Showing papers on "Photoemission spectroscopy published in 1993"
TL;DR: The generalization of the local-density-approximation method for the systems with strong Coulomb correlations is proposed, which restores the discontinuity in the one-electron potential as in the exact density functional.
Abstract: The generalization of the local-density-approximation method for the systems with strong Coulomb correlations is proposed, which restores the discontinuity in the one-electron potential as in the exact density functional. The method is based on the model-Hamiltonian approach and allows us to take into account the nonsphericity of the Coulomb and exchange interactions. The calculation scheme could be regarded as a first-principle method due to the absence of adjustable parameters. The method was applied to the calculation of the photoemission (x-ray photoemission spectroscopy) and bremsstrahlung isochromat spectra of NiO.
1,860 citations
TL;DR: The 266 nm photoelectron spectra of cyanide, NCO−, and NCS− have been recorded with a pulsed time-of-flight photo-electron (POF) spectrometer.
Abstract: The 266 nm photoelectron spectra of CN−, NCO−, and NCS− have been recorded with a pulsed time‐of‐flight photoelectron spectrometer The photoelectron spectrum of CN− has also been recorded at 213 nm revealing transitions to the A 2Π state as well as the ground X 2Σ+ state of the CN radical The following adiabatic electron affinities (EAs) are determined: EA(CN)=3862±0004 eV, EA(NCO)=3609±0005 eV, and EA(NCS)=3537±0005 eV The adiabatic electron affinity of cyanide is in disagreement with the currently accepted literature value Our measurement of the electron affinity of NCS confirms recent theoretical estimates that dispute the literature experimental value By Franck–Condon analysis of the vibrational progressions observed in each spectrum, the change in bond lengths between anion and neutral are also determined For NCO− this yields R0(C–N)=117±001 A and R0(C–O)=126±001 A, and for CN− the equilibrium bond length is found to be Re(C–N)=1177±0004 A The gas phase fundamental for CN− is deter
257 citations
TL;DR: The detailed agreement that is obtained between this fully ab initio theory and experiment is unprecedented for the F + H2 reaction and suggests that the transition state region of the F - H2 potential energy surface has finally been understood quantitatively.
Abstract: The transition state region of the F + H(2) reaction has been studied by photoelectron spectroscopy of FH(2)(-). New para and normal FH(2)(-)photoelectron spectra have been measured in refined experiments and are compared here with exact three-dimensional quantum reactive scattering simulations that use an accurate new ab initio potential energy surface for F + H(2). The detailed agreement that is obtained between this fully ab initio theory and experiment is unprecedented for the F + H(2) reaction and suggests that the transition state region of the F + H(2) potential energy surface has finally been understood quantitatively.
248 citations
TL;DR: The 476-514-nm photoelectron spectra of Cr 2 -, recorded at 4-meV resolution, show vibrationally resolved transitions to the ground state and to one excited electronic state of neutral Cr 2.
Abstract: The 476-514-nm photoelectron spectra of Cr 2 - , recorded at 4-meV resolution, show vibrationally resolved transitions to the ground state and to one excited electronic state of neutral Cr 2 . The measured electron affinity of Cr 2 is 0.505±0.005 eV. Observed vibrational energies in the 1 Σ g + ground state of Cr 2 up to υ=9, 3040 cm -1 above the zero point level, fit a Morse potential with ω c =480.6±0.5 cm -1 and ω e x e =14.1±0,3 cm -1
185 citations
TL;DR: A model based on the energetics of the system which readily explains the apparent contradiction between this tendency for 3D clustering, and the dynamical effect which leads to efficient wetting for coverages up to 1/2 monolayer at low temperatures is presented.
Abstract: The structural and electronic properties of Cu films vapor deposited on the oxygen terminated ZnO(0001)-O surface at 130 K have been characterized using x-ray photoemission spectroscopy (XPS), ${\mathrm{He}}^{+}$-ion-scattering spectroscopy, low-energy electron diffraction, work-function, and band-bending measurements, angular-resolved XPS, and CO and ${\mathrm{H}}_{2}$O chemisorption. These results show that Cu is cationic at tiny coverages, but becomes nearly neutral at coverages beyond a few percent. The Cu clusters into two-dimensional (2D) metallic islands at these coverages. Further deposition of Cu leads to spreading of these 2D islands without forming thicker layers, until about 50% of the surface is covered. Thereafter, these Cu islands grow thicker without filling the gaps between the islands except at a rate much slower than the rate at which Cu is deposited into these clean spaces. The annealing behavior of these films has also been studied between 130 and 850 K. These results show that the Cu has a tendency to cluster into thick 3D islands which only cover a small fraction of the surface. We present a model here based on the energetics of the system which readily explains the apparent contradiction between this tendency for 3D clustering, and the dynamical effect which leads to efficient wetting for coverages up to 1/2 monolayer at low temperatures. This model shows that a large fraction of the surface can first be covered by a 2D film even when the metal's self-adsorption energy significantly exceeds its adsorption energy on the oxide, provided the difference in these energies does not exceed the energy of 2D evaporation from kinks onto terraces. This model helps to explain a variety of confusing results in the growth of metal films on oxide surfaces.
