The collective bands of positive parity states in odd-A (fp) shell nuclei

The low-lying collective bands of positive parity states in (fp) shell nuclei are described in the deformed Hartree-Fock method by projecting states of definite angular momenta from ‘the lowest energy intrinsic states in (sd)⁻¹ (fp) ⁿ⁺¹ configurations. The modified Kuo-Brown effective interaction for (fp) shell and modified surface delta interaction (MSDI) for a hole in (sd) shell with a particle in (fp) shell have been used. The collective bands of states are in general well reproduced by the effective interactions. The excitation energies of the band head states are however off by about one MeV. The calculated magnetic moments of the band headj=3/2⁺ states are in reasonable agreement with experiment. Using effective chargese _p=1.33e ande _n=0.64e we get fairly good agreement forE(2) transitions. The hinderedM(1) transition strengths are reproduced to the correct order however they are slightly higher compared to experiment.     

Infrared Spectra and Configuration of Anion Radical and Dianion of Benzil and Benzil-18o

Abstract

Infrared spectra of the products of one- and two -step reduction of both benzil and benzil-¹⁸0 have been investigated in dimethylsulfoxide-d₆ and tetrahydrofurane solutions. Anion-radicals have been obtained by electrochemical reduction of benzil and benzil-¹⁸0; dinegative ions have been prepared by reduction of the same ketones with potassium mirror in vacuo. The band assignment has been performed using the group vibrational concept and isotopic shift data. The previous assignment of the C[dbnd]O stretching band of benzil anion-radical-has been discussed and corrected. Two bands in the infrared spectra of benzil dianion have been found to be sensitive upon ¹⁸0 isotope labelling. This result certifies the presence of cis-configuration of benzil dianion in the investigated solutions. A decrease of ca. 290 cm-¹ has been found for vC[dbnd]O after the transformation of the neutral benzil into an anion-radical. Conversion of benzil anion-radical into dianion has been accompanied by an additional vC[dbnd]O downward shift of 105 cm^?1     

The interacting states (020), (100), and (001) of H217O and H218O

A fit of about 350 rotational levels of the (020), (100), and (001) vibrational states has been performed for H₂¹⁷O as well as for H₂¹⁸O leading to the determination of 51 rotational and coupling constants for each isotopic species. The Fermi-type interaction and the two Coriolis-type interactions have been taken into account by appropriate rotation-vibration operators and the v-diagonal part of the Hamiltonian is, for each vibrational state, a Watson-type Hamiltonian. The results are very satisfactory since 87% of the experimental levels are reproduced within 15 × 10^?3 cm^?1.     

Electronic structure of TiO<Subscript>2</Subscript> rutile with oxygen vacancies: Ab initio simulations and comparison with the experiment

The electronic structure of TiO₂ rutile with oxygen vacancies, which is a promising insulator, has been analyzed. The ab initio density functional calculations, as well as the comparative analysis of the results obtained in the σ-GGA spin-polarized generalized approximation and those obtained by the σ-GGA + U method with allowance for Coulomb correlations of d electrons titanium atoms in the Hartree-Fock approximation for the Hubbard model, have been performed. It has been found that the effective electron mass in rutile is anisotropic and there are both light (m _e ^* = (0.6–0.8)m ₀, where m ₀ is the free-electron mass) and heavy (m _e ^* > 1m ₀) electrons, whereas holes in rutile are only heavy (m _e ^* ⩾ 2m ₀). It has been shown that the σ-GGA + U method gives a deep occupied level in the band gap and that an oxygen vacancy in rutile is an electron and hole trap.     

Inelastic electron-nucleus interactions at 5 GeV detected by ARGUS

Beam-gas events taken with the ARGUS detector at thee ⁺ e ^?-storage ring DORIS-II have been used to study interactions ofe ^± at 5 GeV with light nuclei mainly¹⁶O. The selection ofe ^{± 16}O events is discussed. The spectra of secondary protons and charged pions are found to be similar to those of hA interactions in accordance with the nuclear scaling. Measurements of like-particle (p p andπ π) correlations at small relative momenta were used to determine the radius of particle emission region ine ^{± 16}O interactions. This radius proved to be equal within errors to the radius of particle emission region in hC interactions. No any narrow diproton resonance has been observed in the mass region from 1.9 to 2.2 GeV.     

