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.     

Erzeugung neuer isomerer Kernzustände durch Kernphotoreaktionen am Antimon und Thallium

The systematic search for new short-lived isomeric states has been continued by irradiation of an additional 32 selected elements with 26 MeV bremsstrahlung. Isomeric transitions were detected using a conventional scintillation spectrometer. Irradiation of antimony led to the production of a new (530±50) μsec isomeric state which decays through emission of partially converted (62±2) keV and (76±3) keV gamma rays. The 530 μsec half-life is tentatively associated with the 136 keV level in Sb¹²². An apparent inconsistency in the previously proposed level scheme of Sb¹²² can be removed if the 3.5 min Sb¹²²-activity is assigned to an isomeric level in Sb¹²² lying less than 15 keV above the 136 keV isomeric state. A new measurement of the half-life of this level yielded a value of (4.1₅±0.2) min. Another new isomeric state with a (2.l±0.2) msec half-life was produced by irradiating thallium. The isomeric state decays by emission of two gamma rays of (335±8) keV and (597±12) keV which were found to be in coincidence. Irradiation of erbium led to the production of a short-lived isomeric transition which may be identical with a previously reported Ho-isomer. Results are discussed in the appendix.     

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 des125m Xe,des127m Xe und des127g Xe

The decay of^125m Xe produced by the reaction¹²²Te(α, n)^125m Xe using a target enriched in¹²²Te (95.4%) and the decay of^127m Xe produced by the reaction¹²⁷J(d, 2n)^127m Xe have been investigated: ^125m Xe decays with a half-life ofT _1/2=(56±3) sec by ayy- cascade withE _γ1=(140.4 ±0.5) keV andE _γ2=(110.5 ±0.5) keV. The experimental conversion coefficients yield multipolarities ofE3 for the 140.4 keV isomeric transition and predominantlyM1 for the 110.5 keV-transition. ^127m Xe decays with a half-life ofT _1/2=(71±2) sec. The decay also proceeds by aγγ-cascade with an isomeric E3 transition ofE _γ1=(172.5±0.3) keV and a predominantlyM1 transition ofE _γ2=(124.6±0.3) keV. In the decay of^127g Xe an additional branching of the electron capture to a level at (618.1±0.3) keV was observed. The relative probability forK-captureP _K618/P_K375=0.40 ±0.07 yields a total transition energyQ _EC=(664 ±4)keV. A spin of 1/2⁺ was assigned to the ground state.     

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.     

Measurements of someK-internal conversion coefficients near threshold

TheK-internal conversion coefficients have been measured by the XPG technique for a number of low energyγ-ray transitions whose energies do not exceed theK-binding energies by more than 4 keV. Using Si(Li) detectors in singles and coincidence arrangements, the following results were obtained: 63.1 keV El in¹⁶⁹Tm(α_K=1.02±0.15), 72.0 keV E1 in¹⁸⁷Re (0.75±0.05), 57.8 keV M1 in¹⁶²Ho (11.42±0.67), 56.6 keV M1 in¹⁶⁴Ho (12.04±0.70), and 67.1 keV M1 in¹⁷⁴Lu(10.25±0.58). The experimental results are compared with the theoretical calculations which include transition energies down to 1 keV above threshold.     

Conversion-electron-gamma and gamma-gamma directional angular correlations in 160Dy

Gamma-gamma and conversion-electron-gamma angular correlations in ¹⁶⁰Dy have been measured for the 298 keV–966 keV and 298 keV–879 keV cascades. Particle parameters of the 966 keV E2 transition were determined to be b₂(E2; e_K) = +1.23±0.08 and b₂(E2; e_{ΣL + ΣM) = +1.27±0.23}. The multipole mixing ratio for the 298 keV radiation was determined to be δ(M2/E1) = +0.04±0.01 and we have confirmed the value δ(E2/M1) = ?13±2 for the 879 keV. The E0–E2 mixture parameter for the 879 keV transition was determined as q_K = ?0.03±0.09 assuming penetration effects to be negligible.     

