Scattering of polarized protons by iron and nickel isotopes

Elastic and inelastic scattering of polarized protons (E = 17.2, 20.4, 24.6 MeV) by ^{54, 56}Fe and ^{58, 60, 62} Ni have been investigated. Most data can be readily accommodated by standard optical-model and DWBA procedures, including full Thomas coupling. The 2⁺₁ state (1.41 MeV) in ⁵⁴Fe is peculiar because the inelastic scattering data require deformation parameters for the central and spin-orbit parts of the nuclear potential that differ by a factor 2 to 3; moreover, this anomaly shows a marked energy dependence.     

The inelastic channel in time-domain Mössbauerspectroscopy

Time-domain Mössbauer spectroscopy has been interpreted by Hamermesh using a classical optical model. One of the most interesting aspects of the experiments is the observation of a “speed-up” effect. This speed-up effect can be observed by measuring the gamma radiation coming from the source after transmission through a nuclear-resonant “filter”, i.e., the elastic channel, using the delayed-coincidence time-to-amplitude conversion method. This time-domain speed-up effect occurs in the coherent forward scattering of the nuclear-resonant gamma radiation. Time-domain nuclear-resonant forward scattering results observing the inelastic channel, i.e., the X-ray following internal conversion, using a radioactive source have not been obtained previously. Such results are presented for the radioactive-source case using both ⁵⁷Fe and ⁷³Ge. These two isotopes were chosen because of the differences in the values of the internal conversion coefficients α, i.e., α is 8 and 1310, respectively, for the two cases. In each case experimental data, using both the elastic channel and the inelastic channel, are given. Commercial sources and absorbers of iron-in-rhodium foils were used for the ⁵⁷Fe experiments. For the ⁷³Ge experiments, we prepared our own sources by electroplating ⁷³As onto Ge single crystals. The Ge absorber was the enriched ⁷³Ge single crystal originally prepared by Pfeiffer. Fits to the experimental elastic-channel data are given using the classical optical model. Our preliminary experimental results using the inelastic channel are inconclusive.     

Observation of interband transitions in polarized electron energy loss spectra of Gd(0001)

We have detected the 4f ⁷(5d6s)³→4f ⁸(5d6s)² interband transition in an angular-resolved, inelastic scattering experiment with spin-polarized, low-energy electrons from ferromagnetic Gd(0001). The spectrum of the inelastic scattering asymmetry clearly reveals the dominant spin-dependent energy loss mechanism involved. Furthermore its comparison with elastic scattering data allows a characterization of the combined role of diffraction and energy loss processes in inelastic electron scattering.     

Site-selective detection of vibrational modes of an iron atom in a trinuclear complex

Nuclear inelastic scattering (NIS) experiments on the trinuclear complex [⁵⁷Fe{L-N₄(CH₂Fc)₂} (CH₃CN)₂](ClO₄)₂ have been performed. The octahedral iron ion in the complex was labelled with ⁵⁷Fe and thereby exclusively the vibrational modes of this iron ion have been detected with NIS. The analysis of nuclear forward scattering (NFS) data yields a ferrous low-spin state for the ⁵⁷Fe labelled iron ion. The simulation of the partial density of states (pDOS) for the octahedral low-spin iron(II) ion of the complex by density functional theory (DFT) calculations is in excellent agreement with the experimental pDOS of the complex determined from the NIS data obtained at 80 K. Thereby it was possible to assign almost each of the experimentally observed NIS bands to the corresponding molecular vibrational modes.     

Elastic and inelastic scattering of 6Li and 7Li by 54Fe at E = 36–50 MeV

Detailed angular distributions for the elastic and inelastic scattering of ⁷Li at E = 36, 42, and 48 MeV and of ⁶Li at E = 38, 44, and 50 MeV by ⁵⁴Fe have been measured. It is not possible to describe both sets of data with the same set of optical-model parameters. The ratio of $\text{U}\text{W}$ is 0.8 for ⁷Li and 1.4 for ⁶Li at the strong absorption radius, implying stronger absorption for ⁷Li than for ⁶Li. No energy dependence in the optical-model parameters was necessary for either ⁶Li or ⁷Li. The inelastic scattering from the ⁵⁴Fe 2⁺, 1.41 MeV state was well described by the DWBA and the extracted deformation length (βR = 0.62) was the same for both ⁶Li and ⁷Li scattering. It was not possible to describe the ⁷Li projectile excitation data with collective-model DWBA calculations showing that more detailed calculations for the projectile excitation are necessary.     

