Experimental And Theoretical Studies On The Photoionization Of Clusters With Rare-gas Atom And Diatomic Molecule

The dissertation mainly introduces the experimental and theoretical studies on the van der Waals cluster of rare gas atom Rg(Rg=Ne,Ar,Kr)and diatomic molecules(CO, NO)with tunable synchrotron VUV photoionization.It also introduces the installation and debugging of the absorption gas cell of atomic and molecular physics beamline and endstation,and the experimental and theoretical studies on ethylbenzene.In the first chapter,it firstly introduces the researches on atom,molecule and cluster of spectroscopy and dynamics.The basic conceptions on photoionization and photodissociation,including adiabatic ionization energy,vertical ionization energy, photoionization,superexcited states,Rydberg states and the fundamental photodissociation mechanism.The common experimental methods,such as photoionization mass spectrometry,fluorescence spectrum,photoabsorption spectrum, photoelectron spectrum,threshold photoelectron spectrum and coincidence technology are also introduced in the third section.Finally,the theoretical calculation methods involved in photoionization are described.In the second chapter,a summary is given on the characteristics and applications of synchrotron radiation,the parameters of storage ring of National Synchrotron Radiation Laboratory(NSRL).It introduces the structure of the atomic and molecular physics beamline and endstation.The undulator beamline can provide the tunable VUV light in the energy range of 7.5-124 eV.Finally,the formation principle of molecular beam,the operating principle of mass spectrometer and pohotoabsorption chamber are described.In the third chapter,an introduction is given about the installation and testing of the gas filter.Higher harmonics present in the undulator spectrum can decrease the data reliability.It introduces several methods of suppressing higher harmonics and the advantages of gas filter.It introduces the structure of gas filter.The two differential pumping regions in addition to the gas cell are its vacuum components to adapt the limited room of beamline.The aperture tubes are special designed to suppress molecular beam.We tested the vacuum and the performance of the harmonic suppressor of gas filter, and the results indicate that this gas filter has the good performances. In the forth chapter,an introduction is given on the content and research of gas cluster:1.The development of cluster science,2.the principium and experimental techniques to compose cluster,3.classification of intermolecular weak interaction,4. several spectroscopys of research cluster,especially mass spectroscopy.In the fifth and sixth chapters,the heterogeneous clusters(Rg·CO,Rg·NO)of rare gas(Rg=Ne,Ar,Kr)and diatomic molecule(CO,NO)is experimentally and theoretically studied with tunable synchrotron VUV Photoionization.They are one of the important prototypes for the study of molecular clusters.In the fifth chapter,the introduction of the present status and experimental methods of Rg·CO clusters research is given.The ionization energies are determined by measuring their photoionization efficiency curves,and are in agree with the ones of the theoretical results.The structures of photoionization efficiency curves are discerned by the results of photoabsorption spectroscopy of CO.The clusters are,calculated and discussed with theoretical methods,and the geometric structures,vibrational frequencies,ionization energies and dissociation energies are calculated.Since the ionization energy of Kr atom is almost agree with CO Molecule,the photoionization efficiency curve of Kr·CO is affected by both Kr atom and CO Molecule,and discerned by the results of photoabsorption spectroscopy of CO and photoionization efficiency spectroscopy of Kr. It is found with the increasing mass of Rg atom,the Rg-C-O bond angle increases,and the ionization energies of Rg·CO decrease.In the sixth chapter,the introduction of the present status and experimental methods of Rg·NO clusters research is given.The photoionization mass spectroscopy and photoionization efficiency spectroscopy of Rg·NO are measured,together with the photoabsorption spectroscopy of NO.Rg·NO clusters and its ions are discussed on the geometric structure,vibrational frequencies,ionization energies,dissociation energies and interaction of Rg·NO with theoretical methods.Photoionization efficiency curve of Ar·NO is mainly determined by NO below the ionization energy of Ar.There's a strong resonance peak at the positions of 12.0 eV is observed in PIES of Ar·NO,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.It is found with the increasing mass of Rg atom,the polarizability,Rg-C-O bond angle,the distance and the interaction of Rg and CO increases,as the ionization energies of Rg·CO decrease. In the seventh chapter,the photoionization mass spectroscopy and photoionization efficiency spectroscopy of Kr and Kr₂ have been obtained using supersonic molecule beam,synchrotron radiation and reflection time of flight mass spectroscopy,and the ionization energies of Kr and Kr₂ were determined from their PIES.The geometries, harmonic vibrational frequencies,and ionization energies of Kr₂ have also been calculated using MP2(Full)/6-31G*,QCISD/cc-pVTZ and B3LYP/6-31G.When the same level of theory is used,the structure and ionization energy are nearly unchanged,and the vibrational frequency is decreased gradually with increasing of m/z of Kr isotope.At the same time,the ionization energies of Kr(84)and Kr₂(168)were calculated using G2 method.The theoretical values of the ionization energy are in agreement with those experimental ones.In the eighth chapter,ethylbenzene has been messured with photoabsorption spectroscopy and the photoionization efficiency spectroscopy,and its main fragmented ion- C₇H₇⁺ with PIES.The ionization energy of ehylbenzene and the appearance potential of C₇H₇⁺ are measured,and the dissociation energy of C₇H₇⁺ iS calculated with empirical correlation.These energies are calculated by Gaussian program with the MP2 method, The theoretical results are reasonable according to the experimental results.