Self consistent description of the nuclear monopole polarization in muonic 208Pb

The monopole part of the nuclear polarization energy in muonic ²⁰⁸Pb, 1s_{$\text{1}\text{2}$} level, is calculated in the Hartree Fock approximation using a number of Skyrme-type forces. The result found, ?0.7± 0.2 keV is smaller than previous estimates.     

Messung der 2P-1S-Übergangsenergie im Myon-Barium-Atom

As a means of studying the nuclear charge radius, the 2P-1S-transition energy of the muon-barium-atom (μ-mesonicK _α -line) was measured. A 3″×3″ NaJ-spectrometer was used at the muon channel of the CERN-synchrocyclotron. Since the muon intensity was high, measurements could be repeated under various conditions. Experiment, checks, and results are described. The 2P-1S-energy obtained, (3981±30) keV, agrees with the value calculated byFord andWills (3974 keV) for a “family II”-charge distribution fitted to the Stanford electron scattering data.     

Measurement of the polarization of positive muons produced in high-energy antineutrino interactions

The question whether scalar-type interactions contribute to weak interactions at large momentum transfer has been investigated by a measurement of the longitudinal polarization of positive muons produced in charged-current interactions of high-energy antineutrinos with iron. At an average momentum transfer <Q ²>=4 GeV² the muon spin is found to be oriented forward with respect to the muon momentum vector, with an average polarization of 1.10±0.24, consistent with positive helicity. A limit on scalar contributions of σ_{s, p}/σ_tot <7% at the 95% confidence level can be deduced. A search for violation of time reversal invariance which could manifest itself by a polarization component perpendicular to the muon production plane gave a limit of σ_tv/σ_tot <16% (95% c.l.). It is concluded that the weak leptonic charged current retains its dominant vector and axial vector structure at large momentum transfers.     

Muon-spin-rotation study of muon polarization losses in plastic scintillators and quartz

Muon polarization losses in plastic scintillators of two types and in fused quartz have been studied by the μSR method. The muon and muonium spin precession spectra have been measured on the μSR setup placed at the output of the muon channel of the Gatchina synchrocyclotron. It has been shown that a significant fraction of stopped muons participate in the formation of the muonium. As a result, these muons lose their polarization completely. The magnitude of muon depolarization depends considerably on the type of plastic. It has been found that the muon spin precession frequency in fused quartz in an external magnetic field (F _{Q, μ} = 0.116 ± 0.002 MHz) is shifted with respect to that in plastic scintillators (F _{1, μ} = 0.101 ± 0.005 MHz and F _{2, μ} = 0.101 ± 0.002 MHz).     

Gamma radiation in the decay of249Cf

Gamma radiation following alpha decay of²⁴⁹Cf was investigated with high resolution Ge(Li) detectors in singles and coincidence arrangements. Nine new γ-rays were identified and placed in the previously-known decay scheme. Their energies in keV and intensities relative to the 388 keV (100) γ-ray are: 37.5±0.1 (0.026), 65.87±0.1 (0.017), 121.5±0.4 (0.070), 229.2±0.2 (0.072), 255.7±0.2 (0.065), 390.5±0.2 (0.025), 405.9±0.1 (0.014), 588.8±0.1 (0.003), and 643.5±0.1 (0.007). Coincidence measurements revealed that the intensity of the 54.7 keV γ-ray is shared by three intraband transitions and that the 121.5 keV crossover transition is present in the ground-state band.     

Decay properties of76m Br

The remeasured half-life of^76m Br was found to be 1.31±0.02s.γ-ray and conversion electron measurements gave for two cascading transition energy values 57.11±0.02 and 45.48±0.02 keV with multipolaritiesM2 and M1, respectively. The 4⁺ isomeric state at 102.59±0.04 keV is placed in the⁷⁶Br level scheme. The intensity of the cross-over transition is less than 0.8% of isomeric decays.     

Spin values of the low lying nuclear levels of201Hg

Gamma-gamma directional correlations have been investigated for the cascades of 135-30 keV and 135-32 keV in²⁰¹Hg from the decay of²⁰¹Tl. A combination of NaI (Tl) and Si (Li) detectors was used for the experiments. Spin values ofI=1/2, 3/2 and 1/2 have been assigned to 1.58, 32.19 and 167.49 keV energy levels. In addition, the relative intensities of theγ rays have been measured with a Ge (Li) detector system. The results are 2.2±0.2, 2.2±0.2, 26.5±1.3, 1.6±0.1 and 100 for theγ rays of 30.60, 32.19, 135.34, 165.88 and 167.43 keV energies, respectively.     

Unelastische Elektronenstreuung am4He bei kleinem Impulsübertrag

Using a liquid helium target, inelastic electron scattering from⁴He was investigated at momentum transfers below 0.5 fm^?1 with improved resolution. The assignment 0⁺ for the state at (20.10±0.05) MeV (measured excitation energy) has been confirmed, and new values for the monopole matrix element (1.10±0.16) fm² and the total width (270±50) keV were derived. The giant resonance region shows evidence for theM2-resonance at 24 MeV.     

