Multiplet States Research Articles

Optical excitations associated with bound exciton states at the vacancy in diamond

The neutral vacancy V0 gives an optical spectra labelled GR1 and the negative vacancy V- a spectra labelled ND1. Between these are lines labelled GR2-8 associated with both V0 and V-. GR2-8 relate to bound exciton states coupled via strong electron-electron correlation into multiplet molecular states of V0. Optical intensities associated with GR2-8 relate more to V- than V0.

Ab Initio Calculations of the Multiplet Terms of (TmP4)3+ Cluster

Multiplet structures of a rare earth ion, Tm 3+ , in tetrahedral symmetry of ligand P atoms are calculated on the basis of configuration interaction calculation with Gaussian basis sets. The spin-orbit interactions of a rare earth ion and the crystal field effect are all taken into account in the ab initio calculations. The calculated results of the splitting between the ground state and excited multiplet states, 3 H 4 → 3 H 6 and 3 H 5 → 3 H 6 , are in good agreement with the former numerical and experimental results.

Exponentially generated configuration interaction (EGCI) method applied to high-spin multiplicity

The exponentially generated configuration interaction (EGCI) method is extended to high-spin multiplicity. This method, in which excited, ionized, and electron attached states are calculated on the basis of the correlated wave function of the ground state, is applicable to quasidegenerate states of various spin multiplicity and various number of excitation processes. The accuracy and efficiency of the EGCI method is examined for the high-spin quasidegenerate states with multiple excitation nature. Test calculations are performed for several high-spin states of C2, C2+, N2, N2+, and m-phenylenebis(methylene) (m-PBM) molecules. The EGCI method reproduces well the full-CI results in total energy, spectroscopic constants, and spin density distributions. The EGCI method is confirmed to be accurate and useful not only for investigating the energetics involved in the study of dynamics and reactions but also for studying spin density distributions of various spin multiplet states.

Electron emission in low-energy grazing collisions of C + ions with W(110) partially covered by alkali atoms

Abstract Electron energy spectra of slow (50 eV) C + ions colliding under grazing incidence with clean and partially alkalated (Li, Na, K, Cs) W(110) surfaces are reported. The spectra can be interpreted as due to various inter- and intra-atomic Auger processes occurring in the vicinity of the surface: for clean W(110) hardly any electrons are observed. For small alkali coverages the emission is due to Auger capture involving two electrons from the surface. For sufficiently large alkali coverages the resonant capture of one or two electrons from the surface leads to the formation of core-excited states of the neutralized projectile (beyond 0.3 monolayer alkali coverage in terms of a completed monolayer, typically) and Feshbach resonancesof the configuration C −∗ (2s 2 2p3 l 3 l ′) (beyond 0.5 monolayer K or Cs coverage). These states manifest themselves by their decay via Auger deexcitation and autodetachment, respectively. The availability of three multiplet states of the C(2s 2 2p 2 ) configuration into which Auger processes can take place produces richly structured spectra. In addition we report the ion scattering spectra (ISS) of the C − ions scattered into 90° as a function of the coverage of W(110) by alkali atoms.

Electron emission in low-energy grazing collisions of C + ions with W(110) partially covered by alkali atoms

Electron energy spectra of slow (50 eV) C + ions colliding under grazing incidence with clean and partially alkalated (Li, Na, K, Cs) W(110) surfaces are reported. The spectra can be interpreted as due to various inter- and intra-atomic Auger processes occurring in the vicinity of the surface: for clean W(110) hardly any electrons are observed. For small alkali coverages the emission is due to Auger capture involving two electrons from the surface. For sufficiently large alkali coverages the resonant capture of one or two electrons from the surface leads to the formation of core-excited states of the neutralized projectile (beyond 0.3 monolayer alkali coverage in terms of a completed monolayer, typically) and Feshbach resonancesof the configuration C −∗ (2s 2 2p3 l 3 l ′) (beyond 0.5 monolayer K or Cs coverage). These states manifest themselves by their decay via Auger deexcitation and autodetachment, respectively. The availability of three multiplet states of the C(2s 22p 2) configuration into which Auger processes can take place produces richly structured spectra. In addition we report the ion scattering spectra (ISS) of the C − ions scattered into 90° as a function of the coverage of W(110) by alkali atoms.

