Fe Reaction Research Articles

A Method for Calculating Double Differential Cross Sections of α Particle Emissions

On the basis of the successful studies on pick-up mechanism of composite particle emission and the angular distribution of single nucleon emissions, a theoretical method for calculating double differential cross sections of α particle emissions is proposed. As an example, the double differential cross sections of α particles in the neutron induced reaction 56Fe(n, xα) have been calculated at En = 14.5 MeV. The theoretical results reproduce the experimental data successfully.

Time-delay effects on K-shell ionization in the elastic scattering 56Fe(p, p)

The K-shell ionization probability P κ has been measured as a function of E p across the strong 2.534 MeV resonance in the reaction 56Fe(p, p) 56Fe. It varies by about 50%. For the present unprecedentedly large ratio U ϰ / gG ⩾ 5, this experimental result is still in good agreement with theoretical calculations based on Blair and Anholt's formula.

Angular distributions of γ-rays from four resonances of the55Mn(p, γ)56Fe reaction

Four resonances in the55Mn(p, γ)56 Fe reaction at the centre-of-mass proton beam energy E P CM =1320, 1504, 1508 and 1649 keV were studied. Angular distributions for some strong γ-rays following the radiative decay of the resonances were measured and analysed in terms of the channel-spin formalism. Spin-parity assignmentI r π =3+, 4+ and 3+ was acquired for the 1320, 1504 and 1649 keV resonances, respectively. No definite assignment was established for the 1508 keV resonance and the resonance is assumed to be a very tight multiplet. Analysis of primary transitions to bound states of the Fe final nucleus permited us to assign these states. The 2+, 2+, 2+, 6+ and 4+ assignments were ascribed to the states at excitation energyE x =5705, 5303, 4738, 4692 and 4658 keV, respectively, while for the 5132 keV state ambiguous assignment 3+ or 4+ was found. Multipole mixing ratioδ was established for some primaries. The coupling of angular momenta of proton and target nucleus in the formation of the 3+ resonances was also roughly discussed.

Possibilities of proton capture spectroscopy in the fp shell

Thin-target yield curves have been measured for the 55Mn(p, γ) 56Fe and 55Mn(p,n) 55Fe reactions in the E p = 1420−1470 keV region. The three resonances at E p = 1441, 1446 and 1455 keV which show strong γ-ray ground-state transitions are interpreted as the fragmented analogue of the 56 Mn J π = 1 + second excited state. With Ge detectors at θ = 90° and 55° (with Compton suppression in the latter case) γ-ray spectra with good statistics have been measured at these resonances and at E p = 1435, 1452 and 1460 keV, which yield resonance branchings, branchings of 42 bound states (of which several were previously unobserved), accurate excitation energies ( ΔE x = 0.03−0.5 keV) of 51 bound states, J π restrictions for many levels, and the DSA lifetimes τ m = 14 ± 3 and 9 ± 4 fs for the strongly excited levels at E x = 4867 and 5023 keV, which can be regarded as fragments of the antianalogue configuration. The 55Mn(p,γ) 56Fe reaction energy has been measured as Q = 10183.84 ± 0.17 keV.

Quantum-mechanical analysis of analysing powers of the 54Fe( 7Li, 6Li) 55Fe reaction at 70 MeV

The differential cross sections, first- and second-rank analysing powers were measured for several states in 55Fe using the 54Fe( 7Li, 6Li) reaction with a 70 MeV polarised 7Li beam. Only the T T 20 exhibits a clear j-dependence while most of the T kq 's are sensitive to the l-values of the final states. The results were successfully described by complex CCBA calculations involving channel coupling in the entrance partition and spectroscopic properties of the projectile. The quantum-mechanical analysis confirms the reaction dynamics assumed in the semiclassical approach to the nucleon transfer process in heavy-ion collisions.

High-spin states in 70As

Levels in 70As have been studied via the 58Ni( 14N, 2p) reaction with E N = 46 MeV and via the 56Fe( 16O, pn) reaction with E 0 = 46–64 MeV. Nuclear properties of excited states have been assigned from investigations of γ-rays using in-beam γ-spectroscopic techniques such as angular distributions, γγ-coincidences, yield functions, lifetime, linear polarization and magnetic moment measurements. New excited states were established above 1 MeV excitation energy and spins and parities were assigned.

Lifetime measurements in 57Fe following the 56Fe(n, γ) and 56Fe(d, p) reactions

The novel method of γ-ray induced Doppler broadening (GRID) after thermal neutron capture has been applied to measure the mean lives of the 1627, 1725 and 3428 keV states in 57Fe excited in the reaction 56Fe(n, γ). The lifetimes of these three and many other states in 57Fe have been determined using the 56Fe(d, p) reaction. From a comparison of the lifetime values obtained in both reactions the stopping power of slow 57Fe atoms ( E < 500 eV) recoiling in the Fe target has been checked. Furthermore, many new transitions have been assigned to 57Fe in the 56(d, p) reaction. Energies, mean lives and transition strengths in 57Fe have been compared with predictions of shell model calculations, involving 3p2h and 4p3h configurations.

