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.     

Decay energy of183Re→183W

The electron capture decay energy of¹⁸³Re has been determined from the fraction ofK-capture in the transition to the 453.08 keV level in¹⁸³W by delayed coincidences. From this value the total decay energy from₁₈₃Re→¹⁸³W is obtained to beQ=555 _?7 ⁺⁹ keV according to the theory ofBrysk andRose with corrections ofBahcall. The resulting logft values and consequences for the decay scheme are discussed.     

On the use of a noncentral velocity dependent potential for the interpretation of the nucleon-nucleon scattering data

A phenomenological nucleon-nucleon potential containing a noncentral velocity dependent term of the form (σ ₁ ·p)(σ ₂ ·p) is used to fit the solutions YLAM and YLAN 3 M of the phaseshift analysis ofBreit et al. andHull et al. for protonproton and neutron-proton scattering respectively. The potential contains altogether 20 parameters. The fit is carried through in the range from 10 to 300 MeV laboratory energy. While the results for thep-p phase parameters are useful only in some cases the results for then-p phase parameters are in general quite satisfactory.     

Suche nach dem Isomer74mAs

An activity with the decay propertiesT _1/2=(8.0±0.3)sec andE _γ=(283±5)keV has been produced bySchardt andGoodman by proton irradiation of thin layers of evaporated⁷³Ge and⁷⁴Ge on thick gold backings. This activity was interpreted as the new isomer^74mAs. In the present experiment a search for^74mAs was carried out using the reactions⁷⁵As(n, 2n),⁷¹Ga(α, n) and⁷⁴Ge(d, 2n).^74mAs could not be detected. Upper limits for the reaction cross sections were determined. It is discussed that the reported properties of^74mAs resemble the known properties of^197mAu.     

Mößbauereffekt in Eisenstilben und FeCl2·H2O

Using Mößbauer effect measurements in the temperature range between 3 °K and 310 °K the magnetic fields at the nucleus in iron-stilbene, FeCl₂·H₂O and FeCl₃ are determined to beH _T=0=(250±10) kOe, (252±18) kOe and (468±10) kOe; a Néel-temperature ofT _N=(23±1) °K is measured for iron-stilbene. The electric quadrupole splittings atT=0 °K for iron-stilbene and FeCl₂ ·H ₂ O, ΔE=(+2.52±0.02) mm/sec and (+2.50±0.05) mm/sec, yield electric field gradients at the iron nucleus ofq _z=+9.7·10¹⁷ V/cm² and +9.6·10¹⁷ V/cm², whereq _z⊥H; Debyetemperatures of θ=162 °K and 188 °K are obtained. The energy of the excited 3d-electron levels in iron-stilbene is estimated to Δ₁=309 cm^?1 and Δ₂=618cm^?1 as deduced from the temperature dependence ofΔE. In contrast to the suggestion ofEuler andWillstaedt bivalence of the iron in ironstilbene is found; its composition is shown to be 4(FeCl₂ ·H ₂O)·stilbene.     

Das kritische Magnetfeld Hc∥ von dünnen supraleitenden Filmen

Thin superconducting films in a surface parallel magnetic field are considered, assuming that the order parameter is constant in space. Without any further restrictions on the film thickness,a, an equation for the critical field is derived. In the clean limit, this equation is valid only in the vicinity of T_c, but in the dirty limit it is valid for all temperatures. Our results, for specular reflection, are identical with those obtained byThompson andBaratoff. But for not too thin films we find essential differences between the results for specular and for diffus reflection. For very thin films (a?v/2πT _c), considered in detail byde Gennes andTinkham and byShapoval, our results are in agreement with those obtained byShapoval. In the opposit limit (a?v/2π T _c), the most essential corrections to the Ginzburg-Landau result obtained byLüders are rederived.     

Spezifischer Energieverlust von schweren Ionen in Aluminium,Silber und Gold

Using a Cf²⁵²-fission source and two semiconductor detectors in 180°-position the specific energy loss of heavy ions in A1-, Ag-, and Au-foils was measured. The agreement with the results ofMoak andBrown, and ofKahn andForgue is better than 15%. The energy loss predicted byLindhard is 10–25% lower than the measured values. A better agreement — especially for absorbers with low atomic numberZ — is achieved by a semiempirical formula proposed byMünzel.     