Anomalous conversion of 127 keV (E3) transition in134Cs

The total conversion coefficient of the 127.49 keV E3 isomeric transition in the decay of^134mCs was measured using the gamma intensity balance method with the help of a high resolution low energy photon detector. Theα _Tvalue was found to be 5.84±0.47 as against the theoretical value of 6.96, thus showing an anomaly of (16.1±6.7)%. TheK-conversion coefficient,α _kwas also measured using the X-ray peak to gamma ray intensity method and found to be 2.24±0.04 as against the theoretical value of 2.72, which shows an anomaly of (17.6±1.4)% consistent with the experimental anomaly inα _T. TheE3 hindrance factor of the isomeric transition was estimated to be (3.44±0.23) ·10⁴.     

TheK-conversion coefficient near threshold of the 30 keV isomeric transition in108mAg decay

With calibrated Ge(Li) x-ray detectorsK x rays in the conversion of the 30 keV isomeric transition in the decay of^108mAg were observed in coincidence with 79 keV γ-rays. Thus, the fraction of 30 keV transitions which take place byK conversion was measured to be (2.44±0.23) × 10^?2. Making use of a theoretical total conversion coefficient (K conversion contributes only a minor part of the total conversion coefficient), an experimental value of theK-conversion coefficient was obtained, α_K=(1.07 ± 0.10) × 10⁴ (where the error represents twice the standard deviation to which the error in the detector efficiency has been added linearly). This value agrees with the theory of Hager and Seltzer forM4 conversion. The energy of the cascading γ-ray was remeasured to be 79.20 ± 0.05 keV.     

In-beam γ-ray spectroscopy of the neutron deficient 100Ag

Conversion coefficients and conversion ratios of someγ-transitions in²⁰¹Tl and²⁰³Tl were measured by means of simultaneous spectroscopy ofγ-quanta and conversion electrons employing intensity calibrated semiconductor detectors. The experiments aimed at a precision as high as possible within the limits of the experimental methode used. Theγ-transitions were of the typeM 1(+E2). From the measured values the penetration parameters of the internal conversion for theM 1 components (λ) together with the multipol mixing ratios (δ²) were deduced. The necessary theoretical coefficients were taken from the tables of Hager and Seltzer. The results are for the ?-forbidden 331 keV transition in²⁰¹Tl,λ=+4.0±1.0,δ ²=1.78±0.16; for the ?-allowed 361 keV transition in²⁰¹Tl,λ=+0.5±0.5,δ ²=0.02±0.02; for the ?-forbidden 279 keV transition in²⁰³Tl,λ=+ 5.71±0.45,δ ²=1.55±0.08.     

The β-decay of 91Sr

Both the continuous β-mray spectrum and the internal conversion electron spectrum of ⁹¹Sr have been studied with a π√2 magnetic spectrometer. The measurements yield an intensity of 30.8% for the first-forbidden unique β-decay to the ground state and a Q-value of 2.684 ± 0.004 MeV. The measured internal conversion coefficient of the 555.6 keV isomeric transition in ⁹¹Y is in excellent agreement with the theoretical value for an M4 transition. Seven less intense internally converted transitions were also studied. The results verify the J^π assignments of earlier studies and also provide new information for the transitions from which level structure configurations can be proposed.     

Investigation of dual decay of70Ga (21 min)

The weakβ ^?-branchings in⁷⁰Ga decay leading to excited states in⁷⁰Ge at 1039 keV, and 1215 keV were measured byβ ^?-ray and γ-ray detection in 4π geometry to be 0.36 ±0.02%, and 0.32±0.01%, respectively. The weak electron capture decay of⁷⁰Ga was confirmed and its intensity measured to be 0.41±0.05%. The energy of the γ-rays was remeasured to be 176.17±0.02 keV, and 1039.20±0.08 keV.     

