In-beamγ-ray spectroscopy of102In

Neutron deficient nuclei close to ¹⁰⁰Snhave been investigated in-beam by γ-ray spectroscopic methods using the NORDBALL detector array. A beam of 270 MeV ⁵⁸Niwas used to bombard a target of ⁵⁴Fe.Reaction channel separation was achieved with a 4π charged particle multidetector setup together with a 1π neutron detector wall placed in the forward direction. Excited states of ¹⁰²Inwere identified for the first time. The level scheme constructed from γ-γ-particle-coincidence and γ-γ-angular correlation analysis is presented. The structure of ¹⁰² In is discussed and compared to neighboring nuclei in the framework of the nuclear shell-model.     

Messung des Elektroneneinfang am Kern Ga70

The electron capture of Ga⁷⁰ has been observed using a x-ray semiconductor Ge(Li) detector. Measuring the ZnK x-rays and the 0.1755 MeV gamma-rays from the beta decay of Ga⁷⁰ the transition probability to the ground state ofZn⁷⁰ was found to be 0.24%. The log(ft) value is 4.8. The half-life of Ga⁷⁰ has been found to be (21.15±0.06) min and the energies of the gamma-rays are (0.1755±0.0005) MeV and (1.040±0.003) MeV.     

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.     

Alpha decay of the new isotope172Au

The first observation of the extremely neutrondeficient nucleus¹⁷²Au is reported, produced using the fusion evaporation reaction⁷⁰Ge+¹⁰⁶Cd→¹⁷⁶Hg^* (E_x?64 MeV). Mass separated evaporation residues were implanted into a double-sided silicon strip detector, and the energy and time of subsequent decay events were recorded. The alpha decay of¹⁷²Au was measured with an energy =6860±10 KeV, corresponding to =7020±10 Kev, and a half-life of 4±1 ms. No evidence was seen for a proton decay branch, implying a limit ofb _p ≤ 2 %.     

Differentielle Wirkungsquerschnitte für die elastische Streuung niederenergetischer Elektronen an Kalium

The 2.41 min ground state decay of¹⁰⁸Ag has been studied with a Ge(Li) detector. Twelve transitions are observed of which seven have not been reported previously. Five of the new transitions are placed in the level scheme which includes the second 2⁺, 930.4 keV level and a new level at 1539.4 keV in¹⁰⁸Pd.     

The decay of143Sm to levels in143Pm

The beta decay of¹⁴³Sm was reinvestigated with the aid of a Ge(Li) detector. Levels of¹⁴³Pm at 271.8, 1,056.5, 1,173.4, 1,342.1, 1,403.2, 1,514.9, 1,752.8, 1,816.3, 1,853.6, (2,000), 2,009.0, 2,080.5, 2,344, 2,443, 2,463, 2,906 and (3,054) keV were established. Logft values for all observed beta transitions have been calculated. Spin and parity assignments have been made from electron capture and positon disintegration considerations and gamma branches. The experimental level scheme of¹⁴³Pm is compared with the results of 1 and 3 q.p. calculations forN=82 nuclei.     

β + ratio andβ-delayedγ-decay of146Eu

The positron decay of¹⁴⁶Eu was investigated, firstly to derive for the allowed transition to the 2046 keV state in¹⁴⁶Sm the electron capture to positron decay ratio. The experimental valueEC/β ⁺=43.7(42) is found to be in agreement within the respective error intervals with the ones calculated from the formalism of allowed decay using the recentQ-values of¹⁴⁶Eu. Further on, theγ-decay properties of¹⁴⁶Eu have been reinvestigated with emphasis on implied modifications of the hitherto accepted decay scheme: 42 new levels and 33 newγ-transitions were placed in the revised level scheme, 12 of the previously reported levels were deleted. The level distribution of¹⁴⁶Sm is discussed within a statistical model. The indication for a non-statisticalβ-strength function is observed.     

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.     

