Ionization Energy Shifts Research Articles

Ionization Energy and Level Shifts of Multiply Charged Ions in Nonideal Plasmas

The Bethe-Salpeter equation for plasmas containing ions with higher charges is solved by perturbation methods. The lowering of the ionization energy as well as the energy level shifts due to nonideality effects are calculated. It is shown that multiply charged ions lead to an essential amplification of nonideality effects. An estimate for the modification of transition rates is given.

Photoemission study of alkali/GaAs(110) interfaces

A detailed core-level photoemission study of interfaces between thin alkali films andn-orp-type GaAs (110) formed at different substrate temperatures 85 K and 300 K) is reported. All the interfaces grown at 85 K (with Na, K, Rb, and Cs) were found to be non-reactive, while at 300 K, the interface with Na is reactive and that with Cs remains non-reactive. In case of the non-reactive interfaces, a strong band bending of ≊1.0 eV is observed forp-GaAs at alkali coverages as low as θ≊0.01 monolayers, but practically none forn-GaAs. This striking asymmetry in band bending is interpreted as a consequence of the donor character of the alkali atoms. On the other hand, an approximately symmetric band bending at low coverages is observed for the reactive interfaces of Na withn- andp-GaAs and assigned to defect states. For high alkali coverages (θ>2 monolayers), the final band bending is characterizeds by the same Fermilevel position forn- andp-GaAs, independent of the reactivity of the interface, and assigned to metal-induced gap states. Furthermore, systematic trends along the alkali series in Fermi-level position ionization energy, plasmon-loss features, and layer-dependent binding-energy shifts of alkali core levels are discussed.

Photoelectron spectroscopy of the nitrogen dimer (N2)2 and clusters (N2)n: N2 dimer revealed as the chromophore in photoionization of condensed nitrogen

The He i photoelectron spectra of gas-phase nitrogen dimer and nitrogen clusters have been measured in a pulsed cluster beam. The dimer (N2)2 is characterized by broad bands with vertical ionization energies which are 0.3±0.1 eV lower than for N2 monomer. The bands observed for a mixture of small clusters, estimated to be of average size N̄=10, are identical to the dimer bands except for further shifts of 0.3 eV to lower ionization energies. The clusters bandwidths and band shapes are virtually the same as measured for thin films of condensed N2, indicating that the nitrogen dimer (N2)2 is the ionization chromophore in each case. This offers support for Haberland’s hypothesis that ionization of any Mn cluster produces the ion M+2Mn−2 provided M is a closed-shell atom or molecule. The theory of electronic relaxation polarization of the dielectric medium, which explains the gas-to-solid ionization energy shifts, is modified for the case of finite clusters and to account for dimer ion formation.

The influence of fluoro substituents on cyclopropa-benzene, -naphthalene, and -anthracene

The He(Iα) PE spectra of cyclopropabenzene, cyclopropa[b]naphthalene, cyclopropa[b]anthracene, their 1,1-difluoro derivatives and of some of their substituted derivatives have been recorded, analyzed and assigned by correlation with the PE spectra of the parent molecules benzene, naphthalene and anthracene. It is shown that the PE spectroscopic data yield no information about the presence or absence of a Mills-Nixon effect in the molecules investigated. The inductive effect of the bridging CH2 group of the cyclopropeno ring is close to zero, whereas that of the CF2 group leads to positive ionization energy shifts in good agreement with previous experience. The hyperconjugative interaction of the local pseudo-π orbital of the CH2 group yields a significant destabilization of the π-orbitals of B1 symmetry.

UPS of xenon atoms adsorbed on metal surfaces

This paper discusses assignments and ionization energy shifts of UPS of xenon atoms adsorbed on metal surfaces. It is suggested that the ordering in split energy levels, which has been controversial in previous publications, may be explained as a function of Xe coverages. It has been shown that the ionization energy shift is due to the final effects. The donimant effect may be a valence force between an adsorbate ion and surrounding Xe atoms.

Ionization energy shifts of photoemission of adsorbed xenon

The magnitude of photoemission ionization (or binding) energy shifts of adsorbed xenons both on clean metal surfaces and on multilayer systems can possibly be interpreted in terms of final-state effects by use of Born-Haber cycles.

