Charge exchange in collisions of C60+ ions with laser-excited aligned Na atoms

We have performed the first measurement of charge exchange in keV C₆₀⁺ ion collisions with Na atoms in their 3s ground state as well as in the laser-excited and aligned 3p state. To interpret the results, we have calculated the correlation diagram of the C₆₀⁺–Na collision system using the Discrete Variational Density Functional Method. Possible channels for electron capture are studied by choosing the collision path along an axis perpendiculax to a pentagon and to a hexagon, respectively.     

Subbarrier fusion of spherical nuclei of intermediate atomic number

A two-humped model was proposed for explaining the suppression of the cross sections for the deep-subbarrier fusion of spherical nuclei that have intermediate atomic numbers. It was shown that the suppression of these cross sections was due to the interference between the incident and reflected fluxes between the two barriers. The results of fitting the cross sections calculated within the two-humped model revealed the invariability of the distance between the vertices of the two barriers. As the charges of colliding nuclei increase, the inner barrier becomes higher than the outer one, and this determines the competition with cross sections for deep-inelastic-transfer reactions.     

Sodium ions in ordered environments in biological systems: analysis of 23Na NMR spectra.

Experimentsthat selectively excite I = 32 nuclei exhibiting residual quadrupolar splittings are used to acquire 23Na NMR spectra from a range of biologically relevant samples containing sodium in ordered environments. Three complementary approaches to the analysis of such spectra are described: (i) measurement of relaxation rates, (ii) extraction of homogeneous linewidths from two-dimensional Jeener-Broekaert spectra, and (iii) simultaneous fitting of detailed theoretical functions to a series of one-dimensional Jeener-Broekaert spectra. Analysis of relaxation rates provides evidence for compartmentation in bovine nasal cartilage. Each approach is used to demonstrate the presence of anisotropy in transverse relaxation in porcine tendon. For certain samples containing collagen, a good theoretical fit to the spectra was obtained using a model that allows for anisotropic relaxation by including the effects of slow lateral and radial diffusion.     

Production of a polarized23Na beam

A vector-polarized²³Na⁺ beam has been produced using an atomic beam source and a surface ionizer. A nuclear polarization t₁₀ ≥ 0.47 was deduced from the circular polarization of the light emitted after beam-foil excitation.     

Fullerene local order in Na2CsC60 by23Na NMR

We have investigated the alkali metal fulleride Na₂CsC₆₀ by²³Na nuclear magnetic resonance (NMR), The NMR line of the tetrahedral site is split below 170 K (T and T′ lines) similarly to the A₃C₆₀ compounds with A=Rb or K. The intensity fraction of the T′ line follows the same temperature dependence as the¹³C NMR line width. We have also found that the spectrum is independent of the cooling rate. Spin-echo double resonance measurements show that T and T′ sites are mingled on a microscopic scale. We propose that the different²³Na NMR lines correspond to different fullerene orientational environments of the tetrahedral alkaline site.     

Study of fusion Q-value rule in sub-barrier fusion of heavy ions

A vast body of fusion data has been analyzed for different projectiles and target nuclei. It is indicated that the sub-barrier fusion depends on the fusion Q-value. In terms of a recently introduced fusion Q-value rule and an energy scaling reduction procedure, the experimental fusion excitation functions are reduced and compared with each other. It is found that the reduced fusion excitations of selected fusion systems show a similar trend. The fusion data for massive nuclei are in agreement with the Q-value rule. In the fusion process, the Q contribution should be considered. Within this approach, the sub-barrier fusion cross sections of most fusion systems can be predicted without involving any structure effects of colliding nuclei. Instances of disagreement are presented in a few fusion systems. The use of the energy scaling as a criterion of possible experimental data inconsistency is discussed. More precise experimental fusion data need to be measured.     

Direct inner shell ionization accompanying nuclear fusion reactions with heavy ions

Probabilities for K-shell ionization prior to fusion (half-trajectory collisions) are determined for ⁵¹V, ⁵⁹Co, ⁶²Ni target atoms and 4.5 MeV/u ⁴⁰Ar projectiles. Also measured are energy shifts of the K_α and K_β X-ray lines of residue atoms resulting from multiple inner shell ionization.     