A study of high spin states in the transitional nucleus90Mo

The reaction⁵⁸Ni(³⁶Ar, 4p)⁹⁰Mo has been studied at a beam energy of 149 MeV. A detector array consisting of the OSIRIS spectrometer (12 Compton-suppressed Ge detectors), four charged-particleδE detectors and seven NE-213 neutron detectors at the VICKSI accelerator in Berlin has been used to measure the gamma radiation inγγ- and particle-γγ-coincidence mode. An additional Ge detector was placed at 162? to the beam direction to provide information on DCO ratios. The level scheme of⁹⁰Mo has been extended up to an excitation energy of about 12 MeV and probable spin 23?. Some 70 transitions and 40 levels have been newly identified. Spin assignments have been proposed on the basis of measured DCO ratios. Shell model calculations in a model space consisting of the proton 1f _5/2, 2p _3/2, 2p _1/2, and 1g _9/2 orbits and the neutron 2p _1/2, 1g _9/2, 1g _7/2, 2d _5/2, 2d _3/2, and 3s _1/2 orbits with some truncation were made for states above 9? and the predicted structure of these states is discussed.     

Evidence for band termination in118Xe

The yrast band of¹¹⁸Xe has been extended up to tentativelyI ^π = 34⁺ in a heavy-ion in-beam γ-spectroscopic study using the NORDBALL detector array. A band crossing is observed at the highest spins and interpreted within the Modified Oscillator Model as a transition to a terminating band.     

K-capture probability in the decay of139Ce(137.5d)

The K-capture probability (P _K) in the decay of¹³⁹Ce (137.5d) has been determined from the analysis of the K x-ray gamma ray sum-peak observed with a Ge (Li) x-ray detector. Furthermore,P _K is estimated independently from the measurement of the K x-ray intensity in the decay, using the known conversion coefficients of the 165.8 keV transition. Using the weighted average ofP _K measured as above, the mass difference between¹³⁹Ce and¹³⁹La is found to be 273 _?13 ⁺²¹ keV.     

Measurement of fast neutron induced fission cross section of thorium using Lexan plastic track detector

Fission-track registration characteristics of Lexan solid state nuclear track detectors have been used to measure the fast neutron induced fission cross section of²³²Th. The fast neutrons (?14.2MeV) were produced with the help of an AN-400 model Van-de-Graaff accelerator at Banaras Hindu University laboratory using³H(²H,n)⁴He reaction and were used to irradiate the fissile target deposited on the plastic detector. The track densityT, registered on the plastic detector is related to the fission cross sectionσ _f, through the relationT=knσ _føt wheren is the number of fissile atoms per cm² in the deposit, ø is the neutron flux,k is fission track registration efficiency andt is the time of irradiation. The fission cross sectionσ _f of²³²Th, relative to the well measured fission cross section of²³⁸U, was found to be 0.36±0.04 barn.     

First observation of low lying states in the doubly odd nucleus132Pr from beta decay of132Nd

Excited states of ¹⁰⁸ Te were populated in the ⁵⁴ Fe + ⁵⁸ Ni (270 MeV) reaction using the NORDBALL detector array equipped with charged-particle and neutron detector systems for reaction channel separation. Gamma rays belonging to the neutron deficient nucleus ¹⁰⁸ Te were identified for the first time. On the basis of γγ-coincidence and angular correlation relations a level scheme was constructed with tentative spin and parity assignments. The structure of the nucleus is discussed in the framework of systematics of heavier Te nuclei.     

Double-β decay of116Cd

The NEMO-2 tracking detector located in the Fréjus Underground Laboratory was designed as a prototype of the detector NEMO-3 to study 0ν and 2ν double-beta decay (ββ) physics. After ten months of nearly continuous running with an enriched cadmium source (0.92 mol·y of¹¹⁶Cd) aββ2ν half-life ofT _1/2=(3.75±0.35(stat)±0.21(syst))·10¹⁹ y was measured. Limits with 90% CL on the¹¹⁶Cd half-lives of 5.0·10²¹ y forββ0ν decay and of 1.2·10²¹ y forββ0νχ ⁰ decay with a Majoron (χ ⁰) were obtained. Theoretical predictions for 0ν and 2ν decays of¹¹⁶Cd are also presented.     

