Electromagnetic properties of levels in 55Mn

Excited levels of ⁵⁵Mn were produced by the reaction ⁵²Cr(α, p) at 10.5 and 11.1 MeV beam energy. A series of γ-ray measurements was made, all in coincidence with protons detected near 180°. A Ge(Li) γ-ray detector was used at 4 angles, and extensive angular-correlation measurements were made with an array of NaI(Tl) detectors. Excitation energies of 25 levels up to 3161 keV were determined, including a new level at 2215 keV. Only the level at 2285 keV and the $\text{1}\text{2}{}^{\mathrm{?}}$ state near 1290 keV were not observed in this range. From Doppler-shift attenuations, the mean lifetimes of 14 levels up to 2565 keV were deduced. Branching ratios and multipole mixing ratios were obtained for most of these levels. The following spin assignments were determined: 1530 keV, $\text{J =}\text{3}\text{2}$; 1885 keV, $\text{J =}\text{7}\text{2}$ or $\text{5}\text{2}$; 2565 keV, $\text{J =}\text{3}\text{2}$. Reduced transition probabilities, B (M1) and B (E2), of many transitions were calculated from these experimental results and are compared with the available theoretical values.     

Spins and lifetimes of levels in 55Mn

The study of excited ⁵⁵Mn levels with the ⁵²Cr(α, pγ) reaction was extended to levels up to 3161 keV. With a Ge(Li) detector, DSA measurements in gold-backed targets were made, as well as angular correlations; both of these experiments were done in coincidence with protons detected near 180°. A multiple-detector NaI(Tl) array was also used in the same reaction geometry for better γ-ray detection efficiency. Mean lifetimes of 12 levels from 2727 to 3161 keV are reported. Spins and sometimes parities of the following levels were deduced from the angular-correlation analyses and lifetime results: 1885 keV, $\text{7}\text{2}$^?; 2199 keV, $\text{7}\text{2}$(^?); 2311 keV, ($\text{13}\text{2}$); 2366keV, $\text{5}\text{2}$^?; 2727 keV, $\text{7}\text{2}$; 2823 keV, $\text{9}\text{2}$. Multipole mixing ratios and M1 and E2 transition rates of the radiations from these and from the 1292 keV level are presented. The similarity of the low-lying level structure and of interlevel transitions in ⁵⁵Mn to those in certain other f_{$\text{7}\text{2}$}³ nuclei is examined.     

Nuclear magnetic resonance of 55Mn and 75As in MnAs

Four sets of NMR signals, two each, from ⁵⁵Mn and ⁷⁵As nuclei have been observed. The temperature dependences of ⁵⁵Mn resonances have been studied from 77 to 311 K and that of ⁷⁵As, from 77 K to about 250 K. The results show that there is a phase transition at T₁ ≈ 220 K. This transition may be due to introduction of a local spontaneous distortion in the region of the domain walls in the lattice, resulting in lowering of symmetry at low temperatures. Another possibility is the canting of spins which would lower the magnetic group symmetry. The observed resonances have been assigned to arise from the nuclei at the edge and the centre of the domain walls at temperatures T >T₁ and from two types of wall edges with inequivalent orientation of atomic spins at T < T₁. The isotropic hyperfine field at 0 K obtained by extrapolating the resonance frequencies are 227 and 285.1 kOe at ⁵⁵As nuclei, respectively. The anisotropy in the hyperfine field is nearly zero at ⁵⁵Mn nuclei and about 5.8 kOe at ⁷⁵As nuclei at 0 K.     

55Mn nuclear magnetic resonance in Mn2Sb

The observation of NMR signals from ⁵⁵Mn nuclei in Mn₂Sb has been reported. A temperature variation study of the domain and domain wall signals in Mn₂Sb confirms that the magnetization is aligned parallel to the c-axis at temperatures higher than 240 K and that it is in the basal plane below 240 K. The temperature dependence of the anisotropy in the hyperfine field at the Mn(I) and Mn(II) sites has been determined.     

Nuclear γ-rays induced by pions stopping in 55Mn

Stopping pions have been shown to excite the 126 keV level in a target of ⁵⁵Mn. A nonlinear variation of yield of the γ-ray versus target thickness suggests that the principal mechanism responsible for the excitation is a two-stage process. The production mechanism for the same γ-ray seen elsewhere in kaonic atoms experiments is discussed.     

Photonuclear reactions in medium weight nuclei 51V, 55Mn and Cu

New results on the photospallation of the medium weight nuclei ⁵¹V, ⁵⁵Mn and Cu at maximum bremsstrahlung energy between 2 and 5 GeV are presented. The yields of residual nuclei were measured by the activation method using a Ge(Li) detector. The results are analyzed with the empirical Rudstam formula and compared with data obtained in lower energy photon and proton induced reactions.     

The reaction 55Mn(d, t)54Mn

Neutron pick-up cross sections and vector analyzing powers have been measured for the reaction ⁵⁵Mn($\text{d}$, t)⁵⁴Mn at 17 MeV. The mixture of $\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ to $\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ transfer to the low-lying l_n = 1 states has been found. Evidence of the $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ hole nature of several strong l_n = 3 states above 1 MeV has been obtained.     