Ionization energy shifts of photoemission of adsorbed xenon

The magnitude of photoemission ionization (or binding) energy shifts of adsorbed xenons both on clean metal surfaces and on multilayer systems can possibly be interpreted in terms of final-state effects by use of Born-Haber cycles.

Origin of phase transition shifts of ionization energies in water

The origin of absolute and differential phase transition shifts of ionization energies of water is investigated by means of perturbation theory, supermolecular models and perturbational model calculations including results from molecular dynamics simulations. Applications are presented for ionization energy shifts following the phase transitions: water vapour-cubic iceliquid water.

On the nature of the ligand core hole states of transition metal carbonyls

Configuration interaction calculations of the O1s and C1s core hole states of Cr(CO)6 and C3O2 are described. The increased shielding of the primary core hole states of these molecules compared to those of CO leads to the shift in core ionization energy being determined by final state effects. The intense satellite band in the O1s and C1s spectrum of Cr(CO)6 arises from M(3d)→L(π*) charge transfer transitions involving all six CO ligands.

Electrostatic and relaxation effects in ionization of molecular dimers and intermolecular complexes

AbstractThe shifts in ionization energies which occur when a molecule is incorporated as an asymmetric dimer or in an intermolecular complex are analyzed theoretically. MOSCF calculations with 4–31G basis sets were performed on closed‐ and open‐shell states of (HF)2, H2O·HF, and their valence–hole ions, as well as on the heterodimers incorporating the higher homologues CH3F, CH3OH, and (CH3)2O. The analysis concerns the influence of electrostatic, polarization, and charge transfer effects associated with complexation on the initial molecular state of each monomer system, as well as monomer–dimer differences in the electronic relaxation mechanism considered as a final state effect in the ionization process. The calculated ionization energy shifts which agree well with the experimental data available for (CH3)2O·HF, show that the shifts are dominated by electrostatic effects, but some effects arising from differences in molecular size and electric polarizability of the monomers can be discerned.

Electrostatic and Relaxation Effects in Ionization of Intermolecular Complexes

The shifts in experimental ionization energy (IE) resulting from complexation between the (CH3hO and HF molecules are analysed theoretically with small basis set molecular orbital calculations. Initial state effects are separated according to the Morokuma decomposition procedure which distinguishes electrostatic, polarization and charge transfer contributions. The electrostatic effect, arising from the HF molecule, changes the potential energy of the no electrons on (CH3hO.

Effects of methyl group substitution on metal-coordinated cyclopentadienyl rings. Core and valence ionizations of methylated tricarbonyl(.eta.5-cyclopentadienyl)metal complexes

Gas-phase He I, He II, and Mg K..cap alpha.. photoelectron spectra are reported for molecules of the type (eta/sup 5/-C/sub 5/H/sub 5-n/-(CH/sub 3/)/sub n/)M(CO)/sub 3/ where n = 0, 1, 5 and M = Mn, Re. The influence of methyl groups on the cyclopentadienyl ring is monitored by shifts in both core and valence ionization energies. This enables effective separation of electron density transfer (inductive) and ring-methyl orbital overlap (hyperconjugative) effects. While the shift in the ring e/sub 1/'' ionization is found to be primarily a hyperconjugative effect, the shift in the metal valence ionizations is caused essentially entirely by a shift of electron density toward the metal atom. A great proportion of this increased density is transferred to the carbonyls in the rhenium complexes than in the manganese complexes, indicating the greater back-bonding ability of the third-row atom. Further evidence of extensive Re-CO back-bonding is provided by the presence of vibrational fine structure on one of the predominantly metal ionizations of the rhenium complexes. This structure is the vibrational progression of the symmetric metal-carbon(CO) stretching mode. The long vibrational progression observed in this band and the frequency of the M-C stretch in the positive ion are direct evidence ofmore » considerable ..pi.. back-bonding from the metal to the carbonyls. The observed vibrational structure in the spin-orbit split rhenium d ionizations also leads to a definitive interpretation of the pattern of metal ionizations in such complexes. The origin of the characteristic splitting of the predominantly ring e/sub 1/'' ionization is also considered in detail. The data suggest that the carbon-carbon bond distances in the ring are distorted an average of 0.01 to 0.02 A from fivefold symmetry when coordinated to a d/sup 6/ ML/sub 3/ species. This is the first indication from gas-phase spectroscopy for such distortions.« less

