Publications (113) View all
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Article: Rotational alignment effects in NO(X) + Ar inelastic collisions: A theoretical study.
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ABSTRACT: Rotational angular momentum alignment effects in the rotational inelastic scattering of NO(X) with Ar have been investigated by means of close-coupled quantum mechanical, quasi-classical trajectory, and Monte Carlo hard shell scattering calculations. It has been shown that the hard shell nature of the interaction potential at a collision energy of Ecoll = 66 meV is primarily responsible for the rotational alignment of the NO(X) molecule after collision. By contrast, the alternating trend in the quantum mechanical parity resolved alignment parameters with change in rotational state Δj reflects differences in the differential cross sections for NO(X) parity conserving and changing collisions, rather than an underlying difference in the collision induced rotational alignment. This suggests that the rotational alignment and the differential cross sections are sensitive to rather different aspects of the scattering dynamics. The applicability of the kinematic apse model has also been tested and found to be in excellent agreement with exact quantum mechanical scattering theory provided the collision energy is in reasonable excess of the well depth of the NO(X)-Ar potential energy surface.The Journal of chemical physics 03/2013; 138(10):104309. · 3.09 Impact Factor -
Article: Rotational alignment effects in NO(X) + Ar inelastic collisions: An experimental study.
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ABSTRACT: Rotational angular momentum alignment effects in the rotationally inelastic collisions of NO(X) with Ar have been investigated at a collision energy of 66 meV by means of hexapole electric field initial state selection coupled with velocity-map ion imaging final state detection. The fully quantum state resolved second rank renormalized polarization dependent differential cross sections determined experimentally are reported for a selection of spin-orbit conserving and changing transitions for the first time. The results are compared with the findings of previous theoretical investigations, and in particular with the results of exact quantum mechanical scattering calculations. The agreement between experiment and theory is generally found to be good throughout the entire scattering angle range. The results reveal that the hard shell nature of the interaction potential is predominantly responsible for the rotational alignment of the NO(X) upon collision with Ar.The Journal of chemical physics 03/2013; 138(10):104310. · 3.09 Impact Factor -
Article: Quantum decoherence mechanism in atom-molecule - collisions: NO+Ar case study
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ABSTRACT: In modern physics, quantum decoherence, a subject still under debate, is viewed as the mechanism responsible for the quantum -to-classical transition as the initially prepared quantum state interacts with its environment in an irreversible manner. As expected, one of the most common mechanisms responsible of the macroscopically observed decoherence involves collisions of an atom or molecule, initially prepared in a coherent superposition of states, with gas particles. In this work, a coherent superposition of quantum internal states of NO molecules is prepared by the interaction between the molecule with both a static and a radiofrequency electric field. Subsequently, NO+Ar collision decoherence experiments, are investigated by measuring the loss of coherence as a function of the number of collisions. Data analysis in the light of the interaction potential of the collisional partners allowed us to unravel the molecular mechanisms responsible for the loss of coherence in the prepared NO quantum superposition of internal states. The relevance of the present work relies on several aspects. On the one hand, the use of radio-waves introduces a new way for the production of coherent beams. On the other hand, the employed methodology, when satisfactorily applied to more collision systems, could be useful in designing experiments to reduce the environmental decoherence rate to levels necessary for quantum information processes.AIP Conference Proceedings 11/2012; 1501:1324-1329. -
Article: The effect of parity conservation on the spin-orbit conserving and spin-orbit changing differential cross sections for the inelastic scattering of NO(X) by Ar.
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ABSTRACT: 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 (ΔΩ = 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 (ΔΩ = 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.Physical Chemistry Chemical Physics 03/2012; 14(16):5420-39. · 3.57 Impact Factor -
Article: Fully Λ-doublet resolved state-to-state differential cross-sections for the inelastic scattering of NO(X) with Ar.
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ABSTRACT: 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.Physical Chemistry Chemical Physics 03/2012; 14(16):5403-19. · 3.57 Impact Factor
