Search

Excited states in the deformed nucleus 168Er have been studied with high energy resolution in the (p, t) reaction, with the Munich Q3D spectrograph. A large number of excited 0+ states (25) and 2+ states (64) have been assigned up to 4.0-MeV excitation energy. This allows detailed investigations along two directions of current interest: first, an extension of microscopic model interpretations into the region of medium level density above the pairing gap; second, a first analysis of the statistical fluctuation (order/chaos) properties of pure sequences of levels, in one deformed nucleus. Predictions of two models (the quasiparticle-phonon model and the projected shell model) are compared to the data, and it is concluded that, in both cases, mixing of more configurations is required in the wave functions.

The B(E2) excitation strength of the first excited 2(+) state in even-even nuclei should directly correlate with the size of the valence space and maximize at mid-shell. A previously found saturation of B(E2) strengths in well-deformed rotors at mid-shell is tested through high-precision measurements of the lifetimes of the lowest-lying 2(+) states of the Hf-168 and W-174 rare earth isotopes. Measurements were performed using fast LaBr3 scintillation detectors. Combined with the recently remeasured B(E2; 2(1)(+) -> 0(1)(+)) values for Hf and W isotopes the new data remove discrepancies observed in the differentials of B(E2) values for these isotopes.

Signatures of criticality in the evolution of the nuclear ground-state shapes across the NxZ plane are discussed. Attention is paid to specific data indicating sudden structural changes in various isotopic and isotonic chains of medium-mass and heavy even-even nuclei, as well as to diverse theoretical aspects of the models used to describe these changes. The interacting boson model and the geometric collective model, in particular, are discussed in detail, the former providing global predictions for the evolution of collective observables in nuclei between closed shells and the latter yielding a parameter-efficient description of nuclei at the critical points of shape transitions. Some issues related to the mechanism of first- and second-order quantum phase transitions in general many-body systems are also outlined.

Background: A recent survey of well-deformed rare earth nuclei showed that B(E2) values from the γ band to the ground band could be explained rather well by a parameter-free description in terms of a partial dynamical symmetry (PDS). Purpose: Our purpose in this paper is to extend this study to deformed and transitional nuclei in the actinide and A ~ 100 regions to determine if the success of the PDS description is general in medium- and heavy-mass nuclei and to investigate further where it breaks down. Method: As with the previous study we study the empirical relative B(E2 : γ to ground) values in comparison to a pure rotor (Alaga) model and to the SU(3) PDS. Results: The data for the actinides, albeit sparser than in the rare-earth region, are reasonably well accounted for by the PDS but with systematic discrepancies. For the Mo isotopes, the PDS improves on the Alaga rules but largely fails to account for the data. Conclusions: As in the rare earths, the parameter-free PDS gives improved predictions compared to the Alaga rules for the actinides. The differences between the PDS predictions and the data are shown to point directly to specific mixing effects. Finally, inmore » the Mo isotopes, their transitional character is directly seen in the large deviations of the B(E2) values from the PDS in the direction of the selection rules of the vibrator.« less

States in 162 Dy have been populated by ( n , γ ) , ( n , e − ) , and ( α , 2 n ) reactions in order to characterize a complete set of low K bands below 2 MeV. The ( n , γ ) and ( n , e − ) measurements were made using high precision curved crystal and β − spectrometers. Gamma–gamma coincidence and DCO measurements were made following the ( α , 2 n ) reaction using an array of Compton-suppressed Ge detectors. Using all these data and employing the Ritz combination principle, a level scheme was developed which represents one of the most complete and extensive spectra of levels available for comparison with nuclear models. The observed positive and negative parity bands are discussed in terms of collective quadrupole and octupole vibrational excitations as well as 2 quasi-particle excitations.

