High-spin levels in 63 145 Eu82

The level scheme of theN=82 nucleus145Eu has been extended toI=(55/2) andEx=11.2 MeV in an experiment with the Tessa Compton-suppressed Ge detector array using the127I(22Ne,4n) reaction. Most of the complicated and irregular level scheme of145Eu can be interpreted as proton multi-quasiparticle states in comparison to the64146Gd82 core nucleus but also excitations across the neutronN=82 core have been observed.

Transition probabilities in negative parity bands of the 119I nucleus

Abstract Lifetimes in four negative-parity bands of 119 I were measured using DSAM and RDM. 119 I nuclei were produced in the 109 Ag( 13 C,3n) reaction, γγ coincidences were collected using the NORDBALL array. RDDSA — a new method of RDM analysis — is described. This method allowed for the self-calibration of stopping power. From 31 measured lifetimes, 39 values of B (E2) were established. Calculations in the frame of the Core Quasi Particle Coupling (CQPC) model were focused on the problem of susceptibility of the nucleus to γ -deformation. It was established that nonaxial quadrupole deformation of 119 I plays on important role. The Wilets–Jean model of a γ -soft nucleus describes the 119 …

The role of the shape driving neutron orbital in 108Cd

Abstract The nucleus 108Cd has been studied using a heavy-ion reaction and the NORDBALL multi-detector array. The yrast band has been extended to Ip = 24+, and nine quasi-rotational side bands have been identified. The n h 11 2 negative-parity orbital is found to play a dominant role both in the low-spin as well as in the high-spin structure of 108Cd. The first band crossing in the yrast band is caused by the h 11 2 neutrons. The 10+ state of the aligned n( h 11 2 ) 2 configuration decays strongly into a low-lying low-spin intruder-like positive-parity band. It is suggested that this intruder structure is dominated by a non-aligned n( h 11 2 ) 2 configuration. For the first time in this mas…

The distribution of the rotational transition strength in warm nuclei studied through γ-ray correlations

Abstract The study of damping of rotational motion applying te rotational plane mapping (RPM) method is presented and discussed. The aim of this technique is to extract the distribution of the rotational transition strength from an analysis of the shape of the “central valley” of two- and three-dimensional γ-ray spectra. The method is applied to a triple γ-coincidence data set of 162,163Tm nuclei formed in 37Cl+130Te reactions. The rotational transition strength is obtained as a function of rotational frequency for selected regions of entry states, and the width is found to be rather constant and approximately equal to 80 keV. This value is significantly smaller than the value predicted the…

Particle octupole multiplet in147Gd

Levels of the N=83 nucleus147Gd have been investigated by in-beam γ-ray and conversion-electron spectroscopy using the147Sm(3He,3n) and Sm(α,n) reactions. We have observed 16 new low-and medium-spin levels in147Gd. In addition to the previously known 13/2+ level we have located the 11/2+,9/2+, 7/2+, 3/2+ and (1/2)+ members of the vf7/2×3 septuplet.

In-beam γ-ray spectroscopy of 56Co

Excited states of Co-56 were studied in the reaction Al-27(S-32,2p1n) Co-56. The NORDBALL array with a Neutron Wall and a Silicon Ball was employed. The excited states were interpreted in terms of ...

Lifetimes in the ground-state band and the structure of 118Te

Lifetimes of excited states in 118Te have been measured using the Doppler Shift Attenuation (DSA) and Recoil Distance (RD) methods in the 109Ag(13C, p3n) reaction at a beam energy of 54 MeV. Lifetime values of the ground-state band levels with spins I π = 2+-16+ have been obtained. The excitation energies and B(E2) values are interpreted in the framework of a version of IBFM ( IBM + 2qp) with the maximum boson number exceeding its standard value. A satisfactory agreement with experimental level scheme and B(E2) values for the ground-state band is achieved.

