K X-ray satellite structures of bromine and molybdenum

The energies and electric dipole rates of Kα X-ray satellites due to 1s-2p transitions in bromine and molybdenum with one to five vacancies in the 2p shell and other shells retaining their normal occupation numbers are computed using Multi-Configuration Dirac Fock wavefunctions with the inclusion of relativistic and quantum electrodynamic corrections. As fully relativistic calculations on all the Kα X-ray fine structure satellites with multiple spectator vacancies in the 2p shell of elements under consideration, to the best of our knowledge, are reported in this work for the first time, the accuracy of the E1 data is analyzed in terms of the agreement between the rates in the length and velocity forms. While the intensities of the strong electric dipole lines in the various groups of 1s - 2p transitions obey the well established Z dependence, many of the weak transitions vary randomly with Z and an attempt is made in this work to understand the behaviour of the spin-forbidden and weak electric dipole lines in the KαL ⁿ X-ray satellite structure of Br, Mo, I, and Au. As the number of closely spaced fine structure transitions range from a few to many depending on the spectator vacancies in the 2p shell, the intensity weighed statistical average satellite energies, line strengths and photo-ionization cross sections are reported to guide in the reliable interpretation of experimental measurements.     

Production of L X rays in energetic Cl → Cl collisions

The L X-ray spectrum from Cl⁷⁺ → Cl₂ collisions at 40 MeV is presented. The large number of lines observed are generally found to be consistent with calculations of X-ray transition energies from the “unit flourescence yield configuration”, 1s²2s²2pⁿ3s¹. The calculations indicate large X-ray energy splittings for transitions from different multiplet states. The assumption of statistical population of the multiplets is found to be consistent with the intensities of the observed lines.     

K X-ray transition energies for first row atoms and ions

X-ray energies are computed using screened, hydrogenic Slater integrals for all configurations [(1s^l2s^m2pⁿ) with l = 0 and 1, m = 0, 1, and 2, and n = 1 through Z-4] of all ionization stages of the elements boron through neon. The results include diagram lines, satellite lines, hypersatellite lines, and two-electron, one-photon lines. Excellent agreement is found between these results and those found by the Hartree-Fock-Slater method. In addition, X-ray energies associated with the spin-orbit forbidden decay of n = 2 three-electron quartet terms and four-electron quintet terms are calculated for the elements beryllium through neon. These results agree closely with those found by 1/Z perturbation theory.     

Study of cross sections for the loss of outer 1s, 2s, and 2p electrons by fast ions and atoms of light elements

In the case of light-element ions propagating with velocities V = 1.83 and 3.65 au in H₂, He, N₂, Ne, and Ar, the loss cross sections σ_{i, i+m} for m electrons (m = 1, 2, 3) are considered. The partial loss cross sections σ_i(nl) for one of the outer 1s, 2s, or 2p electrons are determined using the obtained data. It is shown that the experimental cross sections for the loss of the 1s and 2s electrons by positive ions qualitatively agree with the theoretical values calculated in the Born approximation. In the case of the ion velocity V = 1.83 au, the cross sections σ_i for 2p electrons are greater than the cross sections σ_i (1s) and σ_i (2s) by a factor of 1.2–3 for the same binding energies of electrons in the ion (I _nl > 20 eV). It is found experimentally that, at V = 1.83 au, the cross sections σ_i (2p) for I _nl ～ 10–20 eV are less than the cross sections σ_i (1s) by a factor of 2–3, which is probably caused by a decrease in the screening parameter (θ_2p < 1) of the outer shell of atoms.     

Effective electron mass in high-mobility SiGe/Si/SiGe quantum wells

The effective mass m* of the electrons confined in high-mobility SiGe/Si/SiGe quantum wells has been measured by the analysis of the temperature dependence of the Shubnikov-de Haas oscillations. In the accessible range of electron densities, n _s , the effective mass has been found to grow with decreasing n _s , obeying the relation m*/m _b = n _s /(n _s ? n _c ), where m _b is the electron band mass and n _c ≈ 0.54 × 10¹¹ cm^?2. In samples with maximum mobilities ranging between 90 and 220 m²/(V s), the dependence of the effective mass on the electron density has been found to be identical suggesting that the effective mass is disorder-independent, at least in the most perfect samples.     

Dependence of K-shell fluorescence yields on multiplet states of neon

The K-shell fluorescence yields are calculated to be equal to 0.013 and 0.028 respectively for ³P and ¹P multiplet states of 1s¹ 2s² 2p⁵ configuration of neon. This observation can significantly effect analyses of ion-atom collision experiments where in X-ray production cross-sections are measured.     

