W. Weirauch

Isomerenverhältnisse für die Reaktionen107Ag(α,2n)109g,mIn und109Ag(α,2n)111g,mIn

Isomeric cross-section ratios have been measured for the reactions107Ag(α,2n)109g,mIn and109Ag(α, 2n)111g,mIn for energies of theα-particles between 19 and 40 MeV. The experimental isomeric cross-section ratios are compared with statistical-model calculations. The program ofHafner et al. was extended by including the competition of the (α,n)- and (α, 3n)-reactions and of charged particle emission. Agreement between experiment and theory could be achieved.

Der Zerfall des125mXe, des127mXe und des127gXe

AbstractThe decay of125mXe produced by the reaction122Te(α, n)125mXe using a target enriched in122Te (95.4%) and the decay of127mXe produced by the reaction127J(d, 2n)127mXe have been investigated: 125mXe decays with a half-life ofT1/2=(56±3) sec by ayy- cascade withEγ1=(140.4 ±0.5) keV andEγ2=(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. 127mXe decays with a half-life ofT1/2=(71±2) sec. The decay also proceeds by aγγ-cascade with an isomeric E3 transition ofEγ1=(172.5±0.3) keV and a predominantlyM1 transition ofEγ2=(124.6±0.3) keV.In the decay of127gXe an additional branching of the electron capture to a level at (618.1±0.3) keV was observed. The relative probability forK-capturePK618/PK375=0.40 ±0.07 yields a total transition energyQEC=(664 ±4)keV. A spin of 1/2+ was assigned to the ground state.

Der Zerfall des In109m (0,21 sec)

In109m(0,21±0,01 sec) was produced from natural Ag and enriched Ag107 byα irradiation and investigated using scintillation spectrometers and coincidence techniques. The mass assignment follows from the excitation function for the (α, 2n) reaction on Ag107. The following results were obtained: energy of the isomeric level (2,11±0,02) MeV, determined directly by summing up the cascade transitions in a well-type scintillator; four gamma transitions with energies (0,680±0,015) MeV, (0,405±0,015) MeV, (1,035±0,030) MeV and (1,435±0,020) MeV, respectively. The proposed decay scheme contains the isomeric level (19/2+) at 2,11 MeV and a further level (13/2+) at 1,435 MeV which decays either by the 1,435 MeV transition (80±3)% or by a 0,405–1,035 MeV cascade (20±3)% via an (11/2+) level at 1,035 MeV to the 9/2+-ground state of In109.

Messung der K-Konversionskoeffizienten der isomeren Atomkerne Pd107m und Pd109m

TheK-conversion coefficients αK of the isomers Pd107m and Pd109m have been measured by detecting theKX-rays and gamma-rays from neutron-irradiated Pd-samples with the aid of a NaJ(Tl)-scintillation spectrometer. The results are αK=0,41±0,02 and αK=0,52±0,04, respectively. These values have been compared with those taken from the tables of Rose, confirming the assumption of E3-transitions which was proposed earlier by other authors. In addition, the assignment of the 21 sec-activity to Pd107m has been confirmed.

Suche nach dem Isomer74mAs

An activity with the decay propertiesT1/2=(8.0±0.3)sec andEγ=(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 isomer74mAs. In the present experiment a search for74mAs 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 of74mAs resemble the known properties of197mAu.

Zur Isomerie des Au197

Tl197m was produced by the (α, 4n) reaction on Au197 using 49 MeVα particles. The following results were obtained: Half-lifeT1/2=(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 transitionαK222=0.41±0.05 andαtot222=2.1±0.2, indicating anE3 multipolarity; energy of the second transition (385±3)keV; conversion coefficientsαK385=0.09±0.03 andαtot385<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.

Suche nach dem Einfluß der chemischen Bindung auf die Halbwertszeit des90mNb (T1/2=19,2 sec)

Abstract90mNb was produced by the reaction90Zr(d, 2n). Comparison of its half-lives in two different chemical environments (Nb atoms in metallic Zr and in the niobium-fluoride complex) showed no difference greater than the experimental error of 1%, whileCooper et al. have reported that the half-life of90mNb nuclei is shorter by 3.6% in metallic Nb than in the niobium-fluoride complex. — In addition, the absolute value of the half-life of90mNb in metallic Zr was determined to beT1/2=(19.2±0.3) sec.

Wirkungsquerschnitte und Isomerenverhältnis für die Reaktionen89Y(α, 3n)90gNb und89Y(α, 3n)90mNb

Absolute cross-sections and isomeric cross-section ratios have been measured for the reactions89Y(α, 3n)90g, 90mNb. The energy of the α-particles was varied between 34 and 54 MeV. The experimental isomeric ratios are compared with statistical-model calculations.

Search for nuclear structure effects in the k-conversion coefficient of the 385 keV transition in 197Tl

The gamma-gamma directional correlation of the 92−(E3)32+(M1+E2)12+ cascade in the decay of 197mTl (0.55 sec) was measured yielding an anisotropy A = 0.31±0.05 and an angular correlation coefficient A22 = 0.19±0.03. In addition, the K-conversion coefficient of the 385 keV transition was redetermined from coincidence experiments. The value obtained is αK385 = 0.103±0.010. The experiments were performed in order to search for nuclear structure effects in the internal conversion of the strongly retarded 385 keV M1 transition. The experimental data are consistent with λ = 3.4±3.5 where, λ is defined as the ratio of the penetration matrix element to the normal γ-ray matrix element.

Der Zerfall des 125 m Xe, des 127 m Xe und des 127 g Xe

AbstractThe decay of125mXe produced by the reaction122Te(α, n)125mXe using a target enriched in122Te (95.4%) and the decay of127mXe produced by the reaction127J(d, 2n)127mXe have been investigated: 125mXe decays with a half-life ofT1/2=(56±3) sec by ayy- cascade withEγ1=(140.4 ±0.5) keV andEγ2=(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. 127mXe decays with a half-life ofT1/2=(71±2) sec. The decay also proceeds by aγγ-cascade with an isomeric E3 transition ofEγ1=(172.5±0.3) keV and a predominantlyM1 transition ofEγ2=(124.6±0.3) keV.In the decay of127gXe an additional branching of the electron capture to a level at (618.1±0.3) keV was observed. The relative probability forK-capturePK618/PK375=0.40 ±0.07 yields a total transition energyQEC=(664 ±4)keV. A spin of 1/2+ was assigned to the ground state.