178 citations
IBM1
TL;DR: In this paper, Monte Carlo simulations have been performed to derive the energy dependence of the pair-production rate using these results in combination with published data on the ionization coefficient and on the quantum yield for pair production.
Abstract: The electron dynamics for electron energies up to 5 eV has been studied by soft x‐ray photoemission spectroscopy. Monte Carlo simulations have been performed to derive the energy dependence of the pair‐production rate using these results in combination with published data on the ionization coefficient and on the quantum yield for pair production. The obtained ionization rate shows a very soft threshold at 1.2 eV, approaching the results by Kane [Phys. Rev. 159, 624 (1967)] at higher energies. Several published models have been found to be inconsistent with the full set of experimental data we have considered.
156 citations
TL;DR: The negligible intensity seen at EF using ultraviolet photoemission spectroscopy and bremsstrahlung isochromat spectroscopic indicate an unusual semiconductor-metal transition observed for x≥0.2, consistent with the resistivity data.
Abstract: We study the electronic structure of La1-xSrxMnO3+δ, x=0, 0.1, 0.2, 0.3, and 0.4, across the semiconductor-metal transition, using various electron spectroscopy techniques. The negligible intensity seen at EF using ultraviolet photoemission spectroscopy and bremsstrahlung isochromat spectroscopy (BIS) indicate an unusual semiconductor-metal transition observed for x≥0.2, consistent with the resistivity data. The BIS spectra show doped hole states developing about 1.4 eV above EF as a function of x. Auger electron spectroscopy gives an estimate of the intra-atomic Coulomb energy in the O 2p manifold to be about 6.8 eV. The Mn 2p core-level spectrum of LaMnO3, analyzed in terms of a configuration-interaction calculation, gives parameter values of the charge-transfer energy Δ=5.0 eV, the hybridization strength between Mn 3d and O 2p states, t=3.8 eV, and the on-site Coulomb energy in Mn 3d states Udd=4.0 eV, suggesting a mixed character for the ground state of LaMnO3.
144 citations
TL;DR: In this paper, the authors used both synchrotron radiation photoemission spectroscopy (PES) and Al Kα photoelectron spectroscope (XPS) to determine the suboxide distribution at SiO2/Si (100) interfaces.
Abstract: Both synchrotron radiation photoemission spectroscopy (PES) and Al Kα photoelectron spectroscopy (XPS) are used to determine the suboxide distribution at SiO2/Si (100) interfaces. High resolution PES measurements clearly resolved various suboxides with chemical shifts of 0.97, 1.80, and 2.60 eV for Si+1, Si+2, and Si+3, respectively. A total of 9.3×1014 atoms cm−2 of suboxide is found by PES measurements while only 4.2×1014 atoms cm−2 is measured by XPS on the same sample. This discrepancy is neither caused, as previously believed, by a difference in SiO2/Si (100) quality nor by a difference in methodology in data analysis. The possible factors, e.g., electron mean‐free path and photoionization cross section, which contribute to the difference between PES and XPS data, are considered.
141 citations
TL;DR: In this paper, photoemission spectroscopy was used to compare the effects of a hydrogen or argon plasma on natural-type 2B diamond (111) surfaces, while the diamond was heated to 350 °C.
Abstract: Photoemission spectroscopy was used to compare the effects of a hydrogen or argon plasma on natural‐type 2B diamond (111) surfaces, while the diamond was heated to 350 °C. After the hydrogen plasma the surface exhibits a negative electron affinity, indicative of a hydrogen‐terminated surface. In contrast, the argon plasma was found to result in a surface with a positive electron affinity of 1.0 eV, indicating the removal of hydrogen from the surface. Features characteristic of graphite were not observed. After reexposing the surface to a hydrogen plasma, the spectrum was identical to the spectrum obtained after the initial hydrogen plasma.