Gamma branching and total conversion coefficients of intraband transitions in the groundstate rotational band of245Cm

With calibrated Ge(Li) detectors, γ-γ coincidences have been observed in the decay of²⁴⁹Cf. The total conversion coefficient of the 54.7 and 66.7 keV transitions in the first rotational band have been determined to be 237±30 and 69±15, respectively. The branching ratio of the 121.5keV crossover transition is (22±7)%. The errors are the 2σ statistical uncertainties, linearily added to the errors in the detector efficiencies.     

β-γ-Zirkularpolarisationskorrelation an Ga72

The β-γ circular polarization asymmetry for the β 948—γ 2202 keV transition in Ga⁷² has been measured using the polarimeter developed at Karlsruhe. The result of the measurement isA=?0.203±0.035. From this result and γ-γ angular correlation measurements of other authors we are able to deduce the spin of the 3036 keV level in Ge⁷² to 2^?. The multipolarity of the 2202 keV γ-rays in Ge⁷² is found to beE1.     

Transverse muon polarization in the K µ3 0 decay induced by electromagnetic final-state interaction

A calculation of transverse muon polarization in the K _μ3 ⁰ decay due to the electromagnetic interaction in a final state in one-loop approach is presented. Average transverse muon polarization is found to be (2.4±0.1)×10⁻³ in the Dalitz plot region. From Yadernaya Fizika, Vol. 63, No. 2, 2000, pp. 319–323. Original English Text Copyright ? 2000 by Efrosinin, Kudenko. This article was submitted by the authors in English.     

AnomalousK-conversion coefficient of the 124keV transition in131Cs

The absoluteK-conversion coefficients of the 496 keV-124 keV cascadeγ-rays in¹³¹Cs have been determined from angular correlation experiments using a new approach. The value ofα _K =0.0100±0.0007 obtained for the 496 keV transition is in excellent agreement with the theory whereas a strong case is presented for the existence of an anomalous nuclear-structure-dependent conversion coefficient for the 124 keV transition. TheK-conversion coefficient for this transition has been measured to be 0.742±0.077 giving a value of 1.25±0.13 for the ratioα _K ^(expet) /α _K ^(theory) . The result is interpreted as being due to the presence of electric monopole,E0, electron transition. A value of 0.26±0.14 has been obtained for theE0/E2 electron conversion ratio and the absolute value of the electric monopole matrix element has been determined to be 0.07±0.02.     

Relativmessung der Elektronenpolarisation beimxβ-Zerfall: RaE(Bi210)-P32

An apparatus is described for comparing the longitudinal polarization valuesP ofβ-particles from different emitters by the method of double scattering. For RaE(Bi²¹⁰) and P³² we have measured the ratio of polarization values to be P(RaE)/ P(P³²)=0·757±0·022 at 540 keV. This is in good agreement with previous measurements. Ratios of matrix elements are determined from polarization and spectrum shape data of RaE, but these values are not reliable because the spectrum shape shows a systematic discrepancy between theory and experiment below 200 keV. A discussion of electron polarization and spectrum shape data of P³² shows that deviations of polarization from the allowed value are probably very small.     

Nuclear orientation of negative parity states of 131Xe

The anisotropies of the 177, 326, and 503 keV γ-transitions between negative parity states of ¹³¹Xe have been remeasured in the decay of oriented ¹³¹I nuclei. In addition the linear polarization of the 503 keV radiation has been determined with a Compton polarimeter consisting of two Ge(Li) detectors. A combined analysis of the reported experiment and earlier internal conversion and angular distribution data yields the unique assignments $\text{9}\text{2}{}^{\mathrm{?}}\text{and}\text{7}\text{2}{}^{\mathrm{?}}$ for the levels at 341 and 667 keV. The $\text{E2}\text{M1}$ mixing ratios of the 177 and 326 keV transitions are δ(177) = ?4.5 ± 1.5 and δ(326) = ?4.4 ± 1.6. The intensity of the L = 2 component in the first forbidden β-decay to the 667 keV level is at most 60 %.     

Search for superdeformation in180Os

Two-dimensional γ-ray energy correlations have been measured at high spins in¹⁸⁰0s with the TESSA2 spectrometer. The E_γ ? E_γcorrelation matrix displays ridges characteristic of rotational bands with different energy separations of 96± and 72± keV for the energy regions of 660 to 840 keV and 975 to 1170 keV, respectively. The separation of these ridges remains constant in both energy regions. The dynamical moments of inertia are θ⁽²⁾ =83±3 and 111±5 ?²/MeV, respectively. The latter value suggests superdeformation in¹⁸⁰0s with an axis ratio c/a=1.76 (β₂ ?0.64) at high spins.     

