. The study is made for a crack in anti-plane shear loading condition. The prescribed loading is that of linearized elastostatics conditions at infinity. The geometry of the damaged zone is found and the stationary propagation is discussed when the inertia terms can be neglected. 相似文献
