Photoelectron spectroscopy of GdO^{-} (original) (raw)
Related papers
2020
Photoelectron spectra of Gd2O2− obtained with photon energies from 2.033 eV to 3.495 eV exhibit numerous close-lying neutral states with photon-energy-dependent relative intensities. Transitions to states falling within the electron binding energy window of 0.9 and 1.6 eV are attributed to one- or two-electron transitions to the ground and low-lying excited neutral states. An additional, manifold of electronic states observed in the 2.1 to 2.8 eV window cannot be assigned to any simple one-electron transitions. Because of the relatively simple electronic structure from the half-filled 4f7 subshell occupancy in Gd2O2–, the numerous transitions observed in the spectra are fairly well-resolved, allowing a detailed view of the changes in relative intensities of individual transitions with photon energy. With supporting calculations on the numerous close-lying electronic states, we suggest a description of strong photoelectron-valence electron interactions that result in the photon-energ...
Physical Review B, 2005
The energy levels of lanthanide ions have been studied in great detail in the energy range up to 40 000 cm−1 (250 nm). Recently an increased interest in the high energy levels between 40 000 and 70 000 cm−1 has emerged, partly triggered by the need for new luminescent materials for vacuum ultraviolet (VUV) excitation. Using synchrotron radiation many new energy levels have been discovered for various lanthanide ions. However, the spectral resolution of a synchrotron is limited and to resolve the complete energy level structure higher resolution tunable lasers are required. Unfortunately no high-resolution tunable lasers are available in the VUV. To overcome this problem two-photon spectroscopy may be applied. In this paper resonant two-photon spectroscopy is applied to measure the energy level structure of Gd3+ in fluorides. Excited state excitation (ESE) from the 6P7∕2 level is shown to provide high-resolution spectra of the high energy levels of Gd3+. The extension of the energy level structure is used to improve energy level calculations, which is especially beneficial for Gd3+ where only a limited number of energy levels is available from conventional laser spectroscopy.
Physica B: Condensed Matter, 2003
It was recently discovered that in irradiated germanium doped with oxygen a local vibrational mode occurs at 669 cm À1 which could be ascribed to the negatively charged oxygen-vacancy (VO À) complex. In the 669 cm À1 band and in another band at 731 cm À1 due to a different defect, fine structure which indicated the occurrence of the Ge-isotope splitting of the modes could be partly resolved. We report here the results of high-resolution infrared measurements (res.=0.02 cm À1) at liquid helium temperatures of the two bands. The oxygen-doped germanium ([O i ]=2.7 Â 10 17 cm À3) was first irradiated with 2 MeV electrons to increase the concentration of VO complexes. A second similar specimen received the same treatment but with subsequent anneals to obtain the 731 cm À1 band. The experimentally observed splitting of the 669 cm À1 band and the amplitudes of its individual components are accurately predicted using a model of a non-linear symmetric Ge-O-Ge molecule within a Ge crystal lattice, in agreement with the assignment of the mode to the VO À complex. A similar model also seems to apply to the yet unassigned 731 cm À1 mode and the conclusion is made that the defect also must include a single O atom bonded to two equivalent Ge atoms. The higher annealing temperature of the unassigned band however indicates that the defect must be more complex than the VO center.
Probing vacuum ultraviolet energy levels of trivalent gadolinium by two-photon spectroscopy
Journal of Luminescence, 2003
The energy levels of lanthanide ions have been studied in great detail in the energy range up to 40 000 cm À1 (250 nm). Recently, an increased interest in the high-energy levels between 40 000 and 70 000 cm À1 has emerged, partly triggered by the need for new luminescent materials for vacuum ultraviolet (VUV) excitation. Using synchrotron radiation many new energy levels have been discovered for many lanthanide ions. However, the spectral resolution of a synchrotron is limited and to resolve the complete energy level structure higher-resolution tunable lasers are required. Unfortunately no tunable lasers are available in the VUV. To overcome this problem two-photon spectroscopy may be applied. In this contribution the use of resonant and non-resonant two-photon spectroscopy is applied to measure the energy level structure of Gd 3+ in fluorides. Non-resonant two-photon excitation and resonant excited state absorption from the 6 P 7/2 level is shown to provide high-resolution spectra of the high-energy levels of Gd 3+. The extension of the energy level structure may be beneficial for energy level calculations, especially for Gd 3+ where only a limited number of energy levels is available from conventional laser spectroscopy.