The 5v 3 bands of 18O enriched ozone: line positions of 16O16O18O, 16O18O16O, 16O18O18O and 18O16O18O

The four 5v ₃ bands of ¹⁸O enriched ozone have been observed and analysed for the first time. Two species (¹⁶O¹⁸O¹⁶O and ¹⁸O¹⁶O¹⁸O) belong to the C_2v symmetry group and two other (¹⁸O¹⁸O¹⁶O and ¹⁶O¹⁶O¹⁸O) to the C_s symmetry group. They have been recorded at a resolution of 0.008 cm^?1 with a pathlength of 32.16 m. Despite the very weak absorptions observed, almost 250 energy levels have been derived for each of the 4 species, with J ? 35 and K _a ? 13, and suitable sets of Hamiltonian parameters have been determined. For 3 species it has been necessary to account for the resonance between the (005) and (311) states to correctly reproduce the spectra observed. These resonances, anharmonic for C_2v, and hybrid (both anhar-monic and Coriolis) for C_s symmetry confirm the accidentally extremely strong coupling between the (005) and (311) states for ¹⁶O₃, due in that case to the very close distance between unperturbed energy levels. This work also confirms the excellent prediction of band centres of these four species derived from the recently determined isotopically invariant molecular potential function.     

Excited states in neutron-rich 188W produced by an 18O-induced 2-neutron transfer reaction

Excited states in neutron-rich ¹⁸⁸W have been populated using a ¹⁸⁶W(¹⁸O,¹⁶O) reaction. In-beam γ-rays were measured in coincidence with scattered particles detected by a high-resolution ΔE-E Si telescope. In this experiment, the ground-state band has been identified up to I ^π = 8⁺. The γ band, the K ^π = 2^- octupole band, and a 2-quasiparticle state were also observed. The results are compared with predictions of self-consistent HFB cranking calculations and blocked-BCS multi-quasiparticle calculations.     

First principles theory of hyperfine interactions in spinels: ZnAl2O4

The nuclear quadrupole interactions of²⁷Al and⁶⁷Zn, both at the B-site in the spinel ZnAl₂O₄ have been studied using the Hartree-Fock cluster procedure including the influence of the ions outside the cluster. The theoretical value –3.85 MHz ofe ² qQ for²⁷Al is in very good a agreement with the experimental value of 3.68 MHz (sign undetermined). For⁶⁷Zn at the Al site the theoretical value is –8.26 MHz in reasonable agreement with the experimental value of –11.34 MHz indicating that lattice distortion effects associated with Zn as an impurity at the Al site are relatively small.     

(e, 2e) triple differential cross section for ionization-excitation of helium

Simultaneous ionization and excitation of helium by electron impact is considered in an improved second Born approximation. The wave function of the low energy ejected electron is obtained in the field of residual He⁺ ion in 2s-state. The calculation has been done for the processe ⁻+He→e ⁻+He⁺(2s)+e ⁻ in the coplanar asymmetric geometry with Hartree-Fock wave function of Byron and Joachain for the helium ground state and the results are compared with the absolute experimental data of Dupreet al [J. Phys. B25, 259 (1992)] at ∼ 5.5 keV incident energy. Our results are found to increase the ratio of the recoil peak to binary peak intensity by about 30% over the first Born results and thus to bring it closer to the experimental data.     

MRCI study on spectroscopic and molecular properties of four low-lying electronic states of the BO radical

The potential energy curves (PECs) of four low-lying electronic states of the BO radical, including two ²Σ⁺ and two ²Π states, have been studied using the full valence complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with the cc-pV5Z basis set for internuclear separations from 0.05 to 2.0 nm. The effect on the PECs by the relativistic correction has been taken into account. With these PECs, the spectroscopic parameters (T_e, D₀, D_e, R_e, ω_e, ω_ex_e, α_e and B_e) of two main isotopologues (¹¹B¹⁶O and ¹⁰B¹⁶O) have been determined. These parameters have been compared in detail with those of previous investigations reported in the literature, and excellent agreement has been found between the available data and the present results. By solving the radial Schrödinger equation of nuclear motion, 60 vibrational states for the ¹¹B¹⁶O(X²Σ⁺), 60 for the ¹⁰B¹⁶O(X²Σ⁺), 66 for the ¹¹B¹⁶O(A²Π) and 64 for the ¹⁰B¹⁶O(A²Π) are predicted for the non-rotating molecule. For each vibrational state of the ¹¹B¹⁶O(X²Σ⁺), ¹⁰B¹⁶O(X²Σ⁺), ¹¹B¹⁶O(A²Π) and ¹⁰B¹⁶O(A²Π), the vibrational level G(υ), inertial rotation constant B_υ and centrifugal distortion constant D_υ have been determined. Comparison with the available data shows that the present molecular constants are reliable and accurate. The ro-vibrational levels have been calculated for the X²Σ⁺ and A²Π states of two main species for future laboratory research.     

Directed polymers in Hartree-Fock approximation

A replica trick is used to map the problem of directed polymers into a quantum mechanics problem ofn-body bound states. This bound-state problem is then treated using a self-consistent method of Hartree-Fock. Ford=2, the exact result of the DP exponents is reproduced; and for complex DP, the ground-state energyE _n n² is found, confirming previous numerical results.     