Gamma-ray spectroscopy of 192–195Po

Prompt and delayed γ-rays have been observed from very neutron deficient 192–195Po nuclei by using the recoil-decay tagging (RDT) and recoil gating techniques. The yrast levels up to the (10+) state in the 192Po were identified for the first time. Comprehensive data for 194Po rendered it possible to extend the yrast line and to observe several positive and negative parity non-yrast states. In the odd-mass isotopes 193Po and 195Po, favoured and unfavoured states on top of the 13/2+ state have been identified. The results are discussed within the simple vibrator and rotor pictures as well as in the framework of coexisting spherical and deformed-intruder structures.

On the decay of compound nuclei following alpha-particle and12C induced reactions

Multiple coincidence rates have been measured using a detector system consisting of a Ge(Li) spectrometer and eight NaI(Tl) or eight liquid scintillators. Reactions induced byα-particles with energies of 51–55 MeV and 118 MeV12C ions are studied. The data are analysed to give the first and second central moments of the distribution of the number ofγ-rays feeding individual levels in the final nuclei. When these numbers are compared to spin distributions calculated with the statistical model code GROGI the relative importance of dipole and quadrupole deexcitation modes can be ascertained. In particular, in the122Te(α, 4n)122Xe reaction theγ-decay prior to the entry into the ground band is we…

On the 2485 keV γ-ray line in208Pb

The 2485 keV γ-ray line, which in a GSI experiment originally was suggested to decay from the 6+ state of the double octupole vibration in 208Pb, was in a later experiment in Berlin proposed to belong to 207Pb, populated in one-neutron transfer. It has been searched for in the present experiment using Coulomb excitation.

Interaction strength and shape difference for the h9/2 and h11/2 configurations in163Tm

The strongly shape driving πh9/2[541]l/2− configuration with α=+1/2 exhibits some anomalous, and so far unexplained, features concerning the crossing frequency, ħωc, the aligned angular momentum, ix, and interaction strength, at the alignment of the first pair of i13/2 quasineutrons in several odd-Z rare earth-nuclei. The h9/2[541]1/2− and h11/2[523]7/2− bands have been studied in the stably deformed rare-earth nucleus163Tm to investigate these features. A difference in band crossing frequency of ∼ 80 keV between the two bands is found. Rotational bands built on these two configurations have been found to cross in the spin range I=25/2–29/2 ħ. Theγ-decay pattern between the two bands is est…

Shell structure and shape coexistence in195Pb

Pb-195 was investigated utilizing the reactions Dy-164(S-36, 5n)Pb-195 and Dy-164(S-34, 3n)Pb-195 at beam energies of 170 and 160MeV respectively. Two new dipole bands which feed into the yrast 25/2(+) state, were found in Pb-195. The connection between the bands and the spherical states was established and thus spins and energies of the involved collective states were determined. The deformation is understood as mainly due to excitations of protons across the Z = 82 shell gap. The observed backbends are interpreted as alignment of i(13/2) neutrons.

Competing proton and neutron alignments in neutron-deficient Xe-nuclei

Abstract High-spin structures of the neutron-deficient 117,118,120 Xe isotopes have been studied by in-beam γ-ray spectroscopic techniques. The final nuclei have been identified by means of charged-particle detectors. Collective rotational bands based on the neutron d 5 2 , g 7 2 and h 11 2 configurations have been identified in 117 Xe. In the even 118 Xe and 120 Xe nuclei several new side bands were observed and the previously known bands were extended. The present level schemes include two positive-parity bands constructed to high spin in 118 Xe, whereas in 120 Xe three such bands were observed. In order to explain these bands, both proton and neutron ( h 11 2 ) 2 alignments, as well as t…

Observation of an Intense Quasicontinuum of Superdeformed Rotational Transitions inEu143

Quasicontinuum spectra in coincidence with transitions belonging to the different potential wells of {sup 143}Eu are studied with an increasing number of coincidence folds. An intense bump of rotationally correlated transitions is observed to develop in the high spin region. Fold distributions, angular anisotropies, moment of inertia determinations, and lower limits of lifetimes as a function of the rotational frequency show that the bump originates from highly collective rotationally damped {ital E}2 transitions generated by superdeformed states. {copyright} {ital 1996 The American Physical Society.}

High-spin states in110Cd

Levels of110Cd have been investigated via the96Zr(18O,4n)110Cd reaction by employing the NORD-BALL array of 17 Compton- suppressed Ge detectors. The yrast band has been observed up to I=28 ħ and 14.2 MeV excitation energy with band crossing at ħωc=0.35 MeV. At least three side bands have been constructed. The negative parity bands experience band crossings at ħωc ≈ 0.45 MeV.

