Search results for " Neutron scattering"
showing 10 items of 205 documents
Comparison of woods-saxon and double-folding potentials forα-particle scattering from54Fe at 24.5 MeV
1988
Inelastic-scattering data are presented forα-particles of 24.5 MeV from54Fe over the range 15° to 175° in the centre-of-mass system. The real part of the optical potential is calculated microscopically using the M3Y effective interaction of Bertschet al. and the DDM3Y density-dependent interaction. Elastic scattering has been analysed by using as real part of the optical potential M3Y, DDM3Y and Woods-Saxon forms (WS), taking in all three cases as imaginary part a WS potential. To fit the data the double-folding potential needs to be normalized by a factor of ⋍1.6 for the M3Y interaction and of ⋍1.13 for the DDM3Y interaction. By the study of the invariant-point ambiguity it has been observ…
Spin-coupling topology in the copper hexamer compounds A2Cu3O(SO4)3 (A=Na, K)
2020
The compounds ${A}_{2}\mathrm{C}{\mathrm{u}}_{3}\mathrm{O}{(\mathrm{S}{\mathrm{O}}_{4})}_{3}$ $(A=\mathrm{Na},\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ are characterized by copper hexamers that are weakly coupled to realize antiferromagnetic order below ${T}_{N}\ensuremath{\approx}3\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. They constitute quantum spin systems with $S=1$ triplet ground states. We investigated the energy-level splittings of the copper hexamers by inelastic neutron scattering experiments covering the entire range of the magnetic excitation spectra. The observed transitions are governed by very unusual selection rules that we ascribe to the underlying spin-coupling topology. This…
SANS polarization analysis at V4 SANS instrument of HMI Berlin
2008
The V4 instrument has recently been upgraded with a 3He spin filter cell, placed directly in the homogeneous field B of the sample magnet, to enhance the SANSPOL option for polarization analysis. The prototype setup was still affected by: (a) a quick relaxation of the 3He nuclear polarization in the cell with a time constant of only ?130 min which significantly changes the spin filter transmissions T+ and T? for neutrons polarized parallel I+ and anti-parallel I? to B, and (b) the absence of a flipping aid behind the sample. The usual polarization analysis procedure, expecting virtually time-independent transmissions and a second flipping device, is therefore not applicable. We present an a…
A general approach for the calculation of the energy levels and the inelastic neutron scattering cross-section of highly nuclear magnetic clusters
1997
Abstract We develop here a general approach to calculate in an efficient way the spin levels as well as the spin eigenfunctions and the INS intensities of clusters formed by large numbers of exchange-coupled magnetic metal ions. The approach is based on the successive use of the irreducible tensor operator techniques and takes into account all kinds of magnetic exchange interactions between the metal ions. The potentialities of this approach are illustrated from an example comprising nine exchange-coupled Ni (II) ions.
Magnetic order in a Kondo lattice: A neutron scattering study of CeCu2Ge2
1989
Elastic and inelastic neutron scattering studies of the Kondo lattice CeCu2Ge2 were performed. AtTN=4.1 K an incommensurate magnetic order develops with an ordering wave vectorq0=(0.28, 0.28, 0.54) and an ordered moment µs=0.74 µB. The crystalline electric field splits the 4f1-J-multiplet of the Ce ion into a ground state doublet and a quartet at 191 K. The wave function of the ground state yields an ordered moment of 1.54µB. Thus, due to the onset of the formation of a Kondo singlet the magnetic moment is considerably reduced. The magnetic relaxation rate Λ was investigated via quasielastic neutron scattering. The temperature dependence of Λ(T) is characteristic of heavy-fermion systems wi…
Neutron polarizability and the n-e scattering length
1972
Abstract It is shown that the neutron polarizability contribution to the n-e scattering length is within the present level of precision. The experimental result on this interaction is consistent with a value of the neutron polarizability similar to the proton one.
Study of low-lying states of 51V, 50,52,53Cr, 59Co and 63Cu nuclei by α-particle inelastic scattering
1990
Abstract Differential cross sections for inelastic scattering of α -particles to various levels in 51 V, 50,52,53 Cr, 59 Co and 63 Cu have been measured at incident α-particle energy of 25 MeV. Data corresponding to the odd nuclei have been analyzed in terms of the weak-coupling model and the symmetric rotor model. Even-even nuclei data have been analyzed in the framework of the coupled channels formalism in terms of two collective models: the harmonic vibrational model and the symmetric rotor model. Model predictions reproduce quite satisfactorily experimental angular distributions.
A Ramsey apparatus for the measurement of the incoherent neutron scattering length of the deuteron
2008
Abstract A Ramsey apparatus for cold, polarised neutrons is described, which enables us to measure neutron precession angles with an absolute accuracy of about 1 ∘ . This is necessary to perform a planned high-accuracy measurement of the incoherent neutron scattering length b i , d of the deuteron. The performance of the apparatus is demonstrated in systematic stability measurements as well as in two selected examples using samples containing polarised nuclear spins.
Coulomb breakup of psd-shell neutron-rich nuclei
2005
Inelastic scattering of loosely bound nuclei by Coulomb interaction at intermediate energies (400?600 MeV/nucleon) has been utilized as a spectroscopic tool for exotic nuclei. The observed electromagnetic dipole (E1) strength above the one neutron threshold of neutron-rich C, Be, B and O isotopes can be explained by a non-resonant transition of a neutron into the continuum. The shape of these strength distributions reflects properties of the wavefunction of the released neutron in the nucleus and hence ground-state properties of these isotopes. Neutron capture cross-sections such as for the 14C(n,?) 15C reaction which are of astrophysical relevance can be deduced indirectly.
Angular and polarization dependence of Compton scattering from in the Δ-resonance region
1998
Abstract Using linearly polarized tagged photons from coherent bremsstrahlung, differential cross sections and beam asymmetries for Compton scattering by 4 He have been measured at MAMI in the energy interval between 150 MeV and 500 MeV for scattering angles of θ γ lab =37°, 93° and 137°, thus largely increasing the available data base. Improved calculations in terms of the Δ -hole model completely fail to describe the data at large scattering angles. The same proved to be true for a schematic model, even after taking into account properties of nuclear photo-absorption in very detail.