Fine structure of the giant dipole resonance in 16O as observed by inelastic electron scattering at 180°

Higher resolution measurements on the giant resonance excitation in ¹⁶O have been performed by inelastic electron scattering at 180°. Considerably more structure was found than in previous experiments of Goldemberg and Barber. The results indicate that the integrated strength of the giant resonance plotted as a function of momentum transfer q behaves as predicted by the particle-hole calculations of Lewis and Walecka. However, a pronounced shift in dipole strength turned out to be much smaller than predicted by the theory.     

Resonant structure due to the 3p→3d transition in the photoionization of Ca+

Many-body perturbation theory has been used to calculate the resonance structure (3p→3d) into the photoionization (4s→kp) for ion Ca⁺. This resonance structure results from the interference between a photoionization process or a photoionization with excitation process and a resonant Auger process. The coupled equation method has been improved to calculate this interference by the summation of specific classes of diagrams of perturbation theory to infinite order. The resonance structure in the region of the 3p threshold is enhanced via a super-Coster–Kronig transition. The theoretical results are in good agreement with experiment.     

Excitation of the giant dipole resonance in μ-capture

A previously proposed approximate method of the unified reaction theory is applied to the problem of neutron emission in muon capture. The obtained total first-forbidden transition probability for the reaction ¹⁶O(μ⁻, νn)¹⁵N is in agreement with the experiment. The resonance structure of the neutron spectrum appears as a consequence of the channel coupling.     

Landau damping and frequency-shift of a quadrupole mode in a disc-shaped rubidium Bose–Einstein condensate

The damping and frequency-shift in Landau mechanism of a quadrupole mode in a disc-shaped rubidium Bose–Einstein condensate are investigated by using the Hartree–Fock–Bogoliubov approximation. The practical relaxations of the elementary excitations and the orthometric relation among them are taken into account to obtain advisable calculation formula for damping as well as frequency-shift. The first approximation of Gaussian distribution function is employed for the ground-state wavefunction to suitably eliminate the divergence of the analytic three-mode coupling matrix elements.According to these methods, both Landau damping rate and frequency-shift of the quadrupole mode are analytically calculated. In addition, all the theoretical results agree with the experimental ones.     

Fine structure in the α decay of202Rn

The α decay of mass-separated²⁰²Rn is studied at the ISOLDE separator. Time sequential α-singles spectra together with α-X-t and α-e-t coincidence events are collected. Fine structure in the α decay is observed and feeding of a low-lying 0 ₂ ⁺ state at 816 keV in¹⁹⁸Po is evidenced. This 0⁺ state can be interpreted as the bandhead of an intruder-state based deformed band, coexisting with the spherical groundstate band. Mixing between normal and intruder states is discussed. A preliminary α-decay study of²⁰⁰Rn did not yet reveal any fine structure.     

Admixture of the giant dipole resonance to low lying 1−-states in heavy nuclei

The mass of ¹³ Be has been measured with the reaction ¹³ C(¹⁴ C,¹⁴ O)¹³ Be at E _Lab =337 MeV. A Q-value of Q ₀=–37.02(5) MeV was obtained and the mass excess is M.E.=35.16(5) MeV. If the observed line corresponds to the ground state,¹³ Be is particle unstable with respect to the oneneutron emission by 2.01 MeV. The observed line width of 0.3(2) MeV supports an assignment ofJ =5/2⁺ or 1/2^–, but excludesJ =1/2⁺. An excited state is seen at 3.12(7) MeV; there are indications of a second excited state at 6.5(2) MeV.     

Fine structure period of the thermo-spectrum of the stimulated Raman 8050 Å line in benzene

A fine structure of 2.2°C period on the thermo-spectrum of the 8050 Å stimulated Raman output in benzene is reported, in addition to the previously reported large period.     

Determination of the Landau–Lifshitz damping parameter by means of complex susceptibility measurements

A new experimental method for the determination of the Landau–Lifshitz damping parameter, α$\alpha$, based on measurements of the frequency and field dependence of the complex magnetic susceptibility, χ(ω,H)=χ^′(ω,H)-iχ^″(ω,H)$\chi (\omega ,H)={\chi }^{\prime }(\omega ,H)-\mathrm{i}{\chi }^{″}(\omega ,H)$, is proposed. The method centres on evaluating the ratio of f_max/f_res, where f_res is the resonance frequency and f_max is the maximum absorption frequency at resonance, of the sample susceptibility spectra, measured in strong polarizing fields. We have investigated three magnetic fluid samples, namely sample 1, sample 2 and sample 3. Sample 1 consisted of particles of Mn_0.6Fe_0.4Fe₂O₄ dispersed in kerosene, sample 2 consisted of magnetite particles dispersed in Isopar M and sample 3 was composed of particles of Mn_0.66Zn_0.34Fe₂O₄ dispersed in Isopar M  . The results obtained for the mean damping parameter of particles within the magnetic fluid samples are as follows: 〈α(_{Mn0.6Fe0.4Fe2O4})〉=0.057$〈\alpha ({\mathrm{Mn}}_{0.6}{\mathrm{Fe}}_{0.4}{\mathrm{Fe}}_2{\mathrm{O}}_4)〉=0.057$ with the corresponding standard deviation SD=0.0104$\mathrm{SD}=0.0104$; 〈α(_Fe3O4)〉=0.1105$〈\alpha ({\mathrm{Fe}}_3{\mathrm{O}}_4)〉=0.1105$ with the corresponding standard deviation, SD=0.034$\mathrm{SD}=0.034$ and 〈α(_{Mn0.66Zn0.34Fe2O4})〉=0.096$〈\alpha ({\mathrm{Mn}}_{0.66}{\mathrm{Zn}}_{0.34}{\mathrm{Fe}}_2{\mathrm{O}}_4)〉=0.096$ with the corresponding standard deviation, SD=0.037$\mathrm{SD}=0.037$.     