The beta branching ratio and conversion coefficients in the137Cs decay

The decay of¹³⁷Cs has been reinvestigated using several precision counting methods. The emission rate ofβ-particles plus internal conversion electrons was measured by the 4π-proportional counter method using vacuum evaporated sources free of self-absorption and checked by the liquid scintillation method. TheK-conversion coefficient was determined by the electron X-ray coincidence method using a magnetic spectrometer and a high resolution Si(Li) detector. TheK/(L+M+...) conversion ratio and a second less accurate value for the β-branching ratio were obtained from the recorded electron spectra. Theγ-ray emission rate of all sources was determined to within ±0.14%, on the average, with a calibrated NaI(Tl) crystal detector. As results the intensity of theβ-decay to the ground state of¹³⁷Ba could be determined to (5.4±0.3)% of the¹³⁷Cs decays, theK-conversion coefficient to 0.0916±0.0004, and theK/(L+M+...) conversion ratio to 4.41±0.04. From these values the γ-ray emission intensity is (85.1±0.4)% of the¹³⁷Cs decays and theK X-ray emission intensity is (8.13±0.10)% of the emittedγ-rays. All errors are discussed in detail.     

Gammaübergänge und Energieniveaus im49V aus der Reaktion48Ti(p, γ)49V

Deexcitation gamma rays of⁴⁹V from the⁴⁸Ti (p, γ)⁴⁹V reaction have been investigated at the resonancesE _p=1007, 1209, 1362 and 1374 keV corresponding to excited states in⁴⁹V at 7742, 7940, 8090, 8102 keV. A 4 cm²× 0.35 cm lithium-drifted germanium detector was used. The target was TiO₂ enriched in⁴⁸Ti to 99.4%. 71 gamma transitions have been observed. A level scheme of⁴⁹V is proposed involving 8 new levels in the energy range from 0 to 5.2 MeV excitation energy.     

High spin states in the doubly-closed shell nucleus146Gd

High spin states of¹⁴⁶Gd, populated in heavyion induced reactions, have been investigated by means of in-beamγ-ray spectroscopy using the Compton-suppressed germanium detector arrays OSIRIS and ESSA30. 35 new levels and 47 new transitions could be placed in the level scheme. In addition to the extension to very high spins, a new cascade has been observed at intermediate spins.     

The decay of 8.7 min237Pa

The beta and gamma radiations of²³⁷Pa have been investigated employing semiconductor and scintillation spectrometers and coincidence techniques. Sources of²³⁷Pa were obtained after bombardments of²³⁸U with bremsstrahlung and 14-MeV neutrons and subsequent chemical separation. From the total of 18γ-rays following the decay of 8.7±0.2 min²³⁷Pa 17 transitions, representing 99.9% of theγ-ray intensity, could be placed in a level scheme of²³⁷U. AQ _β- value of 2.25±0.1 MeV has been determined.     

Inelastic electron-nucleus interactions at 5 GeV detected by ARGUS

Beam-gas events taken with the ARGUS detector at thee ⁺ e ^?-storage ring DORIS-II have been used to study interactions ofe ^± at 5 GeV with light nuclei mainly¹⁶O. The selection ofe ^{± 16}O events is discussed. The spectra of secondary protons and charged pions are found to be similar to those of hA interactions in accordance with the nuclear scaling. Measurements of like-particle (p p andπ π) correlations at small relative momenta were used to determine the radius of particle emission region ine ^{± 16}O interactions. This radius proved to be equal within errors to the radius of particle emission region in hC interactions. No any narrow diproton resonance has been observed in the mass region from 1.9 to 2.2 GeV.     

Level schemes of100Y and100Zr from the beta-decay of mass separated100Sr

The beta-decay of¹⁰⁰Sr and the low-spin isomer in the daughter nucleus¹⁰⁰Y were investigated from sources of¹⁰⁰Sr produced from thermal neutron fission in a high-temperature ion source of the online-separator facility OSTIS installed at the Institut Laue-Langevin (ILL), Grenoble. Gamma-single, gamma-multispectra and gamma-gamma-coincidence measurements were performed resulting in the first level scheme of¹⁰⁰Y as well as a considerably extended scheme of¹⁰⁰Zr. The schemes are placed in level systematics and implications for the appearance of shape coexistence atN=60 are discussed.