Der Zerfall des Rh102g,Rh102m und Tc102m

The decays of the 206 day-Rh^102g , 2.9 year-Rh^102m and 4.35 min-Tc¹⁰² m have been investigated using several sizes of Ge(Li)-counters. From the analysis of gamma spectra from several Rh¹⁰²-sources, measured over a period of 2.2 years, the gamma rays associated with each activity were identified. Energies and relative gamma intensities of 71 transitions have been determined. 22 transitions are assigned to the decay of 206 day-Rh^102g , 16 to 2.9 year-Rh¹⁰² and 33, twenty five unreported, to 4.35 min-Tc^102m . All except one transition are placed in a level scheme of Ru¹⁰².     

The mixing parameter for the mixing of gamma-vibrational and ground-state bands in160Dy

The energies and relative intensities of the gamma rays depopulating the first gamma-vibrational level in¹⁶⁰Dy were determined using Ge(Li) detectors. Special care was given to the determination of the intensities of the 682-, 765-, 872-, 962-, and 1069-keV gamma rays. From the measured intensities the reducedE2 transition probability ratios were calculated for the transitions between the gamma band and ground-state band. The deduced Z₂×10³ values are: 51.9±3.5, 38.7±3.6, 31.6±5.3, 34.5±5.9, and 42.0±7.2, with an average value of 39.7±3.5. The internal conversion coefficients of the 682- and 765-keV transitions are also shown to be consistent with the theoreticalE2 values.     

Level density and radiative strength functions from (n th,2γ) reactions and basic properties of the 96Mo nucleus

Published data on the intensities of two-step cascades to 12 final-state levels of the ⁹⁶Mo nucleus are approximated by using a set of possible random dependences of the level density and radiative strength functions for primary E1 and M1 transitions. The average values of these parameters of gamma decay for any excitation energies and for gamma transitions agree well with basic dependences revealed to date from similar experiments for 42 nuclei in the mass-number range 40 ≤ A ≤ 200, but they are inconsistent with the generally accepted ideas of the parameters of the cascade gamma decay of compound states of nuclei having high level densities.     

The decay of75Ga to levels in75Ge

The decay of⁷⁵Ga has been investigated with Ge(Li) spectrometers. Energy and intensity determinations for 37 gamma rays have been performed. A level scheme for⁷⁵Ge was deduced, where 31 gamma transitions could be placed. Beta branch intensities were estimated from the measured gamma intensities. Spin and parity assignments for most of the levels were made in agreement with reaction and neutron capture studies. Half life of⁷⁵Ga was measured to be (130±6) sec and that of the 139.3 keV isomeric state in⁷⁵Ge to be (47.7±0.5) sec.     

Search for weak transitions in the decay of125Sb and accurate gamma intensities

The weak transitions in the decay of¹²⁵Sb have been investigated through gamma ray measurements with high resolution X-ray and with large volume Ge(Li) detectors. The 172.6, 178.8 and 198.5 keV gamma rays are confirmed, while others previously reported were not. Accurate intensities were obtained for the stronger transitions. The weighted averages of these intensities which cover the range of 116 to 670 keV are useful for calibration of Ge(Li) systems.     

High spin states in147Tb

The level scheme of¹⁴⁷Tb has been extended to 116 levels and 198 transitions in two experiments with the OSIRIS Compton suppressed detector array at the HMI Berlin with the reactions¹²²Sn(³¹P, 6n)¹⁴⁷Tb at 160 MeV and¹²⁰Sn(³¹P, 4n)¹⁴⁷Tb at 152 MeV. Evidence for a new high spin isomer atE=7664.1 keV with a life-time of the order of 2 ns has been found.     

Basic parameters of the gamma-decay process and properties of the <Superscript>174</Superscript>Yb nucleus that manifest themselves in radiative resonance-and thermal-neutron capture

An independent analysis of available data on the intensities of primary gamma rays from the capture of ≈2-keV neutrons by a ¹⁷³Yb nucleus is performed. The distribution of the scatter of these intensities around the average value is approximated in various intervals of energies of primary gamma transitions. An extrapolation of the distributions obtained in this way to zero detection threshold for the intensity of a primary gamma transition makes it possible to estimate, independently of other experimental procedures, the expected number of levels of both parities for spins in the range J = 1–4 and the total possible sum of partial widths with respect to electric and magnetic dipole gamma transitions to levels whose excitation energies extend up to about 4 MeV. The results obtained in this way for the level density and the sum of radiative strength functions confirm the characteristic features of analogous data extracted from the intensities of two-step gamma-ray cascades initiated by radiative thermal-neutron capture by 40 ≤ A ≤ 200 nuclei and also make it possible to assess the sign and magnitude of their systematic uncertainty associated with a very strong dependence of radiative strength functions for cascade gamma transitions on the structure of the excited level, at least for excitation energies below half the neutron binding energy. A comparison with model concepts of the level density reveals that the ¹⁷⁴Yb nucleus is in a superfluid states for the bulk of excited levels, at least below 3.5 to 4 MeV.     

