Der Faraday-Effekt an amorphen Selenschichten

Cl^38m was produced by neutron activation of chlorine containing samples in a pneumatic irradiation facility. The decay of the Cl³⁸-isomer was investigated by various scintillation spectrometer technics. The half-life and the internal conversion coefficient α of the 0.66 MeV isomeric transition was found to beT _1/2=0.74±0.03 sec and α=(5.0±1.2)×10^?4. These data suggest aM-3 transition between an isomeric state with the spinI=5^? and the ground-state of Cl-38 (I=2^?).     

Die Konversion des Hg199m

Hg^199m was produced from natural HgO by fastn irradiation. The cascade decay was investigated with scintillation spectrometers by application of the summing technique. The following results were obtained: half-lifeT _1/2=(43±0,5) min; energy of the isomeric transitionE _γ1=(375±3)keV; conversion coefficients α _K375=3,05±0,25; α_total=5,45±0,25; yielding the multipole order of the isomeric transition to beM4+(25±15)%E5; energy of the second transitionE _γ2=(159±2)keV; conversion coefficients α _K159=0,30±0,03; α_total=0,9±0,1, confirming the multipolarityE2 of this transition.     

Zur Isomerie des Tl197

Tl^197m was produced by the (α, 4n) reaction on Au¹⁹⁷ using 49 MeVα particles. The following results were obtained: Half-lifeT _1/2=(0.55±0.02) sec; energy of the isomeric level (607±4) keV, determined directly by summing up the cascade transitions in a well-type scintillator; energy of the isomeric transition (222±2) keV; conversion coefficients of this transitionα _K222=0.41±0.05 andα _tot222=2.1±0.2, indicating anE3 multipolarity; energy of the second transition (385±3)keV; conversion coefficientsα _K385=0.09±0.03 andα _tot385<0.1. This transition was identified asE2 with aM1 admixture of 20 to 30%. Spins and parities are 1/2⁺, 3/2⁺ and 9/2^? for the ground state, the 385 keV state and the 607 keV isomeric state, respectively, in disagreement with the extreme single-particle model. If this model were correct, anotherM1 transition should appear. No furtherM1 transition having an energy greater than theL-shell binding energy of T1 was observed.     

Der Zerfall Co58m →Co58g

Co^58m , Co^58g and Co⁵⁵ were obtained by radiating nickel-foiles with deuterons of energies 11,5 MeV and 2,07 MeV. The γ-radiation was measured with NaJ scintillation spectrometers. For the isomeric transition of Co^58m was determinedT _1/2=(9.15±0.1)h,T _γ=(25±1)keV,α _K=2200±300 and α_L+M=1100±300. From these values it follows, that the radiation is ofM3-type. Twoγ-energies of 95 keV and 1322 keV were found belonging to Co⁵⁵.     

Spins und γ-Multipolordnungen beim Zerfall Fe59→Co59

In the decay of Fe⁵⁹ the following quantities have been measured:γ-ray intensities, conversion coefficients andβ-(circularly polarizedγ) correlations. The conversion coefficients were found to be: for the 1.10 MeVγ-transition, α_tot.=(1.36±0.10)·10^?4 and for the 1.29 MeVγ-transition, α_tot.=(1.07±0.08)·10^?4. The asymmetry parameterA of the correlationβ(0.27 MeV)?γ(1.29 MeV) were measured to beA= ?0.17±0.10, and forβ(0.46 MeV)?γ(1.10 MeV),A=?0.13±0.04. From these data and publishedγ?γ angular correlation measurements the following spins of Co⁵⁹ levels could be deduced: 1.10 MeV,I=5/2^?; 1.29 MeV,I=5/2^?; and 1.43 MeV,I=3/2^?. The two strongβ-ray groups are pure Gamow-Teller transitions (ΔI=1). The multipolarities of all fiveγ-rays are given.     

Die Konversion des79m Br

⁷⁹ mBr was produced by irradiation of natural Br with fast neutrons. The half-lifeT _1/2=(4.87±0.15) sec and the energyE _γ=(208±1) keV were remeasured. For the first time the conversion coefficients were determined to beα _K=0.25±0.02 and α_total=0.28±0.05, yielding the multipolarityE3 for the isomeric transition.     

Radioactive decay of Os191 and Os191m

Beta and gamma spectra of Os¹⁹¹ were studied using a magnetic double-focusing beta-spectrometer and a scintillation spectrometer. The isomeric state Os^191m decays through the 74·4 ± 0·1 keV (E3/M4=50) transition with a half-lifeT _1/2=13·0 ± 0·5 hours. A continuous beta spectrum withE _max=147 ± 3 keV and the gamma transitions 41·83 ± 0·05 keV (E3), 82·5 ± 0·3 keV and 129·4 ± 0·1 keV (70%M1 + 30%E2) were observed in the decay of the ground state of Os¹⁹¹. The conversion coefficient of the last transition was determined as 1·94 ±± — 0·10. Gamma transitions with energies of 47 keV and 185·8 keV were not observed.     