High-spin studies of the neutron deficient nuclei 103In, 105In, 107In, and 109In

High-spin states of the isotopes In-103,In-105,In-107,In-109 have been investigated using in-beam gamma-ray spectroscopic methods. Results from three different experiments are presented. Targets of Fe-54, Cr-50, and Mo-92 were bombarded by a 270 and 261 MeV Ni-58 beam and by a 95 MeV F-19 beam, respectively. Reaction channel separation was achieved with a charged-particle detector array and in the first two experiments also with a 1 pi neutron detector system. As a result of these experiments the level schemes of In-103,In-105,In-107,In-109 were significantly extended. Excited states of these odd-A indium isotopes are discussed within the framework of the nuclear shell model and the hole-co…

In-beam study of 102In, 104In and 106In

Proton-rich odd-odd In isotopes have been investigated by in-beam spectroscopic methods using the NORDBALL detector array. A Ni-58 beam with an energy of 270 MeV was used to bombard a Fe-54 target. ...

Lifetimes of yrast states in 110Cd

Abstract Lifetimes or lifetime limits of 20 yrast levels in 110 Cd have been measured using the recoil-distance method and the NORDBALL array of Compton-suppressed Ge detectors. From the reduced transition probabilities competing rotational and vibrational behaviour of 110 Cd is revealed. Also non-collective states, associated with proton configurations, have been observed.

Two-phonon octupole excitation inGd146

Based on experimental evidence from the $^{144}\mathrm{Sm}$($\ensuremath{\alpha},2n$) reaction, the $3484.7$-keV ${6}^{+}$ state in $^{146}\mathrm{Gd}$ is identified as the highest-spin member of the ${3}^{\ensuremath{-}}\ensuremath{\bigotimes}{3}^{\ensuremath{-}}$ two-phonon octupole quartet. A previously unknown $\ensuremath{\gamma}$ line of $1905.8$ keV and $E3$ character feeding the ${3}^{\ensuremath{-}}$ octupole state has been observed. These results represent the first observation of a ${6}^{+}\ensuremath{\rightarrow}{3}^{\ensuremath{-}}\ensuremath{\rightarrow}{0}^{+}$ cascade of two $E3$ transitions in an even-even nucleus and provide strong support for the interpretation of the ${6…

Excited states of111I and the observation of a 21 ns isomer

Proton rich nuclei close to 100 Sn have been investigated inbeam using the NORDBALL detector array. A beam of 270 MeV58 Ni was used to bombard a 54 Fe target. Reaction channel separation was achieved with a 4π charged particle multi-detector set-up together with a 1π neutron detector wall placed in the forward direction. Gamma-ray transitions belonging to the 111 I nucleus were identified for the first time. A level scheme constructed from γ-γ-particle-coincidence analysis is proposed. The level structure is discussed within the framework of the shell model and the systematics of the heavier odd iodine nuclei.

In-beam?-ray spectroscopy of102In

Neutron deficient nuclei close to100Snhave been investigated in-beam by γ-ray spectroscopic methods using the NORDBALL detector array. A beam of 270 MeV58Niwas used to bombard a target of54Fe.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 of102Inwere identified for the first time. The level scheme constructed from γ-γ-particle-coincidence and γ-γ-angular correlation analysis is presented. The structure of102In is discussed and compared to neighboring nuclei in the framework of the nuclear shell-model.

