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van Der Voort M Rella CW van Der Meer LF Akimov AV Dijkhuis JI 《Physical review letters》2000,84(6):1236-1239
We present results of the first vibrational photon-echo, transient-grating, and temperature dependent transient-bleaching experiments on a-Si:H. Using these techniques, and the infrared light of a free electron laser, the vibrational population decay and phase relaxation of the Si-H stretching mode were investigated. Careful analysis of the data indicates that the vibrational energy relaxes directly into Si-H bending modes and Si phonons, with a distribution of rates determined by the amorphous host. Conversely, the pure dephasing appears to be single exponential, and can be modeled by dephasing via two-phonon interactions. 相似文献
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Luciano A. Leal Wiliam F. da Cunha Luiz F. Roncaratti Geraldo M. e Silva 《Molecular physics》2016,114(3-4):440-445
ABSTRACTBased on ab initio calculations, our research group has built an analytical ground-state potential energy surface (PES) for hydrogen peroxide– noble gas (Ng) interactions, such as H2O2–He, H2O2–Ne, H2O2–Ar, H2O2–Kr, and H2O2–Xe complexes. From this PES, it was verified that the Ng presence does not affect the equilibrium values of the H2O2 dihedral angles. This happens because the H2O2 intramolecular barriers have much higher energies than the atom–bond interaction within these complexes. From this point of view, it is indeed reasonable to consider the H2O2 system as a rigid rotor, frozen at its equilibrium configuration. We present in this work the torsional motion for the H2O2 isolated system, the vibration–rotation energy levels and spectroscopic constants for hydrogen peroxide–noble gas by using the aforementioned PES. The predicted H2O2 torsional motions are in good agreement with both theoretical and experimental results available in the literature. Regarding H2O2–Ng ro-vibrational energies and spectroscopic constants, it is the first time that these calculations are presented in the literature. The current theoretical predictions are expected to be useful in the future experimental investigations. 相似文献
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Pirani F Roncaratti LF Belpassi L Tarantelli F Cappelletti D 《The Journal of chemical physics》2011,135(19):194301
We report new high resolution molecular beam experiments aimed at characterizing the intermolecular interaction in the NH(3)-Ng (Ng = He, Ne, Ar, Kr, Xe) weakly bound complexes. Integral cross section data are obtained over a sufficiently wide velocity range and with rotationally hot NH(3) molecules to produce (except for the NH(3)-He case) a well resolved "glory" quantum interference pattern. Data analysis, carried out by employing a recently proposed potential model, allows unique information on the absolute scale of the intermolecular interaction to be obtained both at long range and at the equilibrium distance. An extensive and internally consistent comparison with the behavior of the corresponding Kr-Ng systems is exploited in order to identify those cases where an interaction component due to charge transfer effects provides an appreciable intermolecular bond stabilization that is clearly distinct from and must be added to the standard van der Waals plus induction picture. The results of the present investigation extend the phenomenology of perturbative charge transfer effects in gas phase complexes involving hydrogenated molecules. 相似文献
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Pirani F Brizi S Roncaratti LF Casavecchia P Cappelletti D Vecchiocattivi F 《Physical chemistry chemical physics : PCCP》2008,10(36):5489-5503
Scattering data, measured for rare gas-rare gas systems under high angular and energy resolution conditions, have been used to probe the reliability of a recently proposed interaction potential function, which involves only one additional parameter with respect to the venerable Lennard-Jones (LJ) model and is hence called Improved Lennard-Jones (ILJ). The ILJ potential eliminates most of the inadequacies at short- and long-range of the LJ model. Further reliability tests have been performed by comparing calculated vibrational spacings with experimental values and calculated interaction energies at short-range with those obtained from the inversion of gaseous transport properties. The analysis, extended also to systems involving ions, suggests that the ILJ potential model can be used to estimate the behavior of unknown systems and can help to assess the different role of the leading interaction components. Moreover, due to its simple formulation, the physically reliable ILJ model appears to be particularly useful for molecular dynamics simulations of both neutral and ionic systems. 相似文献
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Ribeiro LA Neto PH da Cunha WF Roncaratti LF Gargano R Filho DA e Silva GM 《The Journal of chemical physics》2011,135(22):224901
Exciton dissociation and charge recombination processes in organic semiconductors, with thermal effects taken into account, are described in this paper. Here, we analyzed the mechanisms of polaron-excitons dissociation into free charge carriers and the consequent recombination of those carriers under thermal effects on two parallel π-conjugated polymers chains electronically coupled. Our results suggest that exciton dissociation in a single molecule give rise to localized, polaron-like charge carrier. Besides, we concluded that in the case of interchain processes, the bimolecular polaron recombination does not lead to an usual exciton state. Rather, this type of recombination leads to an oscillating dipole between the two chains. The recombination time obtained here for these processes are in agreement with the experimental results. Finally, our results show that temperature effects are essential to the relaxation process leading to polaron formation in a single chain, as in the absence of temperature, this process was not observed. In the case of two chains, we conclude that temperature effects also help the bimolecular recombination process, as observed experimentally. 相似文献
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Ramalho SS da Cunha WF Barreto PR Neto PH Roncaratti LF e Silva GM Gargano R 《The journal of physical chemistry. A》2011,115(29):8248-8254
In this work we analyzed the multiple channels of the reaction NF+F through the evaluation of thermal rate constants with both Wigner and Eckart tunneling corrections. Minimum energy paths and intrinsic reaction coordinates of the systems were obtained and accurately studied in order to ensure the consistency of our results. Specifically, we investigated the NF + F = N + F(2), NF + F = NF + F, and NF(2) = NF + F, reactive systems. As experimental data are available for the latter reaction, we were able to conclude that our thermal rate constants are in agreement for a wide range of temperatures. The here performed study is relevant to the understanding of the decomposition process of nitrogen trifluoride (NF(3)). 相似文献
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Vincenzo Aquilanti David Cappelletti Fernando Pirani Luiz F. Roncaratti 《International journal of mass spectrometry》2009,280(1-3):72
Total integral cross section experiments, for collisions of rotationally hot H2S projectile molecules by He and Xe targets, have been performed in the thermal energy range by using a molecular beam apparatus, which operates under high resolution conditions and exploits a quadrupole mass spectrometer as a detector. Information on the radial dependence of the intermolecular interaction, averaged over all relative orientations of colliding partners, is obtained. This study completes the investigation of H2S–rare gas family [see D. Cappelletti, A.F.A. Vilela, P.R.P. Barreto, R. Gargano, F. Pirani, V. Aquilanti, J. Chem. Phys. 125 (2006) 133111, for Ne, Ar and Kr] and permits us to discover similarities and differences with the analogous H2O–Rg series of systems. In particular, the analysis of the scattering data suggests that while the complexes of H2S–rare gases from He to Kr are essentially bound by nearly isotropic noncovalent interactions of van der Waals type, the H2S–Xe system exhibits a weak, but measurable, additional component which emerges at intermediate intermolecular distance (in proximity of the potential well), and provides a bond stabilization. This observation is of possible interest for the investigation of the phenomenology of the hydrogen bond formation. 相似文献
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