Fusion of aligned deformed heavy ions calculated in the surface friction model

The surface friction model for heavy ion induced fusion is extended to cover collisions of aligned deformed nuclei taking into account dynamic quadrupole and octupole vibrations and rotations of the reaction partners. Calculated fusion cross sections for unpolarized beam and the tensor analyzing powerT ₂₀ for fusion of²³Na +²³Na are compared with data. The analyzing power is found to be sensitive to variations of the tangential friction strength.     

DSA lifetimes in21Na and23Na derived from experimental stopping parameters

The lifetimes for the second excited state in²¹Na and for the second to ninth excited states in²³Na have been determined with the DSA method using Ta₂O₅ and Ta as stopping materials. In the DSA analysis the experimental stopping parameters determined in the present and earlier works were utilized. The reanalysis of some earlier studies has brought very good consistency to the scattered results. Comparison of the observed transition strengths with theory has also been made.     

Multielectron processes in collisions of Xe23+ ions with Ar atoms

We report the measurements of relative cross sections for multielectron processes in collisions of Xe²³⁺ ions with argon atoms in the velocity range of 0.65–1.32 a.u. By means of the coincidence time-of-flight (TOF) technique, the final charge states of both the projectile and target ions for each collision event are determined. The present experimental data are compared with the scaling law by Selberg et al. [Phys. Rev. A 54, 4127 (1996)] and the extended classical over-barrier (ECB) model.     

On the theory of fusion and elastic scattering of deformed aligned heavy-ions

Fusion excitation functions and differential cross sections for elastic scattering of aligned, deformed^Na on spherical⁵⁸Ni nuclei are calculated as functions of the orientation of the projectile axis with respect to the scattering plane. Polarisation effects of up to 20% are predicted for a beam of fully aligned²³Na nuclei.     

A study of the excited states of23Na from the22Ne(p, γ)23Na reaction

The gamma decays of 19²²Ne(p, γ)²³Na resonances in the range ofE _p =400?1300 keV have been investigated by means of a 38 cm³ Ge(Li) detector. Branching ratios of the resonances and bound states were determined. Gamma-ray energy measurements yield the energies of 19 bound states and the value of 8794.0±1.5 keV forQ. The existence of the 3913 keV doublet state was studied through the (p, γ) reaction. No evidence for such a doublet was found.     

Influence of sodium ion dynamics on the 23Na quadrupolar interaction in sodalite: a high-temperature 23Na MAS NMR study

High-temperature ²³Na MAS NMR experiments up to 873 K for a number of different sodalites (Na₈[AlSiO₄]₆(NO₃)₂, Na₈[AlSiO₄]₆(NO₂)₂, Na₈[AlSiO₄]₆I₂, Na_7.9[AlSiO₄]₆(SCN)_7.9 · 0.5H₂O, Na₈[AlGeO₄]₆(NO₃)₂, and Na₇[AlSiO₄]₆(H₃O₂) · 4H₂O) were carried out. The spectra of the first five sodalites consist of a quadrupolar MAS pattern with different quadrupolar coupling constants. The quadrupolar interaction for the thiocyanate sodalite, the nitrate aluminosilicate, and germanate sodalite decreases strongly passing a coalescence state on heating, while the quadrupolar interaction of the iodide and nitrite sample shows nearly no change. The basic hydrosodalite shows an asymmetric lineshape at room temperature and, between 350 and 370 K, a second line due to the evaporation of cage-water emerges. The linewidth increases with rising temperature. The temperature dependence of the quadrupolar interaction seems to be a function of the sodalite β-cage expansion. Two conceivable jump mechanisms are proposed for a tetrahedral two-site jump between occupied and unoccupied tetrahedral sites.     

Absolute quantification of Na+ bound fraction by double-quantum filtered 23Na NMR spectroscopy

A method is described for the absolute quantification of double-quantum filtered spectra of spin-3/2 nuclei ((23)Na). The method was tested on a model system, a cationic exchange resin for which the number of Na(+) binding sites was quantitatively controlled. The theoretical and experimental approaches were validated on samples with different Na(+) concentrations. An excellent agreement between the results obtained by double-quantum and single-quantum acquisitions was found. This method paves the way for absolute quantification of both bound and free fractions of Na(+), which are determining factors in the characterization of salted/brined/dried food products.