The spin of the 2,198 keV level in74Ge and multipole mixing ratios of gamma transitions in the decay of74As

Directional-correlation measurements of several cascades in the⁷⁴As decay have been made with a NaI — Ge(Li) detectors system. In the⁷⁴Ge the following cascades were measured: 608–596 keV, 994–1,204 keV, 994-(608)-596 keV and 887-596 keV. The corresponding results give a unique spin assignment of 2 for the 2,198 keV level and determine theE2/M 1 mixing ratios ofδ(608)=3.4±0.4 andδ(994)=?(2.8 ± 0.2). In the⁷⁴Se it was measured the 635-635 keV cascade. The result obtained assigned the spin of the 1,270 keV level as 2 and fixed the E2/M1 mixing ratio of δ(635)=?(2.6 ± 0.2). Also aγ-intensity study has been made to determine the branching ratios of the transitions that deexcite the 1,270 keV level in⁷⁴Se. From these data aI(635)/I(1,270)=12.5 ± 5.0 is obtained.     

Measurements of γ-γ and γ-electron directional correlations in119Sb

The directional correlations ofγ-γ andγ-electron cascades in¹¹⁹Sb are measured, in the decay of^119mTe. Bothγ-γ andγ-electron directional correlation coefficients are determined for the cascades (energies in keV): 153.5-1212.7, 942.3-270.5, (976.2+979.3)-270.5, 1095.7-270.5 and 1136.8-270.5. For the cascades 912.6-1366.2, 2013.4-270.5 and 2089.9-270.5γ-γ directional correlations are measured. The mixing ratios evaluated are:δ(M2/E1, 153.5 keV)=0.0003±0.0023,δ(E2/M1, 270.5 keV)=-0.39±0.29,δ(E2/M1, 942.3 keV)= ?0.26±0.12,δ(E3/M2,1095.7 keV)=?0.01±0.07, andδ(M3/E2,1212.7 keV) =0.004±0.007. The result is compared with theoretical predictions.     

Elektroneneinfang beim Zerfall des Ti45

Electron capture to the 718 keV, 1238 keV, 1408 keV and 1665 keV excited states of Sc⁴⁵ have been observed in the decay of Ti⁴⁵. The branching ratios were determined to be (0,4±0,04)% (0,05±0,02)%, (0,27±0,03)% and (0,08±0,01)% per decay of Ti⁴⁵ respectively.     

Winkelkorrelationsmessungen an >30y Holmium 166 und Bestimmung desg R -Faktors des 4+-Rotationsniveaus von Erbium 166

The spins of several excited states of Er¹⁶⁶ have been investigated byγγ-angular correlation measurements. The spin sequence 0+, 2+, 4+, 6+ for the ground state rotational band was presumed to be correct. Unique assignments were derived for the states of 1076 keV, 1377 keV and 1785 keV asI=5, 7 and 6 respectively. These results are in agreement with the spins proposed byGallagher jr. andSoloviev. The multipolarities of theγ-transitions of 408 keV, 709 keV, 811 keV and 831 keV were derived as 95%E1+(5±1)%M2, 99·6%E1+(0·4±0·5)%M2, 99·1%E2+(0·9±0·3)%M1, and 96·1%E2+(3·9±1)%M1 respectively. The unusual mixing ratios of the transitions of 811 keV and 831 keV can be understood as a consequence of theK-selection rule. Eachγ-transition from the 1785 keV state should be stronglyK-forbidden and one expects a half-life ofT _1/2≈3·10^?9s. A measurement of the time spectrum of the coincidences between theβ-radiation and the high energyγ-lines gave however:T _1/2(1785 keV state)≦3·10^?10s. The rotation of the angular correlation between the 184 keV line and theγ-group at 820 keV has been measured in an external magnetic field of 53000 gauss as:ω·τ(4+)=0·083±0·006. This value contains small corrections for an additional rotation of the angular correlation of the 831 keV–184 keV triple cascade in the 6+state and for a small attenuation by internal fields. WithT _1/2(4+state)=1·23·10^?10s, andβ=7·08 one gets for theg-factorg _R=+0·266±0·024 in good agreement with recent results for the 2+ state.     

Internal conversion coefficients in the Hartree-Fock atomic model. Calculations and experiments for199Hg

The internal conversion coefficients were calculated for the transitions in¹⁹⁹Hg using both Hartree-Fock and Hartree-Fock-Slater atomic models. The relative conversion line intensities were measured with the magnetic spectrometers in Prague and Heidelberg. The multipolarities were determined to be:M1+(0.20±0.03)%E2, pure E2 and M 1+ (13.4 ±0.4)%E2 for the 50, 158 and 208 keV transitions, respectively. Allowing for the nuclear structure effect in M1 component we obtained: M1+(0.15±0.03) %E2,λ = 2.4±1.0 for the 50 keV and M1+ (10.9±0.7)% E2, λ=3.8±0.5 for the 208 keV transitions. Very good agreement was found between theory and experiment for the atomic subshells,K, L_1?3,M _1?5,N, andO + P.