14N nuclear quadrupole resonance study of the NO−2 ion in simple nitrites

The nitrogen-14 nuclear quadrupole resonance spectrum of several simple nitrites has been observed and found to be relatively insensitive to the particular crystal lattice. The results are interpreted in terms of the electronic structure of the NO⁻₂ ion.     

Is the negative temperature coefficient of the resistivity of the quasicrystals due to chemical disorder?

We have found that the electronic transport of the binary icosahedral (i) Cd-Yb is extremely sensitive to a minute substitution of Mg for Cd atoms; the positive temperature coefficient of the resistivity (TCR) at low temperatures seen in the binary i Cd-Yb disappears by addition of only 0.1 at. % Mg and, moreover, the TCR stays negative well up to 60 at. % Mg. Such sensitiveness of the resistivity in the very dilute Mg concentration region, which is a consequence of the long coherence length (>28 A) of the conduction electrons in the quasiperiodic lattice, has led us to an unexpected conclusion: The negative TCR in the ternary i phase is due to partial chemical disorder; i.e., it is not a consequence of the quasiperiodicity.     

Fine structure in reflectivity near the band gap of Cd1−xZnxS solid solutions

The energy variation of E_∘ reflectivity peaks in Cd₁₋xZn_xS hexagonal single crystals has been measured as a function of x. At 80°K, fine structure associated with splitting of the uppermost valence band is resolved across the whole composition range. The quasi-cubic model of Hopfield is used to calculate the variation in spin orbit and crystal field splittings between CdS and ZnS.     

On the mechanism of the temperature evolution of the symmetric magnetic hyperfine structure of Mössbauer spectra of magnetic nanoparticles to the quadrupole doublet of lines

The multilayer relaxation model of Mössbauer spectra of an ensemble of single-domain particles has been generalized to the case of the presence of the electric field gradient on nuclei with a chaotic orientation of its principal axes. The generalized model makes it possible to take into account the physical mechanisms of the formation of the hyperfine structure of the spectra in the real situation and to numerically describe the qualitative features of the temperature evolution of the spectra from symmetric magnetic sextet to the quadrupole doublet of lines, which is observed in most experimental spectra of ⁵⁷Fe nuclei in magnetic nanoparticles.     

A numerical investigation of the evolution of 2-D disturbances in hypersonic boundary layers and the effect on the flow structure due to the existence of shocklets

~~A numerical investigation of the evolution of 2-D disturbances in hypersonic boundary layers and the effect on the flow structure due to the existence of shocklets~~     

Fine and hyperfine structure in the X2Σ+ state of gas-phase yttrium monoxide

The A²Π_r-X²Σ⁺ visible spectrum of gas-phase yttrium monoxide has been studied at sub-Doppler resolution to obtain information on the spin-rotation and ⁸⁹Y nuclear magnetic hyperfine interactions. The observations were fitted to an effective Hamiltonian model that neglected the nuclear magnetic hyperfine interactions in the excited electronic state. An interpretation of the determined parameters in terms of possible electronic configurations is presented.     

Fine structure and inverse population in the MnKβ1 spectra of MnxZnyFezO4 ferrites

The electronic structure of Mn_xZn_yFe_zO₄ single-crystal ferrites was investigated. The fine structure of their X-ray spectra was found to correlate with the populations of quantum states. A scheme is suggested for the evolution of the electronic structure with strengthening exchange interaction of valence electrons as the chemical composition of the system becomes more complex. The metal-insulator phase transition is possible in the range of compositions corresponding to densities from ρ=5.097 g/cm³ to ρ=5.125 g/cm³, where manganese changes its charge state.     

Fine structure in the α-decay of radium isotopes with mass numbers 209-212

Radium isotopes with mass numbers from 209 to 212 have been produced by heavy-ion fusion reactions ²⁰⁴Pb( ¹²C, xn) ^216-Ra. Radioactive decay properties were investigated by means of α- and α-γ-spectroscopy after in-flight separation of the evaporation residues from the projectile beam by the velocity filter SHIP and implantation into a 16-strip position-sensitive Si detector. For the even-even nuclei ^210,212Ra we identified α transitions into the first-excited 2⁺-state of the daughter nuclei ^206,208Rn. Weak α transitions into excited levels of the odd-A daughter nuclei ^205,207Rn were also observed. Received: 19 August 2002 / Accepted: 6 November 2002 / Published online: 18 February 2003 RID="a" ID="a"e-mail: f.p.hessberger@gsi.de Communicated by D. Guerreau