Nuclear structure of194Pt

The decay of¹⁹⁴Ir has been thoroughly studied resulting in the construction of a decay scheme consisting of 26 excited states and 69 transitions. Nine new levels and 29 new transitions were added to the previously known scheme. Of these, levels at 1,893.6 and 2,053.0 keV as well as 9γ-ray transitions are new to the¹⁹⁴Pt level scheme. Preciseγ-ray energy and intensity measurements as well as quantitative coincidence measurements were performed, and the internal conversion spectrum was investigated with a Si(Li) detector. Directional correlation measurements were performed for selected cascades with the major result being the unique assignment of 0⁺ to the new level at 1,893.6 keV. The structure was interpreted within the framework of the PPQ model as well as the effective-core picture including nuclear triaxiality.     

Non-yrast level structure of121Xe via beta decay of121m+g Cs

The results of measurements of the gamma-ray and conversion-electron singles and coincidence spectra from the decay of the 122 s^121m Cs and the 155 s^121g Cs to levels of¹²¹Xe are reported. TheM 3 multipolarity of the 68.5 keV isomeric transition in¹²¹Cs has been deduced. Numerous low-lying levels below 1.6 MeV excitation energy are found. A negative-parity level at 355.9 keV is observed for the first time. The results supplement the low lying energy level systematics in odd-A xenons. A comparison is made with theN=67 barium isotone.     

The decay of62Zn

Energies and relative intensities of 31γ-transitions from the decay of⁶²Zn have been measured using an anti-Compton spectrometer. Gamma-gamma coincidence measurements were performed. Besides the levels of⁶²Cu for which the population in the decay of⁶²Zn was known, also levels at 644.82, 698.32, 1221.5 and 1525.9 keV in⁶²Cu are found to be populated. The previously proposedβ-feeding of⁶²Cu levels at 1142.5 and 1280.8 keV is ruled out.     

214Po: A γ-γ and γγ(θ) Coincidence study

Extensive γ-γ coincidence measurements have been made on γ rays accompanying theβ ^? decay of²¹⁴Bi using a conventional GeGe coincidence spectrometer. A total of 33 new γ transitions among levels of²¹⁴Po have been established. Twenty-three previously reported but unplaced transitions have now been assigned in the level scheme. In addition to confirming 56 previously proposed levels, four new levels are established at 1015.05, 1712.98, 3003.5 and 3160.5 keV. Directional correlation measurements have been made on six weak cascades which have the first excited state in common. Mixing ratios have been deduced for the transitions concerned.     

Note on the decay of200Au

Gamma and beta rays from the decay of²⁰⁰Au (48.4 min) were studied employing Ge(Li) and plastic detectors in various singles and coincidence arrangements. The intensity of the β-branch to the ground state of²⁰⁰Hg was determined as 79%, and the disintegration energy of²⁰⁰Au to be asQ _β=2.26 ± 0.06 MeV. A tentative spin and parity assignment of (1,2)⁺ is proposed for levels at 1515.2 and 1972.5 keV in 200_Hg     

Experimental study of the decay of53V

The decay of⁵³V was investigated with a Ge(Li) spectrometer and gamma-gamma coincidence methods. Accurate energy, intensity and half-life determinations of 7 gamma-rays have been performed. These gamma-rays fit in a level scheme with levels at 563.6, 1006.0, 1289.1 and 1536 keV.     

Chemical states of57Fe-atoms after ec-decay of57Co-labelled Co(BrO3)2·6H2O studied by coincidence Mössbauer spectroscopy

Two kinds of time differential Mössbauer spectra of⁵⁷Co-labelled Co(BrO₃)₂·6H₂O were measured at room temperature by delayed coincidence technique, i.e., one was the delayed coincidence between 122 keV γ ray and 14.4 keV γ ray (γ, γ-ray coincidence), and another was the coincidence between 6.3 keV KX ray and 14.4 keV γ ray (X, γ-ray coincidence). The time dependence of chemical states of⁵⁷Fe-species were observed on γ, γ-ray and X, γ-ray coincidence Mössbauer spectra. The relative area intensities of⁵⁷Fe(II) observed on the X, γ-ray coincidence spectra were larger than those on the γ, γ-ray coincidence spectra on every time windows.     

