1,721,334 research outputs found
Cold collision dynamics of NH radicals
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92746.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 25 april 2012Promotor : Avoird, A. van der Co-promotor : Groenenboom, G.C.131 p
Nuclear motion of Van der Waals and hydrogen bonded systems
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32795.pdf (Publisher’s version ) (Open Access)Van der Waals and hydrogen bonded systems occur in many areas of chemistry, physics, and biology. A thorough understanding of the nature of these interactions can therefore be of great value. Because of the sometimes great complexity involved, experiments and calculations are done on small model systems which are representative for a particular type of interaction. This type of research is at the most fundamental level of understanding. This thesis is devoted to the quantum chemical investigation of several Van der Waals and hydrogen bonded systems consisting of two diatomic molecules, with a focus on the nuclear motion of these systems. The first system studied is the HF dimer, which is treated in Chapters 2 and 3. Bound states and quasi-bound states are calculated and the infrared photodissociation of this dimer is studied, in particular the vibrational predissociation process. In Chapter 4 attention is shifted to the HCl dimer. In a combined theoretical and experimental study, vibrational predissociation of the HCl-HCl complex is studied. Chapters 5 and 6 deal with the CO dimer. New potential energy surfaces are presented, and calculations of the nuclear dynamics on these surfaces show that they are the first potentials that can qualitatively explain the experimentally observed structure.RU Radboud Universiteit Nijmegen, 15 februari 2005Promotor : Avoird, A. van der Co-promotor : Groenenboom, G.C.135 p
Dynamics of open-shell van der Waals complexes
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60679.pdf (Publisher’s version ) (Open Access)This thesis deals with open-shell atom-diatom complexes which are of interest because they can be considered as model systems for complexes of larger open-shell molecules. Intermolecular potential surfaces were computed by means of ab initio electronic structure calculations or taken from the literature. The bound levels of the complex were obtained by solving the Schrödinger equation for the nuclear motion problem. The standard harmonic oscillator approach to solve this problem is not applicable here, because of the large amplitude internal motions in these weakly bound complexes. Instead, the bound levels were obtained by solving a coupled-channel problem in Jacobi coordinates. Photodissociation of complexes, a half-collision, was studied with the aid of full coupled-channel scattering calculations. The two-step procedure to treat the electronic and nuclear motion problems is similar to the Born-Oppenheimer model, but it should be emphasized that the standard Born-Oppenheimer or adiabatic approximation is not valid for these open-shell complexes. The electronic states of the complex become degenerate, i.e., the corresponding adiabatic potential energy surfaces coincide, at linear geometries and for a large distance between the interacting molecules. Non-adiabatic coupling between different electronic states that originates from the nuclear kinetic energy operator becomes important in these regions. A generalized Born-Oppenheimer model was applied that involves the multiple asymptotically degenerate electronic states simultaneously and takes into account the non-adiabatic coupling between these states. This coupling was not explicitly considered, however, but the adiabatic states were transformed into diabatic states that are no longer coupled by the nuclear kinetic energy operator. This approach is briefly explained in Chapter 2 of the thesis. It was applied to several atom-diatom complexes with either the atom or the diatom being an open-shell system in Chapters 3 to 7RU Radboud Universiteit Nijmegen, 17 maart 2004Promotor : Avoird, A. van der Co-promotor : Groenenboom, G.C.161 p
Theoretical study of open-shell van der Waals complexes
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72451.pdf (Publisher’s version ) (Open Access)The present thesis is devoted to a theoretical study of van der Waals open-shell atom-diatom and diatom-diatom complexes occurring in the entrance channels of the hydrogen transfer chemical reactions. The study of the Cl-HF and Br-HCN systems can be split into two main parts. The first part concerns ab initio electronic structure calculations for potential energy surfaces and the analytic fit of these potentials. The second part consists of dynamics (bound state) calculations with the fitted potentials. For OH-HCl a dynamics study has been carried out using potential energy surfaces obtained earlier by another authors. For the Cl-HF and Br-HCN systems we have employed various dynamical models (1D, 2+1D, and 3D), for OH-HCl we have used 3+1D and 4D models; all of these are explained and compared in the corresponding chapters. From the dynamics calculations we have derived spectroscopic parameters, such as bend and stretch frequencies, red shifts, and Renner-Teller effects. The theoretical data were compared with available experimental results and found to agree well.Radboud Universiteit Nijmegen, 10 november 2008Promotor : Avoird, A. van der157 p
Photoinduced dynamics in OH, H2, and N2O
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71907.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 26 mei 2008Promotor : Avoird, A. van derVIII, p
Ab Initio Study of Inelastic Collision. Processes for Astronomical Applications
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155534.pdf (Publisher’s version ) (Open Access)This thesis is devoted to a quantum mechanical study of inelastic collision processes for astronomical applications. We were interested, in particular, in the scattering of CO with its collision partners in space, such as H, He and H2. The main goal of the work was to provide state-to-state rate coefficients for pure rotational and ro-vibrational transitions of CO induced by inelastic collisions with H atoms. The calculated results were imported into the Leiden Atomic and Molecular Database (LAMDA) in use for current and future astrophysical modeling. Furthermore, we investigated He-CO, H2-CO and Ar-CO collisions. For those systems, differential cross sections and/or polarization dependent differential cross sections were calculated at the collision energies corresponding to the measurements of our experimental collaborators in this work. Our results, in comparison with the data from molecular beam experiments, allowed us to check the accuracy of the ab initio intermolecular interaction potentials used in our studies and to obtain detailed information on the dynamics of the collision processes.Radboud Universiteit Nijmegen, 03 maart 2016Promotores : Groenenboom, G.C., Avoird, A. van der168 p
Collision-induced absorption by oxygen and nitrogen molecules
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190319.pdf (Publisher’s version ) (Open Access)Radboud University, 06 april 2018Promotores : Groenenboom, G.C., Avoird, A. van derxiv, 268 p
Ab initio calculations of Van der Waals interactions between molecules
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Some model calculations for adsorption on transition metals
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7057.pdf (Publisher’s version ) (Open Access
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