排序方式: 共有84条查询结果,搜索用时 15 毫秒
51.
Aldegunde J Alvariño JM de Miranda MP Sáez Rábanos V Aoiz FJ 《The Journal of chemical physics》2006,125(13):133104
This article uses theoretical methods to study the dependence on stereodynamical factors of the mechanism and reactivity of the F+H2 reaction at low and ultralow collision energies. The impact of polarization of the H2 reactant on total and state-to-state integral and differential cross sections is analyzed. This leads to detailed pictures of the reaction mechanism in the cold and ultracold regimes, accounting, in particular, for distinctions associated with the various product states and scattering angles. The extent to which selection of reactant polarization allows for external control of the reactivity and reaction mechanism is assessed. This reveals that even the simplest of reactant polarization schemes allows for fine, product state-selective control of differential and (for reactions involving more than a single, zero orbital angular momentum partial wave) integral cross sections. 相似文献
52.
Martínez-Núñez E Vázquez SA Aoiz FJ Castillo JF 《The journal of physical chemistry. A》2006,110(4):1225-1231
Classical trajectory calculations have been performed to investigate the collision-induced dissociation (CID) of the CH(3)SH(+) cation with Ar atoms. A new intramolecular potential energy surface for the CH(3)SH(+) cation is evaluated by interpolation of 3000 ab initio data points calculated at the MP2/6-311G(d,p) level of theory. The new potential energy surface includes seven accessible dissociation channels of the cation. The present QCT calculations show that migration of hydrogen atoms, leading to the rearrangement CH(3)SH(+) <--> CH(2)SH(2)(+), is significant at the collision energies considered (6.5-34.7 eV) and that the formation of CH(3)(+), CH(3)S(+), and CH(2)(+) cations takes place primarily by a "shattering" mechanism in which the products are formed just after the collision. The theoretical product abundances are found to be in qualitative agreement with the experimental data. However, at high collision energies, the calculated total cross sections for the formation of CH(3)(+) and CH(2)SH(+) cations are noticeably larger than the experimental determinations. Several features of the dynamics of the CID processes are discussed. 相似文献
53.
Balucani N Casavecchia P Bañares L Aoiz FJ Gonzalez-Lezana T Honvault P Launay JM 《The journal of physical chemistry. A》2006,110(2):817-829
In this paper, we report a combined experimental and theoretical study on the dynamics of the N(2D) + H2 insertion reaction at a collision energy of 15.9 kJ mol(-1). Product angular and velocity distributions have been obtained in crossed beam experiments and simulated by using the results of quantum mechanical (QM) scattering calculations on the accurate ab initio potential energy surface (PES) of Pederson et al. (J. Chem. Phys. 1999, 110, 9091). Since the QM calculations indicate that there is a significant coupling between the product angular and translational energy distributions, such a coupling has been explicitly included in the simulation of the experimental results. The very good agreement between experiment and QM calculations sustains the accuracy of the NH2 ab initio ground state PES. We also take the opportunity to compare the accurate QM differential cross sections with those obtained by two approximate methods, namely, the widely used quasiclassical trajectory calculations and a rigorous statistical method based on the coupled-channel theory. 相似文献
54.
Jambrina PG García E Herrero VJ Sáez-Rábanos V Aoiz FJ 《The Journal of chemical physics》2011,135(3):034310
Rate coefficients for the mass extreme isotopologues of the H + H(2) reaction, namely, Mu + H(2), where Mu is muonium, and Heμ + H(2), where Heμ is a He atom in which one of the electrons has been replaced by a negative muon, have been calculated in the 200-1000 K temperature range by means of accurate quantum mechanical (QM) and quasiclassical trajectory (QCT) calculations and compared with the experimental and theoretical results recently reported by Fleming et al. [Science 331, 448 (2011)]. The QCT calculations can reproduce the experimental and QM rate coefficients and kinetic isotope effect (KIE), k(Mu)(T)/k(Heμ)(T), if the Gaussian binning procedure (QCT-GB)--weighting the trajectories according to their proximity to the right quantal vibrational action--is applied. The analysis of the results shows that the large zero point energy of the MuH product is the key factor for the large KIE observed. 相似文献
55.
