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An in-beam study of the transfermium nucleus 252No has been performed using the JUROSPHERE II array of germanium detectors coupled to the gas-filled recoil separator RITU. A new technique of recoil-fission tagging was used to extract tagged γ-ray data. Having significant spontaneous fission and α-decay branches, 252No is an ideal candidate for a comparative study. In a similar manner to α-decay tagging the fission events can be used to obtain γ-ray data. The recoil-fission tagged γ-ray spectrum showed a similar structure to the α-decay tagged γ-ray spectrum. By comparing the α-tagged and fission-tagged spectra and decay curves, it was shown that the spontaneous fission originates from the same initial state as the α decay. This extension of the tagging method allows in-beam spectroscopic data to be obtained from heavy nuclei with significant spontaneous-fission branches.

In recent years, the exploitation of the iecoil-decay tagging (RDT) technique with,large arrays of germanium detectors has revealed much information about the structure of heavy nuclei approaching the proton drip line. The yrast bands of the N

Prompt and delayed gamma-ray spectroscopy of very neutron-deficient bismuth isotopes 187, 189Bi has been performed using the recoil decay tagging method. A rotational band has been observed in 189Bi and is interpreted as a complete decoupling of a single proton from the deformed lead core. The results for 187Bi suggest a similar structure and coupling scheme. This study gives the first evidence for a prolate band in a light bismuth nucleus and confirms the prolate character of the low-lying rotational band observed in the core nuclei 188Pb and 186Pb.

Gamma rays from excited states of 190Po have been observed using the Jurosphere Ge-detector array coupled to the RITU gas-filled separator. They were associated with a collective band which from spin 4 onwards resembles the prolate rotational bands known in the isotones 188Pb and 186Hg. This indicates that in 190Po the prolate configuration becomes yrast above I = 2. The experimental results are interpreted in a two-band mixing calculation and are in agreement with α-decay data and potential energy surface calculations.

A number of previously unobserved gamma-rays emitted from the neutron-deficient nuclide Pt-171 have been identified using the recoil decay tagging technique. The level scheme has been updated using ...

The low-energy nuclear structure and decay properties of the neutron-deficient isotopes 195At and 191Bi have been studied. 195At was produced in the reaction 142Nd(56Fe,p2n)195At and 191Bi as the daughter activity of 195At. The activities were implanted in a position-sensitive silicon detector after being separated from the primary beam by a gas-filled recoil separator. The 1/2+ intruder state was determined to be the ground state in 195At with an alpha-decay energy of E α = 6953(3) keV and a half-life T 1/2 = 328(20) ms. Another state with an alpha-decay energy E α = 7075(4) keV and a half-life T 1/2 = 147(5) ms was found to decay to a 148.7(5) keV excited state in 191Bi for which a spin and parity of 7/2- were deduced. Consequently, the same 7/2- character was assigned to the initial state at 32(7) keV in 195At on the basis of unhindered alpha-decay. The 9/2- state, being the ground state in heavier odd-mass astatine isotopes, was not observed.

Gamma-rays from the alpha- and proton-unstable nuclide 171Au have been observed for the first time. The gamma-rays were correlated with both a proton- and an alpha-particle decay branch, confirming that the nucleus decays by alpha and proton emission from a single (11/2-) state. The measurement confirms the previously determined half-lives for these particle decays but the present values are of higher precision. In addition, a longer half-life than determined in previous work was measured for the proton-unstable tentative ground state. The results are discussed in relation to structures in neighbouring nuclei and compared with a Strutinsky-type TRS calculation.

In recent years (1996-2001) the recoil-decay tagging technique has been employed with great success at the Department of Physics of the University of Jyvaskyla. Various arrays of germanium detectors have been coupled to the RITU gas-filled separator in order to study nuclei far from stability. An overview of the physics studied with these arrays, along with discussion of technical development of the RITU separator, is presented. Even with a comparatively modest array of germanium detectors it has been possible to study nuclei produced with cross-sections as low as 200 nb.

Prompt and delayed gamma-ray spectroscopy of very neutron-deficient bismuth isotopes 187, 189Bi has been performed using the Recoil Decay Tagging (RTD) method. The isomeric i 13/2 states have been identified and their lifetimes have been measured. The systematics of these long-lived M2 isomers has been extended to the proton-unbound isotopes. The general behaviour of single-proton states is discussed within the systematics and interpreted within the shell-model framework.