Experimental studies of few-body systems at MAMI

Few-body experiments at the Mainz Microtron were focused on a number of selected topics. Double-polarization experiments to determine the neutron electric form factor G_en have been performed using both deuterium and polarized helium-3 targets. The structure of ³He has been studied in the reactions ³H e⃗ e(e⃗e,e′n) and ³H e⃗ e(e⃗e,e′p) with large (transversal) missing momenta and in quasi-elastic electron scattering. Electromagnetically induced two-nucleon knockout has been investigated in order to study the role of correlated nucleon-nucleon motion in the nucleus. Measurements of the (e,e′pn) reaction on ³He and ¹⁶O were performed for the first time. A triple-polarization experiment of type ³H e⃗ e(e⃗e,e′e⃗p⃗)d has been performed, where, in addition, the spin of the knocked out proton is analyzed. This measurement provides information on the spin-dependent momentum distribution of proton-deuteron clusters in the ³He nucleus. Hence, by tagging the outgoing deuteron spin-polarized ³He might also serve as an effective polarized proton target for electron scattering experiments. Moreover, in inclusive ^3,4He(e,e′) measurements at low momentum transfer, the effect of 3-body-forces has been studied.     

Nuclei in the vicinity of ‘island of inversion’ through the fusion reaction

The level structures of N ～ 19 nuclei such as ^32,34P have been investigated using the ¹⁸O(¹⁸O,xnyp) and ¹⁸O(¹⁶O,xnyp) reactions at an incident beam energy of about 34 MeV. The de-exciting γ-transitions were recorded using an array of clover detectors. These detectors have the dual advantage of higher efficiency at E _γ ≥ 2 MeV, and are capable of providing information on the linear polarization of the observed γ-transitions. These polarization measurements when coupled with the angular correlations help us to assign uniquely the spin parity for the observed levels. The experimental results have been compared with the predictions of the spherical shell model. The shell-model calculations are able to reproduce the observed energy levels to a reasonable degree. However, the observed transition probabilities are not reproduced by the calculations. Hence there is a need to re-visit these calculations using more detailed and microscopic effective interactions.     

Collective states in 48V

The low-lying positive parity states of ⁴⁸V have been studied in the framework of deformed configuration mixing model calculations based on projected Hartree-Fock theory, within the full fp shell space. The modified Kuo-Brown effective interaction has been used. The calculated spectrum and the electromagnetic properties of these states are in good agreement with the experiment. The calculation predicts an excited low-lying collective K = 2⁺ band in the spectrum of ⁴⁸V and accounts for the observed breakdown of the “signature” selection rule arising in the shell-model calculation within the ($\text{f}\text{7}\text{2}\text{)}{}^{\mathrm{nd}}$ space. It does not favour a 5⁺ assignment to the observed 1.099 MeV level. Two sets of proton and neutron effective charges (i) e_p = 1.32e and e_n = 0.89e and (ii) Kuo and Osnes charges e_p = 1.25e and e_n = 0.47e were employed. The observed decay properties appear to favour the latter charges. Our model also explains in a semiquantitative way the observed K-value, moment of inertia parameter and the intrinsic quadrupole moment of the K = 1^?1 rotational band.     

Approximate SCF calculations on the [Mn(H2O)6]2+ complex with a minimal basis set

In the restricted Hartree-Fock scheme approximate SCF-LCAO calculations have been performed for the [Mn(H₂O)]₆ ²⁺ complex using a minimal basis set consisting of nine Slater-type orbitals of the manganese ion and four Slater-type orbitals of the water molecule. The 1s, 2s and 2p orbitals of the manganese ion and the 1s orbital of the oxygen atom are treated as frozen core orbitals. In evaluating the different parts of the Hartree-Fock operators we used a two-centre approximation for the multicentre integrals. A new aspect of the calculations is the use of the Hartree-Fock orbital energies of the free water molecule as a first approximation for the corresponding orbital energies of the complex. The calculations have been done for the ground states and six excited states of the complex with symmetry T _h and also for the ground states of two distorted complexes. From the resulting eigenvectors we calculated the hyperfine interaction of the valence electrons of the central ion with the protons of the water molecules for three different geometries. The excited states give two different ways of finding values of 10 Dq and the Racah parameters B and C. The results are encouraging.     

Initiation and Sustainment of Unipolar Arc Discharges by a Microsecond Pulse Plasma

Unipolar arcs have been produced by contacting metal surfaces with microsecond pulse plasmas. Plasma temperature T_e, density n_e and potential (with respect to ground) were controlled in the limits 7–12 eV, 10¹⁸–10¹⁹ m^?3, 20–40 V, respectively, and the influence of these parameters on arc current amplitude (50–500 A) and ignition probability has been investigated. It was found that the ignition is the most limiting process requiring surface contaminations as well as the transport of net currents to the surface. The amplitude of the current was proportional to n_eT_e^1/2.     