Coexisting structures in 119I

Abstract High-spin structures of 119 I have been studied by using 13 C and 15 N induced reactions. In all, fifteen ΔI = 1 or 2 bands belonging to 119 I were found. No evidence was found for bands with collective oblate shape, instead, all the observed rotational bands were interpreted to possess a collective prolate shape. A rich tapestry of noncollective states of both negative and positive parity was observed. Based on TRS calculations various configurations at β 2 ≈ 0.17 and γ = 60° were assigned to these states.

Level Scheme of 102In first observed

Neutron deficient nuclei close to 100Sn have been investigated in-beam by particle and γ -ray spectroscopic methods using the NORDBALL detector array following the bombartment of a 54Fe target with a beam of 270 MeV 58Ni. Protons and α particles were identified with a 4 π ΔE -type Si-multidetector and neutrons with a 1π liquid-scintillator-detectorassembly placed in the forward derection. Excited states of 102 In were identified for the first time. The level scheme constructed from γ - γ -particle-coincidence and γ angular correlations is discussed and compared to the structure of neighboring nuclei in the framework of the nuclear shell model.

The two particle-phonon multiplet ?h 11/2 ?f 7/2 � 3? and higher-lying four-nucleon yrast states in the doubly-odd nucleus 146 63 Eu83

From in-beamγ-ray measurements we have established the high-spin states in146Eu up to 3.5 MeV excitation andIπ=(15+). The highest levels observed are formed by alignment of four nucleons, involving excitation of the144Sm core. Negative-parity states at about 2 MeV are classified asπh11/2νf7/2 × 3− octupole excitations. Quantitative analyses for the octupole multiplet members and for theν=4 states based on empirical data from neighbouring nuclei are presented.

High spin band structures in104Cd

High spin states in Cd-104 have been investigated by means of heavy ion induced reactions using the Nordball detector array. The level scheme constructed from yy-coincidences is dominated by three ...

Determination of the intrinsic quadrupole moment of the superdeformed band in 143Eu

The intrinsic quadrupole moment, Q0, of the superdeformed band in 143Eu has been extracted from nuclear lifetimes, measured in a Doppler shift attenuation method experiment. Data were collected with the NORDBALL gamma-ray spectrometer following the reaction 110Pd (37Cl, 4n) 143Eu at a beam energy of 160 MeV. A centroid shift analysis of the data was carried out, using the Braune stopping powers to model the slowing down of the recoil nuclei in the target and backing materials. This gave a value of Q0 = 13.0 ± 1.5 eb for the band. The result is in good agreement with the theoretical prediction of Total Routhian Surface calculations, and supports the assigned single particle configuration, in…

In-beam spectroscopy of 110Te

The neutron-deficient nucleus Te-110 has been investigated by in-beam spectroscopic methods using the NORDBALL multi-detector array. Except for the energy of one level observed in alpha-decay, exci ...

Shell model and octupole states in148Gd from in-beam experiments

Through (α, 4n) and (τ, 3n) reactions the high-spin states in the two-neutron nucleus148Gd were populated up toI π=21− at 7.2 MeV, including numerous states above the yrast line. The148Gd energy spectrum is interpreted in terms of the spherical shell model. Identification of the (νf 7/2 i 1 3/2)10− state gives the νi 13/2 single particle energy free of octupole admixtures as 2.1(1) MeV. Eight high-spin states between 1.2 and 3.7 MeV were identified as the couplings of the two valence-particles to the146Gd octupole phonon, and three above-lying levels are assigned as double-octupole excitations including a 12+ state which decays by anE3-E3 stretched cascade. All these octupole levels can be …

In-beam spectroscopy at the proton-drip line. First observation of excited states in 106Sb and 107Sb

Neutron deficient nuclei close to Sn-100 have been investigated in-beam using the NORDBALL detector array. A target of Fe-54 was bombarded with a beam of Ni-58 at 270 MeV. Evaporation residues were identified by detecting protons and alpha particles in a 4 pi charged particle multi-detector set-up and neutrons in a 1 pi neutron detector wall in coincidence with gamma rays. Excited states of the proton drip line nucleus Sb-106 and of Sb-107 were identified for the first time. The yrast level schemes constructed from gamma-gamma-particle coincidence and gamma-gamma angular correlation analysis are presented and discussed within the framework of the nuclear shell model.