Systematization of tensor mesons and the determination of the 2<Superscript>++</Superscript> glueball

It is shown that new data on the (J^PC=2⁺⁺) resonances in the mass range M～1700–2400 MeV support the linearity of the (n, M²) trajectories, where n is the radial quantum number of the quark-antiquark state. In this way, all the vacancies for the isoscalar tensor qq mesons in the range up to 2450 MeV are filled in. This allows one to fix the broad f₂ state with M=2000±30 MeV and Г=530±40 MeV as the lowest-tensor glueball.     

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.     

Die Lebensdauer des 23/2-Dreiteilchenniveaus des Hafnium 177 und sein Zerfall durchK-verbotene Gamma-Übergänge

An isomeric state of Hf¹⁷⁷ withT _1/2=(1,12±0,10)s was found by a fast chemical separation of the hafnium daughter from the 155d Lu^177m activity. We measured the same half-life by observing the delayedβ-γ-coincidences. A systematic investigation of the whole region 5s≧T _1/2≧10^?7s by the technique of delayed coincidences gave no further isomerism. We assign the observed half-life to the 23/2 three particle state of Hf¹⁷⁷ at 1315 keV and assume that the second hypothetical three particle state at 1337 keV does not exist. The 21/2 rotational state of theK=9/2 band is populated by a strongly converted 14,16 keVγ-transition from the isomeric state at 1315 keV. The 14,16 keVM _I andN _I conversion lines were observed by use of a double focusing magneticβ-spectrometer. The isomerism is caused by theK-selection rule. The retardation of the following threeγ-transitions by different degrees ofK-forbiddeness is discussed. The pulse height spectrum, measured by means of a Li-drifted Ge-detector, does not show the 36,52 keV-γ-transition which was previously assumed to populate the 1301keV-state. In addition to the knownγ-transitions we found a 40,9 keV-line. This is probably the transition between the 1301,1 keV and the 1260,3 keV-states.     

Der Zerfall des Co60m und Zr90m

Co^60m was produced by the reaction Co⁵⁹ (n,γ) Co^60m ; its decay has been investigated by scintillation spectrometers. The half-period has been remeasured yielding a value ofT _1/2=(10·35 ±0·20) min. The isomeric decay mainly leads to the Co⁶⁰ ground state by a (58·6±0·6) keV transition. TheK-conversion coefficientα _K= 41±3 and the total conversion coefficientα=47±3 indicate the transition to beM3 and the spin of Co^60m to be 2⁺. Further Co^60m decays by beta transitions to Ni⁶⁰. The beta component (8·6±1·2)·10^?3%, log ft=7·32 leading to a (2·16±0·02) MeV level has been measured for the first time. A second component (0·24±0·03)%, log ft=7·23 leads to the 1·33 MeV level. The 2·16 MeV level decays to the Ni⁶⁰ ground state mainly by a 0·83–1·33 MeV cascade, in a few cases by a direct transition. The spin of the 2·16 MeV level is 2⁺. Zr^90m was produced by the reaction Zr⁹⁰ (n,n′) Zr^90m . The half-period was measured yielding a value ofT _1/2=(0·83±0·03) sec. Zr^90m decays in the following way: (77±5) % by a direct (2·31±0·02) MeV —E 5 transition to the Zr ground state and (23±5)% by a (132·5±1·5) keV-(2·18±0·03) MeV cascade detected for the first time in the isomeric decay. TheK-conversion coefficient of the 132·5 keV transition isα _k=(2·2±0·3) indicating this transition to beE3 and the spin of the 2·18 MeV level to be 2⁺. The Zr^90m -decay sheme is in accordance with the level sequence of Zr⁹⁰ as measured in the Nb⁹⁰ decay.     

Das Auger-Spektrum derL III- Schale von Wismut

A thin Bi layer is irradiated by X-rays so thatL-Auger electrons are emitted. A magnetic lens spectrometer is used to measure the electron spectrum. Energy, transition, and relativ intensity are given for 14 lines. Under the most favourable conditions the number ofL _III ionisations is about ten times that ofL _II ionisations. In this case only a small intensity ofL _II-Auger electrons is superposed on theL _III-Auger spectrum. The ratiod of intensities of line groupL _III M N to line groupL _III M M is found by extrapolation to bed=0·46±0·02. This combined with earlier results gives anL _III-Auger yielda ₃= 0·64±0·04. TheL _III fluorescenc yield isω ₃=0·36±0·04, correspondingly. A further application of the experimental method is described.     