136 citations
TL;DR: In this article, the electron affinity of Ca@C60 was found to be 3.0 eV and the spectrum suggests that Ca donates its two 4s electrons to the C60 t1u LUMO.
120 citations
TL;DR: In this article, the bonding interactions between the metal dm orbitals and the acetylide π orbitals were determined using gas-phase He I and He II photoelectron spectroscopy.
Abstract: Gas-phase He I and He II photoelectron spectroscopy is used to experimentally determine the bonding interactions of η 1 -acetylide ligands in (η 5 -C 5 H 5 )Fe(CO) 2 C≡CR compounds (R=H, t Bu, or phenyl). The spectra show a large amount of interaction between the metal dm orbitals and the acetylide π orbitals. Evidence for this is obtained from the splitting of metal-based ionization bands, from the shifts in Cp-based and acetylide-based ionizations, from the changes in ionization cross sections between the He I and He II spectra, and from vibrational fine structure in the metal-based ionizations
TL;DR: In this paper, the rotationally resolved, one-photon threshold photoelectron spectrum of the methyl radical, CH3, produced by supersonic-jet, flash pyrolysis was reported.
Abstract: We report the rotationally resolved, one‐photon threshold photoelectron spectrum of the methyl radical, CH3, produced by supersonic‐jet, flash pyrolysis. Only rotational transitions with ΔK=0, ±2 are observed and this result is shown to be consistent with photoionization selection rules in D3h symmetry. Assignment of the threshold photoelectron spectrum results in an adiabatic ionization potential of 79 349±3 cm−1.
TL;DR: In this paper, photoelectron spectra of the F+H2+ reaction were used to determine the sensitivity of the spectrum to the bend potential near the F +H2 transition state.
Abstract: The transition state region of the F+H2 reaction is studied by photoelectron spectroscopy of FH2−. The photoelectron spectra consist of overlapping electronic bands with different angular distributions. The ground state band shows partially resolved features which differ depending on whether the anion is made from normal or para hydrogen. This dependence on the anion nuclear spin statistics implies that these features are due to progressions in bending levels of the neutral FH2 complex. In order to confirm this, and to determine the sensitivity of the photoelectron spectrum to the bend potential near the F+H2 transition state, three‐dimensional simulations of the FH2− photoelectron spectrum were performed assuming various potential energy surfaces for the F+H2 reaction. We found that the London–Eyring–Polanyi–Sato surface proposed by Takayanagi and Sato gave better agreement than either the T5a or 5SEC surfaces. From the higher energy band, we can extract information on the F+H2 excited electronic states,...
TL;DR: In this paper, the two-color threshold photoelectron spectra of naphthalene in a supersonic free jet have been recorded via nine vibronic levels of the S1 electronic state up to about 1420 cm−1 above the S 1 band origin.
Abstract: The two‐color (1+1’) threshold photoelectron spectra of naphthalene in a supersonic free jet have been recorded via nine vibronic levels of the S1 electronic state up to about 1420 cm−1 above the S1 band origin. The threshold photoelectron spectra recorded via the S1 band origin and via totally symmetric ag vibronic levels show significant intensity in Δν=+1 transitions in nontotally symmetric vibrations having b1g symmetry indicating that the ionization transition gains significant intensity through a vibronic coupling mechanism between the two lowest doublet cationic states. The strongest departure from the expected Δν=0 propensity in the threshold photoelectron spectra occurs through excitation of the totally symmetric 8 mode having ag symmetry indicating that a considerable displacement occurs along the normal coordinate of this 8 mode upon ionization from the S1 state. The superior resolution of the threshold photoelectron technique over conventional photoelectron methods has allowed accurate values ...
TL;DR: Synchrotron radiation photoemission spectroscopy suggests that the room temperature grown Au/Si(111) interface is an abrupt interface with the contact made by metallic Au and bulk Si.
Abstract: Synchrotron radiation photoemission spectroscopy suggests that the room temperature grown Au/Si(111) interface is an abrupt interface with the contact made by metallic Au and bulk Si. Si 2[ital p] core level spectra show no sign of an interface component, but only the surface reacted and bulk Si components during the growth of the interface. A surface Au-Si alloy film is first formed for Au coverages below 3 monolayers. The alloy is then stabilized into an Au[sub 3]Si-like film and detached from the Si substrate when metallic Au starts nucleation in between.
