States In 56Fe Research Articles

The $\gamma$ γ -ray angular distribution in fast neutron inelastic scattering from iron

The angular distribution of $ \gamma$ -rays emitted after inelastic scattering of fast neutrons from iron was determined at the n ELBE neutron time-of-flight facility. An iron sample of natural isotopic composition was irradiated by a continuous photo-neutron spectrum in the energy range from about 0.1 up to 10 MeV. The de-excitation $\gamma$ -rays of the four lowest excited states of 56Fe and the first excited state of 54Fe were detected using a setup of five high-purity germanium (HPGe) detectors and five LaBr3 scintillation detectors positioned around the sample at $ 30^\circ$ , $55^{\circ}$ , $90^{\circ}$ , $ 125^{\circ}$ and $150^{\circ}$ with respect to the incoming neutron beam. The resulting angular distributions were fitted by Legendre polynomials up to 4th order and the angular distribution coefficients $a_{2}$ and $ a_{4}$ were extracted. The angular distribution coefficients of three transitions in 56Fe are reported here for the first time. The results are applied to a previous measurement of the inelastic scattering cross section determined using a single HPGe detector positioned at $125^{\circ}$ . Using the updated $\gamma$ -ray angular distribution, the previous cross section results are in good agreement with reference data.

Fast-neutron Induced Reactions at the nELBE Time-of-flight Facility

The compact neutron-time-of-flight facility nELBE at the superconducting electron accelerator ELBE of Helmholtz-Zentrum Dresden-Rossendorf is being rebuilt and extended with a low-background experimental hall. The neutron radiator consists of a liquid lead circuit without additional neutron moderators. The useful neutron spectrum extends from some tens of keV to about 10 MeV. nELBE is intended to deliver cross section data of fast-neutron nuclear interactions e.g. for the transmutation of nuclear waste and improvement of neutron physical simulations of innovative nuclear systems. Before the extension of the facility, the photon production cross section of 56Fe was measured with an HPGe detector and the inelastic neutron scattering cross section to the first few excited states in 56Fe was determined. The neutron total cross sections of Au and Ta were determined in the energy from 200 keV to 7 MeV in a transmission experiment.

Inelastic scattering of fast neutrons from excited states in 56Fe

Abstract Inelastic scattering of fast neutrons from 56Fe was studied at the photoneutron source nELBE. The neutron energies were determined on the basis of a time-of-flight measurement. Gamma-ray spectra were measured with a high-purity germanium detector. The inelastic scattering cross sections deduced from the present experiment in an energy range from 0.8 to 9.6 MeV agree within 15% with earlier data and with predictions of the statistical-reaction code Talys. In addition to the γ-ray production cross sections, level cross sections for the 2 + , 4 + and 6 + yrast states in 56Fe were deduced.

Low-lying states of56Fe

Low-lying states of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow /><mml:mrow><mml:mn>56</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">Fe</mml:mi></mml:math>

Evidence for electron orbital dependence of ion-beam induced attenuations of transient magnetic fields

From measurements of transient magnetic fields (TF) on56Fe(21+) ions in Gd host there is evidence that beam induced attenuations of TF not only depend on the energy loss of the beam ions in the ferromagnet but also on the electron ns-orbitals of the probe ion contributing to the field. This has been demonstrated for 2s- and 3s-electron states of56Fe ions which are preferentially populated by setting the ion velocity to their respective orbital Bohr velocities.

Mean lifetimes and transition probabilities in56Fe

Using a two-target DSAM technique, results on the mean lifetimes have been obtained for 17 excited states of 56Fe, four for the first time (3449, 3607, 4101 and 4395 keV). Transition probabilities have been calculated for the transitions of known multipole mixing ratio.

Level spins and transition multipolarities in56Fe studied by nuclear orientation of56Co

Gamma-ray distribution and linear polarisation measurements on transitions in 56Fe from the decay of 56Co oriented in an iron host matrix at 6.24(2) mK are reported. The data confirm the spin values 4 (4100.3 keV and 4298.0 keV) and 3 (4120.0 keV and 4395.0 keV) and yield E2/M1 mixing ratios for 19 transitions which are new (for the weaker decays) or generally more precise than existing values. Comments on the theoretical interpretation of the excited states of 56Fe are suggested.

Direct extraction of the isovector deformation parameter β(1)2 from the (p, n) reaction of 56Fe

The reaction 56Fe(p, n) 56Co leading to the analog of the ground state and the first excited 2 + state of 56Fe has been studied at E p=20, 28, 32 and35MeV. The direct process dominates at higher energies, thus the direct extraction of the isovector deformation parameter β (1) 2 is feasible. It is found that β (1) 2 is about three times larger than β (0) 2, the isoscalar deformation parameter.

A microscopic classification of high-spin states in 56Fe

A large-scale shell-model calculation on 56Fe including positive parity states with spins up to J = 15 shows that several states in the yrast region may be of a particular nature. These states can be locd in groups of which the gamma decay and quadrupole moments show a collective behaviour. The signature of each group is the f 7 2 hole structure. This structure is coupled to a definite J hole and T hole with the spin J hole being as large as possible. The level density above the yrast region turns out to be largely independent of J.

Gamma competition in the decay of unbound states in 56Fe produced by the 56Fe(n, n′) reaction with 14 MeV neutrons

Iron was bombarded with 14 MeV neutrons and both the singles spectrum of the secondary neutrons and the coincidence spectrum with the 846 keV γ-line from the decay of the first excited state of 56Fe were measured. From there the ratio of the average γ-width to neutron width in 56Fe could be determined for 56Fe as a function of excitation energy in the energy region 0–3 MeV above the neutron binding energy.