Inner shell excitation,valence excitation and core ionization in NF3 studied by electron energy-loss and X-ray photoelectron spectroscopies

Electron energy-loss Spectroscopy (EELS) at impact energies of 2.5–3 keV has been used to obtain the electron excitation spectra for the N 1s (K-shell), F 1s (K-shell) and valence shell regions of NF₃. The inner shell spectra were recorded using small angle scattering (?1° ) while the valence shell spectrum was obtained at zero degree scattering angle. The inner shell excitation spectra show a strongly enhanced 1s→ δ^* type transition and continuum features which are typical for molecules with highly electronegative ligands. One of the peaks in an earlier published photoabsorption study of the N 1s region has been shown to be due to a N₂ impurity. The valence shell electron energy-loss spectrum shows a number of transitions which are considered to be mainly due to valence-valence type transitions, with also some evidence of Rydberg structure.The X-ray photoelectron spectra (XPS) of the N 1s and F 1s electrons along with their associated satellite structures have also been recorded using Al Kα (1486.58 eV) radiation. The vertical ionization potentials for the N 1s and F 1s electrons were found to be 414.36 (10) eV and 693.24 (10) eV, respectively. Both spectra exhibit a rich and different satellite structure. These “shake-up” features in the satellite XPS spectra are compared with continuum features of the inner shell electron energy-loss spectra and also with the valence shell spectrum.     

EPR measurements on chromium doped GaAs,GaP and InP

EPR measurements have been made on chromium doped GaAs samples at 4.2 K. An n-type sample doped with chromium and silicon was irradiated with 2 MeV electrons to lower the Fermi level. No resonance from substitutional Cr⁺ (3d⁵) was detected, although the Cr_s²⁺ spectrum was observed. The generally accepted assignment of a spectrum to Cr_s⁺ for photoexcited samples must therefore be revised. An isotropic resonance with g = 2 is observed in p-type chromium doped GaAs, GaP and InP but it is still not clear whether this is due to Cr_s⁴⁺ or interstitial Cr_i⁺ (3d⁵).     

X-ray photoelectron spectroscopy of FeP phosphide

The structure of the outer and inner electron spectra of iron (2p, 3p, 3s, and 3d) and phosphorus (3s and 3p) atoms in FeP monophosphide is studied in detail by the X-ray photoelectron spectroscopy (XPS) method. On the basis of the analysis of the binding energy of electrons, as well as the parameters characterizing the structure of experimental spectra, a conclusion is made that Fe³⁺ (d ⁵) cations in FeP are stabilized in a state with intermediate value of the total spin (IS, S = 3/2). The range of values of intra-atomic parameters (10Dq, J _H ) is established in which the consideration of the high degree of covalence of Fe–P bonds may lead to the stabilization of (FeP₆)^15– clusters in the IS state.     

Electronic structure of the valence bands of H2-, Mg- and Pt-phthalocyanine derived from soft X-ray emission and photoelectron emission spectra

The soft X-ray emission and photoelectron emission spectra of H₂-, Mg- and Pt- phthalocyanine (PC) obtained using synchrotron radiation are reported and compared. In this way, an overall view of the pattern of valence bands is obtained and the electronic structure determined in terms of the component partial densities of states. In particular, from the valence p → 1s carbon and nitrogen K-emission spectra we determine for all three compounds the C and N 2p-like valence-band density of states with strong maxima located at binding energies of 8, 11 and 13.5 eV (carbon 2p) and 8 eV (nitrogen 2p) below the vacuum level. For PtPC the partial density of d-like valence states is determined from photoelectron emission difference-spectra and compared to previous XPS results. The sharp (1.2 eV FWHM) maximum of the Pt-derived partial density of states, observed at 6.9 eV binding energy, is assigned to the ⁴F term of a 5d⁸6s final-state configuration. A second, broader maximum at around 9.5 eV binding energy contains contributions from other terms of this 5d⁸ configuration, as well as from a 5d⁷ satellite (shake-up multiplet).     