Symmetry-adapted cluster–configuration interaction method applied to high-spin multiplicity

The SAC–CI (symmetry-adapted cluster–configuration interaction) method is extended to high-spin multiplicity and applied to the quartet, quintet, sixtet, and septet states of N2, N2+, OH, and m-phenylenebis(methylene) (m-PBM) molecules. The results show good agreement with those of the full-CI reference calculations, though the dimensions of the calculations are much smaller than those of the full-CI method. The smallness of the calculational efforts and the excellent agreement with the full-CI results assure that the SAC–CI method is useful and accurate not only for singlet, doublet, and triplet states but also for high-spin multiplet states.

Level scheme of 68Ga from (p, nγ) reaction

γ-ray, γγ-coincidence and internal-conversion electron spectra of the 68Zn(p, nγ) 68Ga reaction were measured with Ge(HP and LEPS) γ-ray detectors, as well as with a combined magnetic plus Si(Li) electron spectrometer at different proton energies between 4.5 and 5.1 MeV. Energies and relative intensities have been determined for 116 (among them 87 new) transitions in 68Ga. Internal-conversion coefficients of 25 68Ga transitions have been determined for the first time, enabling deduction of many new γ-ray multipolarities. A more complete 68Ga level scheme was deduced, which was based mainly on γγ-coincidence measurements. From the internal-conversion coefficients of transitions, Hauser-Feshbach analysis of (p, n)-reaction cross sections and other arguments spin and parity values have been deduced. The energy splitting of different pn multiplets has been calculated on the basis of the parabolic rule. Several pn multiplet states have been identified.

Electronic and geometric structures of the high- and low-spin multiplets of the Cr(C 6H 6) π complex

We report results of a theoretical investigation of four multiplet spectroscopic states for the open faced Cr(C 6H 6) π complex. The calculations are performed using a spin-polarized density functional method. The optimized structures are obtained in an all-electron description within basis sets of bis zeta+polarization quality. The ground state is found to be the state which has the highest spin multiplicity, namely septet 7A 1. The other, higher-lying, states are 5E 2, 3B 1 and 1A 1. The minimum energies of their potential surfaces are found to be placed respectively at 0.04, 0.30 and 1.02 eV above the potential surface minimum of the ground state. For the four states 7A 1, 5E 2, 3B 1 and 1A 1, the equilibrium distances between Cr and the benzene ring are found to be respectively 2.64, 1.92, 1.62 and 1.55 Å.

The effect of amplified spontaneous emission on the measurement of the multiplet state distribution of ground state oxygen atoms

Amplified spontaneous emission (ASE) is a process which competes with laser-induced fluorescence (LIF) in three level systems. This was demonstrated in the case of oxygen atoms, for which both ASE and LIF were observed at 845 nm. Ground state oxygen atoms were generated by photodissociating O2, SO2, and NO2 in a pump and probe experiment. Both nascent and thermalized O(3Pj″) atoms were measured using two-photon LIF at 226 nm. The fine structure populations deduced from the 845 nm (3p3Pj′→3s3S) emission were considerably hotter than the distributions obtained from the 130 nm (3s3S→2p3P) transition. A kinetic model is developed showing that the distributions observed at 845 are distorted by ASE, which selectively depletes the populations of atoms originating from more highly populated multiplet levels.

Structure of 118Sb nucleus.

{gamma}, {gamma}{gamma}-coincidence, internal conversion electron, and {gamma}-ray angular distribution spectra of the {sup 118}Sn({ital p},{ital n}{gamma}){sup 118}Sb reaction were measured at different bombarding proton energies between 5.5 and 7.5 MeV. {gamma}, {gamma}{gamma}-coincidence, and internal conversion electron spectra of the {sup 115}In ({alpha},{ital n}{gamma}){sup 118}Sb reaction were also measured at {ital E}{sub {alpha}}=14.5 MeV. Ge(HP), Ge(Li), Ge(LEPS) {gamma}-ray detectors, as well as a superconducting magnetic lens electron spectrometer (with Si(Li) detectors), were used in the experiments. About 210 (including {similar to}130 new) {gamma} rays have been assigned to {sup 118}Sb. The deduced {sup 118}Sb level scheme contains more than 70 new levels. On the basis of the internal conversion coefficients, Hauser-Feshbach analysis of ({ital p},{ital n}) reaction cross sections, {gamma}-ray angular distributions, and other arguments spin and parity values have been determined. The parabolic rule'' prediction of the energy splitting of different proton-neutron multiplets enabled the identification of many proton-neutron multiplet states. The energy spectrum and electromagnetic properties have been calculated in the framework of the interacting boson-fermion-fermion--odd-odd truncated quadrupole phonon model, and reasonably good agreement has been obtained between experimental and theoretical results.