Single-step link from yrast SD band in 143Eu

A discrete γ-ray transition from the yrast SD band to the region of near-yrast discrete normal-deformed states has been identified in 143Eu. It has an energy of 3360.6 keV and an intensity corresponding to 3.2% of the full intensity of the SD band and feeds a nearly-spherical state above spin 352(+) and Ex=4947 keV. This agrees well with the picture of the decay out of the SD band gained previously from two-step links. The angular distribution analysis favours a stretched dipole character for the transition. Due to the complicated structure of the level scheme in the region of interest it has not been possible to place the transition exactly.

Investigation of Gamma Rays from the36S(p,γ)37Cl Reaction

The excitation curve of the 36S(p,γ)37Cl reaction has been measured in the proton energy range 1 000-1 900 keV. 109 resonances were observed. The decay schemes for 13 resonances and energies and branching ratios of 15 bound states have been obtained by means of Ge(Li) detectors. Seven of the bound states have not been reported earlier. Lifetimes or lifetime limits of 5 bound states have been measured by means of Doppler-shift attenuation method.

Coexistence of collective and quasiparticle structures in 106Sn and 108Sn

New levels in the neutron deficient nuclei 106Sn and 108Sn have been investigated by using the NORDBALL detector array combined with charged particle and neutron detectors. The excited structures are discussed in terms of collectivity and the shell model. The excitations are interpreted to be based on d52, g72 and h112 both for protons and neutrons and g92 for protons. The systematical behaviour of the specific states in the Sn isotopes is studied in the mass range of A = 106–118.

The 235 ns 9+ isomer in 63 148 Eu85

From (p, xn) in-beamγ-ray and electron measurements aT1/2=235(14) ns isomer at 720 keV was identified in63148Eu85 and the levels populated in its decay have been characterized. The results determineIπ=9+ for the isomeric state, and we assign it as the (πh11/2j0−2ν f72/3)9+ shell model state, analogous to the configuration of the 235 μs isomer in63146Eu83.

First observation of excited states inPo192

\ensuremath{\gamma} rays following the $^{160}\mathrm{Dy}$${(}^{36}$Ar,4n${)}^{192}$Po reaction have been identified by employing a high-transmission gas-filled separator in recoil decay tagging measurements. The deduced level scheme reveals a flattening of the energy systematics, when going towards the neutron midshell indicating that the deformed intruder structures have become yrast. \textcopyright{} 1996 The American Physical Society.

Rotational features of vibrator nucleus118Te

High-spin states in ${}^{118}\mathrm{Te}$ have been populated via heavy-ion induced reactions. Excited states were observed up to $I=32\ensuremath{\Elzxh}$ and, in addition to irregular level sequences, several bands were identified for the first time. The decoupled negative parity bands based upon ${7}^{\ensuremath{-}}$ and ${8}^{\ensuremath{-}}$ states are interpreted to arise from the proton ${h}_{11/2}{g}_{7/2}$ configuration coupled to the $2p\ensuremath{-}2h$ intruder states in ${}^{116}\mathrm{Sn}.$ These bands show very smooth alignment behavior, in accordance with the proton ${h}_{11/2}$ bands in neighboring Sb and I nuclei. Above $I=20$ the yrast positive parity band is built on t…

Search for High-Spin Isomers in 150Dy

A search for yrast traps in 150Dy has been made by studying the γ-ray decay following the 144Nd (12C, 6n) 150Dy and 146Nd (12C, 8n) reactions. Although an average value of about 30 units of angular momentum is imparted to the final nucleus using these reactions, no evidence is found for the existence of isomers with half-lives longer than 10 ns.