The level structure of 56Fe

High-spin states in 56Fe have been investigated in three reactions, 50Cr( 12C, α2p), 54Fe(α, 2p), 56Fe(α, α). The level scheme, the spin and parity assignments and lifetime measurements of these states were obtained through in-beam γ-ray spectroscopy techniques. Calculations were performed in the frame of the shell model with a relatively small configuration space and in the aligned scheme model: the experimental results can be interpreted as due to the interplay between three converging sequences of states of different shapes.

Absolute excitation energy measurements using an electrostatic analyzer

The excitation energies of several states in 6Li, 11B, 12C, 27Al and 56Fe have been measured in terms of the standard meter and the standard volt. The energy of the electron beam from a FN Tandem Accelerator was measured absolutely with a 61 cm radius electrostatic analyzer to an uncertainty of 0.037%. Thin target bremsstrahlung produced by this beam was used to excite the states in question. The excitation energies are as follows: (2126.5 ± 1.5) keV for the 2.12 MeV state in 11B; (2984.2 ± 1.5) keV for the 2.98 MeV state in 27Al; (3451.3 ± 1.7) keV for the 3.45 MeV state in 56Fe; (3569.0 ± 1.7) keV for the 3.56 MeV state in 6Li; (4439.4 ± 1.6) keV for the 4.44 MeV state in 12C; (4446.4 ± 1.8) keV for the 4.44 MeV state in 11B; and (5021.1 ± 1.8) keV for the 5.02 MeV state in 11B. These results are compared with particle-reaction and gamma ray spectroscopy measurements.

Phonon admixtures in states of56Fe excited by3He scattering

The elastic and inelastic scattering of 3He ions from the 0+, 21+, 41+ and 22+ states of 56Fe have been analysed using an anharmonic vibrational model with the coupled channels code JUPITOR-KARLSRUHE. Appreciable one-phonon admixtures are found for the so-called two-phonon states. Values derived for the reduced transition probabilities B(E2), are in good agreement with experimental data providing the calculations use the radius of the imaginary potential.

Excitation of32S and56Fe by inelastic scattering of 14.1 MeV neutrons

Differential cross sections for the inealstic scattering of 14.1 MeV neutrons to the 2.24 MeV state of32B and the 0.845 MeV state of56Fe were measured and compared with coupled-channel calculations. They are in reasonable agreement. The deformation parametersβ2 are quite similar to the electromagnetic values.

Spin assignments to excited states of 56Fe using inelastic proton scattering

Abstract Inelastic proton scattering from 56Fe at 49.35 MeV has been studied with protons from a linear accelerator. Angular distributions for thirty excited states up to an excitation of 7.5 MeV in 56Fe were obtained. Spin and parity assignments to most of the states were made using DWBA analysis with first order collective form factors. The structure of this nucleus is discussed in the light of the present data.

Low-energy excited levels of 15Fe and 54Cr

The states of 56Fe and 54Cr are calculated by the introduction of a neutron-proton interaction. The differences between a few of the lowest energy states of singly closed shell nuclei ( 54Fe, 58Ni, etc.) and those of almost doubly closed shell nuclei ( 56Fe, 54Cr, etc.) are essentially explained by our calculation.

Implantation perturbed angular correlation experiments in iron after inelastic proton scattering

Hyperfine interactions in iron metal have been studied by the standard IMPACT technique, populating the 0.847 MeV, 10.4 ps state of 56 Fe and the 1.408 MeV, 1.42 ps state of 54 Fe via the ( p, p' ) nuclear reaction. Several experiments on 56 Fe were performed independently at the University of Wisconsin Tandem Van de Graaff accelerator laboratory and at the Rutgers-Bell facility. In all cases, the experiments yielded shifts of less than 0.005 rad in the correlation pattern. The low results imply that the average hyperfine field in iron implanted into iron is less than 175 kG during the first 10 ps after implantation. The results are discussed in terms of possible radiation damage and transient field effects, and microscopic details of the IMPACT process are considered.

Inelastic Scattering of Deuterons from 56Fe

Inelastic scattering has been found to be an extremely useful tool in studying the collective states in nuclei. Following the early work of Cohen and Rubin (1958) there has been tremendous interest in the investigation of vibrational states, particularly in the first 2+ and "anomalous" 3- states, in even-even nuclei and in their possible interplay with the well-defined single-particle levels in stripping and pickup reactions and even in (p, n) reactions (Guglet 1960). These states in 56Fe have recently been studied mostly through the inelastic scattering of a-particles (McDaniels et al. 1960) and protons (Matsuda 1962; Aspinall, Brown, and Warren 1963; Brown, Warren, and Middleton 1966). Except for a few measurements on some of these states (Jahr et al. 1961; Gofman and Nemets 1962) no systematic information is vailable on the inelastic scattering of deuterons from 56Fe. The present work was undertaken with this in view, and in this communication we report on the properties of a few levels of 56Fe, including the 2+ state at O� 844 MeV and the 3- state at 4�503 MeV, deduced from the inelastic scattering of 12 MeV deuterons

The decay schemes of 56Co and 56Mn and their use as calibration standards

The gamma rays accompanying the beta decays of 56Co and 56Mn have been studied using Ge(Li) and NaI(Ti) detectors in singles and in coincidence experiments. Excited states in 56Fe are placed at 846.6±0.5, 2084.8±0.7, 2657.6±0.8, 2960.1±0.8, 3123.7±1.2, 3369.9±0.7, 3445.0±0.7, 3856.2±11.2, 4049.7±0.7, 4101.0±0.7, 4120.7±0.7, 4298.3±0.7 and 4394.2±2.1 KeV. The usefulness of the 56Co decay as a gamma-ray energy and relative intensity standard is indicated.