We perform a comparison of electron affinities (EA) of the conjugated molecules bithiophene, azulene, naphthalene, and their water clusters. Bithiophene and azulene monomers have positive EAs of +49±5 meV and +790±8 meV, but naphthalene has a negative EA. Despite their different EAs and their different molecular orbital energies the three molecules show very similar microsolvation shifts per water unit. This is explained by similar sizes of the π orbitals in which the surplus electron is delocalized leading to a similar electrostatic water to charge interaction. This qualitative dependence of solvation energy on anion size agrees well with classical solvation concepts. A comparison of our binding energies with previous calculations for other systems shows that formation of a water subcluster can be assumed. For all three molecules the cluster EAs increase nearly linearly with the number of waters. Using a linear approach and a calibration for the error in the first solvation step we extrapolated the naphthalene (H2O)n cluster series to a monomer EA−200 meV±50 meV, in good agreement to previous measurements. To become new insights B3LYP/6-31++G** structures and energies have been calculated for azulene, naphthalene, and their clusters with one water and compared with experimental EAs.
This article presents detailed internal and kinetic energy dependent cross sections and reaction rates for the hydrogen atom transfer processes N+2(X 2Σ+g, v+=0–4, J+=2)+H2→N2H++H, which were obtained under single-collision conditions in a guided-ion beam/scattering gas experiment. Preparation of ions in specific states relied on single-color excitation within a resonantly enhanced (2+1) multiphoton ionization scheme. The translational energy of the ions, Elab, was varied from 0.1 eV to approximately 30 eV. A small activation barrier impedes the reaction. Vibronic state preparation of the nitrogen ion is influential on the nature of the energy surface—N+2+H2 or H+2+N2—along which the H atom transfer proceeds. Calculations of model potential energy surfaces suggest that the reaction pathway must involve several exoergic and endoergic channels which open successively as the collision energy increases. A purely collision determined cross section—as would be evidenced by the E−1/2 dependence formulated in the Langevin–Gioumousis–Stevenson model—is observed only within a narrow window of kinetic energies.
W e report on the application of a broad-band NbN film detector which has high sensitivity and picosecond response time for detection of radiation from millimetre wavelengths to visible light. From a study of amplitude modulated radiation of backward-wave tubes and picosecond pulses from gas and solid state lasers at wavelengths between 2 m m and 0.53 pm, we found a detectivity of 10" W-' cm Hz-'I2 and a response time of less than 50 ps at T = 10 K. The characteristics were provided by using a 150 A thick NbN film patterned into a structure of micron strips. According to t h e proposed detection mechanism, namely electron heating, we expect an intrinsic response time of -20 DS at t h e same temperature.
Dynamics of the D+ + H2 → HD + H+ reaction at the low energy regime by means of a statistical quantum method J. Chem. Phys. 139, 054301 (2013); 10.1063/1.4816638 Nuclear spin dependence of the reaction of H 3 + with H2. I. Kinetics and modeling Absolute state-selected total cross sections for the ion-molecule reactions O+ (4S,2D,2P)+H2(D2)The widely accepted model descriptions of ion-molecule reactions suggest identical rate constants for the title reaction and the analogous, isoelectronic system N 2 ϩ ϩH 2 , which has been the topic of a previous publication from this laboratory. A comparison of both data sets, however, reveals substantial disagreement which we attribute to the absence of energetic resonances between the reagents which characterized the N 2 ϩ /H 2 system. Resonantly enhanced photoionization was exploited to accomplish the state-specific preparation of CO ϩ ͑X 2 ⌺ ϩ , v ϩ ϭ0,1͒. A monoenergetic beam of vibrationally selected ions, tuned within the range 0.01 eVрE cm р10 eV, transits a scattering chamber which confines the neutral, H 2 . The title reaction was the only channel observed-no evidence of charge transfer or dissociative ionization could be detected. The hydrogen atom transfer turns out to proceed directly. The reactive cross section fails to show the E Ϫ1/2 dependence indicative of collision determined processes. The experimental data are perfectly mimicked by an expanded Langevin model which includes additional attractive potential terms. In contrast to the N 2 ϩ /H 2 case, vibrational excitation does not affect the rate of the reaction.
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