Energie-Relaxation warmer Ladungsträger in Germanium und Silizium

Experimental data on warm carrier energy relaxation times in germanium and silicon are reported. Measurements were done by the method of harmonic mixing of microwaves 1 in the temperature range between 77 and 200 °K. Relaxation times obtained forn-type germanium are in agreement with data reported byMorgan 2 as well as that ofSeeger 3 andGibson et al. 4. Measured energy relaxation times forp-type germanium as well as forn- andp-type silicon are reported here for the first time. A qualitative interpretation is given in terms of scattering by acoustic and optical phonons.     

Investigation of the two quasiparticle rotational band at 1172 keV in172Yb and determination of theg R -factor of the 3+ 3 band head

Investigations of the rotational band based on the 3⁺ 3 two quasiparticle state in¹⁷²Yb have shown that some of its properties can be well described by the collective model of Bohr and Mottelson. As a result of these investigations we have derived the ratio (g _k – g _R )/Q _o =? (0.0136 ± 0.0007). The magneticg-factor of the band head has also been determined by an integral angular correlation measurement perturbed by an external magnetic field. As a result we foundg=0.201 ± 0.030. Using this value and our result of (g _k – g _R )/Q _o we have calculated theg _R -factor of the two quasiparticle state asg _R =0.283 ± 0.018 which is out of the errors smaller than theg _R -factor of the ground state rotational band. An analysis of our angular correlation experiments gave for the mixing parameter δ of theK-forbidden 1094 keV intraband transition: δ=? (3.63 _?0.06 ^+0.14 ) in agreement with the results of other authors.     

Untersuchung der vier ersten angeregten Zustände des6Li-Kernes durch Elektronenstreuung

Inelastic electron scattering cross sections were measured for energies below 60 MeV and momentum transfersq between 0.2 and 0.6 fm^?1. Ground state radiative widths Γ _γ ⁰ and transition radiiR _tr were deduced. 2.18 MeV: Γ _γ ⁰ (E2)=(4.40±0.34) · 10^?4 eV,R _tr=(4.28±0.39)fm; 3.56MeV: Γ _γ ⁰ (M1)=(8.31±0.36)eV,R _tr=(2.90±0.10)fm; 4.27 MeV: Γ _γ ⁰ (E2)=(5.4±2.8) · 10^?3 eV,R _tr=(3.4±1.2) fm. The excitation of the 5.37 MeV level shows a transverse angular dependence.     

Infrared and raman studies of some naphthols

Vibrational spectra of α-naphthol,β-naphthol andβ-naphthol-OD have been recorded in the solid and solution phases. A number of bands, common to all the three compounds, have been correlated with earlier naphthalene assignments and an attempt has been made to identify certain frequencies with vibrational modes that are centred in the substituentsOH andOD. TheC _s symmetry is assumed for each molecule.     

Determination of theg j -factor in the72 P 3/2-state of133Cs by optical double resonance in a strong magnetic field

The hfs in the 7² P _3/2-state of¹³³Cs has been investigated by optical double resonance in a strong magnetic field. From the positions of the magnetic dipole transitions Δm _j =± 1, Δm _i =0 the magnetic hfs coupling con slanta (7² P _3/2)=16.591(25) MHz and theg _j -factorg _j (7² P _3/2)=1.33410(15) could be derived. Contrarily to recent measurements,g _j agrees well with the value calculated from the Lande formula.     

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.     

Neutral strange particle production in proton-proton collisions at\sqrt s = 63 GeV

The inclusive cross section for the production ofK _s ⁰ mesons, Λ and \(\bar \Lambda\) particles in proton-proton interactions at \(\sqrt s = 63\) GeV is presented. The produced particles have been detected in the full phase space. Behaviour of the longitudinal and transversal depandences of the cross sections are discussed. The total production cross sections for _s ⁰ mesons and Λ particles was determined to \(\sigma _{{\rm K}_S^0 } = (25.5 \pm 1.4)\) mb andσ _Λ =(7.8±1.2) mb respectively. A strong energy dependence of the production cross sections is observed.     