Differential Cross Sections and Collision-Induced Rotational Alignment in Inelastic Scattering of NO(X) by Xe 下载免费PDF全文
Mark Brouard Helen Chadwick Sean D.S. Gordon Cornelia G. Heid Balazs Hornung Bethan Nichols Jacek K?os Pablo G. Jambrina F.Javier Aoiz 《化学物理学报(中文版)》2020,33(2):217-233
Fully \begin{document}$ \Lambda $\end{document} -doublet resolved differential cross sections and collision-induced rotational alignment moments have been measured for the NO(X)–Xe collision system at a collision energy of 519 cm\begin{document}$ ^{-1} $\end{document} . The experiments combine initial quantum state selection, employing a hexapole inhomogeneous electric field, with quantum state resolved detection, using (1+1\begin{document}$ ' $\end{document} ) resonantly enhanced multiphoton ionization and velocity map ion imaging. The differential cross sections and polarization dependent differential cross sections are shown to agree well with quantum mechanical scattering calculations performed on ab initio potential energy surfaces [J. K?os et al. J. Chem. Phys. 137 , 014312 (2012)]. By comparison with quasi-classical trajectory calculations, quantum mechanical scattering calculations on a hard-shell potential, and kinematic apse model calculations, the effects of the attractive part of the potential on the measured differential cross sections and collision-induced rotational alignment moments are assessed. 相似文献
56.
A complete formulation of a statistical quasiclassical trajectory (SQCT) model is presented in this work along with a detailed comparison with results obtained with the statistical quantum mechanical (SQM) model for the H+ +D2 and H+ +H2 reactions. The basic difference between the SQCT and the SQM models lies in the fact that trajectories instead of wave functions are propagated in the entrance and exit channels. Other than this the two formulations are entirely similar and both comply with the principle of detailed balance and conservation of parity. Reaction probabilities, and integral and differential cross sections (DCS's) for these reactions at different levels of product's state resolution and from various initial states are shown and discussed. The agreement is in most cases excellent and indicates that the effect of tunneling through the centrifugal barrier is negligible. Some differences are found, however, between state resolved observables calculated by the SQCT and the SQM methods which makes use of the centrifugal sudden (coupled states) approximation (SQM-CS). When this approximation is removed and the full close coupling treatment is used in the SQM model (SQM-CC), an almost perfect agreement is achieved. This shows that the SQCT is sensitive enough to show the relatively small inaccuracies resulting from the decoupling inherent to the CS approximation. In addition, the effect of ignoring the parity conservation is thoroughly examined. This effect is in general minor except in particular cases such as the DCS from initial rotational state j=0. It is shown, however, that in order to reproduce the sharp forward and backward peaks the conservation of parity has to be taken into account. 相似文献
57.
Aldegunde J Aoiz FJ González-Sánchez L Jambrina PG de Miranda MP Sáez-Rábanos V 《Physical chemistry chemical physics : PCCP》2012,14(8):2911-2920
Based on quantum mechanical scattering (QM) calculations, we have analyzed the polarization of the product hydrogen molecule in Cl + H(2) (v = 0, j = 0) inelastic collisions. The spatial arrangements adopted by the rotational angular momentum and internuclear axis of the departing molecule have been characterized and used to prove that two distinct mechanisms, corresponding to different dynamical regimes, are responsible for the inelastic collisions. Such mechanisms, named as low-b and high-b, correlate with well defined ranges of impact parameter values, add in an essentially incoherent way, and can be clearly differentiated through the quantum mechanical polarization moment that measures the orientation of the products rotational angular momentum with respect to the scattering plane. Other directional effects turn out to fail when it comes to distinguishing the mechanisms. Quasiclassical trajectories (QCT) calculations have been used as a supplement to the purely quantum mechanical analysis. By combining QM and QCT results, which are in very good agreement, we have succeeded in obtaining a clear and meaningful picture of how the two types of collisions take place. 相似文献
58.