Measuring the neutron-induced fission cross-sections of short-lived nuclei represents an experimental challenge due to target activity and the low intensity of neutron beams. One way to alleviate the problems inherent in the direct measurement is to use the surrogate method, where one measures the decay probability of the same compound nucleus formed using a charged beam and a stable target. The decay probability of the compound nucleus is then used to estimate the neutron-induced cross-section. As an extension to the surrogate method, we introduce a new method of reporting the fission probabilities of two compound nuclei as a ratio, which has the advantage of removing most of the systematic uncertainties. The ratio method was checked in a known case, the 236U(n, f)/238U(n, f) cross-section ratio, which turned out to be the same as the probability ratio of P(236U(d, pf))/P(238U(d, pf)). As an application, the 237U(n, f)/235U(n, f) cross-section ratio was inferred, on the basis of the measured P(238U(d, d'f))/P(236U(d, d'f)) probability ratio.

Lifetimes for decays linking near-yrast states in 107Cd have been measured using the recoil distance method (RDM). The nucleus of interest was populated via the 98Mo(12C,3n)107Cd fusion–evaporation reaction at an incident beam energy of 60 MeV. From the measured lifetimes, transition probabilities have been deduced and compared with the theoretical B(E2) values for limiting cases of harmonic vibrational and axially deformed rotational systems. Our initial results suggest a rotor-like behaviour for the structure based on the unnatural-parity, h11/2 orbital in 107Cd, providing further evidence for the role of this 'shape-polarizing' orbital in stabilizing the nuclear deformation in the A ~ 100 transitional region.

The triaxial strongly deformed (TSD) bands in 167Lu were populated by the 123Sb(48Ca, 4n) reaction with a beam energy of 203 MeV. Gamma rays, requiring five fold or more in prompt coincidence, were detected with the Gammasphere spectrometer. Of particular interests are TSD bands 1 and 2 which have previously been interpreted as zero phonon and one phonon wobbling bands, respectively. Using the Doppler shift attenuation method (DSAM), a preliminary transition quadrupole moment of 6.9+0.3−0.3 eb was extracted for the TSD1 band. Data analysis continues for TSD2 which is considerably more weakly populated.

The puzzling nature of 0 + excitations, especially in transitional and deformed nuclei, has attracted new attention. Following a recent experiment studying 158 Gd, we investigated 15 additional nuclei in and near the rare earth region. Our aim was to map out the energies of as many 0 + states as possible. A series of (p, t) experiments was performed at the Q3D magnetic spectrograph at the University of Munich MP tandem accelerator laboratory. These reactions are particularly sensitive to 0 + states. Outgoing tritons were recorded at various lab angles, and their relative cross sections are compared to those calculated using the distorted wave Bom approximation (DWBA). The L = 0 angular distribution is easily discerned. New 0 + states are found in each of these nuclei, and their systematics are discussed.

Low-energy excited states of 210 Ra and 208 Ra were investigated at the Wright Nuclear Structure Laboratory of Yale University. Fusion evaporation recoils were selected using the gas-filled spectrometer, SASSYER. Delayed γ-rays, following isomeric decays, were detected at the focal plane of SASSYER with a small array of HPGe detectors. Transitions following the proposed J π = 8 + isomers were observed, and the half-lives measured. The experiments are discussed and results compared to expectations from the seniority scheme.

B(E2;0+1→2+1) values for the unstable, neutron-rich nuclei 132,134Te were determined through Coulomb excitation, in inverse kinematics, of accelerated beams of these nuclei. The systematics of measured B(E2) values from the ground state to the first excited state have been extended to the N=82 shell closure in the Te nuclei and have been compared with the predictions of different theories. The measurements were performed at the Holifield Radioactive Ion Beam Facility (HRIBF) using the GRAFIK detector. The success of this approach, which couples a 5.7% efficient through-well NaI(Tl) γ-ray detector with thin foil microchannel plate beam detectors, also demonstrates the feasibility for Coulomb excitation studies of neutron-rich nuclei even further from the valley of beta stability, both at present-generation ISOL facilities and at the proposed Rare Isotope Accelerator.