TL;DR: In this article, the interplay between the Ti3dO2p hybridization and the intra-atomic multiplet coupling was analyzed in formally tetravalent Ti compounds such as TiO 2, SrTiO 3 and BaTiO3, by means of a TiO 6 cluster model.
TL;DR: In this article, the surface of titanium before and after calcium-ion implantation by amounts of 1016, 1017, and 1018 ions cm−2, has been characterized using X-ray photoelectron spectroscopy (XPS).
TL;DR: A well-defined silicon oxide/silicon interface was synthesized by the reaction of the precursor cluster H 8 Si 8 O 12 with a Si(100) surface and characterized using Si 2p core level photoemission spectroscopy.
Abstract: A well-defined silicon oxide/silicon interface was synthesized by the reaction of the precursor cluster H 8 Si 8 O 12 with a Si(100) surface and characterized using Si 2p core level photoemission spectroscopy. Information gained regarding the assignments of silicon oxide group shifts and peak widths is used to evaluate assumptions and assignments of photoemission spectra of silicon oxide interfaces
TL;DR: The 488 and 514 nm negative ion photoelectron spectra of FeCO−, obtained at an instrumental resolution of 5 meV (40 cm−1), show vibrationally resolved transitions from the anion ground state to the ground state and a low-lying excited state of the neutral molecule as mentioned in this paper.
Abstract: The 488 and 514 nm negative ion photoelectron spectra of FeCO−, obtained at an instrumental resolution of 5 meV (40 cm−1), show vibrationally resolved transitions from the anion ground state to the ground state and a low‐lying excited state of the neutral molecule The ground state of FeCO is assigned as the 3Σ− state and the excited state, lying 1135±25 cm−1 higher in energy, as the 5Σ− state The fundamental vibrational frequencies are νCO=1950±10, νFeC=530±10, and νbend=330±50 cm−1 in the 3Σ− state, and νCO=1990±15, νFeC=460±15, and νbend=180±60 cm−1 in the 5Σ− state Principal force constants are estimated from these results Based on a Franck–Condon analysis of the spectrum and other considerations, the Fe–C bond is determined to be 015±004 A shorter, and the C–O bond 005±002 A longer, in the 3Σ− state than in the 5Σ− state These results demonstrate the importance of sdσ hybridization in reducing the σ repulsion between the metal 4s electron and the CO 5σ lone pair, a mechanism that is available
TL;DR: In this article, high-resolution helium Iα (584 A) photoelectron spectra of H2CO and D2CO were used to reveal vibrational structure detail in the ionic first excited state of formaldehyde.
Abstract: High resolution helium Iα (584 A) photoelectron spectra of H2CO and D2CO are reported The present study reveals much new vibrational structure detail in the ionic first excited state of formaldehyde Weak excitations of the ν3 (in H2CO) and ν1 (in D2CO) modes along with the strong excitations of the ν2 mode in the ionic first excited states are fully resolved for the first time The weak excitations of the ν4 out‐of‐plane bending mode in the ionic ground and first excited states of formaldehyde cations indicate that they may have nonplanar equilibrium geometries Strong isotope effects on vibronic (vibrational) couplings are observed in the cation first and second excited states Vibrational autocorrelation functions are calculated from the high‐resolution photoelectron spectra The correlation functions calculated for the first electronic excited states show rather slow decay rate on the femtosecond time scale The ultrafast decay of the formaldehyde cations implied by the correlation functions calculated for the third electronic excited states suggest that dissociation and intramolecular dynamic processes are the main decay pathways
15 Aug 1993
TL;DR: In this article, the decay pathways of all the valence states of CF+4 and SF+6 in the range 15-28 eV were measured at fixed photon energies with good time resolution.
Abstract: Threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy has been used to measure, state selectively, the decay pathways of all the valence states of CF+4 and SF+6 in the range 15–28 eV. Radiation in the vacuum UV from a synchrotron radiation source ionises the parent molecule, and the electrons and ions are detected by threshold electron analysis and time-of-flight mass spectroscopy, respectively. TPEPICO spectra are recorded continuously as a function of photon energy, allowing both threshold photoelectron spectra and yields of all the fragment ions to be obtained. Kinetic energy releases are measured at fixed photon energies with good time resolution. The results orf the X 2T1, A 2T2 and B 2E states of CF+4 (all below the energy of He I radiation) confirm earlier measurements; results for the C 2T2 and D 2A1 states at 21.7 and 25.1 eV, respectively, are new. They confirm previous measurements that radiative decay from both states is an important process, and we have measured their state-selected fluorescence quantum yields. For SF+6, fluorescence does not occur from any of the excited valence states, and we have measured the fragmentation channels and branching ratios for all of the valence states.