Die Konversion des86mRb

^86mRb was produced by irradiation of natural Rb and Rb enriched in⁸⁷Rb (99.2%) with fast neutrons. The half-life ofT _1/2=(61.2±1.0) sec and the energy ofE _ρ=(556.03±0.25) keV were remeasured. The experimental conversion coefficients α_tot=0.0184±0.0015 andα _K =0.0158±0.0015 yield the multipolarity of E4 for the isomeric transition. The spin of 6^? was assigned to the isomeric state. It is proposed that the spin 6^? is formed by coupling ap _3/2-proton and ag _9/2-neutron according to Nordheim's “weak” rule.     

Die isomeren Atomkerne: Yb169m,Yb175m,Yb177m

Short lived isomers of Yb were produced by neutron irradiation of enriched isotopes and have been investigated with the aid of scintillation spectrometers. Yb^169m decays with a half-life ofT _1/2=(46±2) sec emitting only L-radiation. This decay is assumed to be the same as the E 3-transition of 24 keV following the electron capture of Lu¹⁶⁹. Yb^175m [T _1/2=(0,072±0,005) sec] emitsγ-rays of (495±15) keV. The measured K-conversion coefficientα _{K 495}=0,24±0,04 and the total conversion coefficientα _{4 5}=0,6±0,3 indicate the transition to be M3. Yb^177m [T _1/2=(6,4±0,1) sec] decays by a cascade of twoγ-rays. The isomeric (228±3) keV-transition is followed by a (104±1,5) keV-radiation. The measured conversion coefficients areα _{K 228}=4,1±0,4 andα _{K 228}=6,5±0,5 for the first transition andα _{K 104}=0,39±0,05 andα ₁₀₄=0,51±0,05 for the second, indicating a M3-E1-cascade. For the M 3-transition the measured coefficients agree well with those calculated for a nucleus of finite size, but they differ by a factor of 1,5 for the E1-transition.     

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.     

High resolutionL- andM-subshell internal conversion studies of low energy transitions in149Sm and151Eu

The internal conversion subshell intensities of the (21.529±0.014) keV transition in¹⁵¹Eu and the (22.494±0.011) keV transition in¹⁴⁹Sm have been determined in a high resolution investigation using a double-focussing iron-core spectrometer. The subshell ratios yielded unambiguousM1+E2 multipole mixtures for both transitions. δ²(E2/M1) for the 21.53 keV transition was determined to be (8.8±0.7)·10^?4 and for the 22.49 keV transition to be (5.5±1.2)·10^?3.     

Nuclear structure effect in internal conversion of the isomeric transition in 191Os

Measurements have been performed on relative conversion line intensities of the hindered 74.38 keV isomeric transition in ¹⁹¹Os with the $\text{1}\text{2}\text{π√13}$ iron-free β-ray spectrometer. Anomalies were observed for the L, M and N subshell intensity ratios and were explained with a nuclear structure parameter λ = 9.4 ± 0.5 and a mixing ratio $\text{¦δ(}\text{E4/M3}\text{)¦ = (3.0 ± 0.3) × 10}{}^{\mathrm{?3}}$.     

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.     

Scheme of the β-decay of <Superscript>234</Superscript>Th

The scheme of the β-decay of ²³⁴Th is still not completely clear. Only the upper bound (10 keV) of the energy of the isomeric transition from level T_1/2 = 1.17 min of the ²³⁴Pa nucleus is known, and the correspondence between gamma quanta of several energies emitted in the β-decay of ²³⁴Th and specific nuclear levels of ²³⁴Pa has not been established. In this work, the isomeric transition energy of 2.6 ± 0.5 keV is determined via the γ-spectrometry of a ²³⁴Th source in γγ-coincidences, and a new ²³⁴Pa level populated in the β-decay of ²³⁴Th is introduced.