Experiments on exotic nuclei, in both “near” and “far” regions off stability, are discussed from the complementary standpoints of improvements in experimental techniques, on the one hand, and the exploitation of simple signatures of structure on the other.

The role of highly efficient detector systems and highly efficient signatures of structure in the study of exotic nuclei is discussed. The discovery of “critical point symmetries” in the study of phase transitional behavior in nuclei, with applications to unknown regions, is also discussed.

The Yale Rochester Array for SpecTroscopy, YRAST Ball, is described. Containing up to 30 Compton suppressed Ge detectors YRAST Ball is a powerful new array for c-ray spectroscopy. Several of its auxiliary detectors, including a multi-element solar cell array for heavy charged fragment detection and a new state of the art plunger system for recoil distance measurements are also described. ( 2000 Elsevier Science B.V. All rights reserved.

Different classes of evolutionary tracks in nuclear spherical-deformed transition regions are discussed. For each trajectory we associate a characteristic behavior for simple observables based on low-lying energy levels. The usefulness of this morphological classification for the study of exotic nuclei is stressed.

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}

Lifetimes of the 0 2 + and 2 γ + states in 154 Sm were measured using the Doppler-shift Attenuation Method following Coulomb excitation. The experiment employed the gamma-ray detector array YRAST Ball at Yale University in conjunction with an array of photo-electric cells. 154 Sm was identified as one of the few deformed nuclei where the first excited 0 + state is the β -vibration of the ground state. The 0 3 + level has no collective decay to the ground state band and is interpreted as a spherical shape coexisting state based on its decay properties and calculations in the framework of the interacting boson model (IBM) and geometric collective model (GCM).

Ultraprecise energies and absolute B(E2) values associated with K=0{sup +} excitations in {sup 158}Gd, measured with the GRID technique, reveal significant information relating to the possible existence or absence of two-phonon vibrational excitations in deformed nuclei. A strong B(E2:K=0{sub 2}{sup +}{r_arrow}{gamma}) is observed but reflects band mixing rather than a {gamma}{gamma} mode. For the K=0{sub 3}{sup +} band, measurement of precise {gamma} transition energies shows that suggested existing placements of strong deexcitation transitions are incorrect and that there is, again, no evidence for {gamma}{gamma}-phonon character in this band either. A weak B(E1:K=1{sup {minus}}{r_arrow}K=0{sub 1}{sup +}) value is interpreted in terms of the microscopic structure of K=0{sup {minus}} and K=1{sup {minus}} excitations. {copyright} {ital 1999} {ital The American Physical Society}

Cross sections for the (p,t) reaction to ground states of even-even nuclei from Zr to Hg are interpreted in a simple approach. They are shown to be sensitive both to the degree of shell filling (which is related to the number of L=0 pairs in the ground state) and to the difference in the number of these pairs between target and final nuclei (that is, to the overlap of the initial and final systems). The cross sections separate according to the two broad classes of nuclei{emdash}vibrational and rotational. The analysis is carried out in both a model-independent way and within the framework of the interacting boson approximation. thinsp {copyright} {ital 1998} {ital The American Physical Society}

Two techniques for determining B(E2:01+ → 21+) values using low-energy Coulomb excitation of Radioactive Nuclear Beams in inverse kinematics are presented. One method, applicable if the lifetime of the excited state is ∼1 ns, uses a linear array of NaI(Tl) detectors to measure the decay curve, and thus the 21+ state lifetime, for Coulomb excited radioactive beam nuclei as they decay in flight downstream from a carbon excitation target. In the second method, useful when lifetimes are short