1H and 13C NMR Spectral Study of Some 2r-Aryl-6c-phenylthian-4-ones,Their 1-Oxides and 1,1-Dioxides

ABSTRACT

Four 2r-aryl-6c-phenylthian-4-ones 1b?1e and their 1-oxides 2b?2e and 1,1-dioxides 3b?3e have been newly synthesized. ¹H and ¹³C NMR spectra have been recorded for all these compounds and 2r,6c-diphenylthian-4-one 1-oxide 2a. ¹³C NMR spectrum has been recorded for the sulfone 3a of 1a. For selected compounds ¹H-¹H COSY, HSQC, HMBC, and NOESY spectra have been recorded. The vicinal proton–proton coupling constants suggest that in all these compounds, the heterocyclic ring adopts chair conformation with equatorial orientations of the aryl and phenyl groups. Proton and carbon chemical shifts suggest that in the sulfoxides, the S=O bond is axial and enhances the J _aa value by some special effect. The S = O bond causes a significant upfield shift even on carbons without hydrogens. Significant solvent shifts also were observed.     

Line positions and strengths of OCO, OCO and OCO between 2200 and 7000 cm

Line positions and strengths of ¹⁶O¹²C¹⁸O (628), ¹⁸O¹²C¹⁸O (828) and ¹⁷O¹²C¹⁸O (728) were measured between 2200 and 7000 cm⁻¹ using 22 near infrared (NIR) absorption spectra recorded at 0.01-0.013 cm⁻¹ resolution with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. These data were obtained at room temperature using absorption cells with optical path lengths ranging from 2.4 to 385 m; the cells were filled with natural and ¹⁸O-enriched samples of CO₂ at pressures ranging from 0.54 to 252 torr. The observed line positions were analyzed to obtain the upper state band centers and rotational constants for 17 bands of ¹⁶O¹²C¹⁸O, 19 bands of ¹⁸O¹²C¹⁸O and 8 bands of ¹⁷O¹²C¹⁸O. The majority of the ¹⁸O¹²C¹⁸O and ¹⁷O¹²C¹⁸O bands were measured for the first time. In addition, the rotational constants for the lower states 00001, 01101e and 01101f were derived for all three species using the method of combination differences in which the averaged values obtained from the line positions of two or more bands were least-squares-fitted. Rovibrational parameters were also obtained for the 02201e, 02201f, 10002 and 10001 states of ¹⁸O¹²C¹⁸O. The line position analysis revealed that transitions of the levels 38 ? J′ ? 46 of the 11111f ← 01101f band of ¹⁸O¹²C¹⁸O are perturbed. Perturbed transitions were also observed for the 12212 ← 02201 band and in the high-J transitions (J′ ? 49) of the 20012 ← 00001 band of ¹⁸O¹²C¹⁸O. Band strengths and Herman-Wallis-like F-factor coefficients were determined for 21 bands of ¹⁶O¹²C¹⁸O, 25 bands of ¹⁸O¹²C¹⁸O and 8 bands of ¹⁷O¹²C¹⁸O from least-squares fits to more than 3700 measured transition intensities; band strengths and line positions for 34 of these bands were obtained for the first time.     

The Dual Mode Microwave Afterglow Apparatus for Measuring the Electron Temperature Dependence of the Electron‐Ion Recombination

Three dual mode microwave apparatus (one using S ‐band and two using X ‐band) have been developed to determine ambipolar diffusion and electron‐ion recombination rates under conditions such that T_gas = 300K and T_e is varied from 300 K to 6300 K, in the afterglow period of the dc glow discharge. TheTM₀₁₀ cylindrical cavity (in S ‐band) and TM₀₁₁ open cylindrical cavity (X ‐band) are used to determine the electron density during the afterglow period and a non‐resonant waveguide mode is used to apply a constant microwave heating field to the electrons. To test the properties of the apparatus the neon afterglow plasma has been investigated. At T_e = 300 K a value of α (Ne⁺₂) = (1.7± 0.2) × 10^–7cm³/s is obtained which is in good agreement with values of other investigators. Also similar variations of α as T^–0.4_e (S ‐band) and as T^–0.42_e (X ‐band) obeyed over the range 300 ≤ Te ≤ 6300K are in good agreement with some other previous measurements. The simplicity of the X‐band microwave apparatus also allows the measurements of the gas temperature dependency and the study of electron attachment and may be used simultaneously with optical or mass spectrometry investigations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)