A finite number of regular rotational bands in the superdeformed well of 143Eu

Abstract The number of excited superdeformed bands in 143 Eu is measured by use of the Fluctuation Analysis Method. Between 10 and 40 rotational bands, displaying typical rotational energy correlations over two consecutive transitions, are populated within a rather narrow range in transition energy, E γ ≈ 1300–1500 keV. These numbers are close to the values found for normally deformed nuclei and agree with microscopic cranking + band mixing calculations for the specific superdeformed nucleus, which predict the onset of rotational damping to occur at the excitation energy U 0 = 1.3–1.6 MeV above the yrast line.

Non-yrast level structure of135Pr

Levels of135Pr populated in the (p,2n) reaction were studied using methods of in-beamγ-ray and conversion electron spectroscopy. Many low-lying positive-parity states give evidence of a deformation ofβ=0.15–0.20. The same conclusion is evident from band structures built on these positive-parity states and on theh11/2 negative-parity state. The triaxial rotor-plus-particle model reproduces quite well band structures withβ=0.20 andγ= 21°.

Coexisting structures in 115Sn and 116Sn

Abstract Excited states up to I ≈ 20 in 115 Sn and 116 Sn, populated via the ( 18 O, αxn) reactions, have been studied using the DORIS Ge detector array in conjunction with charged particle detectors. In both nuclei, spherical as well as regular, deformed level structures were found. The spherical states are interpreted to arise from pure neutron configurations, while the deformed, intruder bands obviously involve proton 2p-2h excitations across the Z = 50 shell gap.

High spin shell model excitations in149Gd

The high spin level structure of the three-neutron nucleus149Gd has been investigated by in-beamγ-ray and electron spectroscopy with (α, xn) reactions. The observed levels are characterized as members of the shell model multipletsνf 7 2/3 ,νh 9/2 f 7 2/2 ,νf 7 2/3 ×3−,νh 9/2 f 7 2/2 ×3−, and tentativelyνf 7 2/3 ×(3−)2. The energies of theν f 7 2/3 states agree only moderately with those calculated using empirical two-nucleon interactions taken from148Gd, which indicates the importance of long range contributions already atN=85.

Collectivity in ‘‘spherical’’Eu143,144nuclei

Long cascades of stretched E2 transitions have been observed in $^{143}\mathrm{Eu}$ and $^{144}\mathrm{Eu}$ nuclei which at low excitation exhibit spherical shape. Lifetime experiments demonstrate high collectivity values up to B(E2)\ensuremath{\approxeq}100 W.u. among these E2 cascades. The total Routhian surface calculations indicate many crossing rotational bands of the nucleus with triaxial shape at ${\mathrm{\ensuremath{\beta}}}_{2}$\ensuremath{\approxeq}0.25 and \ensuremath{\gamma}\ensuremath{\approxeq}30\ifmmode^\circ\else\textdegree\fi{}. The E2 cascades in $^{143}\mathrm{Eu}$ are proposed to represent the \ensuremath{\nu}${\mathit{h}}_{11/2}^{2}$\ensuremath{\pi}${\mathit{h}}_{11/2}…

A 15 ?s isomer in thez=70n=83 nucleus153Yb

Gamma-ray measurements following mass analysis of102Pd+245 MeV54Fe reaction products have characterized a 15 μs isomeric decay in153Yb and elucidated the systematics of proton-rich N=83 nuclei.

Two-Phonon Octupole Excitation in 146Gd

The excited states in 146Gd have been re‐investigated with the 144Sm(α,2n) reaction using a modern Ge γ‐ray array including a polarimeter. Amongst the non‐yrast states populated in this reaction we have identified the aligned 6+ member of the two‐phonon octupole quartet from the observation of the E3 branching to the one phonon 3− state. Our results represent the first observation of a 6+→3−→0+ E3 cascade in an even‐even nucleus.

Coexistence of collective and quasiparticle structures in 106, 108Sn nuclei

New revels in two neutron deficient nuclei Sn-106.108 have been found by using the Nordball detector array extended with the arrangements of charged particle and neutron detectors. The excited stru ...