The low energy octupole states in {sup 134}Ba were examined using the inelastic scattering of 22 MeV protons. Strong fragmentation of the low energy octupole strength, which was observed in {sup 196,198}Pt and was identified as a signature of the O(6) dynamical symmetry limit of the interacting boson approximation (IBA), does {ital not} occur in {sup 134}Ba, which has been proposed to have O(6) structure. The model calculations demonstrate that there is, in fact, little difference in the structure of the low-lying positive parity levels between certain nuclei in a U(5){r_arrow}SU(3) (vibrator{r_arrow}rotor) transition and an O(6) nucleus ({gamma}-soft nucleus), but that the octupole fragmentation has an enhanced sensitivity to the d-boson composition of the wave functions and thereby reveals differences in structure that are not easily discernible with other observables. {copyright} {ital 1997} {ital The American Physical Society}

Enhanced proton-neutron interactions occur in heavy nuclei along a trajectory of approximately equal numbers of valence protons and neutrons. This is also closely aligned with the trajectory of the saturation of quadrupole deformation. The origin of these enhanced p-n interactions is discussed in terms of spatial overlaps of proton and neutron wave functions that are orbit-dependent. It is suggested for the first time that nuclear collectivity is driven by synchronized filling of protons and neutrons with orbitals having parallel spins, identical orbital and total angular momenta projections, belonging to adjacent major shells and differing by one quantum of excitation along the z-axis. These results may lead to a new approach to symmetry-based theoretical calculations for heavy nuclei., 6 pages, 4 figures

Background: Low-lying octupole collective excitations play an important role in the description of the structure of nuclei in the actinide region. Ground state alternating parity rotational bands combining both positive and negative parity states are known in several nuclei. However, only recently it has been discovered in ${}^{240}$Pu an excited positive parity rotational band having an octupole nature and demonstrating strong anharmonicity of the octupole motion in the band head energies.Purpose: To suggest a model describing both ground state and excited alternating parity bands, which includes a description of the anharmonic effects in the bandhead excitation energies and can be used to predict the energies of the excited rotational bands of octupole nature and the $E1$ transition probabilities.Methods: The mathematical technique of the supersymmetric quantum mechanics with a collective Hamiltonian depending only on the octupole collective variable which keeps axial symmetry is used to describe the ground state and excited alternating parity rotational bands.Results: The excitation energies of the states belonging to the lowest negative parity and the excited positive parity bands are calculated for ${}^{232}$Th, ${}^{238}$U, and ${}^{240}$Pu. The $E1$ transition matrix elements are also calculated for ${}^{240}$Pu.Conclusions: It is shown that the suggested model describes the excitation energies of the states of the lowest negative parity band with the accuracy around 10 keV. The anharmonicity in the bandhead energy of the excited positive parity band is described also. The bandhead energy of the excited positive parity band is described with the accuracy around 100 keV.

Storage-ring mass spectrometry was applied to neutron-rich ${}^{197}$Au projectile fragments. Masses of ${}^{181,183}$Lu, ${}^{185,186}$Hf, ${}^{187,188}$Ta, ${}^{191}$W, and ${}^{192,193}$Re nuclei were measured for the first time. The uncertainty of previously known masses of ${}^{189,190}$W and ${}^{195}$Os nuclei was improved. Observed irregularities on the smooth two-neutron separation energies for Hf and W isotopes are linked to the collectivity phenomena in the corresponding nuclei.

Excited states in 132,134Nd were populated in the β+/e decay of 132,134Pm and studied through off-beam γ-ray spectroscopy. Level spins and multipole mixing ratios of transitions were determined through an angular correlation analysis. In 132Nd, a new excited 0+ state is identified and in 134Nd the level scheme is significantly extended. Differences in the location of the 02+ state and the γ bandhead above and below N=82 suggest that the lighter isotopes are much more γ-soft than the heavier Nd and that a first-order phase transitional description is not applicable in the N

Two measurements of $\ensuremath{\gamma}$ rays from the slow-neutron capture reaction on a $^{101}\mathrm{Ru}$ target were performed at the PF1B cold-neutron facility and the DuMond GAMma Spectrometer GAMS5 of ILL Grenoble, to study in detail excitations in the transitional nucleus $^{102}\mathrm{Ru}$. A band structure on top of the ${0}_{2}^{+}$ level has been identified and its nature is discussed. Mixing between the ${0}_{1}^{+}$ and ${0}_{2}^{+}$ levels in Ru isotopes with $50lNl66$ neutrons and its role in the development of deformation in the ground state of the Ru nuclei have been studied.