Multiple-ionization satellites in LII,III X-ray emission of elements of period four in compounds

A study has been made of the influence of multiple-ionization satellites on the form of L_II,III in emission spectra of elements of the beginning of period four in compounds. In order to simulate the influence of the environment on the intensity of the satellite radiation in KCl and Sc₂O₃, the calculation was carried out in KH₆ and ScH₆ clusters. A one-channel approximation of the one-center method was used to calculate the one-electron orbitals of the clusters. It was found that the polarization of the functions of valence electrons during the appearance of an additional vacancy in the 3p shell the almost-tenfold increase in the lifetime of the 2p^–13p^–1 configuration relative to the 2p^–1 configuration leads to an appreciable influence of the multiple-ionization satellites on the L_III,III emission spectrum of potassium. In the case of scandium, the effect is slightly smaller because of the appearance of valent states located in the region of the central atom (which leads to a decrease in the lifetime of the 2p^–13p^–1 configuration), a decrease in the probability of emission of a 3p electron, and a reduction of the polarization of valent electrons upon the appearance of a 3p vacancy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 65–71, June, 1985.     

Relative intensities in X-ray photoelectron spectra.: Part VIII

The photoionization cross-sections for the 3s and 3p shells of atomic Si, P, S, and Cl and the S²⁺ ion, and for the 2s and 2p shells of atomic F have been calculated using the random-phase approximation with exchange (RPAE) for the average-configuration term. Using the theoretical atomic cross-section values, the partial cross-sections for photoionization of the SF₆ molecule have been calculated for hv ? 54 eV and the photoelectron spectra have been interpreted. The calculation of relative intensities in the photoelectron spectra of H₂S is presented. The influence of the effective charge of an atom on the photoionization cross-section value for a molecular level is shown.     

Isotopieverschiebungskonstanten von Th,U, Pu und Am

The isotope shifts of unperturbed electron configurations have been determined from isotope shift measurements in the spectra of Th, U, Pu, and Am. The screening of the 7s electron charge density at the nucleus by 6d, 7s, and 7p electrons is discussed. It turns out that the same screening factors as for the 6s electron in lighter elements can be used. The screening of the 7s electron charge density at the nucleus by one 5f electron amounts to about 25%: [δT(f ⁿ s)?δT(f ⁿ )]/[δT(f ⁿ }s)?δ(f ^n} )]=0.7₅. The charge density at the nucleus due to the filleds (andp _1/2) shells is considerabely screened by anf electron. The isotope shiftδT(f^n}-1 d ^m +2)?δT(f ⁿ d ^m ) produced by this effect is of the same order of magnitude as the isotope shiftδT(f ⁿ d ^m s)-δT(f ⁿ d ^m ) due to ans electron. The experimental isotope shift constants are found to be:Β C _exp(Th²³⁰–Th²³²)=880±120;Β C _exp(U²³³–U²³⁵)=1000±180;Β C _exp(U²³⁴–U²³⁶)=1070±200;Β C _exp(U²³⁶–U²³⁸)=1080±180;Β C _exp(Pu²³⁸–Pu²⁴⁰)=1200±120;Β C _exp(Pu²³⁹–Pu²⁴¹)=1060±100;Β C _exp(Pu²⁴⁰–Pu242)=900 ±90;Β C _exp(Am²⁴¹–Am²⁴³)=890±50 [10^?3cm^?1]. The ratiosΒ C _exp/C _th are discussed.     

Shubnikov-de Haas effect of n-inversion layers in InSb grain boundaries

Hall effect and Shubnikov-de Haas effect have been investigated in a n-inversion layer adjacent to the grain boundary in p-InSb bicrystals. The observed quantum oscillations of the magnetoconductivity result from a superposition of the Shubnikov-de Haas effect in two occupied subbands. The electron densities of the subbands n_si(n_s1=3.5 × 10¹¹cm^-2;n_s0= 1.1 × 10¹²cm^-2) and the effective cyclotron mass of the lower subband m_c0=(0.023 ± 0.002)m₀ have been evaluated.     

Impact broadening and shifts for 6sns 1S0 and 6snd 1D2 series of barium

Impact broadening and shifts of Ba transitions to parity forbidden Rydberg states have been measured using two-photon laser spectroscopy techniques. Broadening and shift rates for the 6sns ¹S₀ (10 < n < 19) and 6snd ¹D₂ (8 < n < 26) levels due to thermal collisional interactions with Xe, Kr and Ar as perturber gases are plotted. Perturbations due to configuration interactions are discussed.     

Microstructural changes induced in borosilicate glasses by 1 MeV electrons

Radiation damage to borosilicate glass has been studied using a high voltage electron microscope to simultaneously generate and image structural changes At low doses and dose rates (φ ? 5 × 10²⁴ electrons m^-2, F ? 5 × 10²² el m^-2 s^-1), ionic depletion generates a new crystalline phase rich in S₁O₂ For incubation doses exceeding 5 × 10²⁴ electrons m^-2, gas bubbles are observed High damage rates are necessary for bubble nucleation though not for their subsequent growth The critical nucleation flux increases rapidly with irradiation temperature, whereas the gas precipitation efficiency remains constant above 300 K.     