Half lives of the 482.2 keV and 615.3 keV levels in181Ta

The half lives of the excited levels at 482.2 keV and 615.3 keV in¹⁸¹Ta have been measured by the delayed coincidence technique. In the nanosecond time range (482.2 keV level) the most serious sources of errors are jitter, walk and drift phenomena. To minimize those the time pick-off has been defined carefully by means of modern fast timing detectors and electronics. In the microsecond time range (615.3 keV level) the ratio of true delayed coincidences to chance coincidences influences considerably the final accuracy of the half-life measurements. It has been reduced as much as possible. From a series of independent measurements half lives ofT _1/2=(10.67±0.05) ns andT _1/2=(17.64±0.14) μs have been deduced for the 482.2 keV and 615.3 keV levels, respectively. The results have been compared with other values published before.     

Low lying energy levels of56Fe from γ-γ coincidences

The level scheme of⁵⁶Fe was built up from γ-γ coincidence measurements using Ge(Li) detectors and a Dual Parameter data collection system. The previously suggested γ-transitions [8] of 263.3, 410.9, 485.2, 674.7 and 1,462.3 keV were confirmed and evidence found for a new 655.0 keV γ-transition between the levels at 4,100.32 and 3,445.32 keV. No evidence was found for the transition of 2,657.4 keV and the previously proposed β⁺-feeding of the level at 3,600.3 keV is ruled out, while the existence of a level at 4,447.5 keV is suggested. The relative intensities and branching ratios of 44 transitions were determined. A calculation of experimentalK-shell internal conversion coefficients α(K) showed large discrepancies from previous studies for the 3,009.6 and 3,451.2 keV transitions, the latter being assigned a different multipolarity. Logft values were calculated and spins and parities of the levels deduced. In particular the assignment of 3⁺ is verified for the level at 4,297.97 keV.     

Verzweigungsverhältnisse und Konversionskoeffizienten von angeregten Zuständen des208Tl

The branching ratios of theγ rays of the second and fourth excited states of²⁰⁸Tl have been investigated by coincidence measurements between the α rays of²¹²Bi and subsequent 40keVγ ray. The detectors employed were a silicon surface barrier counter for α particles, and a 1.5 in ×2 mm NaJ (Tl) crystal forγ rays. It has been found that (75.6±3.7)% of all transitions of the 328 keV state and (94±7)% of all transitions of the (492 keV+473 keV) states populate the first excited state of²⁰⁸Tl. The 40 keV state is excited to (3.4±0.3)% by transitions of higher excited states relative to the direct excitation by α particles. The number of α particles with energyE _α = 6.047 MeV and the number of subsequent 40keVγ rays resulted in a conversion coefficient α(40keV)=22.55± 0.46. Similarly coincidence measurements between Tl-x rays and α particles have been used to determine theK- conversion coefficients α_K(328 keV)=0.31±0.03 and α_K(492 keV+ 473keV)=0.100±0.015. The experimental results are in good agreement with the theoretical values ofSliv.     

Excited states in195Pt from the decay of 2.3h195Irg, 3.7h195Ir m and 183d195Au

The decay of two previously reported isomers in¹⁹⁵Ir has been investigated with Ge(Li) and Si(Li) detectors by observing β and γ rays as well as conversion electrons in single and coincidence measurements. To about 30 of the 85 observed transitions a multipolarity was assigned. The energies of the gamma rays from¹⁹⁵Au were also determined accurately. The decay scheme of¹⁹⁵Ir shows 13 new levels in¹⁹⁵Pt between 389 and 931 keV. Probable spin and parity assignments could be made to most levels. The results are compared with those of a recent Coulomb excitation study, reaction work and theoretical calculations.     

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.     

Studies on the energy levels of153Eu following the β−-decay of153Sm

The level scheme of¹⁵³Eu was investigated by observing the gamma-rays following theβ ^?-decay of the 47 h¹⁵³Sm using a high purity Ge(HPGe) detector and a Ge(Li)-Nal(Tl) fast-slow coincidence spectrometer. The energies and relative intensities of about fifty six gamma-ray transitions were determined. Five of them at energies of 124.91, 431.65, 443.24, 487.75 and 623.73 keV were observed and confirmed for the first time in the present singles and/or gamma-gamma coincidence measurements. These new transitions could be fitted into a proposed level scheme of¹⁵³Eu. Theβ ^?-decay branching ratios as well as the log (ft) values were obtained.     

