Nuclear spin lattice relaxation of191mIr in Fe

Thermal cycling of the lattice temperature was used to determine the nuclear spin lattice relaxation of^191m IrFe in polarizing fields of 0.05 to 1.3 T. At low temperatures, the relaxation time is not very much shorter than the lifetime of^191m Ir. In the first part of the paper, the master equation formalism is extended to include a finite lifetime. Our result for the reduced relaxation constant, ² C _K =(1.48±0.11)·10¹⁴ K s^–1 T^–2 (high field limit) is in serious disagreement with that of a spin echo measurement of¹⁹³IrFe, but fits much better into the general systematics. A comparison of relaxation rates for 3d-, 4d-, and 5d-impurities in Fe is given. As a by-product, a Kapitza conductivity constant ofl _K =1.5 mW cm^–2 K^–4±30% was found between Fe and dilute³He/⁴He.     

Nuclear magnetic resonance on oriented192Ir in Fe and Ni

The hyperfine interaction of¹⁹²Ir nuclei as dilute impurities in Fe and Ni has been investigated with NMR on oriented nuclei. With the use of highly dilute and pure alloys the line widths could be reduced so far that the quadrupole splitting of¹⁹²IrFe and¹⁹²IrNi could be resolved. Taking hyperfine anomalies into account the ground state nuclear moments of¹⁹²Ir are deduced as |μ|=1.924(10)μ _N andQ=2.36(ll) b. The hyperfine field of IrNi was investigated as a function of the Ir concentrationc between 0.01 at % and 5 at %. The dependence ofH _HF onc was found to be significantly smaller than that reported from Mössbauer effect measurements. Forc=0.01 at %H _HF=?454.7(2.3)kG is deduced. The resonance shift with an external magnetic field has been studied precisely, yieldingK=0.012(23) andK=0.026(12) for the Knight-shift of¹⁹²Ir in Fe and Ni, respectively.     

Hyperfine fields in the 5sp series studied by the low temperature nuclear orientation of83Rb,83Sr,85Sr and85Ym in iron

The hyperfine fields B_hf (RbFe), B_hf (SrFe) and B_hf (YFe) have been determined by the low temperature nuclear orientation of dilute samples of⁸³Rb,^83,85Sr and⁸⁵Y^m in an iron lattice to be B_hf (RbFe)=+54 (10) kG, B_hf (SrFe)=(?)100 (30) kG and B_hf (YFe)=?226 (10) kG. These results are compared with recent calculations for these fields (1), (2).     

Measurement of theg-factor of the 21 + state of192Pt in an external magnetic field

Theg-factor of the 2₁ ⁺ state of¹⁹²Pt has been measured by the IPAC technique in an external magnetic field as:g(2₁ ⁺,¹⁹²Pt)=+0.287(17). An additional IPAC experiment with an¹⁹²IrFe sample was performed with the same level in order to investigate the hyperfine field. The result:ω _L τ(2₁ ⁺,¹⁹²PtFe)=0.1115(9) gives the hyperfine field:B _hf ^4.2k (PtFe)=126.8(71) T. The result of an LTNO experiment with the same level is compatible with the assumption that 100% of the¹⁹²Ir atoms were on unique sites.     

Hyperfine interaction of Ce and La in 3-d ferromagnets

NMR/ON measurements on¹⁴¹CeFe show the sign of the hyperfine field of CeFe to be negative. For the¹⁴¹Ce nucleus a g-factor of ¦g_N¦=0.311±0.011 is found. With this g-value a hyperfine field of H_hf=?41±2 T for CeFe is derived. Low temperature nuclear orientation experiments on¹⁴¹CeCo and¹⁴⁰LaFe yield ¦H_hf¦=30±3 T and ¦H_hf¦=46±5 T respectively. The valence of cerium impurities in Fe, Co and Ni is discussed.     

NMR/ON of206BiFe produced by decay of cold implanted206Po

²⁰⁶Po was implanted into iron at T<0.2 K. After electron capture decay to²⁰⁶Bi nuclear magnetic resonance of oriented²⁰⁶BiFe was observed with an asymmetric resonance line shape. Evaluation of the data with the superposition of two Gaussian lines results in ν=693.7(2) MHz for the center frequency of the narrow one of the two lines at external field zero. From this B_hf (BiFe)=119.0(1.3) T is derived. The effective spin-lattice relaxation time of²⁰⁶BiFe at T=13 mK was measured as Ti=0.94(5) s.     