The JYFL gas-filled recoil separator RITU, combined with Ge detector arrays and a SACRED magnetic solenoid spectrometer, has been successfully employed in recoil-decay-tagging (RDT) experiments in order to probe structures of very neutron-deficient heavy nuclei. The present contribution focuses on the light Pb region where the new data extend the systematics of shape-coexisting yrast states towards the proton dripline. Similarities between band structures and their relation to possible multi-particle multi-hole intruder excitations will be discussed.

In-beam conversion electron spectroscopy experiments have been performed on the transfermium nuclei 253, 254No using the conversion electron spectrometer SACRED in nearly collinear geometry in conjunction with the gas-filled separator RITU at the University of Jyvaskyla. The experimental setup is discussed and the spectra are compared to Monte Carlo simulations. The implications for the ground-state configuration of 253No are discussed.

Excited states in the very neutron-deficient isotopes Os-167 and Os-168 have been observed using the reaction Sn-112(Ni-58, 2pxn). The JUROSPHERE gamma -ray spectrometer array was used in conjuncti ...

The gas-filled recoil separator RITU, combined with Ge detector arrays at the Department of Physics, University of Jyvaskyla (JYFL), Finland, has successfully been employed in recoil-decay-tagging (RDT) experiments for probing structures of several very neutron-deficient heavy nuclei for the first time. In this paper new data for Hg, Pb and Po nuclei are summarized and discussed. These data shed new light on the behaviour and role of the proton multiparticle-multihole intruder states in nuclei at the 82

This contribution discusses the recoil-isomer tagging technique and its application to study isomeric states near the mass 140 proton drip line. The recoiling nuclei from a fusion-evapn. reaction were implanted into a silicon detector at the focal plane of a gas-filled separator, where prompt and delayed g-ray transitions were correlated across isomeric states. New states were established upon a known 15 ms isomer in 142Tb and the feeding and decay of a new 0.5(2)ms isomeric state was established in 144Ho. This measurement represents the first observation of excited states in 144Ho. [on SciFinder (R)]

Using conversion electron and γ-ray spectroscopy combined with a recoil gating method, excited states in 188Pb have been investigated. Further evidence for two excited low-lying 0+ states has been found leading to an interpretation as a multiple shape coexistence in 188Pb.

An excited isomeric state has been identified in the 196At nucleus using the recoil decay tagging technique. This is the first identification of an excited state in this neutron-deficient odd-odd nucleus. Several tentative prompt γ-rays have also been correlated with 196At α-decay, although it has not been possible to assign them to specific energy levels in 196At. The mean lifetime of the isomeric state has been measured as τ = 11±2 µs. The new level is compared with similar low-lying states in neighbouring nuclei and is de-excited by an E2 γ-ray transition, the large hindrance of which is not expected.

Lifetime measurements of states in nuclei with A=187 and 188 have been performed, using reactions between 155Gd and 36Ar and following the transport of evaporation residues to the focal plane of a gas-filled recoil separator. In a separate experiment using the 159Tb(32S, 4n) reaction the γ-decay of isomeric levels in 187Tl has been studied using delayed γ-γ coincidence measurements. From observation of their subsequent γ decay, the mean lifetimes were measured to be 1000 ± 55 ns and 1600 ± 100 ns. Although it was not possible to characterize the isomers completely, they are proposed as candidates for one-proton, two-neutron excitations. In the course of this study, the decay of an isomer in 188Pb was also observed and its lifetime was measured as 1150 ± 30 ns, and limits of 20–600 ns were placed on the meanlife of an isomer conjectured in 187Pb.

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.

Excited states in 171Ir have been observed for the first time. Gamma-rays were assigned to the nucleus by the recoil-decay tagging method. The ground-state band has a structure consistent with an h 11 2 proton coupled to a core of large triaxial deformation. At high spins, a bandcrossing occurs which is interpreted as a change in shape to a prolate deformation. Band-mixing calculations are performed for 171–175Ir. These show that shape-coexistence between triaxial and prolate states in these nuclei follows the same systematics found in their Pt and Os neighbours. The systematics are also compared with deformations calculated for 171–179Ir using the code “Ultimate Cranker”. Dipole bands were also observed, but tilted axis cranking calculations suggest that they are associated with a collective rotation.