A study of the 51V(6Li,d)55Mn reaction

Alpha particle spectroscopic strengths extracted for transitions to low-lying levels in ⁵⁵Mn observed in a study of the ⁵¹V(⁶Li, d) reaction at 32 MeV are compared with the results of shell-model calculations. These reproduce well the relative strengths of the levels.     

States in 53Mn from the 52Cr(p, γ)53Mn reaction

Eight resonances have been observed in the ⁵²Cr(p, γ)⁵³Mn reaction between E_p = 0.90 and 1.03 MeV. Gamma-ray spectra have been accumulated at four of the resonances. Spin assignments have been made to the resonant states on the basis of the measured angular distributions of primary γ-rays. Excitation energies and γ-ray branching ratios have been determined for 36 levels between 2.0 and 5.6 MeV. Mean lives for nine of the states have been extracted by the Doppler shift attenuation method.     

Reaction 55Mn + 159Tb : preparation for the synthesis of new elements

The complete fusion reaction of \begin{document}$^{55}$\end{document}Mn + \begin{document}$^{159}$\end{document}Tb was studied on the gas-filled recoil separator SHANS2. Nineteen ER - α\begin{document}$_{1}$\end{document} - α\begin{document}$_{2}$\end{document} decay chains from \begin{document}$^{210}$\end{document}Th produced from the 4n evaporation channel were observed. The α-particle energy and half-life of \begin{document}$^{210}$\end{document}Th were determined as 7922(14) keV and 14(4) ms, respectively. In addition, the decay properties of \begin{document}$E_{\alpha}$\end{document} = 7788(14) keV and \begin{document}$T_{1/2}$\end{document} = 36\begin{document}$^{+15}_{-8}$\end{document} ms were obtained for \begin{document}$^{211}$\end{document}Th. The measured α decay properties of \begin{document}$^{210}$\end{document}Th and \begin{document}$^{211}$\end{document}Th were consistent with literature data. The cross sections were measured to be 0.59\begin{document}$^{+0.25}_{-0.23}$\end{document} nb and 0.19\begin{document}$^{+0.12}_{-0.09}$\end{document} nb for \begin{document}$^{210}$\end{document}Th and \begin{document}$^{211}$\end{document}Th, respectively. The equilibrium charge state of the recoiled nucleus \begin{document}$^{210}$\end{document}Th was determined experimentally. The new data were helpful for estimating the equilibrium charge states of elements 119 and 120, which could be produced via the \begin{document}$^{240}$\end{document}Pu(\begin{document}$^{55}$\end{document}Mn, 3n)\begin{document}$^{292}$\end{document}119 and \begin{document}$^{243}$\end{document}Am(\begin{document}$^{55}$\end{document}Mn, 3n)\begin{document}$^{295}$\end{document}120 reactions, respectively.     

Electromagnetic transitions in 51Mn

The nuclear structure of ⁵¹₂₅Mn was studied by γ-ray spectroscopy in the ⁵⁴Fe(p, α)⁵¹ Mn reaction (E_p = 9.0–13.2 MeV) and the ¹⁴N+³⁹K, ¹⁶O+⁴⁰Ca and ¹⁴N+⁴⁰Ca fusion-evaporation reactions (E_beam = 36 MeV). In the ⁵⁴Fe(p, αγ)⁵¹Mn reaction γ-rays were detected in coincidence with α-particles emitted near 180°; mean lifetimes and γ-ray mixing and branching ratios were deduced from Doppler shift attenuation and α-γ angular correlation measurements, respectively. Definite spin assignments are: 237 and 2416 keV, $\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{?}}$; 1140 keV, $\text{9}\text{2}$^?; 1488 keV, $\text{11}\text{2}$^?; 1825 and 2140 keV, $\text{3}\text{2}$^?. The results for other states below 3 MeV are consistent with the existence of rotational bands (/kh²/2/OI/t~ 95 keV) built on the ($\text{3}\text{2}$⁺) 1817 keV and $\text{1}\text{2}$⁺ 2276 keV hole states. The various measurements together with an earlier value for the lifetime of the first-excited state determine unambiguously the B(M1) and B(E2) values for all of the decay branches of the $\text{7}\text{2}$^?, $\text{9}\text{2}$^? and $\text{11}\text{2}$^? lowest three excited states. From the γ-singles and γ-γ coincidence observations with fusion-evaporation reactions, the yrast cascade proceeds through these three states and higher states at 2957, 3250,3680 and 4139 keV which are suggested to have $\text{J}{}^{\mathrm{\pi }}\text{=}\text{13}\text{2}{}^{\mathrm{?}}$, $\text{15}\text{2}$^?,$\text{15}\text{2}$^? and $\text{19}\text{2}$^?, respectively. The various experimental results for the $\text{5}\text{2}$^? → ($\text{19}\text{2}$^?) yrast states are in good overall agreement with shell-model calculations in the (f_{$\text{7}\text{2}$}¹ space.     