TL;DR: In this paper, the two-color, two-photon (1+1') resonanceenhanced multiphoton ionization spectrum of the hydrogen-bonded phenol dimer has been recorded in reasonable agreement with previously reported spectra.
Abstract: The two‐color, two‐photon (1+1’) resonance‐enhanced multiphoton ionization spectrum of the hydrogen‐bonded phenol dimer has been recorded in reasonable agreement with previously reported spectra. However, more features are obtained in this work and this has allowed a more detailed analysis of the spectrum. Five intermolecular vibrations (out of a possible six) are observed for the S1donor state, while only two modes are obtained for the S1acceptor state. Zero‐kinetic‐energy (ZEKE) photoelectron spectra were recorded via different intermediate vibronic states. The spectrum recorded via the vibrationless level of the S1donor state is rich in structure and indicates a large change in the geometry on ionization. Progressions in the intermolecular stretch mode and at least one other mode are obtained. ZEKE spectra were also recorded via a number of S1donor vibronic levels, and the S1acceptor vibrationless level. The lowest value measured for the ionization energy of the donor is 63 649±4 cm−1 (7.8915±0.0005 eV...
TL;DR: In this paper, the photoelectron spectrum of dichlorocarbene, CCl 2, is reported and a protocol for calculating polyatomic Franck-Condon factors is given and compared to two less general approaches.
Abstract: The photoelectron spectrum of dichlorocarbene, CCl 2 , is reported. Simulation of the partially resolved vibrational structure is used to extract the adiabatic ionization potential, IP ad [CCl 2 ]=9.27±0.04 eV, and the heat of formation, ΔH o f,298 [CCl 2 ]=51.0±2.0 kcal/mol. A protocol for calculating polyatomic Franck-Condon factors is given and compared to two less general approaches
TL;DR: In this article, rotationally resolved zero kinetic energy −pulsed field ionization (ZEKE•PFI) photoelectron spectra of NH3 were obtained by nonresonant two-photon ionization from the X(1A1') electronic ground state.
Abstract: Rotationally resolved zero kinetic energy‐pulsed field ionization (ZEKE‐PFI) photoelectron spectra of NH3 were obtained by nonresonant two‐photon ionization from the X(1A1’) electronic ground state. The ZEKE spectra were recorded up to an internal ion energy of 9500 cm−1 by pulsed field ionization of long‐lived Rydberg states of very high principal quantum numbers. Rovibronic bands of the NH3+ cation with v2+=1–9 (umbrella mode), v4+=1, and for the first time the mode ν1 in the combination band v+=1121 of the X+(2A2‘) electronic ground state are observed in the ZEKE spectra. Rotational constants and band origins are determined in the analysis. The adiabatic ionization energy obtained by a recent ZEKE measurement is confirmed at 82 159±1 cm−1.
TL;DR: In this paper, the first adiabatic ionization energies of NaO2 and KO2 were measured as AIE[NaO2(X 2A2)]=(6.2±0.1) eV and AAE[KO(X ǫ 2A2)=(5.7± 0.1 ) eV.
Abstract: Products of the gas‐phase reactions M+N2O and M+O3, where M=Na or K, have been investigated with UV photoelectron spectroscopy and bands have been assigned with the assistance of results from ab initio molecular orbital calculations. For the M+N2O reactions, the observed products were MO+N2. Measurement of the photoelectron bands associated with the metal monoxide MO allowed determination of the first adiabatic ionization energies of NaO and KO. The values obtained were AIE[NaO(X 2Π)]=(7.1±0.1) eV and AIE[KO(X 2Π)]=(6.9±0.1) eV. A similar study of the Li+N2O reaction gave AIE[LiO(X 2Π)]=(7.6±0.2) eV. The reactions M+O3, with M=Na or K, were observed to give MO+O2 as the major reaction products. However, for each reaction, a band was observed which was assigned to the first ionization energy of the secondary reaction product MO2. From the spectra obtained, the first adiabatic ionization energies of NaO2 and KO2 were measured as AIE[NaO2(X 2A2)]=(6.2±0.2) eV and AIE[KO2(X 2A2)]=(5.7±0.1) eV. For both the M+...