Excited states of the Z = 102 nuclide 254No have been studied in the reaction 208Pb(48Ca,2n) by means of in-beam γ -ray spectroscopy in combination with recoil gating and recoil decay tagging. A Ge detector array, consisting of four clover detectors, and a gas-filled separator were used. Six γ-ray lines were observed and associated with E2 transitions in the ground state band of 254No, the highest-lying of these being the 16+→ 14+ transition. Based on global systematics and the extrapolated 2+ 1 excitation energy, the value β2= 0.27 ± 0.03 was extracted for the quadrupole deformation. An improved value for the half-life of 254No, T1/2= (48 ± 3) s, was determined.

The high-spin structure of {sup 205}Rn has been investigated for the first time following the {sup 170}Er({sup 40}Ar,5n) and {sup 197}Au({sup 14}N,6n) reactions at beam energies of 183 MeV and 90{endash}110 MeV, respectively, using the Jurosphere and YRAST Ball arrays. Two new cascades have been identified which dominate the high-spin decay. One of these, consisting of ten stretched M1 transitions with unobserved E2 crossover transitions, is interpreted as a shears structure based on the {nu}i{sub 13/2}{sup {minus}1}{circle_times}{pi}i{sub 13/2}{sup 2} (or {nu}i{sub 13/2}{sup {minus}1}{circle_times}{pi}h{sub 9/2}i{sub 13/2}) configuration. {copyright} {ital 1999} {ital The American Physical Society}

The nucleus Os-171 has been populated using the reaction Sn-116(Ni-58,2pn). Four new bands are identified, and the previously known bands are extended in spin, to a maximum of 53/2 (h) over bar. On ...

The low-lying level structure of the neutron-deficient isotope ${}^{198}\mathrm{Rn}$ has been studied for the first time, using the ${}^{166}\mathrm{Er}{(}^{36}\mathrm{Ar},4n)$ reaction at a beam energy of 175 MeV. Evaporation residues were selected using an in-flight gas-filled separator, RITU, and implanted at the focal plane into a 16-element position-sensitive, passivated ion-implanted planar silicon detector. Prompt $\ensuremath{\gamma}$ rays in ${}^{198}\mathrm{Rn}$ were observed at the target position using the JUROSPHERE array of 24 Compton-suppressed germanium detectors, and were identified by the subsequent radioactive decay of associated recoiling ions in the silicon detector. Isotopic assignments of the nuclei produced were made on the basis of the energy and half-life of their $\ensuremath{\alpha}$ decay. The estimated production cross section for ${}^{198}\mathrm{Rn}$ in this reaction was 180 nb. The excitation energy of the ${2}_{1}^{+}$ state indicates inconsistency with theoretical predictions of large stable ground-state deformation in this isotope. The systematics of other low-lying excited states suggests the presence of deformed intruder states falling in energy with increasing neutron deficiency.

Excited states have been identified for the first time in very neutron deficient Pt-171.172 nuclei using the recoil-or-decay tagging technique. The ground-state band in Pt-172 has been established up to I-pi = 8+. A similar level sequence, presumably built on the I-pi = 13/2(+) state, is observed for Pt-171. The data are compared with theoretical calculations based on the mean field approach and the random phase approximation and are put into the context of the systematics of platinum isotopes. (C) 1998 Elsevier Science B.V. All rights reserved.

In-beam \ensuremath{\gamma}-ray and \ensuremath{\gamma}-\ensuremath{\gamma} coincidence measurements have been made for the very neutron-deficient nucleus ${}^{176}\mathrm{Hg}$ using the recoil-decay tagging (RDT) technique. The irregular yrast sequence observed up to $I=10\ensuremath{\Elzxh}$ indicates that the prolate intruder band, seen in heavier Hg isotopes near the neutron midshell, crosses the nearly spherical ground-state band of ${}^{176}\mathrm{Hg}$ above $I=6\ensuremath{\Elzxh}.$