The elastic and inelastic scattering of 33 MeV polarized 3He from oxygen and iron isotopes

Angular distributions of differential cross sections and analysing powers have been measured for elastic and inelastic scattering of polarized 33 MeV ³He from ¹⁷O, ¹⁸O, ⁵⁴Fe and ⁵⁶Fe targets. The elastic data have been analysed to deduce the optical model parameters. The inelastic scattering together with the elastic scattering have been interpreted in terms of a macroscopic model within a coupled-channels framework. From this analysis the deformation parameters, β, were deduced.     

Depolarization in proton inclusive inelastic scattering and in the (d,p) reaction on medium-weight nuclei

The energy-averaged depolarization parameter K_y^y′ has been measured for the inelastic scattering of 18 MeV protons from ⁵⁴Fe, ⁶³Cu and ⁹²Mo at 45°, 90° and 135°, and for 14.35 MeV protons from ⁶³Cu at 45° and 135°. In all cases K_y^y′ varies from approximately unity for scattering with low energy loss to approximately zero for inelastic scattering to high excitation energies. The change from one of these values to the other occurs over a region ≈ 6 MeV wide centered at about 5 MeV excitation. A simple two-component model fits both the K_y^y′ and inelastic crosssection data. K_y^y′ has also been measured for the ⁵⁴Fe($\text{d}$, $\text{p}$)Fe reaction with 16 MeV deuterons incident. Here K_y^y′ changes from approximately the maximum possible value, $\text{2}\text{3}$, to about zero in a 6 MeV region centered at roughly 13 MeV excitation. The ($\text{d}$,$\text{p}$) data can be fitted by an extension of the model used for the proton scattering data.     

Mössbauer and vibrational DOS studies of diluted magnetic tin oxides and nano iron oxides

The magnetic properties and Mössbauer results for SnO₂ doped with ⁵⁷Fe are reviewed, and the values of isomer shift and quadrupole splitting are compared with the results obtained by ab initio calculations. It is concluded that the exchange interactions between oxygen defects and magnetic atoms are responsible for long range magnetic interactions of dilute Fe ions dispersed in SnO₂. Fe atom precipitated clusters may be formed in highly Fe doped SnO₂ samples by annealing at relatively high temperatures for several hours. The reduction of the particle size to nano-scale dimensions induces magnetization, which can be associated with oxygen defects. We have measured the nuclear inelastic scattering (NIS) spectra of Fe oxides, and ⁵⁷Fe and (Co or Mn) doped SnO₂ synthesized mainly by sol–gel methods and we have derived the vibration density of states (VDOS). The local phonons are sensitive to the presence of precipitated clusters.     

Elastic properties of filled-Skutterudite compounds probed by Mössbauer nuclei

We have carried out Mössbauer spectroscopy and nuclear resonant inelastic scattering to elucidate the lattice dynamics in filled-Skutterudite compounds, especially phosphides. The second-order Doppler shift obeys the Debye model in RFe₄P₁₂. Nuclear quadrupole interaction reveals an unusual temperature dependence in these compounds. An anomaly is observed in ⁵⁷Fe nuclear resonant inelastic scattering of these compounds. The energy where the anomaly observed in SmFe₄P₁₂ agrees with the phonon excitation energy observed by ¹⁴⁹Sm nuclear resonant inelastic scattering. We have also performed the ⁹⁹Ru Mössbauer measurements of SmRu₄P₁₂.     

An in situ M?ssbauer study using synchrotron radiation

We have been developing a system for in situ M?ssbauer studies using synchrotron radiation (SR) to elucidate the mechanism of hydrogenation processes. In the system, samples reacts in a pressure-temperature chamber and SR-based M?ssbauer spectra using variable-frequency nuclear monochromator and energy spectra of inelastic nuclear resonant scattering (NRS) of SR are measured. As a feasibility study, the temperature dependence of the M?ssbauer and inelastic NRS spectra of ⁵⁷Fe in c-GdFe₂H₃ under vacuum were measured. In both spectra, clear differences were observed between 373?K and 573?K. These differences can be interpreted by the change of microscopic environment around Fe at the dehydrogenation. Thus, it is confirmed that this system works well enough to perform the in-situ M?ssbauer study on the dehydrogenation of c-GdFe₂H₃.     

Search for M1 strength in 51V and the difference in 51V(e,e′) and 51V(p,p′) spectra

Following the studies of the distribution of M1 strength in the even-even N = 28 isotones ⁴⁸Ca, ⁵⁰Ti, ⁵²Cr and ⁵⁴Fe by inelastic electron scattering, the result of a search for M1 transitions in the odd-even N = 28 nucleus ⁵¹V is reported. No strong M1 excitation has been detected, in contrast to a recent (p, p') experiment. There is no immediate explanation for this discrepancy. Shell-model calculations indicate that a part of it might be accounted for by an interference between the spin and orbital term of the electromagnetic transition operator in the (e, e') experiment.     