TL;DR: In this paper, a study of hexagonal GaN thin films grown by low-pressure chemical vapor deposition on sapphire substrates was presented, where synchrotron radiation photoemission spectroscopy was used to probe the electronic density of states and test the validity of existing band structure calculations.
Abstract: We present a study of hexagonal GaN thin films grown by low-pressure chemical vapor deposition on sapphire substrates. We used synchrotron radiation photoemission spectroscopy to probe the electronic density of states and test the validity of existing band structure calculations. Parallel studies of surface composition and atomic structure by means of Auger spectroscopy and reflection high-energy electron diffraction were performed following sputtering/annealing cycles using argon, xenon and nitrogen ions. We found that sputtering with nitrogen ions followed by annealing in vacuum is an effective method to reduce nitrogen surface depletion and produce quasi-stoichiometric ordered GaN(0 0 0 1)1 × 1 surfaces.
TL;DR: It has been proved that a major part of the observed discrepancy between the angular distribution of photoemission from atoms and from solids can be ascribed to elastic photoelectron scattering, improving the reliability of the mathematical formalism of XPS, and consequently the accuracy of quantitative analysis.
Abstract: A convenient experimental method for determining the relative angular distribution of photoemission from solid materials has been proposed. Experiments were simultaneously simulated with the Monte Carlo model describing realistic photoelectron transport in solids. It has been proved that a major part of the observed discrepancy between the angular distribution of photoemission from atoms and from solids can be ascribed to elastic photoelectron scattering. The formalism of x-ray photoemission spectroscopy (XPS) can be easily extended to account for the observed effects by introducing the effective asymmetry paramter ${\mathrm{\ensuremath{\beta}}}_{\mathit{e}\mathit{f}\mathit{f}}$. This parameter well describes the decrease in anisotropy of photoemission, thus improving the reliability of the mathematical formalism of XPS, and consequently, the accuracy of quantitative analysis.
TL;DR: Pb substitution for Bi induces new states of Pb 6s character outside the band gap of BaBiO 3 and does not induce in-gap spectral weight unlike in cuprate superconductors; the splitting of the Bi 6s band is not significantly reduced by Pb substitution throughout the semiconducting region.
Abstract: We have studied the electronic structure of BaPb 1-x Bi x O 3 and its changes across the composition-dependent metal-semiconductor transition using photoemission and O 1s x-ray-absorption spectroscopy. For the parent insulator BaBiO 3 , the peak-to-peak splitting of the Bi 6s band is found to be large, whereas, the minimum gap is much smaller, qualitatively consistent with the large (∼2 eV) optical gap of the direct type and the smaller (∼0.5 eV) transport gap of indirect type. Pb substitution for Bi induces new states of Pb 6s character outside the band gap of BaBiO 3 and does not induce in-gap spectral weight unlike in cuprate superconductors; the splitting of the Bi 6s band is not significantly reduced by Pb substitution throughout the semiconducting region
TL;DR: The C 1s photoelectron spectrum of CO has been measured with high resolution in the threshold region as well as new features in the satellite region, which are attributed to conjugate shakeup processes.
Abstract: The C 1s photoelectron spectrum of CO has been measured with high resolution in the threshold region. The data exhibit hitherto unresolved vibrational structure on the C 1s main photoelectron line as well as new features in the satellite region. The vibrational energy of the CO + ion is 301±3 meV. The vibrational structure changes dramatically with photon energy due to the influence of the σ * shape resonance. The new satellite lines which are not present at high photon energies are attributed to conjugate shakeup processes
TL;DR: The zero-kinetic energy photoelectron spectra of p-difluorobenzene (p-DFB) were obtained by two-color 1+1' photoionization via the S 1, 0 0, 3 1, 6 1, 9 2, 17 1, 27 1, and 30 1 vibrational states as intermediate resonances as mentioned in this paper.
Abstract: ZEKE (zero-kinetic-energy) photoelectron spectra of p-difluorobenzene (p-DFB) were obtained by two-color 1+1' photoionization via the S 1 , 0 0 , 3 1 , 6 1 , 9 2 , 17 1 , 27 1 , and 30 1 vibrational states as intermediate resonances. The ZEKE spectra show substantial activity in transitions to combination bands with totally symmetric modes and a number of transitions which are symmetry forbidden under D 2h symmetry. New fundamentals and combination bands of the electronic ground state of the cation are assigned, and improved vibrational frequencies are derived. Ab initio SCF calculations on the S 0 and S 1 states of p-DFB and the ground ionic state are presented and discussed in comparison to the experimental results