Excited states have been observed for the first time in 168 Pt and 170 Pt using the α -decay recoil-tagging technique. The trend of decreasing deformation moving away from the N =104 mid-shell continues for 170 Pt but the structure of 168 Pt is significantly different. The low spin level energy systematics in 168 – 184 Pt are presented and discussed within the framework of the interacting boson model.

gamma-ray spectroscopy of the high-spin states of the neutron-deficient nucleus Pb-187 has been conducted with the Gd-155(Ar-36,4n) reaction. A cascade of three transitions was deduced from gamma-gamma coincidence data gated by detection of recoiling evaporation residues in a gas-filled recoil separator. In an earlier, separate experiment, two of these gamma rays were positively identified with Pb-187 by recoil-gamma coincidence measurements with a high-resolution, recoil mass spectrometer. From comparison with similar sequences in heavier odd-A lead isotopes, the cascade in Pb-187 is associated with the sequence of three E2 transitions from the yrast 25/2(+) level to a low-lying 13/2(+) isomer. The variation of excitation energy with mass number of the levels concerned suggests that their structure can be associated with weak coupling of an odd i(13/2) neutron to states in the spherical well. However, the possibility that they are influenced by mixing with states in the prolate-deformed well cannot be discounted. [S0556-2813(98)00411-7].

Excited states have been identified for the first time in 184Pb, the first even-even Pb isotope beyond the 82 < N < 126 mid-shell, using the recoil-decay tagging (RDT) technique. A collective band built on the first-excited 2+ state has been observed. This resembles those seen in 186,188Pb and the Hg isotones, and can thus be associated with a prolate-deformed shape. Variable moment of inertia (VMI) fits of the prolate 0+ level energies in 184,186,188Pb indicate that the minimum appears at N= 103, the same neutron number at which the corresponding minimum in Hg isotopes is observed.

High-spin states have been populated in 54 119 Xe via the 96 Mo( 27 Al,p3n) reaction at 133 MeV, using the Jurosphere γ-ray spectrometer to record triple γ-ray coincidences. The known level scheme has been significantly extended and several band crossings identified. In particular, the νh 11 2 yrast band has been extended to I π = ( 83 2 − ) and shows features which are consistent with those of smooth band termination at high spin. Theoretical results for 119 Xe at high spin are discussed within the framework of cranked Nilsson-Strutinsky calculations, together with results for 117 Xe.

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.

A ${K}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ collective rotational band has been established upon the 6 $\ensuremath{\mu}$s isomeric state in the very neutron-deficient nucleus ${}^{138}\mathrm{Gd}.$ The band was observed using a technique involving the correlation of $\ensuremath{\gamma}$-ray transitions across the isomeric state. The single-particle configuration of the isomer has been deduced from the $\ensuremath{\Delta}I=2$ to $\ensuremath{\Delta}I=1$ intensity branching ratios. In addition, a series of other $\ensuremath{\gamma}$-ray transitions were observed which are reasoned to be part of a higher-lying four quasiparticle structure which decays through the ${K}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ isomeric state. The properties of the ${K}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ band are discussed in relation to the systematic properties of ${K}^{\ensuremath{\pi}}{=8}^{\ensuremath{-}}$ bands in the neighboring $N=74$ isotones.

The JYFL gas-filled recoil separator, RITU, combined with efficient Ge-detector arrays has been employed in in-beam γ-ray studies of very neutron-deficient nuclei close to theZ=82 shell. Gamma-rays from nuclei produced at the few μb cross-section level have been detected.

The transitional nuclei {sub 42}{sup 100}Mo, {sub 44}{sup 104}Ru, and {sub 46}{sup 108}Pd have been studied as products of binary reactions formed by a {sub 36}{sup 86}Kr beam impinging on a {sub 46}{sup 110}Pd target. The yrast states are observed above the region of the first backbend. In each case this backbend is associated with the breaking of the first neutron (h{sub 11/2}){sup 2} pair. The results are consistent with the predictions of cranked shell model calculations and the systematics of neighboring nuclei. {copyright} {ital 1997} {ital The American Physical Society}

In-beam gamma-ray and conversion electron spectroscopic studies have been performed on the 253 No nucleus. A strongly coupled rotational band has been identified and the improved statistics allows an assignment of the band structure as built on the $\ensuremath 9/2^-[734]_{\nu}$ ground state. The results agree with previously known transition energies but disagree with the tentative structural assignments made in earlier work.