Molecular Photodetachment Spectrometry. II. The Electron Affinity ofO2and the Structure ofO2−
Physical Review A
A beam of 02 ions, extracted from a glow discharge in N20, is crossed with the linearly polarized intracavity photon beam of an argon-ion laser (4880 A). Electrons photodetached at right angles to the crossed beams are energy filtered by a hemispherical analyzer. The electron energy spectra are characteristic of photodetachment from the v' =0 state of 02 to the X Z~a nd a A~s tates of 02. Vibrational state analysis is facilitated by the use of isotopes. The electron affinity obtained is 0.440 + 0. 008 eV. Additionally, we have measured the relative transition probabilities as a function of final vibrational state and the angular distributions of the outgoing electrons. The relative intensities, corrected by the angular distributions, determine through Franck-Condon-factor analysis the internuclear distance for the negative ion. We find r~" =1.341 + 0.010 A and therefore B~"=1.17 + 0.02 cm~.
Ab-Initio Studies of Electronic and Spectroscopic Properties of MgO, ZnO and CdO
Journal of the Korean Physical Society, 2008
We present ab-initio calculations of excited-state properties within single-particle and two-particle approaches in comparison with corresponding experimental results. For the theoretical treatment of the electronic structure, we compute eigenvalues and eigenfunctions by using a spatially nonlocal exchange-correlation potential. From this starting point, quasiparticle energies within the fully frequency-dependent G0W0 approximation are obtained. By solving the Bethe-Salpeter equation, we evaluate optical properties, including the electron-hole attraction and the local-field effects. The results are compared with experimental spectra from soft X-ray emission, as well as from X-ray photoelectron spectroscopy or ellipsometry measurements. In more detail, we compute the valenceband densities of states, bound excitons, and the dielectric function. For the latter, we discuss both the absorption edge and higher critical points.
Physical Review A, 2010
The photodetachment dynamics of the atomic oxygen anion O − has been investigated at 266 nm (4.67 eV) by photoelectron detection in a crossed-beam experiment using a magnetic-bottle electron spectrometer. Taking explicit advantage of the Doppler shift imposed by the moving ion beam on the photoelectron energies, we report both the final-state branching ratio and photoelectron angular distributions. After photoabsorption at 266 nm, the formed electron-oxygen scattering state disintegrates, forming either the excited 1 D or the ground 3 P state of oxygen with a partition of 1 D: 3 P = 0.32 ± 0.06. The detachment leading to the production of O(3 P) shows an angular distribution of photoelectrons characterized by β P = 0.00 ± 0.10 mimicking a pure s-wave detachment, while the detachment into excited O(1 D) occurs with β D = −0.90 ± 0.10, giving direct evidence of interference between the outgoing s and d waves.
Photoelectron Spectroscopy of SO 3 - at 355 and 266 nm
Journal of Physical Chemistry A, 2000
Photoelectron spectra of SO 3were recorded at 266 and 355 nm to study photodetachment of the SO 3anion ( 2 A 1 ) to the ground state of neutral SO 3 ( 1 A′ 1 ). A long vibrational progression in the 355 nm spectrum is attributed to excitation of the umbrella mode, ν 2 , consistent with predictions that C 3V symmetry SO 3yields D 3h symmetry SO 3 upon photodetachment. At 266 nm, photodissociation of SO 3to SO 2 + Owas also observed. The geometry and normal-mode frequencies of SO 3and SO 3 as well as the adiabatic electron affinity (AEA) and vertical detachment energy (VDE) of SO 3 have also been calculated with ab initio (MP2 and CCSD(T)) and DFT methods. Using theoretical predictions and experimental data, Franck-Condon simulations of the photoelectron spectra were found to be in good agreement with experiment. The calculated AEA agreed well with experiment, but the VDE was found to be less accurate, presumably because of the large geometry change between anion and neutral.
Physical Review B, 2009
The valence-band density of states of single-crystalline rock-salt CdO͑001͒, wurtzite c-plane ZnO, and rocksalt MgO͑001͒ are investigated by high-resolution x-ray photoemission spectroscopy. A classic two-peak structure is observed in the VB-DOS due to the anion 2p-dominated valence bands. Good agreement is found between the experimental results and quasi-particle-corrected density-functional theory calculations. Occupied shallow semicore d levels are observed in CdO and ZnO. While these exhibit similar spectral features to the calculations, they occur at slightly higher binding energies, determined as 8.8 eV and 7.3 eV below the valence band maximum in CdO and ZnO, respectively. The implications of these on the electronic structure are discussed.
The electronic structure of "-Ga 2 O 3
The electronic structure of "-Ga 2 O 3 thin films has been investigated by ab initio calculations and photoemission spectroscopy with UV, soft, and hard X-rays to probe the surface and bulk properties. The latter measurements reveal a peculiar satellite structure in the Ga 2p core level spectrum, absent at the surface, and a core-level broadening that can be attributed to photoelectron recoil. The photoemission experiments indicate that the energy separation between the valence band and the Fermi level is about 4.4 eV, a valence band maximum at the point and an effective mass of the highest lying bands of -4.2 free electron masses. The value of the bandgap compares well with that obtained by optical experiments and with that obtained by calculations performed using a hybrid density-functional, which also reproduce well the dispersion and density of states.