H. Graber

Der Zerfall von 162Tb und 163Tb

Abstract The decay of 162 Tb and 163 Tb has been investigated with a Ge(Li) detector and a two-dimensional scintillation coincidence spectrometer. The half-lives of these isotopes are 8.0±0.5 min and 19.5±0.5 min, respectively. The activities were produced by (γ, p) reactions using the bremsstrahlung of a betatron. A decay scheme of 162 Tb is proposed which contains a 2 − level in 162 Dy at 1148 keV interpreted as a two-quasi-particle state K , K +11 of the proton system with the quantum numbers [411↑+523↑]. The ground state of 162 Tb has the spin and parity J π = 1 − . In the decay of 163 Tb about 30 gamma lines were observed. A proposal for the decay scheme is given and the characteristics of the levels in 163 Dy are discussed in the framework of the unified model.

Zum Elektroneneinfang-Zerfall des Hf175

By measurements of the KX-γ-coincidence spectra of Hf175 the K electron capture probability of the transition to the 433 keV level in Lu175 was found to be PK = 0.68±0.04. From this one obtains a decay energy Q433 = 157±2030 keV for the transition to this level. The log ft values of the electron capture transitions determined with the total decay energy Q = 590keV are in good agreement with data of corresponding transitions in neighbouring nuclei. In the γγ-coincidence spectra the 319 keV γ-transition was observed, the intensity relative to the 343 keV transition being I319I343 = 2.0 · 10−3.

Der elektroneneinfang-zerfall des 140 d Lu174i

Abstract In the decay of Lu sources produced by the reactions Yb(d, 2n) and Lu(n, 2n) we found two new cascades 995-280-175-76.5 keV and 630-365-280-175-76.5 keV. The intensity ratio of the cascades 995-280 keV and 630-365 keV is I995−280/I630−365=41±5. The measurement of the half life time permits the attribution of the transitions to the electron capture decay of the isomeric state of Lu 174 (T 1 2 = 140 d ) . A level scheme is proposed which contains a level at 1526 keV with Iπ = 7− interpreted as a two quasiparticle state K, K+2 of the neutron system with the characteristic [624↑+512↑]. Coming from this state the 995 keV and 630 keV transitions populate a 532 keV level (6+) and a 897 keV level (8+), belonging to the ground state rotational band.

Neue niveaus im Dy161

Abstract The beta and gamma spectra and the γγ- and βγ-coincidence spectra in the decay of Tb161 (7.2 d) have been measured, and new gamma transitions with energies of 290±5, 340±10, 410 ±7, 470±7 and 545±7 keV have been found. Their intensities pr decay are 0.1, 0.02, 0.01, 0.02 and 0.04 per cent, respectively. The gamma lines fall off with a half life time of 7.3±0.6 d. A beta transition in coincidence with the 290 keV gamma line is reported the maximum energy being 220±10 keV. A proposal for the decay scheme contains in addition to the known levels with the characteristics 25.62 keV ( 5 + 2 ), 43.77 keV ( 7 + 2 ), 74.50 keV ( 3 − 2 ), 102.98 keV ( 7 − 2 ), and 131.65 keV ( 5 − 2 ) , three new levels at energies of 365, 415 and 545 keV, which are interpreted as one particle 1163 0854 V 3 excitations of the 95th neutron 1 2 , 1− 2 [521]; 3 2 , 1− 2 [521]; and 3 2 , 3+ 2 [651] .

Energieniveaus und rotations-teilchen-kopplung IM 155Eu

Abstract The γ-spectrum from the decay of 155 Sm has been measured by means of a Ge(Li) detector. The present data confirm the decay scheme of 155 Sm, which we proposed earlier as a result of scintillation measurements. In addition several new γ-transitions were found and a level at 1226 keV was introduced in the level scheme 155 Eu. An analysis with the improved energy and intensity data shows that in 155 Eu just as in 153 Eu a rotation-particle-coupling of the bands 3 2 + [411] and 5 2 + [413] is present. The matrix element A K for this coupling has an experimental value of about 15 keV. The anomalous rotational constants ħ 2 /2 I of 9.0 and 7.74 keV for the 5 2 − [532] band in 155 Eu and 153 Eu point to the coupling with the 7 2 − [523] band.

Neue niveaus im Eu155

Abstract The beta and gamma ray spectra and the γγ- and βγ-coincidence spectra in the decay of Sm155 (22 min) have been measured, and new gamma transitions with energies 30, 65, 70, 75, 135, 175, 205, 310, 630, 700, 770, 850, 1030 and 1200 keV were found. Beta transitions in coincidence with gamma rays between 450 and 650 keV, 900 and 1050 keV and 1100 and 1300 keV were observed the maximum energy being 850±50 keV, 550±30 keV, and 300±20 keV. A proposal for the decay scheme is given containing in addition to the known levels with the characteristics 105 keV ( 5 2 − ) and 245 keV ( 3 2 + ) new levels at energies of 75, 175, 310, 765, 875, 1095 and 1275 keV. Three of these may be interpreted as one particle states of the 63rd proton with characteristics 1 2 , 1 2 + [411], 3 2 , 3 2 − [541] and 3 2 , 3 2 + [422], the remaining probably being rotational states.

Niveaus im 157Tb

Abstract The decay of 157Dy has been investigated with a magnetic Siegbahn-Slatis spectrometer, Ge(Li)-detector and a two-dimensional scintillation coincidence spectrometer. In addition to the known transitions in 157Tb, new γ-transitions with energies of 296, 404, 498, 897, 932, 992, 1043 and 1104 keV are observed. From the relative K-electron and γ-ray intensities the K-conversion coefficients are deduced and the possible multipolarities of the transitions are given. The 992 keV transition has a value αK = (3.9±1.5) · 10−2, from which one obtained a mixing ratio 95% E2+5% E0. Based on the present observations, levels at 992, 1043, 1095 and 1104 keV were introduced in the level scheme of 157Tb. The 992 keV level may be interpreted as the β-vibrational level based of the ground state 3 2 + [411] of 157Tb. The possible character of the other levels is discussed.

Gamma-Übergänge und energieniveaus im 161Dy

Abstract The γ-spectrum from the decay of 161Tb has been measured with a Ge(Li)-detector. Ten γ-transitions with energies between 237 and 551 keV were found. The results confirm the existence of three levels in 161Dy at 368, 419 and 551 keV. Furthermore a new level at 452 keV is proposed. It is suggested that the levels 368, 419 and 452 keV are members of a rotational band based on the one-particle state 1 2 − [521] .

Zum Zerfall des 169Ho

Abstract The γ-spectrum from the decay of 169Ho has been measured using a Ge(Li) detector and a two-dimensional scintillation coincidence device. The sources were produced by the irradiation of Er2O3 (97% 170Er) with the bremsstrahlung of a betatron. Levels in 169Er with the following energies were found: 65, 75 and 222 keV (ground state rotational band 1 2 -[521]), 850 and 920 keV ( 5 2 -[523] band).

Der Zerfall des 163Er

Abstract The γ-spectra from the decay of 163Er produced by the reactions 164Er(γ, n) and 162Ern(n, γ) were investigated with a Ge(Li) detector and a γγ-scintillation-coincidence spectrometer. As a result of these measurements the level scheme of 163Ho is given containing levels up to 1110 keV. The characteristics of the levels are discussed on the basis of the unified model.