Side-feeding times and level lifetimes measured in the reaction 54Fe( 32S, 3p) 83Y

We have performed recoil-distance and Doppler-shift-attenuation lifetime measurements in the reaction 54Fe( 32S, 3p) 83Y at 103–107 MeV beam energy. By analyzing the Doppler-broadened line shapes of the 964 keV 21 2 + → 17 2 + yrast transition in coincidence with feeding and depopulating transitions, the average side-feeding time and lifetime of this state have been deduced as τ F = 0.6(2) ps and τ = 0.62(10) ps, respectively. A similar analysis of the 811 keV 17 2 +→ 13 2 + transition gave values of τ F = 0.65(25) ps and τ = 1.5(2) ps, respectively for the 17 2 + yrast state. Feeding times of the higher transitions in the positive-parity yrast band have been estimated from their Dopplerbroadened lineshapes measured in coincidence with depopulating transitions only. The feeding times are compared with the results of Monte Carlo calculations of the time development of the continuum γ-ray flux, and a damping width of 2–3 MeV has been deduced. The measured level lifetimes support the regular band structures with the deformation β 2 = 0.33 previously inferred from the transition energies.

High-spin states in neutron deficient 106Sn and 108Sn isotopes

High-spin states in 106Sn and 108Sn nuclei formed with the reaction 54Fe + 58Ni at 268 MeV have been investigated up to an excitation energy of 10 MeV. The experiment concerns γγ- coincidence, γ-ray angular distribution and γ-ray linear polarization. A deformed band above the J = 14 h ̵ level has been identified in 108Sn which is of the same nature as the band seen in 110Sn. No collective structures have been seen in 106Sn indicating a strong dependence of the nuclear shape on the number of neutrons at high excitation energy.

The variation of k-shell ionization probability across a narrow p-wave resonance

The projectile energy dependence of K-shell ionization probability have been measured across the narrow resonance 2.522Mev with large ratio of Uk/Γ=5.3 in the reaction 56Fe(p, p) 56Fe. The frame work of the theory proposed by Blair and Anholt was introduced to analyze the results.

Study of wear and galling in aircraft fuel pump drive shafts and gears using the surface layer activation technique

The surface layer activation technique (SLA) has been applied to study galling and wear in moving parts of Boeing 747 engines. Radioactive 56Co was formed by the reaction 56Fe(p, n) 56Co in fuel pump drive shafts and gears, and their residual activities in these activated parts were measured in situ during routine inspections over more than one year. The study of the wear was done on shafts made of a new alloy and on gears having a new tooth geometry. Wear determined by SLA was corroborated by a profile measurement made when one of the pumps was disassembled. The study of the galling (with release of metallic fragments) of a drive shaft consisted in checking the condition of the critical zone of the splines with the SLA technique. The main originality of the present work is that for the first time such measurements were performed on engines in revenue service.

Excitation functions for some output channels following the p +55Mn interaction atE p=1·3–2·0 MeV

Excitation functions for the55Mn(p, p′ γ)55Mn,55Mn(p, n γ)55Fe and55Mn(p, γ)56Fe reactions are studied for proton beam energyEp=1·3–2 MeV. The excitation functions are established from yield functions for γ-rays emitted from the first excited states of final nuclei. Many resonances are observed and competition of their decay into all three output channels is analysed. Spin-parity assignment for some resonant states in the56Fe compound nucleus is deduced.

A study of states in 57Co via the reaction 56Fe(7Li, 6He)57Co at 38 MeV

Abstract Observations have been made on twenty states in 57 Co via the 56 Fe( 7 Li, 6 He) 57 Co reaction at 38 MeV. J π values have been extracted for seventeen of these states using the J -dependence of the small-angle cross sections for this reaction. Full finite range DWBA predictions have been made for these states and the values of (2 J f + 1) C 2 S f obtained by least squares fitting. These spectroscopic values agree well with previous determinations from the ( 3 He, d) reaction where these exist. The analyses show an excess of 7 2 − strength and a deficiency of 3 2 − strength leading to the conclusion that there may be reduced occupancy of the f 7 2 proton orbitals in 56 Fe with the missing protons populating normally empty 2 p 3 2 orbitals.