C/N/O centred metal clusters: super valence bonding and magic structure with 26 valence electrons

By using genetic algorithm combined with B3LYP and QCISD methods, this paper investigates the stabilities and electronic structures of Al₆OM_m (M?=?Na, K; m?=?2,4,6) and a few other Al_nXNa_m (X?=?C, N, O) clusters. The results show that the nonmetal doped metal clusters with 26 valence electrons have enhanced stabilities and large energy gaps. This paper extends the Jellium model for the application to the nonmetal doped metal clusters and explains the electronic origin of this strong magic structure. The nonmetal X atom is situated in the centre of the magic clusters. The 2s/2p orbitals of the central atom interact strongly with the superatomic 1S/1P orbitals and form bonding and antibonding orbitals. The bonding orbitals make the C/N/O atoms form s²p⁶ shell closure, and the antibonding orbitals make the metal moieties form closed 2S²2P⁶ shells. The 26 valence electrons form closed s²p⁶S²P⁶D¹⁰ shells, and this electronic configuration can be taken as the combination of the octet rule and 18-electron rule. The octahedral Al₆O^2? core is a superatomic anion with great stability, and it can be used as building blocks to assemble Zintl phase materials by interaction with alkali metals.     

Low-lying intrinsic energy levels in the nucleus170Ho

The band-head energies of the two-quasiparticle states expected in the doubly odd deformed nucleus¹⁷⁰Ho are calculated for a zero range residual interaction. The results are compared with the available experimental information. It is concluded that the ground state has the Nilsson configuration 6⁺{7/2^?[523↑] _p }+5/2[512↑] _n being the 2.76m isomer whereas the 43s isomer is the 1⁺ ∑=0 state arising from the same configuration and lies at about 100 keV excitation energy in agreement with the experiment. The first excited state in this nucleus is predicted to be the 4^?{3/2⁺[411↑] _p +5/2^?[521↑] _n } state close to the ground state with the corresponding 1^? ∑=0 member expected to appear well above the 1⁺ isomer.     

Description of the smooth rms charge radius surface R(N, Z) and prediction of neutron skin by a two-liquid drop model

The smooth N and Z dependence of nuclear rms charge radii is interpereted by a two-liquid drop model with ?_p+?_n=?₀=const. Proton and neutron radii R _p and R _n are given in closed form. In addition to rms charge radii, the model yields the nucleon number dependence of the skin thickness, s, e.g. ds=0.00124×dA for Sn isotopes, in agreement with experimental results and theoretical calculations. A strong correlation between the two global parameters of the model — including s _stthe skin thickness of the stable isotope — is established. If s _stis taken from experiment, the other parameter is also fixed; this parameter (m) characterizes the restoring force responsible for the skin thickness. Its value m=2.2 suggests that — in addition to the number of nucleons in the skin — the skin thickness also influences the distribution of “surplus” nucleons between volume and skin.     

Effect of oxygen content and charge on the structure,stability and optoelectronic properties of yttrium oxide clusters

The electronic and geometrical structures of neutral and charged YOn (n=2–12) clusters have been investigated using density functional theory (DFT) with generalized gradient approximation. The oxygen atom in YOn has been found to be in oxo, peroxo and in superoxo forms. The geometrical structures and topologies of small size anionic clusters resemble that of neutral clusters. Yttrium showed higher coordination number than scandium. Computed results reveal the existence of YO₁₀ cluster to have a penta-peroxo oxygen with a homoleptic Y(η² –O₂)₅ geometrical configuration. The HOMO–LUMO gaps decrease with increasing n due to the increase in 2p orbital population of oxygen atoms. It has been shown that in these clusters bonding are predominantly ionic in nature and anions are thermodynamically more stable, due to the charge delocalization between the metal atom and oxygen ligands. YO₁₀⁺ and YO₁₂⁺ were found to be highly exothermic to release one and two oxygen molecules, while YO₁₁⁺ dissociates though the ozonide dissociation channel. Computed absorption spectra of small clusters are mainly contributed by yttrium metal d and s valence orbitals. The absorbance spectra, shifts towards lower energy with cluster size increase, while charge has no substantial effect on the absorption spectrum.