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

The reaction ⁵⁵Mn(p, nγ)⁵⁵Fe 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 ⁵⁵Fe 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.     

New evidence for magnon-induced pseudoquadrupole processes in ferromagnets: 55Mn IN BMn

Using a recently published theory, the existence of a significant magnon-induced pseudoquadrupolar interaction in a new ferromagnetic system is predicted. A large magnetization-dependent quadrupole-like term, attributed to the predicted magnon-induced mechanism, is actually observed in a resonance study of ⁵⁵Mn in the ferromagnetic phase of BMn.     

Pionic 3d → 2p X-ray measurements in 50,52,54Cr, 45Sc, 51V, 55Mn and Fe

We report the measurement of the strong interaction shifts and widths of the pionic 3d → 2p transitions in separated isotopes of ^50,52,54Cr and natural Sc, V, Mn, and Fe. Using these new data in combination with earlier low-Z pionic data (6 ? Z ? 20) we have studied the phenomenological pion-nuclear potential. Employing nuclear structure information from measured charge densities and Hartree-Fock calculations, we have fitted the pion-nuclear potential parameters to the pionic-atom data. We have explored the sensitivity of these data to the value of the Lorentz-Lorenz parameter ξ. The addition of an isovector dependence to the s- and p-wave two-nucleon terms is shown to be unnecessary at the present level of experimental accuracy. We have used the deduced optical potentials to determine the neutron radii of the nuclei 20 ? Z ? 26 and find reasonable agreement with Hartree-Fock predictions and with the results of other hadronic probes for 20 ? Z ? 23 but poor agreement for 24 ? Z ? 26.     

Excitation functions and isobaric analogue states in the 55Mn(p, γ)56Fe reaction

Four excitation functions with proton energy range 1.3 to 1.85 MeV and γ-ray energy thresholds from 1.5 to 8.0 MeV were determined for the reaction ⁵⁵Mn(p, γ)⁵⁶Fe. Gamma-ray spectra were taken for two close-lying resonances at proton energies 1531 and 1537 keV. An analysis of the spectra suggests the spin-parity assignments for those two states to be 4⁺ and 2⁺, respectively, consistent with their being isobaric analogues to the close-lying third and fourth excited states in ⁵⁶Mn.     

Investigation of isobaric analog resonances in 53Mn

The isobaric analog resonances in ⁵³Mn with different spins and parities are investigated by means of the ⁵²Cr(p, p), (p, p′), (p, p′γ), and (p, γ) reactions. Spectroscopic factors are derived and the experimental (p, γ) strengths are compared with theoretical single-particle estimations.     

Recoil-distance lifetime measurements in 51Cr, 53Cr, 53Mn and 53Fe

Levels in ⁵¹Cr, ⁵³Cr, ⁵³Mn and ⁵³Fe were excited via (α, n) or (α, p) reactions. Using the recoil-distance method, mean-lives (in ps) have been obtained for excited states (keV) in the residual nuclei: ${}^{51}\text{Cr}\text{(2256) = 66±2,}{}^{53}\text{Cr}\text{(1536) = 21.5±3.5,}{}^{53}\text{Cr}\text{(2173) = 6.7±3.1,}{}^{53}\text{Mn}\text{(2564) = 20}{}^{\mathrm{+8}}{}_{\mathrm{?6}}\text{and}{}^{53}\text{Fe}\text{(1424) = 4.0±1.0}$. Reduced transition probabilities calculated from these values are compared with the available theoretical values.     

High-resolution measurements of analogue states in 53Mn

Using a high-resolution proton beam, differential cross sections were measured for the ⁵²Cr(p, p) and ⁵²Cr(p, p') reactions at incident energies between 3.20 and 4.76 MeV. Spins, parities and partial widths were determined for all resonances observed. Two p-wave and two d-wave analogue states were identified in this energy region. Spectroscopic factors and Coulomb displacement energies were extracted for the analogue states. The width distributions were analyzed for $\text{1}\text{2}{}^{\mathrm{+}}\text{,}\text{1}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{+}}\text{and}\text{5}\text{2}{}^{\mathrm{+}}$ resonances. Proton strength functions were also deduced for each J^π value, and their proton energy dependence was discussed.     

31P and 11B NMR in amorphous NiPB alloys near the paramagnetic-ferromagnetic transition

Knight-shift and nuclear spin-lattice relaxation time measurements have been performed between 4.2°K and room temperature on ¹¹B and ³¹P in amorphous NiPB alloys near the para-ferromagnetic transition. The EFG parameters on ¹¹B were found to be ν_Q=200(±20)kHz and η = 0.35 (±0.10). Knight-shift and Korringa spin-lattice relaxation are mainly due to mechanisms involving p electrons. The effect of Ni magnetic clouds results in a broadening of the linewidth. We observed also the occurence of a Giovannini-Heeger-like contribution to the spin-lattice relaxation rate.