Levels in152Gd and152Sm populated by the decay of152Eu

The energy level schemes of¹⁵²Gd and¹⁵²Sm have been established on the basis of singlesγ-spectra, andγ- γ coincidence measurements. Ge(Li) detectors were used to study the gamma spectra produced in the EC/β⁺ and β^? decays of¹⁵²Eu to¹⁵²Sm and¹⁵²Gd, respectively. Thirteen new transitions are reported and data from eleven coincidence gates enabled five new levels to be suggested. Relative intensities and logf t values were calculated and spin/parities deduced. Comparisons are made with new predictions of the Interacting Boson Model.     

Study of the radioactive decay of192Ir

Theβ ^? and electron capture decays of¹⁹²Ir to the levels of¹⁹²Pt and¹⁹²Os respectively have been investigated to verify the existence of some of weak gamma transitions reported earlier. Gamma-gamma directional correlation measurements have been done for 13-cascades. Multipole admixture of 201, 283, 485 keV gamma transitions in¹⁹²Os and 296, 308, 416, 604 keV gamma transitions in¹⁹²Pt have been deduced. A spin value of 4⁺ has been reaffirmed on the basis of almost zero intensity of 1201 keV gamma ray (4⁺→0⁺) and 416→(468)→316 keV cascade directional correlation measurements.     

Internal conversion coefficients of the transitions in Tm169

The conversion electron spectrum of Tm¹⁶⁹ has been measured by an iron-yoke double focusing spectrometer. Gamma-ray energies and gamma-ray intensities were measured by a bent crystal spectrometer. Conversion coefficients and conversion ratios were determined from the electron and gamma intensities. The conversion process of the retardedM 1 transitions of 177 keV and 198 keV was found to be normal, in agreement with our earlier directional correlation results. No penetration effects were found in the conversion process of the retarded 63 keVE1 transition.     

A study of the radiation from Am241

The radiation from the alpha decay of Am²⁴¹ has been investigated by studying the fine structure of the alpha spectrum and by performing alpha-gamma and gamma-gamma coincidence measurements. For the daughter nucleus Np²³⁷ a level scheme is proposed which comprises 21 excited states and 39 gamma transitions. Evidence was found for the existence of previously unknown gamma rays at (80), 82, 88, (90), 100, 150 (two transitions), 170, (~210), 295, (300), 360, 420, 460 and 690 keV, as well as for the probable occurrence of a new fine structure alpha group at 4754 keV corresponding to a level at 804 keV. For the alpha groups and for most of the gamma rays absolute intensities are given. For some transitions theK-conversion coefficients and multipolarities were determined. The results are discussed within the framework of the unified model. The level density agrees well with the predictions of the superfluid model and is approximately twice the density yielded fromNilsson's theory.     

Levels and transitions in125Te

Gamma transitions and levels of¹²⁵Te following the decay of¹²⁵Sb have been studied using Ge(Li) detector and NaI(Tl)-NaI(Tl) sum-coincidence spectrometer incorporated with a fast-slow coincidence circuit. In all, twenty five gamma rays have been reported, out of which two weak gamma rays with energies 366·0 and 402·0 keV have been observed and confirmed for the first time. These gamma rays have been fitted by assigning a new level of 402 keV energy. An ambiguous transition of energy 122·1 keV has also been confirmed. No evidence was found for the existence of 145·9, 315·0, 489·8, and 497·4 keV transitions. The accurate intensities for various transitions have been determined.     

Studies of the low-lying levels in192Pt and192Os

The energy level schemes of¹⁹²Os and¹⁹²Pt have been established on the basis ofγ- γ coincidence studies using a dual parameter data collection system. Ge(Li) detectors were employed to study the gamma spectra produced in the E.C. andβ ^? decays of¹⁹²Ir to¹⁹²Os and¹⁹²Pt, respectively. Thirteen new transitions and three new levels at 1,146.95, 1,237.35 and 1,913.76 keV are suggested. Relative intensities from singles measurements, branching ratios,α(K) and log ft values were calculated and multipolarities, spins and parities deduced. Comparisons are made with predictions of the Interacting Boson Model calculated on the basis of an O(6) to SU(3) transition.     

Die (n, α)-Reaktion mit 15 MeV-Neutronen an den Kernen138Ba,140Ce und142Nd

Gamma transitions in the decay of Nd¹⁴⁷ have been studied using a Ge(Li) spectrometer. The results of determinations of gamma energies and intensities are presented and compared to other recently-reported data.     