The photoelectron spectrum of tetramethyldiazetine: The elucidation of ring size effects on azo group ionization potentials

The photoelectron spectrum of 3,3,4,4-tetramethyldiazetine (4-Me 4) has been measured. By comparison with the previously reported photoelectron spectra of 3,3-dimethyldiazirine and 3,3,5,5-tetramethylpyrazoline, 4-Me 4 has three resolved low energy ionization (8.87, 10.36, and 11.65 eV) with an anomalously low second ionization potential. MINDO/3-and ab initio STO-3G calculations on 3-, 4-, and 5-membered ring azo compounds (diazenes) have been carried out, and these allow definite conclusions about the order of n −, n +, and π ionization potentials to be made for the diazetine (n − < N + < π) and for 3,3-dimethyldiazirine and 3,3,5,5-tetramethylpyrazoline(n − < π n +), in agreement with the predictions of Heilbronner. Ab initio STO-3G calculations on the nitrogen and alkyl fragments of the cyclic diazenes reveal the origin of ionization energy shifts with changes in ring size.

Determination of chalcogen structures on nickel surfaces from orbital energies added to pairwise atomic repulsions

A simple theory whose forte has been the determination of structures and energy levels for large nonionic systems is found to be applicable to ionic systems when the effects of self-consistent charge transfer are incorporated. The theory confirms the LEED structural analyses for O, S, and Se on Ni(100) and S on Ni(111) as found by Demuth, Jepsen, and Marcus. Further, the atomic valence ionization energy shifts are in agreement with the surface oxide photoemission spectrum of Conrad, Ertl, Küppers, and Latta.

The He(I) photoelectron spectra and valence electronic structures of η 5-C 5H 5Mn(CO) 2N 2 and η 5-C 5H 5Mn(CO) 2NH 3

The He(I) photoelectron spectra of η 5-C 5H 5Mn(CO) 2N 2 and η 5-C 5H 5Mn(CO) 2NH 3 have been obtained. The general features of these spectra resemble those of the parent carbonyl complex, η 5-C 5H 5Mn(CO) 3. The major differences appear in the ionizations associated predominantly with the metal d levels, where shifts in ionization energies and loss of degeneracy reflect the differences in bonding of the nitrogen ligands and a carbonyl ligand with the metal center. Non-empirical molecular orbital calculations were used as an aid for the interpretation of these binding energy shifts. In the case of N 2 bound to the metal, the shifts in ionization potentials are predicted with extreme accuracy by the shifts in eigenvalues of the calculations. Thus the electronic structure of transition metal dinitrogen complexes, as compared to carbonyl complexes, is accurately described. The quantitative prediction of binding energy shifts for the amine complex are less satisfactory, although the qualitative behavior is reproduced quite well.

Hartree-Fock-Slater Calculations of the ESCA Chemical Shifts for Transition Metal Atoms

Abstract Hartree-Fock-Slater calculations have been carried out for inner-shell orbitals of some transition metal atoms (Ni, Rh, and Pt), and the core ionization energies computed by the transition state approximation. It is found that the ionization energy shifts do not conform to the conventional charge-potential approximation; the electron populations in individual valence d and s orbitals need to be considered separately.

Photoelectron and Auger spectra of xenon (VIII) in solid perxenates

The chemical shift of core shell ionization energies in various perxenates relative to gaseous xenon is strongly compensated by interatomic relaxation. This effect is even more clear-cut on the Auger signals moving in the opposite direction of a (Hartree + Madelung) potential model.

Photoelectron spectroscopy of 9,10-dihaloanthracenes

The photoelectron spectra of anthracene and its 9,10-dichloro- and dibromo-derivatives have been obtained. Analysis of the spectra is based mainly on the shifts in the anthracene molecular orbital ionization energies observed upon substitution. These shifts are interpreted on the basis of a perturbation model comprising short-range and long-range inductive terms and a mesomeric term. The electronic perturbation caused by the halogen atom is observed to depend largely on the unperturbed energy of the halogen np electrons and the charge distribution in the anthracene molecular orbitals. It has been possible to separate out Coulombic interactions and mesomeric interactions which depend on the energy gap between hydrocarbon and substituent orbitals. Although the observations are not conclusive, owing to the fact that only two orbitals have measurable mesomeric shifts, results indicate that αCl′, the Coulombic perturbation parameter, may well be negative, in contrast to previous work.