Structure of odd-odd Sb nuclei

The structure of112,114,116,118Sb nuclei was studied with complex γ and electron spectroscopic methods via (p, nγ) and also (α,nγ) reactions (in the case of116Sb,118Sb)at 5.5–9.2 MeV proton and 14.5–16.0 MeV α-particle energies. New level schemes have been deduced. The energy splitting of the proton-neutron multiplet states of116,118,120,122,124Sb was calculated on the basis of the “parabolic rule”. Manyp−n multiplet states have been identified and conclusions have been drawn on the applicability of the parabolic rule as a simple guideline for experimental investigations. Detailed description of the energy spectra and electromagnetic properties of116,118,120,122,124Sb nuclei is given on the basis of the interactingboson-fermion-fermion/ odd-odd truncated quadrupole phonon model (IBFFM/OTQM). The calculations give account both of the “regular” and “irregular” behaviour of the energy splitting of thep−n multiplets, as well as of the electromagnetic moments, γ-branching and γ-mixing ratios. Conclusions have been drawn on the role of different interactions in the multiplet energy splitting. The IBFFM interpretation of the high-spin intruder bands and the spectroscopic factors of the neutron transfer reactions are also shortly discussed for Sb nuclei.

Structure of the 120Sb nucleus

The energy spectrum and electromagnetic properties of the low-lying states of 120Sb have been calculated in the framework of the interacting boson-fermion-fermion model. Proton-neutron multiplet states have been identified. The characteristic features of multiplets are reasonably described by the theory.

OH product energy partitioning and absolute reactive cross section of the reaction H + H 2 O → OH + H 2

Using 193 nm photolysis of HBr, we have studied the reaction H+H 2 O→OH+H 2 at a center of mass energy of 2.52 eV. Laser induced fluorescence has been used to measure the nascent rotational quantum-state distribution and the translational energy of the OH product molecules. Within the experimental uncertainty no vibrational excitation of the OH products could be found ( v =1/ x =0<0.1). The degree of OH( v =0) rotational excitation is also very low. We found that only 4% of the total available reaction energy is channeled into OH rotation. The results of sub-Doppler measurements of the OH line profiles show that most of the available energy in the reaction ends up as c.m. translational energy of the products (67%). The population of two spin orbit multiplet states shows a slight preference for the low lying 2 Π 3/2 state. The ratio of the lambda doublet state population shows a preference for the (A′) state at high rotational quantum numbers. Together with the very low vibrational and rotational excitation of the OH products, this suggests that many of the reactive collisions are in character planar stripping collisions, with the OH bond acting as a spectator during the reaction. Using the H 2 O 2 photolysis at 193 nm as a reference source of well defined concentrations of OH radicals we determined an absolute reactive cross section: σ(2.52 eV)=(0.26±0.09) 2 . The experimental results show excellent agreement with predictions of dynamic calculations using a ab initio potential energy surface.

Electronic structure of epitaxial erbium silicide films on Si(111)

The present study is mainly motivated by the recent interest in rare-earth/Si interfaces for technological applications. Furthermore there is by now a rather poor understanding of their electronic structure. We present the first spectroscopic investigaton of epitaxial erbium silicide using angle-resolved ultraviolet photoemission spectroscopy (ARUPS) and low-energy electron diffraction (LEED). Thermal treatment at 700°C of a 15 monolayers Er deposit results in epitaxial ErSi1.7 formation characterized by sharp √3 × √3 R30° LEED pattern. The relevant ARUPS spectra exhibit essentially emission of Er4f multiplet states in the 4–11 eV binding energy window and structures at lower binding energies assigned to hybridized Er5d and Si 3sp states. Finally, we have shown that in contrast with pure Er, there is apparently no surface-related 4f component for monocrystalline ErSi1.7.

Electronic structure of epitaxial erbium silicide films on Si(111)

Abstract The present study is mainly motivated by the recent interest in rare-earth/Si interfaces for technological applications. Furthermore there is by now a rather poor understanding of their electronic structure. We present the first spectroscopic investigaton of epitaxial erbium silicide using angle-resolved ultraviolet photoemission spectroscopy (ARUPS) and low-energy electron diffraction (LEED). Thermal treatment at 700°C of a 15 monolayers Er deposit results in epitaxial ErSi 1.7 formation characterized by sharp √3 × √3 R30° LEED pattern. The relevant ARUPS spectra exhibit essentially emission of Er4f multiplet states in the 4–11 eV binding energy window and structures at lower binding energies assigned to hybridized Er5d and Si 3sp states. Finally, we have shown that in contrast with pure Er, there is apparently no surface-related 4f component for monocrystalline ErSi 1.7 .

