Debugging Of Atomic And Molecular Physics Beamline And Endstation And Experimental And Theoretical Study Of Some Molecules And Clusters

The dissertation includes two parts: The first part is the debugging of atomic and molecular physics beamline and endstation and the experimental study of some molecules. The second one is the experimental and theoretical study of van der Waals clusters.Part 1: Debugging of Atomic and Molecular Physics Beamline and Endstation and the Experimental Study of Some MoleculesIn the first chapter, a summary is given on the development and characteristics of synchrotron radiation. At the same time, a brief introduction is supplied about the application of synchrotron radiation in a variety of research fields. For the view of emphasis, it is reviewed that the application of synchrotron radiation in atomic and molecular physics with VUV light. The basic conceptions, including adiabatic ionization energy, vertical ionization energy, superexcited states, photoionization cross section, Rydberg state of atomic and molecular, dissociation and predissociation are discussed in detail. The common experimental methods, such as phoionization mass spectrometry, fluorescence spectrum, photoabsorption spectrum, photoelectron spectrum and coincidence technology are also introduced in this chapter.In the second chapter, an introduction is given about the debugging process and results of the atomic and molecular physics beamline and endstation of National Synchrotron Radiation Laboratory in the Phase II projects. The beamline consists of a spherical grating monochromator with two including angles, a pre-focusing mirror system and a post-focussing system. Firstly, a brief description is given on the optical alignment. A concrete introduction is given about the installation of every optical element. The beamline can provide the tunable VUV light in the energy range of 7.5-124eV. The methods of beamline's detection and confirming the zero order's position of gratings are given. For three gratings, energy calibration is done, and the energy resolving power and the reproducibility precision error is tested using the special peaks of some atoms and molecules. The photon flux is greater than 10 photons s^-1. The beam spot size at the sample is less than 0.5×0.8mm². In addition, the detailed introduction is given on the endstation of atomic and molecular physics. The formative mechanism of molecular beam is discussed. The theory of time of flight mass spectrometry and multi-photoionization chamber are also discussed in this chapter. Last, the method of data acquisition is described. By the spectra calibration of this beamline, the results indicate that this beamline and endstation have the good performances.In the third chapter, the photoabsorption of NO, CO, acetonitrile, acrylonitrile, benzene and toluene of benzene series have been measured by using a homemade experimental apparatus of cylindrical multi-stage ion chamber with high flux SR source. The ionization energies of some electron states are given. Their superexcited states, autoionization Rydberg states have been analyzed. By the analysis and comparison, our results are accurate and credibility. Some results are first obtained by using a cylindrical multi-stage ion chamber. These researches can supply the data for foundational study, and are of a definite importance for foundational study of application and the protection of atmosphere and entironment.Part 2: Experimental and Theoretical Study of van der Waals ClustersIn the first chapter, an introduction is given on the definition of cluster, the development of cluster research and the present status of cluster science. The experimental techniques and methods of neutral and ionic cluster are discussed. The review is given about the several typical technique of ionic complex, such as flow technique, static gas technique, beam technique and trap-ion technique. The foundational knowledge with respect to cluster is introduced, for example, bind energy, entropy value of associated reaction, classification of intermolecular weak interaction and magic number. Last, the introduction is done about the diversified method of theory. The detailed description is made for basis-set choice, basis-set superposition error, structural optimization and frequency calculation. These methods are specially introduced about the natural bond analysis, the atoms in molecules, GAUSSIAN-2.Some experimental and theoretical results of van der Waals clusters are given in the second chapter. They include:1. A supersonic beam of NO molecule mixed with Ar atom is ionized by VUV synchrotron radiation from Hefei Light Source(HLS) at National Synchrotron Radiation Laboratory (NSRL). Photoionization efficiency spectroscopy (PIES) is first measured for NO, Ar and heterogeneous clusters NO·Ar. In PIES of NO·Ar, a strong resonance peak at the positions of the atomic rare gas resonance lines (11.5—12.0 eV) is observed, and it is shown that the excitation energy of the rare gas atom is transferred to the attached NO molecule within a heterogeneous cluster, leading to ionization of the molecule NO.2. Rg·NO cluster is one of the important prototypes for the study of molecular clusters. Among the different theoretical levels and basis sets of quantum chemistry calculation, the theoretical level CCSD(T) and the basis set cc-PVDZ is selected to calculate the equilibrium geometries and harmonic vibrational frequencies of Rg·NO and Rg·NO⁺(Rg=He, Ne, Ar and Kr)clusters. It is indicated that the geometry of Rg·NO cluster is a skewed T-shape, with the Rg atom located on the nitrogen side of the NO molecule, and the Rg—N—O bond angle augments with the increasing mass of Rg atoms. The ionization energies of Rg·NO and the dissociation energies of Rg·NO⁺ are calculated using G2 method. Some ionization energies are firstly obtained. We firstly found that with the increasing polarizability of the Rg atoms, the ionization energies decrease linearly from 9.265eV for He·NO to 9.132eV for Kr·NO, while the dissociation energies increase from 0.017eV for He·NO⁺ to 0.156eV for Kr·NO⁺ in linearly. The AIM and NBO analyses are also performed using the geometry from optimization. On the basis of the AIM topological analysis, we firstly get the bond critical points of complexes, the electron density of bond and the corresponding Laplacian value. According to the NBO analysis, occupation numbers of some important orbits, the charge transfer between orbits and second order perturbation energies are also obtained.3. The geometric structure and interaction energies of Ar·CO and Ar·CO⁺ complexes are calculated with cc-pVTZ basis set at QCISD level of theory. The electron density and Laplacian value at the bond critical point are first analyzed using the AIM and NBO theory. From these analyses, we can obtain the occupation numbers of some important orbits, charge transfer and second order perturbation energies between orbits. The geometric structure and vibrational frequencies of Rg·CO and Rg·CO⁺ complexes are calculated with QCISD/cc-pVTZ method. The bind energies and ionization energies of Rg·CO complexes and dissociation energies of Rg·CO⁺ complexes are calculated using the G2 method. Some ionization energies, dissociation energies and bind energies are first obtained. From the results, we deduce some rules. These theoretical results are in agreement with the ones of present experiments. However, because of the scare experimental datum presently, the farther experimental researches must be performed for these typical systems.