Cross section for reactions between neutrons and matter

The excitation functions for the reactions 51V(n, α) 48Sc, 54Fe(n, α) 51Cr, 58Ni(n, 2n) 57Ni, 93Nb(n, 2n) 92mNb, 181Ta(n, 2n) 180mTa and Pt(n, χn) 195mPt were measured in the range of 0.144–5.5, 8.6 and 12.3–18.3 Mev, using activation techniques. The reactions 7Li(p, n) 7Be, D(d, n) 3He and T(d, n) 4He were used to produce the neutron. The neutron flux was determined by means of associated particle counting for Nb and reference cross sections for V, Fe, Ni, Ta and Pt. Activity measurements were performed using a 8 × 8 cm NaI(Tl) detector or 136 cm 3 Ge(Li) detector. Some of the cross sections were evaluated through experimental data from other articles and ours.

D5/2 isobaric analog state in 57Co from 56Fe(p, gamma ) and 56Fe(p,p' gamma ) reactions.

The resonances at E/sub p/ = 3774 and 3794 keV in /sup 57/Co are identified as fragments of the d/sub 5/2/ isobaric analog resonance from /sup 56/Fe(p,..gamma..) and /sup 56/Fe(p,p'..gamma..) reactions. Gamma-decay schemes and angular distributions have been studied. From angular distributions and symmetry potential considerations, the level at 4675 keV in /sup 57/Co is considered to be the antianalog state. The M1 transition strength of the analog-antianalog state has been measured and is compared with theoretical predictions. Additional information on the M1 strength systematics in the isovectorial (5/2)/sup +/..-->..(5/2)/sup +/ transitions in the f-p shell nuclei is provided.

Investigation of charged papticles froy (n, p) and (n, α) reactions

Abstract Alpha-particles and protons from the reactions 55-Mn(n, xα), 59-Co(n, xα), nat-Ag(n, xp) and nat-In(n, xp) were investigated at En=14.1 MeV by means of the Vienna multitelescope system. Charged particle spectra were measured at 16 angles between 22° and 164°. The (n, xα) results are very similar to our previous studies of 56-Fe(n, xα) and 60-Ni(n, xα) reactions. 1 They proceed predominantly by compound nucleus formation and decay with some direct contribution at the highest α-energies. Total α-emission cross-sections are in excellent agreement with determinations by other methods. The (n, xp) reactions on natural silver and indium, however, proceed predominantly by precompound processes as indicated by the angular distributions which show a strongly energy-dependent forward-backward asymmetry.

Thin layer activity depth distribution for wear measurements of cast iron

Theoretical activity distribution was determined for 56Co obtained from the 56Fe (p, n) reaction. The reaction was induced by an 8.3 MeV proton beam in a thin surface layer of cast-iron. The distribution was then verified experimentally. The standard deviation of the measured points from the theoretical curve was 3.3 μm. For the thickness range between 5 and 35 μm, frequently used in wear studies, a linear approximation was suggested by the experimental results. Standard error of estimate was 0.69 μm for this range. The S.D. of the experimental points from the theoretical curve 3 as 1.14 μm for the same range. The studies were made with a view to their prospective application in the measurements of wear of car engine components.

First cascades in73Br and high-spin states in75Br

The reaction 54Fe(28Si, xpyn) at 128 MeV was employed to identify two cascades in 73Br for the first time. The cascades were identified by employing the technique of measuring gamma rays in coincidence with reaction products of mass 73, separated in a recoil mass spectrometer. The energy spacings in the bands indicate that the quadrupole deformation in 73Br is larger than that of 75Br. The previously known bands in 75Br were extended up to 29/2+ for the positive-parity band and up to 33/2- for the negative-parity band.

Nuclide distributions for Fe-like fragments in the 136Xe + 56Fe reaction

The nuclide distributions of Fe-like reaction products from the reaction 5.9 MeV/u 136Xe on. 56Fe were measured as a function of total kinetic energy loss at a laboratory angle of 55°. The first and second moments of N, Z and A were obtained in addition to the correlation coefficients and the isobaric variances. We compare these results for the Fe-like fragment to those implied by previous measurements of the secondary distribution of the Xe-like fragment. We incorporate the effects of particle evaporation on both the light and heavy complementary primary distributions. There is overall qualitative agreement, but the variances are somewhat smaller than those obtained previously even after correction for particle evaporation. Evaporation calculations are also performed on the primary distributions predicted by a nucleon exchange model, and yield distributions in good agreement with the present experimental data.

Energy levels, decay scheme, γ-ray branching ratios and lifetimes in 55Fe from the 55Mn(p, nγ)55Fe reaction

Abstract The reaction 55 Mn(p, nγ) 55 Fe has been studied at E p = 4.0 and 6.0 MeV using a pulsed beam. From the experiments at 6.0 MeV, the energy levels of 55 Fe up to an excitation of 3810 keV, their decay scheme and the γ-ray branching ratios have been determined. Levels have been identified for the first time in the (p, nγ) reaction. The results have been compared with those available from the literature. From the 4.0 MeV experiment, the mean lifetime of the 1408 keV level has been determined to be 142.7 ± 6.6 ps by direct timing techniques.