Der Zerfall des163Tb

The beta and gamma radiations of¹⁶³Tb have been investigated employing scintillation and semiconductor spectrometers and coincidence techniques. The sources were produced by the¹⁶³Dy(n,p)¹⁶³Tb reaction. A half-life of 19.5 min has been measured without evidence for an isomeric state in the half-life range of 2 sec to 7 d; especially a 6.5 h activity previously assigned to¹⁶³Tb could not be confirmed. 76 of the total of 82 gamma-ray transitions, representing 99.6% of the gamma-ray intensity, could be assigned to 23 levels in¹⁶³Dy. From beta and beta-gamma coincidence measurements aQβ-value of 1.7 ± 0.1 MeV has been determined. Spin and parity of 3/2⁺ are deduced for the ground state of¹⁶³Tb with the Nilsson configuration [411↑]. The level at 884 keV is interpreted as aJ ^π=1/2⁺ state with a high contribution of the three-quasiparticle configurationp[411↑]-p[523↑]-n[523↓] because of an allowed unhindered beta-ray transition to this level.     

Band mixing in156Gd and158Gd

A detailed investigation of the energies and intensities of the γ-rays that depopulate the low spin levels of the β- and γ-vibrational bands of¹⁵⁶Gd and the γ-vibrational band of¹⁵⁸Gd has been conducted. Both singles and γ-γ coincidence measurements were made on sources of 15-d¹⁵⁶Eu and 46-min¹⁵⁸Eu by use of large volume, high resolution Ge(Li) detectors. In addition to the γ-band at 1154.09 keV, twoK ^π=0⁺ bands were observed in¹⁵⁶Gd with band heads at 1049.45 and 1168.11 keV, respectively. The 2⁺ and 3⁺ members of the γ-vibrational band in¹⁵⁸Gd were observed at 1187.12 and 1265.43 keV, respectively, as well as a newK ^π=0⁺ band at 1195.98 keV. A first order perturbational treatment of the branching ratios was applied to both nuclei. In addition, the mixing between the ground state, the β-, and the γ-vibrational bands of¹⁵⁶Gd is considered from two approaches, but neither satisfactorily explains all the experimentalB(E2) ratios.     

γγ-Winkelkorrelationsmessungen an155Gd

Two Ge(Li) detectors were used to investigateγ transitions in¹⁵⁵Gd produced by the decay of¹⁵⁵Eu. Relative intensities were determined for the weak lines at 18.8, 26.5, 58.0, and 86.0 keV. Angular correlations for fourγ cascades were measured. As results, the mixing ratios of the 45.3 and 86.5 keVγ lines were determined, and it was shown that the sign of the mixing ratio is positive for theγ line at 18.8 keV and negative for the line at 60.0 keV. Spins 5/2 and 3/2 for the 86.5 and 105.3 keV levels, respectively, are consistent with the data, and spin 5/2 for the 105.3 keV level is inconsistent with it.     

Der Zerfall des122Xe (T 1/2=20,l h) und des122J (T 1/2=3,6min)

Theγ spectra emitted in the decay of¹²²Xe and¹²²I have been investigated using Ge(Li) detectors and a Ge(Li)-NaI coincidence apparatus. 14γ transitions with energies between 61.8 and 416.9 keV have been identified in the decay of¹²²Xe, 44 transitions between 564.0 and 3,291.0 keV in the decay of¹²²I. Level schemes having 7 excited levels for¹²²I and 21 excited levels for¹²²Te are proposed.     

Electron capture ratios in206Bi

The level scheme of⁹⁷Tc has been investigated by observing theγ-rays following the decay of 2.9-d⁹⁷Ru.γ-singles andγγ-coincidence measurements were carried out with Ge(Li)-detectors. The time difference of coincident γ-rays was measured as a third parameter. From the coincidence events, the intensities ofγγ-cascades were extracted. The⁹⁷Ru decay gives rise to 18γ-lines which could be fitted into a level scheme of⁹⁷Tc consisting of 9 levels. Spin and parity assignments of the levels were made from log(ft) values andγ-ray branching ratios. Discrepancies concerning the energy of the first 3/2^? state and the existence of a 946 keV level are discussed.     

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.     

Decay of78Br

The decay of⁷⁸Br was investigated with a Ge(Li) spectrometer and Ge(Li)-NaI(Tl) coincidence methods. Accurate energy and intensity determinations of 14 gamma rays have been performed. A level scheme with levels at 614.0, 1,308.1, 1,498.4, 1,758.5, 1,993.7, 2,334.4, 2,538, 3,090 and 3,253 keV is deduced. Spin and parity indications for most of the observed levels are given from electron capture and positon decay considerations and gamma branches.