Nuclear magnetic resonance on oriented189,191 Pt in iron

Nuclear magnetic resonance measurements have been performed for¹⁸⁹Pt and¹⁹¹Pt oriented at 7 and 15 mk in iron host. The magnetic hyperfine splitting frequencies, ν=¦μB_HF/Ih¦, of the¹⁸⁹Pt and¹⁹¹Pt ground states were determined to be 277.61(5) and 319.88(3) MHz. With the hyperfine field of B_HF=-1280(26) kG the nuclear magnetic moments were deduced to be: ¦μ(¹⁸⁹Pt;3/2^?)¦=0.427(9) μ^N; ¦μ(¹⁹¹Pt,3/2^?) ¦=0.492(10) μ_N. The effective spinlattice relaxation time for¹⁹¹PtFe at 7 mK in a polarizing magnetic field of 2 kG has been found to be 30(2) s using a single-exponential fit.     

Nuclear magnetic resonance on oriented194Ir (T 1/2=19.4 h) in Fe and Ni

The hyperfine interaction of¹⁹⁴Ir (j ^π =1^?;T _1/2=19.4 h) in Fe and Ni has been investigated with the technique of nuclear magnetic resonance on oriented nuclei. For both systems the electronic-orbital-momentum induced electric quadrupole splitting could be resolved. The magnetic and electric hyperfine splitting frequencies,v _M =¦gμ _N ^B _HF/h¦ andv _Q =e ² qQ/h, respectively, were measured as:¹⁹⁴IrFe:v _m =408.54 (23) MHz;v _q =?2.47(20) MHz;¹⁹⁴IrNi:v _M =135.24(5) MHz;v _q =?1.23 (3) MHz. Taking into account a 3% uncertainty arising from hyperfine anomalies theg-factor is deduced as ¦g¦=0.39 (1). The electric quadrupole moment,Q=+0.352 (18)b, is slightly smaller than expected from the known systematics of deformation parameters in this mass region.     

Core vibration of99Tc

The gyromagnetic ratios and the half-lifes of the 141 keV and 181 keV states of⁹⁹Tc have been remeasured. The results,g(141 keV)=+1.280(44);g(181 keV)=+1.446(20) andT _1/2(141 keV)=0.205(4)ns;T _1/2(181 keV)=3.44(3) ns are in only fair agreement with prior published data but more precise. They confirm that both states are members of the ground state core vibration multiplet. The hyperfine field of TcFe has been determined asB _hf ^10K (TcFe)=30.42 (30)T;B _hf ^290K (TcFe)=29.47 (29)T     

NMR-on of182Ta and183Ta in Fe

Nuclear magnetic resonance has been observed on radioactive¹⁸²Ta and¹⁸³Ta oriented at low temperature in an Fe host, by detection of the change in spatial anisotropy of γ-rays emitted during nuclear decay. By measuring the resonant frequencies of¹⁸³Ta in four different applied magnetic fields the nuclear magnetic moment and hyperfine field have been deduced. These are: $$|\mu \left( {{}^{183}Ta; I = \tfrac{\user2{7}}{\user2{2}}} \right)| = 2.28(3)\mu _{\rm N} and B_{hf} \left( {Ta\underline {Fe} at 0 K} \right) = - 67.2(1.3)T$$ . The spin of the ground state of¹⁸²Ta has been determined asI=3 by comparing resonance results with those obtained in a thermal equilibrium nuclear orientation study. The ratio of the resonant frequencies observed for¹⁸²Ta and¹⁸³Ta at one applied field value yields a magnetic moment for the former of $$|\mu \left( {{}^{182}Ta; I = \user2{3}} \right)| = 2.91(3)\mu _{\rm N} $$ . The spin lattice relaxation time for¹⁸³TaFe (0.12 at% Ta) at 18 mK in an applied field of 0.5 T has been found to be 40(10) s.     

Nuclear larmor precession of the 14 keV state of57Fe in α-iron following the reaction56Fe (d,p)57Fe

The spin precession of the 14 keV state of⁵⁷Fe, excited by the⁵⁶Fe(d,p) reaction was observed in ferromagnetic Fe. The data yield a magnetic field of ? 330±4 kG and a relaxation time τ _r > 500 ns at room temperature.     