Mössbauereffektmessungen am 79,5 keV-Niveau von Gd158

Mössbauer effect measurements with the 79,5 keVγ-transition in Gd¹⁵⁸, populated by thermal neutron capture in Gd¹⁵⁷ are reported. In Gd metal, GdF₃ and GdCl₃, the values obtained for the electric field gradient are (?0.7±0.4), (11.9±5.0) and (?7.5±0.5) · 10¹⁷ V/cm² respectively. The internal magnetic field in Gd metal was measured to beH _int=312±23 kG and we derived for theg factor of the 2 + level the valueg _R=0.385±0.022. The change of the mean square nuclear radius between the ground state and the first excited stateΔ 〈r²〉=+(0.4±0.3) · 10^?3 fm², as extracted from the measurements, will be compared with model calculations of nuclear rotation.     

Study of penetration effects in the <Emphasis Type="Italic">E</Emphasis>1 and <Emphasis Type="Italic">M</Emphasis>1 transitions in <Superscript>44</Superscript>Sc

Conversion coefficients for the E1 and M1 transitions in the ⁴⁴Ti decay have been measured with high accuracy using the sum peak and multidimensional coincidence methods. The following values have been obtained: α_K(E1) = 0.077 ± 0.003 and α_K(M1) = 0.014 ± 0.001. A significant contribution of the penetration effects for the M1 transition has been shown. The penetration parameter λ is determined to be ?260 ± 30 has been determined.     

Bestimmung von Moleküleigenschaften des Tl205F19 aus kombinierten Stark-Zeeman-Effekt-Messungen mit der Molekularstrahlmethode

An electric Molecular-Beam-Resonance-Spectrometer has been used to measure simultanously the Zeeman- and Starkeffect splitting of the hyperfinestructure of TlF. Electric fourpole lenses served as focusing and refocusing fields of the spectrometer. A homogenous magnetic field (Zeeman-Field) was superimposed to the electric field (Stark-Field) in the transition region of the apparatus. The observedΔm _J =±1 -transitions were induced electrically. Completely resolved spectra of Tl²⁰⁵F¹⁹ in theJ=1 rotational, andυ=0 vibrational state have been measured. The obtained quantities are: The rotational magnetic momentμ _J of Tl²⁰⁵F¹⁹ in the stateJ=1,υ=0, and the difference of the magnetic shielding (σ _1,±1?σ _1,0) of both nuclei as well as the difference of the molecular susceptibility (ξ _1,±1?ξ _1,0) in the states (J, m _J)=(1,±1) and (J, m_J)=(1, 0). The sign of the rotational magnetic moment could be determined unambigously by the influence of offdiagonal matrix elements. The numerical values for Tl²⁰⁵F¹⁹ in the stateJ=1 andυ=0 are:μ _J =?29,153(21) · 10^?6 μ _Bohr (σ _1,±1?σ _1,0)^Tl=?0,002291 (33) (σ _1,±1?σ _1,0)^F=?0,000206(9) (ξ _1,±1-ξ _1,0)=+3,02(15) · 10^?30erg/Gauß² The quantities in brackets are root-mean-square deviations in units of the last digit. From these data and the known values for the spin-rotational interaction constants a number of expressions are derived which characterise the electronic charge distribution in the molecule.     

Refinement of the hadronic contribution to the muon anomalous magnetic moment and to α(<Emphasis Type="Italic">M</Emphasis><Stack><Subscript>z</Subscript><Superscript>2</Superscript></Stack>)

The contribution of the muon anomalous magnetic moment aμ(hadr) to the vacuum polarization and electro-magnetic coupling constant α(q²) for q²=M _z ² is refined by using a new, more accurate value of the ρ-meson width. The values aμ(hadr)=678(7)×10^?10 and δα(M _z ² =0.02786(6) were obtained in a QCD model with an infinite number of vector mesons.     

The formation of the superheavy hydrogen isotope <Superscript>6</Superscript>H in the absorption of stopped π<Superscript>−</Superscript>-mesons by nuclei

An experimental search for the superheavy hydrogen isotope ⁶H was conducted through studying the absorption of stopped π^?-mesons by ⁹Be and ¹¹B nuclei. A structure in the missing mass spectrum caused by the resonance states of ⁶H was observed in three reaction channels, namely, ⁹Be(π^?, pd)X, ¹¹B(π^?, d³He)X, and ¹¹B(π^?, p⁴He)X. The parameters of the lowest state E_r=6.6±0.7 MeV and Γ=5.5±2.0 MeV (E_r is the resonance energy with respect to the disintegration into the triton and three neutrons) are evidence that ⁶H is a more weakly bound system than ⁴H and ⁵H. Three excited states of ⁶H were observed. Their resonance levels (E_1r=10.7±0.7 MeV, Γ_1r=4±2 MeV, E_2r=15.3±0.7 MeV, Γ _2r=3±2 MeV, and E_3r=21.3±0.4 MeV, Γ_3r=3.5±1.0 MeV) are energetically capable of disintegrating into six free nucleons.     