Gadolinium as a ferromagnetic host for IMPAC experiments

The properties of ferromagnetic Gd as a host for IMPAC measurements have been investigated. The transient and internal magnetic fields at Cd, Nd, Sm, Dy, Er, Yb and Hf nuclei recoil implanted into polarized Gd at 80 K have been studied by the IMPAC technique. All available experimental transient field data for Gd have been analysed in the framework of the Lindhard-Winther theory. Empirical values of the parametersv _p andC _ion C _atom have been deduced which give good agreement between experiments and theory. Internal magnetic fields at rare-earth nuclei in magnetized Gd at 80 K have been deduced. The results areH _h.f. (NdGd)=?1370±440 kG,H _h.f.(SmGd)=?1440±120 kG,H _h.f.(DyGd)=1410±400 kG,H _h.f.(ErGd)=2310±420 kG andH _h.f.(YbGd)=?216±32 kG. The signs of these fields are, except for Yb which is in a 2⁺ ionic state, consistent with a ferromagnetic coupling between the 4f spins of the implanted ion and the Gd host. The deduced internal field at Hf in Gd is ?440±90 kG. The observed time-dependent interactions for rare-earth nuclei in ferromagnetic Gd are consistent with the Abragam-Pound theory. For the Cd isotopes,g-factors of the first 2⁺ states were deduced from the experiments. The results areg(¹¹⁰Cd)=0.49±0.11,g(¹¹⁴Cd)=0.34±0.09 andg(¹¹⁶Cd)=0.41±0.11. The use of transient magnetic fields forg-factor measurements on high-spin rotational states is discussed.     

Measurement of internal conversionK/L 3 andK/L ratios forE2 transition

Internal conversionK/L ₃ ratio forE2 transitions was measured for nuclei with mass numbers from 152–198, and the energy interval of 80–500keV. The results of all the 11 transitions measured are in good agreement with theoretical values ofSliv andBand, Pauli, Bhalla andHager andSeltzer.¹⁵²Eu,¹⁶⁰Tb,¹⁶⁶Ho,¹⁸²Ta,¹⁸⁶Re,¹⁸⁸Re, Radioactivity¹⁹²Ir,¹⁹⁸Au/all (n, γ)/measuredc c ratios.     

Magnetic hyperfine field at Cr site in AgCrO2 given by Perturbed angular correlations

This work presents an electric field gradient and magnetic hyperfine field study, in the AgCrO₂ multiferroic with triangular spin lattice. The temperature dependence of the electric field gradient (efg) and magnetic hyperfine field (mhf) at Cr site was studied at isolde via perturbed angular correlation measurements with the ¹¹¹In probe, at room temperature and below the Néel temperature (T?≤?21 K) down to 12 K. The results show the presence of two distinct local environments. One axial symmetric efg with a very low mhf, and a non axially symmetric efg with a much higher one. The temperature dependences of mhf magnitude and of the angle between the mhf and the principle component of the efg are investigated.     

The parameters ofK 0→2π decay and the magnitude of ℛ(A 2/A 0)

The phenomenological analysis ofK ⁰→2π decay proposed byWu andYang is carried out without any assumption about the magnitude of the parameters. The smallness of? and?′ is verified, and it is shown how the unknown parameter ?(A ₂/A ₀) could be determined from experiment.     

TheK conversion coefficient near threshold of theM3 transition in191Os

TheK conversion coefficient α _k of the 74.38 keVM3 isomeric transition in¹⁹¹Os was measured with a curved crystal spectrometer of DuMond type. The experimental result α _k =106±11 is in agreement with theoretical calculations taking the dynamic correction coefficient λ=9.4±0.5 into account.     

Bestimmung der Kernquadrupolmomente der beiden stabilen Europiumisotope aus dem Eu II-Spektrum

The hyperfine structure of the transitions 4f ⁷ 6p ⁹ P _3,4,5?4f ⁷ 6s ⁹ S ₄,⁷ S ₃ in the spark spectrum of europium was investigated by a digital recording double-Fabry-Perot-spectrometer. Enriched samples of¹⁵¹Eu and¹⁵³Eu were used in hollow cathode light sources cooled in liquid air. As the hyperfine splitting of the⁹ P levels was not completely resolved the patterns were analysed by a computer. TheA- andB-values of the⁹ P levels were determined for both isotopes. Together with the experimentalA-values of the⁷ P levels theseA-values were used to check the eigenfunctions ofBordarier, Judd, andKlapisch, which have been calculated for intermediate coupling. Good agreement between observed and calculatedA-values was reached only if the spherical-symmetric part of the magnetic hyperfine interaction operator of the 6p-electron was used as a free parameter. In this way the configuration interaction between 4f ⁷ 6p and 4f ⁶ 6s 6d can be taken into account. Fortunately this mixing does not affect the quadrupole interaction. Therefore the quadrupole moments were derived from the measuredB-values using the unperturbed eigenfunctions. The resultsQ(¹⁵¹Eu)=(1.12 ±0.07) · 10^?24 cm² andQ(¹⁵³Eu)=(2.85 ± 0.18) · 10^?24cm² are in complete agreement with the values obtained byMüller, Steudel, andWalther in the 4f⁷ 6s 6p levels of the arc spectrum of europium. The values found for the hyperfine anomaly agree very well with the values derived from levels in Eu I and Eu III.