Electron-Proton Decoupling in Excited-State Hydrogen Atom Transfer in the Gas Phase.

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.

Formation and localization of a solvated electron in ground and low-lying excited states of Li(NH3)n and Li(H2O)n clusters: a comparison with Na(NH3)n and Na(H2O)n.

A theoretical study of the ground and low-lying excited states of Li(NH(3))(n) and Li(H(2)O)(n) (n = 1-8) clusters is presented. Their structures, binding energies, vertical ionization energies and vertical transition energies were calculated using ab initio molecular orbital methods at correlated levels. Compared with Na(NH(3))(n) and Na(H(2)O)(n), the incremental binding energies and the spectroscopic energies are found to be almost metal-independent, but solvent-dependent after first-shell closure in both M(NH(3))(n) and M(H(2)O)(n) (M = Li and Na) clusters(.

Hydrogen transfer dynamics in a photoexcited phenol/ammonia (1:3) cluster studied by picosecond time-resolved UV-IR-UV ion dip spectroscopy.

The picosecond time-resolved IR spectra of phenol/ammonia (1:3) cluster were measured by UV-IR-UV ion dip spectroscopy. The time-resolved IR spectra of the reaction products of the excited state hydrogen transfer were observed. From the different time evolution of two vibrational bands at 3180 and 3250 cm(-1), it was found that two isomers of hydrogenated ammonia radical cluster .

Hydration process of Na2- in small water clusters: photoelectron spectroscopy and theoretical study of Na2- (H2O)n.

Photoelectron spectroscopy (PES) of Na2- (H2O)n (n < or = 6) was investigated to examine the solvation of sodium aggregates in small water clusters. The PES bands for the transitions from the anion to the neutral ground and first excited states derived from Na2 (1(1)Sigmag+) and Na2 (1(3)Sigmau+) shifted gradually to the blue, and those to the higher-excited states correlated to the 3(2)S + 3(2)P asymptote dropped down rapidly to the red and almost degenerated on the 1(3)Sigmau+-type band at n = 4. Quantum chemical calculations for n up to 3 showed that the spectra can be ascribed to structures where one of the Na atoms is selectively hydrated.

Electronic states of sodium dimer in ammonia clusters: theoretical study of photoelectron spectra for Na2-(NH3)n (n = 0-6).

The geometries, energetics, and vertical detachment energies of Na2-(NH3)n (n = 0-6) were examined by ab initio molecular orbital methods in connection with their photoelectron spectra. One of the Na atoms is selectively solvated in the most stable structures for each n. The solvated Na is spontaneously ionized and the formation of a solvated electron occurs with increasing n, giving rise to the Na-Na+(NH3)n(e-)-type state.

Theoretical study of the electronic state and H-elimination reactions for solvated magnesium cluster ions.

The potential-energy curves of the ground and low-lying excited states for Mg(+)NH(3) along the N-H distance were examined by the ab initio configuration interaction method. The photoinduced hydrogen elimination reaction found by the recent experiment is considered to occur via the ground-state channel. The geometries, energetics, and electronic nature of the ground-state Mg(+)(NH(3))(n) and MgNH(2) (+)(NH(3))(n-1) (n=1-6) were also investigated by second-order Møller-Plesset perturbation theory and compared with those of the corresponding hydrated species.

Four-color hole burning spectra of phenol/ammonia 1:3 and 1:4 clusters.

The hole burning spectra of phenol/ammonia (1:3 and 1:4) clusters were measured by a newly developed four-color (UV-near-IR-UV-UV) hole burning spectroscopy, which is a kind of population labeling spectroscopy. From the hole burning spectra, it was found that single species is observed in an n = 3 cluster, while three isomers are observed simultaneously for n = 4. A possibility was suggested that the reaction efficiency of the hydrogen transfer from the electronically excited phenol/ammonia clusters, which was measured by a comparison with the action spectra of the corresponding cluster, depends on the initial vibronic levels.