Messung des gR-Faktors des 2+-Rotationsniveaus von Dy160 nach der Spinrotationsmethode und Bestimmung der Multipolmischungen mehrerer γ-Übergänge im Zerfall des Tb160

A differential measurement of the spin rotation of Dy¹⁶⁰ in the 2+ rotational state was performed by using liquid sources of TbCl₃ solved in 3M HCl and applying an external magnetic field of 33 500 Gauss. No change of the Larmor precession frequency could be detected within the first 10·10^?9 s. It is concluded that the ground state of the electronic shell of Dy⁺⁺⁺ is reached in 6·10^?10 s after theβ-decay of Tb¹⁶⁰. The valueg _R=+0.364±0.011 was derived using 〈r^?3〉_eff=8.92 a. u. for the 4f-shell of Dy⁺⁺⁺. A comparison with the result ofCohen who studied the Mössbauer-effect in Fe₂Dy shows that the value of 〈r^?3〉_eff must be 10% larger in this compound. A measurement of the effective magnetic field at the position of the nucleus in a source of terbium metal was performed for different temperatures. It revealed a temperature dependence which is very similar to the paramagnetic susceptibility χ(T). We observed a strong attenuation ofγ γ-angular correlations in the 2+ rotational state. For liquid sources of TbCl₃ solved in 3M HCl the following attenuation parameters were measured:

$$\begin{gathered} \lambda _2 = (0.122 \pm 0.013) \cdot 10^9 {\text{s}}^{ - {\text{1}}} , \hfill \\ \lambda _4 = (0.235 \pm 0.024) \cdot 10^9 {\text{s}}^{ - {\text{1}}} . \hfill \\ \end{gathered}$$     

Die absolute Intensität der durch Elektronenstoß in einer dicken Wolfram-Antikathode erzeugtenL α -Strahlung

The number\(N_{L_\alpha }^{dir} \) (produced) ofL _α -photons produced by electron-bombardment in a thick target of tungsten per incident electron has been measured absolutely with the Ross-filter method and relatively with the crystal-spectrometer method in the energyregion up to the 3.6 times theL _III-ionization energy\(E_{L_{III} } \). The result can be presented in the following empirical form:\(N_{L_\alpha }^{dir} \) (produced)=4π·?·(U ₀?1) ⁿ with ?=0.52·10^?4±5% andn=1.44±0.02\((U_0 = E_0 /E_{L_{III} }< 3.6)\). Out of this the number\(n_{L_{III} } \) ofL _III-ionizations per electron which is slowed down to the energy\(E_{L_{III} } \) within the target, has been evaluated. The computation of\(n_{L_{III} } \) out of the elementary process by usingBethe's non-relativistic formulae for totalL _III-ionization cross sectionQ _L and energy loss-dE/ds is in full agreement with experiment in the region 2<U ₀<3.6, if the constants in\(Q_{L_{III} } \) are chosen as follows:\(B = 4E_{L_{III} } , b_{L_{III} } = 0.25 \cdot 5.89\). By comparison of this result for\(b_{L_{III} } \) with the corresponding value ofb _K in the totalK-ionization cross-sectionQ _K for copper (b _K=0.35·2.26) it is concluded that\(Q_{L_{III} } \) is considerably higher than predicted by theory. The necessary correction factors as e.g. loss ofL _III-ionizations by rediffusion of electrons and portion of indirectly producedL _α -radiation-radiation are determined for tungsten quantitatively.     

Specific features of anion transfer in HoF<Subscript>3</Subscript> crystals at high temperatures

The anionic conductivity of HoF₃ single crystals with a β-YF₃ structure (orthorhombic crystal system, space group Pnma) is investigated over a wide range of temperatures (323–1073 K). The unit cell parameters of HoF₃ crystals are as follows: a=0.6384±0.0009 nm, b=0.6844±0.0009 nm, and c=0.4356±0.0005 nm. It is revealed that the conductivity anisotropy of the HoF₃ crystals is insignificant over the entire temperature range covered. The crossover from one mechanism of ion transfer to another mechanism is observed near the critical temperature T_c≈620 K. The activation enthalpy of electrical conduction is found to be ΔH₁=0.744 eV at T<T_c and ΔH₂=0.43 eV at T>T_c. The fluorine vacancies are the most probable charge carriers in HoF₃ crystals. The fluorine ionic conductivities at temperatures of 323, 500, and 1073 K are equal to 5×10^?10, 5×10^?6, and 2×10^?3 S cm^?1, respectively.