Magnetic properties of simple alkylene–aromatic polymers

This paper describes the results of the magnetization and the electron-spin resonance (ESR) measurements of the simplest members of alkylene–aromatic polymers (AAPs). In contrast with the previous claim of the observation of the ferromagnetism in AAPs, a distribution of the spin alignment giving 1&amp;lt;S&amp;lt;3/2 on the average has been concluded from the magnetization measurement. The spin concentration certainly coming from carbon π spins has turned out to be relatively small (∼1017–1018 spins⋅g−1 ). The ESR observation has revealed a forbidden Δms=±2 transition characteristic of a triplet or higher multiplet state of radical pairs in agreement with the observation of the local spin alignment. The relationship between the spin state and the chemical structure of AAPs has also been examined with the use of the 13C NMR spectroscopy. It is concluded that in the present material there is a ferromagnetic coupling between a few of spins such as triphenylmethyl radicals forming spin clusters of triplet or higher spin multiplet state diluted in the whole bulk.

Valence Auger and X-ray participator and spectator processes for neon and argon atoms

The rates of decay, both radiative and non-radiative, have been calculated for the valence shake-up states (vs, vp)nl of Ne(v = 2) and Ar(v = 3) for the five lowest n values. The various decay channels are discussed and trends for large n are examined. The calculations are performed at the single-configuration non-relativistic Hartree-Fock level. Inner-valence and valence-multiplet Auger channels are shown to be completely dominant, with maximum fluorescence yields of 2.7% in Ne and 0.2% in Ar. The total decay rates can be larger than the corresponding atomic K-shell rates for certain states, an extreme example being the Ar (3s, 3p)(1P)3d(2P) rate of 0.148 au. The calculated widths are shown to be consistent with the experimental results of Svensson et al (1988). The valence-multiplet participator Auger transition is a mode of decay involving a change of multiplet state for the same initial and final two-hole valence configuration, and has been shown to account for the difference in width between certain photoelectron satellites in Ne. The experimental spectrum of Becker et al (1989) is discussed in the light of present results. The valence decay mechanisms identified are expected to have general applicability to light atoms and to molecules containing first or second row atoms.

The multiplet state distribution of O(3P J) produced in the photodissociation of O2 at 157 nm

The fine structure population of O(3P) produced in the photodissociation of O2 at 157 nm was measured in a pump-and-probe experiment. The population of the ground state (J=2) was found to be 93%, with only 6% in the J=1 level and 1% in J=0. The predominance of J=2 is consistent with direct dissociation on the B 3Σ−u potential energy surface. Based on available information in the literature we rule out excitation of the 3Πu state and curve crossing to the 5Πu state as possible origins of the population with J&amp;lt;2. We infer that the populations of J&amp;lt;2 is due to nonadiabatic transitions at large distances. Two mechanisms consistent with the data are a Demkov-type interaction, which is caused by coupling by the radial kinetic energy operator.

Resonant photoemission study of the electronic structure of CuO and Cu2O.

The electronic structures of CuO and ${\mathrm{Cu}}_{2}$O have been investigated by resonant photoemission at the copper 3p threshold. The experimental data from CuO are compared with the results of a cluster calculation. From this analysis we confirm the dominant ${\mathit{d}}^{8}$ character of the states between 8 and 16 eV, and that singlet and triplet final states behave quite differently at the (3p\ensuremath{\rightarrow}3d) resonance. It is necessary to specify the multiplet state when calculating the d-d Coulomb interaction in this case since the total energy spread of the ${\mathit{d}}^{8}$ multiplets is about 8 eV. The results confirm the charge-transfer nature of the band gap in CuO. The resonance behavior in ${\mathrm{Cu}}_{2}$O is explained in terms of strong O 2p--Cu 4(sp) hybridization.

The multiplet state distribution of O(3P J) produced in the 193 nm photodissociation of SO2

The multiplet state distribution of oxygen atoms produced in the photodissociation of SO2 was measured in a pump-and-probe experiment. An ArF laser was used to dissociate the parent molecule, while the O(3P) product was detected by two-photon laser-induced fluorescence under collisionless conditions. The multiplet populations were found to be 59.2%±5.0%, 29.5%±3.2%, and 11.4%±3.3% for J=2, 1, and 0, respectively. These results are indistinguishable from the statistical distribution of 5:3:1.