A remark concerning 20 plet dominance in charm decays

Based onV spin consideration, it is argued that20 dominance in the effective weak Lagrangian does not strongly reduce theinclusive decay rate ofD ⁺ mesons. Decays of the typeD→Kρ,K ^*π, ρπ are discussed in pointing out that 20 dominance should lead to a large enhancement of \(D^ + \to \bar K^0 \rho ^ + ,\left( {\bar K^0 } \right) * \pi ^ + \) over \(D^ + \to \bar K^0 \pi ^ + \) ;W exchange, on the other hand, leads to a sizeable suppression ofD ⁰→K ^? ρ ⁺,(K ^?)*π⁺ relative toD ⁰→K ^?π⁺.     

Nuclear structure and the hyperfine interaction of oriented152Eu,155Eu,and153Gd in gold

Nuclear orientation of^152,155Eu and¹⁵³Gd in Gold has been used to determine the nuclear magnetic moment of¹⁵⁵Eu, (μ¹⁵⁵Eu)=1.93±0.26 n.m., and several mixing ratios of γ and β^? transitions in the decays. The hyperfine field of dilute EuAu alloys was found to beH _hf=134±10 kOe and for GdAu, |μH| was found to be in the range 0 to 1.0×10⁵ Oe·n.m.     

The determination by an independent method ofP k electron capture probabilities in133Ba and139Ce decays gamma decay of133Ba

The electron capture decays of¹³³Ba (10.4 y) and¹³⁹Ce (140 d) were investigated with high resolution Ge(Li) detectors. By x-ray — γ-ray coincidences values of the quantityP _k ω _k ? _k for various transitions in the decay of¹³³Ba and¹³⁹Ce are obtained. The factor ω _k ? _k was measured independently by means ofK-conversion electron-K x-ray coincidences and was then used to determineP _k , theK-capture probability. The independent measurement of the product ω _k ? _k , together with recent accurate values of ω _k , provides a new method for the accurate calibration of semiconductor x-ray detectors. In the decay of¹³⁹Ce, a value ofP _k =0.78±0.03 is found (where the error represents twice the standard deviation) from whichQ _ec =326 _?30 ⁺⁷⁰ keV to the¹³⁹La ground-state is found by use of theory. In¹³³Ba decay, values are found ofP _k 1=0.72±0.04 for theEC transition to the 437 keV level in¹³³Cs,P _k 2=0.80±0.07 to the 384 keV level, and from an independent measurement, the ratioP _k 1/P _k 2=0.87±0.07. From these results the ground-state value ofQ _ec =522 _?10 ⁺²⁰ keV is derived from theory for¹³³Ba decay. The gamma spectrum of¹³³Ba also was remeasured. From the present gamma intensities and previous conversion electron intensities, new values forK-shell conversion coefficients are obtained. Previously reported γ-rays at 35 and 391 keV are not confirmed.     

Nuclear orientation and resonance studies of96TcFe

Low temperature nuclear orientation and nuclear magnetic resonance (NMRON) have been used to measure the magnetic hyperfine interaction in⁹⁶TcFe and the decay scheme properties of⁹⁶Tc. The spin of the⁹⁶Tc ground state is confirmed as 7. Its magnetic moment μ(⁹⁶Tc)=5.37±0.17 n.m. The magnetic hyperfine field for⁹⁶TcFe is ?298±10 kOe. The anisotropies of the 778, 813, 850 and 1126 keV transitions in⁹⁶Mo agree with pure E2 multipolarity assignments. The spin-parity of the 2876 keV level is 7⁺.     

Description of high-spin isomers in theN=82 region

The high spin states and of those especially the yrast isomers are studied in the region near the rare earth nuclei. The deformation energy surface is calculated with a method modelled in principle according to a shape constrained cranked HF theory (CHF). In practice, the expectation value of the many-body Hamiltonian is calculated with cranked Nilsson functions. One finds rotation around a slightly deformed oblate or prolate symmetry axis in front or behind the rare earth region, respectively. Near the Hf isotopes strongly prolate deformed nuclei rotating around the symmetry axis are found in agreement with the knownK isomers in this region. These results are explained also qualitatively with the help of the MONA (Maximisation of theOverlap ofNucleonic wave functions byAlignment of single particle angular momenta) effect. In the second part high spin states and yrast isomers in theN=82 region are calculated in the cranked Hartree-Fock-Bogoliubov approach with four and six quasi-particle excitations. For the excitation energies in¹⁴⁶Gd and¹⁵²Dy and a measuredg factor one finds satisfactory agreement.     