QCD at lowQ 2—A correspondence relation for moments of structure functions

The precocious validity of QCD predictions in deep inelastic lepton nucleon scattering ande ⁺ e ^? annihilation is interpreted as a signal for an underlying “correspondence principle” relating perturbative and nonperturbative physics on theQ ² average. Correspondence relations for nonsinglet moments of deep inelastic structure functions are formulated, discussed and successfully tested against experiment. The relations provide an independent determination of the QCD ?-parameter from lowQ ² data in perfect agreement with results from largeQ ² analyses.     

Elastic and inelastic scattering of 178 MeV protons from 58Ni and 60Ni

The elastic and inelastic scattering of 178 MeV protons from ⁵⁸Ni and ⁶⁰Ni has been studied. Angular distributions were measured for the differential cross sections for elastic scattering as well as inelastic scattering from excited states below about 5 MeV, all with natural parity. For the elastic and for the inelastic scattering from the first excited state (2⁺ in both nuclei, the angular distributions for the polarization were also measured. The measurements extend out to c.m. angles of about 60°, corresponding to a momentum transfer of about 600 MeV/c.The elastic and inelastic scattering data were compared to the results of coupled-channel calculations in the vibrational model using a deformed spin-orbit interaction of the full Thomas form. Good agreement was found in general showing that the main features of the experimental results are well described in this model.     

Correlations between reduced neutron and radiative widths in neutron resonances

A mechanism underlying the correlation between the reduced neutron and radiative widths for the chromium and nickel isotopes has been derived. This theory combines a channel together with a compound nucleus component. The bound-state single-particle reduced widths for ⁵⁷Fe, ⁵³Cr and ⁶¹Ni were obtained by fitting the cross-section and partial radiative width data from the (γ, n) experiments using R-matrix neutron scattering phase shifts. The thermal (n, γ) cross sections for ⁵⁶Fe, ⁵²Cr and ⁶⁰Ni as well as the total radiative widths for resonances of several of these isotopes were obtained. The correlations between the neutron and total radiative widths are attributed to transitions to a few strong low-lying bound p-states which have large reduced widths.     

Inelastic scattering of neutrinos on nuclei

The cross section of inelastic neutrino interaction with ⁵⁶Fe and ²⁰⁸Pb nuclei is calculated. Investigation of these processes caused by neutral currents is essential for considering phenomena that occur during Supernova explosions and designing astrophysical neutrino detectors. The inelastic neutrino scattering cross section is calculated using the model independent approach, which is based on experimental data on nuclear structure. The values of the matrix elements of the considered reaction are determined from the characteristics of electromagnetic dipole М1 transitions in nuclei, obtained by means of nuclear resonance fluorescence.     

Elastic and inelastic scattering of 11.8 MEV polarized deuterons from 34S

The elastic and inelastic scattering of 11.8 MeV vector polarized deuterons from ³⁴S has been studied. Angular distributions of the cross section σ(θ) and vector analyzing power iT₁₁(θ) have been measured for the ground state and the first three excited states in ³⁴S. Optical model parameters were first obtained by fitting the elastic deuteron scattering data alone. DWBA calculations with a collective model form factor were performed for the inelastic scattering to the excited states. Coupled-channels calculations were also done both for the one-phonon and the two-phonon excited states. The optical model parameters were suitably modified to obtain simultaneous fit to elastic and inelastic data when channel coupling was introduced. The values of the vibrational parameter β₂ for one- and two-phonon states are discussed and compared with those obtained from γ-decay width studies.     

Structure of 10C and 11C from elastic and inelastic scattering on a proton target

We measured elastic and inelastic scattering to the low-lying states of ¹⁰C and ¹¹C isotopes on a proton target with respective incident energies 45.3 and 40.6 A MeV. Data are analyzed with a microscopic complex potential. Elastic data are sensitive to the rms matter radius, which has been deduced for both isotopes. The moment of the neutron transition density was deduced for ¹⁰C from inelastic scattering.     

Temperature effect for an inelastic neutrino scattering cross section

The influence of temperature on inelastic neutrino scattering on hot nuclei is studied with the ⁵⁴Fe nucleus as an example. The strength distribution of charge-neutral Gamov-Teller transitions in ⁵⁴Fe at finite temperature is calculated within the framework of a random phase approximation using the thermo field dynamics formalism. It is shown that for neutrino energies lower than the energy of the Gamov-Teller resonance, the inelastic scattering cross section depends substantially on temperature.