Expérience à JYFL cyclotron (Jyväskylä, Finlande); The Kr isotopes are considered to be among the best cases for shape coexistence studies in the mass A$\sim$70 region. Our campaign to investigate in detail the development of the shape coexistence in the neutron deficient Kr isotopes was started with the stable nucleus $^{78}$Kr. To obtain the information about the intrinsic shape, Coulomb excitation experiments were performed. A total of 26 matrix elements were determined for $^{78)$Kr. Simple geometrical and algebraic models do not reproduce all details of the electromagnetic structure. A good interpretation of the complex structure of the nucleus with competing oblate and prolate shapes comes from a study within the complex EXCITED VAMPIR approximation using Hartree–Fock–Bogoliubov transformations with symmetry projection before variation. The measured matrix elements are compared with the predictions of this model.

We report on a set of in-beam studies of excited states in $^{250}\mathrm{Fm}$. We detected prompt \ensuremath{\gamma} rays by using the JUROSPHERE IV array and conversion electrons by using the SACRED spectrometer. Both devices were used in conjunction with the RITU gas-filled recoil separator located at the University of Jyv\"askyl\"a. $^{250}\mathrm{Fm}$ nuclei were produced through the $^{204}\mathrm{Hg}$($^{48}\mathrm{Ca}$,$2n)$$^{250}\mathrm{Fm}$ fusion-evaporation reaction. An experimental excitation function gave a maximum reaction cross section of (980 \ifmmode\pm\else\textpm\fi{} 160) nb at an energy of 209 MeV in the center of the target. Tagging techniques were employed, and a number of E2 transitions were observed that connected the ground-state band levels from spin ${4}^{+}$ up to ${18}^{+}$. The highly converted ${4}^{+}\ensuremath{\rightarrow}{2}^{+}$ transition is observed only by use of conversion electron spectroscopy. The observed ground-state band transitions indicate a rotational structure. We deduce a quadrupole deformation parameter of ${\ensuremath{\beta}}_{2}=0.28$ \ifmmode\pm\else\textpm\fi{} 0.02. A low-energy background of apparent nuclear origin is observed in conversion electrons and postulated to arise from the decay of high-K bands. The half-life of $^{250}\mathrm{Fm}$ is measured to be 30.4 \ifmmode\pm\else\textpm\fi{} 1.5 min.

A series of experiments to study the properties of transfermium nuclei have been performed at the Department of Physics of the University of Jyvaskyla. The experiments are carried out by a large group of collaborating institutes. These studies have been rendered possible by the coupling of various state‐of‐the‐art detector systems to the RITU gas‐filled recoil separator. In‐beam conversion‐electron and gamma‐ray measurements have been made using the SACRED silicon and JuroGam germanium‐detector arrays, respectively. The introduction of the GREAT spectrometer and TDR data acquisition system have greatly improved the quality of the data obtained at RITU. A brief overview of the instrumentation used and highlights from recent experiments are presented.

\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.

Over the past few years a great deal of new spectroscopic data has been obtained for transfermium nuclei. Recoil separators, coupled with modern target position and focal-plane spectrometers, allow detailed studies of the structure and decay properties of transfermium nuclei to be peformed. In-beam studies using the recoil-gating and recoil-decay tagging techniques mainly provide information on yrast states, whilst complementary focal-plane decay studies give access to non-yrast and isomeric structures. In-beam studies of nuclei in this region have largely been performed at ANL and JYFL, and decay experiments at GSI, JYFL, GANIL and ANL. The present contribution is focussed on recent developments and experiments carried out by a number of collaborating institutes at JYFL.

The energy of the ${2}^{+}\ensuremath{\rightarrow}{0}^{+}$ transition in $^{226}\mathrm{U}$ has been measured as $81.3(6)\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ and the energy of the ${4}^{+}\ensuremath{\rightarrow}{2}^{+}$ transition in $^{254}\mathrm{No}$ has been measured as $101.1(6)\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$, both for the first time, by means of electron spectroscopy. The results are close to the estimates of the energies of these transitions from earlier $\ensuremath{\gamma}$-decay work. Absolute values of electromagnetic decay intensities have been measured for yrast transitions in both nuclei.