Gyromagnetic ratios of the 4+ and 6+ rotational states of184W

The nuclear Larmor precession has been observed for the 2⁺, 4⁺ and 6⁺ rotational states of¹⁸⁴W in the hyperfine field of WFe by application of the TDPAC and the IPAC techniques. A carrier free radioactive source of^184m Re alloyed with high purity iron was used for all three measurements. From the Larmor precession observed in the 2⁺ state by TDPACω _L = 944(15) MHz and the knowng-factor the hyperfine fieldB _{300 K} ^hf (WFe)=?69.6(27)T was derived. The deviation from the result of a spin echo experiment with¹⁸³WFe extrapolated to room temperature may be caused by the Bohr-Weisskopf effect (hyperfine anomaly). IPAC measurements with the same sample polarized in an external magnetic field of 1.6T gave for the 4⁺ and 6⁺ rotational states: ω _L τ(4⁺)=0.0609(22) andω _L τ(6⁺)=0.00735(102). By use of experimentalB(E2)-values theg _R -factors were derived asg _R (4⁺)=+0.276(26) andg _R (6⁺)=+0.281(45). The directional correlation of the 537?384 keVγ-γ cascade has been analysed in terms of anE1/M2/E3 mixture for theK-forbidden 537keV transition. We obtained the mixing ratiosδ(M2/E1)=±0.086(16),δ(E3/E1)=?0.028(5) with the sign convention of Krane and Steffen.     

Description of high-spin isomers in theN=82 region

The high spin states and of those especially the yrast isomers are studied in the region near the rare earth nuclei. The deformation energy surface is calculated with a method modelled in principle according to a shape constrained cranked HF theory (CHF). In practice, the expectation value of the many-body Hamiltonian is calculated with cranked Nilsson functions. One finds rotation around a slightly deformed oblate or prolate symmetry axis in front or behind the rare earth region, respectively. Near the Hf isotopes strongly prolate deformed nuclei rotating around the symmetry axis are found in agreement with the knownK isomers in this region. These results are explained also qualitatively with the help of the MONA (Maximisation of theOverlap ofNucleonic wave functions byAlignment of single particle angular momenta) effect. In the second part high spin states and yrast isomers in theN=82 region are caluclated in the cranked Hartree-Fock-Bogoliubov approach with four and six quasi-particle excitations. For the excitation energies in¹⁴⁶Gd and¹⁵²Dy and a measuredg factor one finds satisfactory agreement.     

Optical detected ESR in the4 S 3/2 excited state of Er:YCl3

The electron spin resonance in the⁴ S _3/2 excited state of Er³⁺ in yttrium trichloride was studied by optical detection techniques. From angular dependence of the resonance field the principle value of theg-tensor in direction of the twofold crystal axis was deduced to beg∥=3.350±0.004 and the perpendicular valueg⊥ in the crystallographica-b-plane was extrapolated to beg⊥=2.857±0.004. The lifetime of the excited state is found to be temperature independent with τ _r =(1.62±0.02)·10^?3 sec and the spin lattice relaxation timeT ₁ was determined in the temperature region 1.5 to 2.1 °K by observing the recovery of the fluorescent light signal after a microwave saturation pulse was switched off.T ₁ is found to follow a direct process with \(T_1^{ - 1} = k \cdot cth\left( {\frac{{\rlap{--} h\omega }}{{2kT}}} \right)\) .     

Ion implantation a powerful technique for the production of metastable superconducting alloys

Ion implantation at liquid helium temperatures is a new method of producing metastable alloys. The special features of this alloying technique are illustrated by two selected examples of dilute and concentrated alloys, respectively. Superconductors containing small amounts of paramagnetic (3d)-impurities such asHgMn, PbMn andSnMn exhibit strong pair breaking effects. In the case ofSnMn the Kondo effect is observed. Concentrated alloys of Pd and Pd-noble metal alloys with hydrogen (deuterium) are only superconducting in a very high concentration range, being unstable at room temperature. Such concentrations can be achieved by ion implantation at liquid He-temperatures. The superconducting transition temperature can thus be raised to a maximum value of 16.6 K in aH/Pd _0.55 Cu_0.45?0.7 alloy.