Photoelectron Spectroscopic And Infrared Pre-Dissociation Spectroscopic Studies On Mass-selected Ions In The Gas Phase

The spectra structures, bonding and reactivities of ions are of fundamental importance and have been the subjects of considerate investigations. In this thesis, photoelectron spectroscopy is employed to study the electronic structures of selected ions. In addition, an infrared predissociation spectroscopy apparatus is designed and constructed, which is suitable for investigating the vibrational structures of selected ions in the gas phase.Photoelectron imaging is one kind of photoelectron spectroscopy which is a powerful experimental technique to obtain the electronic structure of molecules. The photoelectron images of Ag-(H2O)x(x=1,2), AgOH-(H2O)y(y=0-4), Ag-(CH3OH)z (z=1,2) and AgOCH3- are reported. The photoelectron spectra of Ag-(H2O)x, AgOH-(H2O)y and Ag-(CH3OH)z show a gradual increase in adiabatic detachment energy (ADE) and vertical detachment energy (VDE) with increasing solvent molecular number due to the solvent stabilization. The increased spectral width is owing to the large anion-neutral geometry changes upon electron detachment and the coexistence of multiple low-lying isomers. The Ag-(H2O)x(x=1,2) and Ag-(CH3OH)z(z=1,2) anions can be characterized as metal atomic anion solvated by solvent molecules with the electron mainly localized on the metal. The vibrationally well-resolved photoelectron spectra allow the adiabatic detachment energy (ADE) and vertical detachment energy (VDE) of AgOH- and AgOCH3- to be determined as 1.18(2) and 1.24(2) eV,1.29(2) and 1.34(2) eV, respectively. The Ag- atomic anion interacts more strongly with H2O molecules than the CH3OH. The solvated Ag- anions exhibit surface solvation. In the global minimum structures of Ag-(H2O)2 and Ag-(CH3OH)2, the ionic hydrogen bond (IHB) formed between Ag- and solvent molecule is cooperatively enhanced by the traditional hydrogen bond between the two solvent molecules.The photoelectron imaging studies on lanthanide oxides are also reported. The well resolved photoelectron spectra allow the electron affinities (EAs) of lanthanide monoxides to be determined as 0.99(1) eV for LaO,1.00(1) eV for CeO,1.00(1) eV for PrO,1.01(1) eV for NdO, and 1.37(2)eV for HoO. Density functional (DF) calculations and natural atomic orbital (NAO) analyses show that the 4f electrons tend to be localized and suffer little from the charge states of the molecules. The extra charge mainly resides in the 6s orbital of the metals in the lanthanide monoxides anions. Ln2O1/2-(Ln=La, Ce, Pr, Nd, Ho) have similar adiabatic detachment energies (ADEs) and vertical detachment energies (VDEs). It is interesting to know that the ADEs and VDEs of Ln2O- are larger than those of Ln2O2-, respectively. The studies on PrxOy- and HoxOy-(x, y=1,2,3) also reveal interesting relationships between the ADEs (VDEs) and the relativistic and electron correlation effects.Infrared predissociation spectroscopy is one of the most important methods in probing vibrational spectra of ions. This method is very sensitive and is a convenient experimental approach to work with a molecular beam of mass selected ions in the gas phase which can not be studied by the conventional absorption spectroscopy. An infrared photodissociation spectrometer, in combination with a Wiley-McLaren time-of-flight mass analyzer and a laser vaporization source, is designed and constructed. The laser vaporization source is used to generate ions and clusters. The infrared photodissociation spectrometer adopts a single-field deceleration together with single-field acceleration configuration. The performance of the apparatus is demonstrated on the infrared predissociation spectra of Al+(CO2)5 and Al+(CO2)6, which are comparable to the results using a reflection time-of-flight mass spectrometer configuration. Preliminary results suggest that this apparatus is a powerful tool to get the vibrational information of the ions and clusters.