Properties of isomeric states and the ?d 3/2-vi 13/2 multiplet in194Au

The level structure of194Au has been studied by observing prompt and delayedγ-rays following194Pt(p,n) and195Pt(p,2n) reactions. The conversion electron andγ-ray spectra from the decay of the 0.42s (10−) and 0.60s (5+) isomers at 476 keV and 107.4 keV, respectively, have been measured using the He-jet method. The half-lives of the 6+ (278.2 keV, 1.1±0.4 ns), 7+ (224.6 keV, 2.6±0.2 ns) and 8+ (406.8 keV, 2.9±0.4 ns) members of theπd3/2-vi13/2 multiplet have been obtained from the time distributions between cyclotron beam pulses andγ-rays depopulating these levels. A calculation made assuming a pure two-particle configuration for the multiplet predicts very well theB(E2) values for the transi…

Medium-spin levels and the character of the 20.4 ns isomer in 145Gd

Abstract Levels of the N = 81 nucleus 145Gd have been investigated by in-beam γ-ray and conversion electron spectroscopy with the 144Sm(3He, 2n) reaction. Fourteen new low- and medium-spin states between 1.0 and 2.4 MeV excitation, the known yrast levels up to spin 21 2 + , five other high-spin non-yrast states and a new 20.4 ns 13 2 isomer at 2200.2 keV in 145Gd have been observed. The isomer decays via a fast 927.3 keV E3 transition with B(E3) = 48 ± 7 W.u. Another weaker decay branch is a mixed, strongly hindered E1 + M2 + E3 transition to the v h −1 11 2 state. We propose an octupole v f 7 2 j −2 × 3 − main configuration for the isomer, analogous to the 997 keV 13 2 + isomer in 147Gd. T…

High-spin studies near 100Sn with NORDBALL: New results on 102In, 104In and 108Sb

The NORDBALL detector array has been used in a gamma-ray spectroscopic study of neutron deficient nuclei close to 100Sn. A beam of 270 MeV 58Ni ions was used to bombard a target of Fe-54. Reaction channel separation was achieved with a 4pi charged particle Si-ball together with a 1pi neutron detector wall. Altogether 29 final nuclei were identified and excited states were observed for the first time in 8 of them. The weakest identified channel was 100Cd which represented 4.10(-3) % of the observed total yield. Level schemes Of 102In, 104In and 108Sb constructed from gamma-gamma-particle-coincidence and gamma-gamma-angular correlation analyses are presented. The observed structures are discu…

Identification and spectroscopy of the108Te nucleus

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.

Four independent decay properties in the super-deformed well of 143Eu

Abstract The flow of γ-transitions through the superdeformed minimum of 143Eu is investigated by studying the intensities of four different types of γ-rays of superdeformed origin, obtained with a variety of gating conditions. They can all be explained rather well by schematic simulation calculations assuming only well known statistical properties. Information on level density, competition between E1 and E2 strengths and rotational damping width in the SD well is obtained, yielding a rather complete picture of the feeding mechanism into different regions of the second minimum.

First observation of excited states in 108Sb

A spectroscopic study of Sb-108 has been carried out as a part of a larger experiment where in total twenty-nine different residual nuclei were identified. This study gives the first information on excited levels in this nucleus. A low-lying two-quasi-particle multiplet together with some of the higher lying levels are discussed within the framework of the nuclear shell model. A rotational, strongly coupled, band is identified as, most likely, being built on the deformed pig9/2(-1) nuh11/2 configuration in accordance with total routhian surface calculations. Tentative spins and parities are presented as well as B(M1)/B(E2) ratios for some of the transitions in the strongly coupled band.

Medium-spin levels in the N=83 nucleus147Gd

Levels of theN=83 nucleus147Gd have been investigated by methods of in-beamγ-ray and conversion electron spectroscopy using the147Sm(3He, 3n) and144Sm(α, n) reactions. Sixteen new low- and medium-spin levels have been observed in147Gd. We have located six members of thevf7/2×3− particle-octupole septuplet and several neutron single-particle states in147Gd. The levels of147Gd are discussed on the basis of the spherical shell model.

Competing proton and neutron alignments in 117−120Xe