OnE0 transitions in the decay of152Eu m (9.3 h)

The conversion electron spectrum of the decay of¹⁵²Eu ^m (9.3 h) has been specially investigated forE0 transitions with the aid of a magnetic spectrometer and coincidence techniques. Besides the knownE0 transitions of 685 keV in¹⁵²Sm and 615 keV in¹⁵²Gd two further pureE0 transitions of 432 keV and 1048 keV have been observed. It is shown that theseE0 transitions are identical with those observed previously in the decay of¹⁵²Tb. NoE0 transitions could be found from a 0⁺ state of 1083 keV in¹⁵²Sm. The measured intensities together with the gamma spectrum measured by Barretteet al. give a consistent decay scheme of¹⁵²Eu ^m . Furthermore the half-life of the 0⁺ level at 615 keV in¹⁵²Gd was measured using the method of “delayed coincidences”. The result was (0.2≦t _1/2≦2.1)×10^?10 s. From this theE0 transition probability for the level was derived as (0.3≦W _K (E0)≦3.7)× 10⁹ s^?1 and theρ-value as 0.10≦¦ρ¦≦0.36. The results are discussed within the framework of the collective model.     

Low energy nuclear states in124Te

The energy level scheme of¹²⁴Te has been established on the basis of singlesγ-spectra, andγ-γ coincidence measurements carried out using a dual parameter data collection system. Ge(Li) detectors were used to study the gamma spectra produced in theβ ^? decay of¹²⁴Sb. Eleven new transitions and two new energy levels are proposed. Relative intensities, branching ratios,α(K) and logft values were calculated and multipolarities, spins and parities deduced. Comparisons are made with predictions of the Interacting Boson Model: in a first order perturbation approximation to theSU (5) limit, using the complete IBA-1 Hamiltonian, and in theO(6) limit.     

Radioactive decay of 1.7-h149Nd to levels of transitional149Pm

Sources of¹⁴⁹Nd were produced by thermal-neutron irradiation of enriched¹⁴⁸Nd. High resolution Ge(Li) spectrometers were used to collect gamma-ray singles and coincidence spectra in the study of the decay of 1.7-h¹⁴⁹Nd. A total of 214 gamma rays have been assigned to the decay of¹⁴⁹Nd, and 201 of these transitions have been placed in a level scheme of¹⁴⁹Pm involving 42 excited states. Absolute values for the beta-group intensities were determined for transitions to the¹⁴⁹Pm levels, and spin and parity assignments were made for many of the observed states. The experimentally determined level structure of¹⁴⁹Pm was compared with corresponding levels in other odd-mass Pm and Eu nuclides. Interpretations were made in terms of the core-coupling model. Radioactive decay¹⁴⁸Nd(n, γ)¹⁴⁹Nd; measuredE _γ,I _γ,γ-γ coinc.¹⁴⁹Pm deduced levels,J,π. Compton-suppression. Ge(Li) detector. Enriched targets.     

New isotope227Rn and revised halflives for223Rn and226Rn

Neutron-rich isotopes of radon, produced by spallation reactions in a ThC² target and selected chemically, were mass-separated and used as samples for radiation counting experiments. Assignments of the activities to radon isotopes were confirmed by genetic relationships to the previously known francium daughters. The halflife for the new isotope²²⁷Rn is 23±1 s and that for²²⁶Rn is 7.4±0.1 min. X-rays,γ-rays, and conversion electrons from the²²³Rn activity were measured. The decay patterns ofK X-rays and known gamma transitions in the²²³Fr daughter yield a halflife of 23.2± 0.4 min for²²³Rn, in contrast to the value of 43± 5 min reported earlier. Energies, intensities, and likely multipolarities for the most prominent gamma transitions in the²²³Rn→²²³Fr decay are presented.     

A γγ coincidence study of transitions in239Np and239Pu from decay of243Am

Gamma-gamma coincidences and singles measurements with Ge detectors have been made on transitions in²³⁹Np and²³⁹Pu. Eighteen transitions in²³⁹Pu and three in²³⁹Np have been verified by coincidence data. High resolution singles measurements were made and new values for the energy and intensities ofγ-rays below 350 keV were obtained.     

Gamma-gamma directional correlations and coincidence studies in154Gd

The intensities, placements andE2/M1 mixing ratios of transitions in the decay of¹⁵⁴Eu have been carefully studied to provide accurate data for microscopic calculations. Coincidence relationships in the decay of¹⁵⁴Eu have been studied extensively with a multiparameterγ-γ coincidence system with two large volume Ge(Li) detectors. Spectra in coincidence with twenty energy gates were analyzed. Twenty-nine new coincidence relationships were established and confirmed most, but not all, of several levels previously assigned by energy fits only. From an analysis of coincidence spectra and singles spectra with a 18% efficiency Ge(Li) detector new information on the gamma-ray intensities were obtained. Precise values of theE2/M1 mixing ratios of transitions from the gamma- and beta-vibrational bands to the g.s. band have been determined fromγ-γ directional correlation measurements with a NaI(Tl)-Ge(Li) detector coincidence system. Mixing ratios were obtained for a number of other transitions including those fromK ^π =0^? and 2⁺ bands from direct and skipped cascade correlations.