Eyles CJ Brouard M Chadwick H Aoiz FJ Kłos J Gijsbertsen A Zhang X Stolte S 《Physical chemistry chemical physics : PCCP》2012,14(16):5420-5439
The fully Λ-doublet resolved state-to-state differential cross sections (DCSs) for the collisions of NO(X, (2)Π, v = 0, j = 0.5) with Ar have been shown to depend sensitively on the conservation of the total parity of the NO molecular wavefunction. Parity changing collisions exhibit a single maximum only in the DCS, while parity conserving transitions exhibit multiple rainbow peaks. This behaviour is shown to arise directly from the constructive or destructive interference of collisions impacting on the two pointed ends and on the flatter middle of the NO molecule. A simple hard shell, four path model has been employed to determine the relative phase shifts of the paths contributing to the scattering amplitude. The model calculations using the V(sum) potential, together with the results of a quasi-quantum treatment, provide good qualitative agreement with the experimental spin-orbit conserving (Δ? = 0) DCSs, suggesting that the dynamics for all but the lowest Δj transitions are determined largely by the repulsive part of the potential. The collisions leading to spin-orbit changing transitions (Δ? = 1) have been also found to be dominated by repulsive forces, even for the lowest Δj values. However, they are less well reproduced by hard shell calculations, because of the crucial participation of the V(diff) potential in determining the outcome of these collisions. 相似文献
59.
Eyles CJ Brouard M Chadwick H Hornung B Nichols B Yang CH Kłos J Aoiz FJ Gijsbertsen A Wiskerke AE Stolte S 《Physical chemistry chemical physics : PCCP》2012,14(16):5403-5419
Fully Λ-doublet resolved state-to-state differential cross-sections (DCSs) for the collisions of the open-shell NO(X, (2)Π(1/2), ν = 0, j = 0.5) molecule with Ar at a collision energy of 530 cm(-1) are presented. Initial state selection of NO(X, (2)Π(1/2), j = 0.5, f) was performed using a hexapole so that the (low field seeking) parity of ε = -1, corresponding to the f component of the Λ-doublet, could be selected uniquely. Although the Λ-doublet levels lie very close in energy to one another and differ only in their relative parities, they exhibit strikingly different DCSs. Both spin-orbit conserving and spin-orbit changing collisions have been studied, and the previously unobserved structures in the fully quantum state-to-state resolved DCSs are shown to depend sensitively on the change in parity of the wavefunction of the NO molecule on collision. In all cases, the experimental data are shown to be in excellent agreement with rigorous quantum mechanical scattering calculations. 相似文献
60.
N. Balucani P. Casavecchia F. J. Aoiz L. Banares J. F. Castillo V. J. Herrero 《Molecular physics》2013,111(13):1703-1714
This paper describes crossed beam experiments and quasiclassical trajectory (QCT) calculations for the 'insertion' reaction O(1D)+D2 at a collision energy (Ec=25.9 kJ mol-1) much higher than the calculated barrier (~8.4 kJ mol-1) for the competitive 'abstraction' mechanism, which takes place along the excited state potential energy surfaces (PES). Adiabatic QCT calculations were carried out on the ground 11A' and first excited 11A'' PESs developed by Dobbyn and Knowles. Non-adiabatic contributions from the excited 21A' PES to the reaction were considered by means of a trajectory surface hopping method. QCT calculations were also performed at Ec=22.2 kJ mol-1 to compare with previous experimental results. Excellent agreement was found between experiment and QCT predictions at Ec=22.2 kJ mol-1, while at the higher Ec of 25.9 kJ mol-1 only a qualitative agreement was noted. In all cases, the comparison was significantly improved with respect to QCT calculations on a previous version of the ground state PES. 相似文献