Excited states in the neutron-deficient nucleus Re-167 have been observed in a recoil-tagging experiment performed with the Jurosphere gamma-ray spectrometer in conjunction with the RITU gas-filled ...

The concept of magnetic rotation in nuclei was introduced to explain the observed regular bands with enhanced M1 transitions and weak or absent E2 crossover transitions in nearly spherical nuclei around 198Pb [1]. These bands can be described by the coupling of high-j proton and neutron configurations to a total spin tilted at an angle of ~ 45° with respect to the symmetry axis. As the proton and neutron spins align with increasing excitation energy, a sequence of ΔI = 1 levels of fixed parity (“shears band”) is formed [2].

Techniques have been developed to study isomeric states in nuclei with the use of RITU (gas filled separator) at the University of Jyvaskyla. The first was the recoil-isomer tagging technique initially, utilised by D.M. Cullen to study the K π = 8− isomeric state in 138Gd [1]. The juro-sphere array was employed in conjunction with ritu and a focal plane array which consisted of several Compton-suppressed Germanium detectors, placed in close geometry around a multi wire proportional counter (mwpc) and a silicon strip detector used for the implantation of recoiling nuclei. This technique correlates prompt and delayed γ-ray transitions across isomeric states and identifies the lifetime of the isomer. The main constraint of this technique is the timing electronics. Only isomers with a half-life greater than the flight time through RITU(~ 300ns) and less than the collection time of the tdc’s (32 μs) can be identified. This time range and hence technique is ideal for the region of mass A = 140 near proton drip line nuclei which have small production cross-sections in comparison to their more neutron rich neighbours and lack charged particle emission suitable for recoil-decay-tagging. Subsequent experiments to ref.

Prompt and delayed γ rays from in 191,193Bi have been identified using the recoil‐decay tagging (RDT), isomer tagging, and recoil gating techniques, resulting in extensive level schemes for both nuclei. Excitation energies of the isomeric 13/2+ states have been established and rotational bands based on them have been observed. The nearly spherical 9/2− ground‐state bands appear to be crossed by more deformed low‐lying structures. TRS calculations have been performed and B(M1)/B(E2) ratios have been extracted for the observed strongly‐coupled bands. In 193Bi, a 3 μs isomer has been interpreted as a h9/2 proton coupled to the 12+ state of the 192Pb core.

In-beam γ-ray spectroscopy measurements provide important information on coexisting normal and intruder configurations in lead nuclei. However, in these experiments the yrast states are preferentially populated so that in many cases nothing is known about non-yrast states that are essential for obtaining a fuller understanding. Complementary experiments designed to study fine structure in the a decays of polonium nuclei have led to the discovery of low-spin non-yrast states in the daughter lead nuclei, while higher-spin states can be identified through the γ decays of isomeric states. The α-decay studies have the additional benefit of allowing information on configuration mixing in the polonium parents to be deduced from the measured hindrance factors.

Shape coexistence is well known to occur in nuclei, in particular near closed shells [1], where particle-hole excitations across the shell gap can create deformed intruder states. In the neutron-deficient lead isotopes (Z = 82), deformed structures appear at low excitation energy. The isotope 188Pb [2] shows for example a triple shape coexistence with oblate and prolate excited 0+ states that compete with the spherical ground state. The study of the odd-proton single-particle excitations in Bi isotopes allows to obtain information on the orbitals involved in the different shapes observed in this mass region.

Several technical developments have recently taken place at the RITU [1] focal plane detector system. Due to these developments the gas-filled recoil separator RITU is now, in the best case, up to an order of magnitude more sensitive than before.

Excited states in the neutron-deficient isotope Os-169 have been identified for the first time in an experiment using the Jurosphere gamma-ray spectrometer in conjunction with the Ritu gas-filled r ...

The spectrum of prompt conversion electrons emitted by excited 2 5 4 No nuclei has been measured, revealing discrete lines arising from transitions within the ground state band. A striking feature is a broad distribution that peaks near 100 keVand comprises high multiplicity electron cascades, probably originating from Ml transitions within rotational bands built on high K states.