Valence electronic structure and photofragmentation of 1,1,1,2-tetrafluoroethane (CF3-CH2F)

The electronic structure and fragmentation of the hydrofluorocarbon compound 1,1,1,2-tetrafluoroethane (CF3-CH2F) were studied using spectroscopical methods and quantum chemical calculations. Valence photoelectron spectra and the ionic fragmentation products were recorded with synchrotron radiation in the vacuum ultraviolet (VUV) region. The geometric and electronic structures of the CF3-CH2F molecule were calculated using the complete active space perturbation theory of second order. The calculated vertical ionization energies were used to interpret the experimental photoelectron spectrum. VUV photodissociation of the sample molecule was studied with photoelectron-photoion coincidence spectroscopy. Coincident ion yields are shown for several cations as a function of electron binding energy. The experimental data are discussed in comparison with theory and previous work

Synchronizing gas injections and time-resolved data acquisition for perturbation-enhanced APXPS experiments

An experimental approach is described in which well-defined perturbations of the gas feed into an Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS) cell are fully synchronized with the time-resolved x-ray photoelectron spectroscopy data acquisition. These experiments unlock new possibilities for investigating the properties of materials and chemical reactions mediated by their surfaces, such as those in heterogeneous catalysis, surface science, and coating/deposition applications. Implementation of this approach, which is termed perturbation-enhanced APXPS, at the SPECIES beamline of MAX IV Laboratory is discussed along with several experimental examples including individual pulses of N-2 gas over a Au foil, a multi-pulse titration of oxygen vacancies in a pre-reduced TiO2 single crystal with O-2 gas, and a sequence of alternating precursor pulses for atomic layer deposition of TiO2 on a silicon wafer substrate.Peer reviewe

Instrumentation for spectroscopy and experimental studies of some atoms, molecules and clusters

Abstract Experimental synchrotron radiation induced electron- and ion spectroscopies together with electron-ion and ion-ion coincidence techniques as well as electron energy loss spectroscopy have been used to study the electronic properties of several vapor phase samples. In this thesis studies of the electronic structure and fragmentation of Sb4 clusters, photo- and Auger electron spectroscopy of atomic Si and Pb as well as ultra high resolution VUV absorption of vapor phase KF molecules have been performed. The instrumentation and techniques used in the studies, especially the electron energy loss apparatus and the newly built ultra high resolution FINEST beamline branch, are presented

Special Issue “Advanced Spectroscopy Techniques in Food Analysis: Qualitative and Quantitative Chemometric Approaches”

The globalization of the food market has created a pressing need for food producers to meet the ever-increasing demands of consumers while ensuring adherence to stringent food safety and quality standards [...

Distorted angular distribution of the 2p photoelectrons in argon

Two consecutive hemispherical electron energy analyzers have been used to measure the argon angular distribution of 2p photoelectron lines over two quadrants of the dipole plane. A significant anomaly in the intensity of the photolines is observed at several electron emission angles, suggesting asymmetry with respect to the electric field vector of synchrotron light. As a possible cause for the observed behavior, we consider an external field affecting the photoelectrons, and show that it is capable of breaking the left-right asymmetry of the angular distribution, giving rise qualitatively to the observed behavior

Behavior of relative state selective photoionization cross sections of RbBr molecules in the valence region

The photon energy dependence of relative photoionization cross sections in the valence ionization energy region of 5 to 45 eV for 4p and 4s orbitals of Rb and Br ions in RbBr vapors has been investigated. The behavior of state selective cross sections of molecular valence orbitals has been analyzed by comparing the observed 4p to 4s photoelectron intensity branching ratios with atomic state selective photoionization cross sections of Kr, taking into account the mixing between Br 4s(-1) and Rb 4p(-1) molecular states. Using atomic dipole matrix elements to calculate the photoionization intensity of alkali halides has been suggested

3d photoionization and subsequent decay of atomic gallium

We present an experimental and theoretical study of 3d photoionization and subsequent Auger decay of atomic gallium. The synchrotron radiation-induced electron spectra have been compared and analysed using multiconfiguration Dirac-Fock calculations. It has been shown that the theoretically predicted photoelectron spectrum is in rather good agreement with the experiment allowing us to identify the main spectral features. However, prediction of the Auger decay intensities fails due to calculational difficulties for the continuum wavefunctions of very low kinetic energy Auger electrons

Dissociation of As-4 clusters following valence photoionization and 3d core excitation

The VUV-induced photofragmentation of As-4 clusters was studied using photoelectron-photoion-coincidence (PEPICO) spectroscopy. The fragmentation pathways subsequent to outer and inner valence photoionization and resonant photoexcitation were studied by examining the cationic production as a function of electron energy. In addition, regular photoelectron spectroscopy and partial ion yield absorption spectroscopy were employed. In order to enhance the weak signal from the inner valence states, resonant core 3d excitation was used in the PEPICO experiment. The fragmentation pathways were inspected with the aid of ab initio and thermochemical calculations. The many-electron effects were found to play a major role in the observed inner valence structure and resulting photofragmentation