We studied ${0}^{+}$ states in ${}^{198}$Hg after the ${}^{200}$Hg${(p,t)}^{198}$Hg transfer reaction up to 3 MeV excitation energy. The experiment was performed using the high-resolution Q3D magnetic spectrograph at the Maier-Leibnitz Laboratory Tandem accelerator in Munich. In total, only four ${0}^{+}$ states were observed in ${}^{198}$Hg, significantly fewer than in other experiments of the $(p,t)$ transfer campaign. We discuss the low-energy ${0}^{+}$ state density as a function of the valence nucleon number ${N}_{\mathrm{val}}$ and test if the ${0}^{+}$ density can be used as a signature for the prolate-oblate shape-phase transition in the Hf-Hg region.

A recently proposed correlation of quasiground band energies in collective nuclei is shown to provide a highly sensitive indicator of different classes of nuclei and to lead to an empirical analytic formula for these energies. {copyright} {ital 1996 The American Physical Society.}

For the first time an ({ital n},{gamma}) reaction has been extensively studied using a large array of Compton-suppressed Ge detectors (the TESSA array). The nucleus {sup 168}Er was studied and the data show substantial improvement, in both quantity and quality, over previous coincidence data. Even though {sup 168}Er is perhaps the best studied deformed nucleus, over 250 new coincidence relations and a number of new levels in {sup 168}Er were disclosed, demonstrating the usefulness of this approach. Nuclear physics applications relate to the extension of nearly complete spectroscopy to higher excitation energies and to the study of statistical and chaotic features of the decay of low spin compound nuclear levels. {copyright} {ital 1996 The American Physical Society.}

We have made experimental measurements in {sup 170}Tm of the following: secondary {gamma} rays, conversion electrons, and {gamma}-{gamma} coincidences from thermal neutron capture in {sup 169}Tm, primary {gamma} rays from average resonance capture with 2-keV and 24-keV neutron beams, and proton spectra from the ({ital d},{ital p}) reaction on {sup 169}Tm. From these data and those of previous investigations, we have identified more than 130 excited levels in {sup 170}Tm below 1550 keV. Of these, 62 (with connecting transitions) are placed in 18 rotational bands with assigned Nilsson configurations. These results are in good agreement with a semiempirical modeling of {sup 170}Tm level structure. Values for seven Gallagher-Moszkowski splittings and four Newby shifts have been obtained. These matrix elements show remarkably good agreement with calculation. Among the observed {ital K}{sup {pi}}=1{sup {minus}} and 2{sup {minus}} rotational bands, configuration mixing appears to play a significant role. {copyright} {ital 1996 The American Physical Society.}

All known unique parity structures in precollective odd-A nuclei (having cores with E(4 1 + ) E(2 1 + ) ) are shown to behave similarly to the yrast quasibands in the neighboring even-even nuclei. This is interpreted in terms of a pair addition mode. With previous results on collective nuclei, this gives a tripartite classification of the evolution of the unique parity quasibands in odd-A nuclei. A simple index for signature splitting is also developed which avoids the need for complex analysis of Routhian structures.

It is shown that hexadecapole deformations can be estimated from B(E2; 21+ → 01+) values alone. Application of this method in the actinide nuclei gives semi-quantitative β4 values for 250,252Cf. A comparison with theoretical values provides general insight into the relative roles of shell gaps at Z = 114 and 126 which are important for the binding and stability of the heaviest nuclei.

A relation is presented stating that a sum of certain products of E2 matrix elements connecting the 0+ and 2+ levels in the ground, β-, and γ-bands in the limit of strong quadrupole deformation vanishes. As a consequence β → g E2 matrix elements are much smaller than β → γ matrix elements, contrary to the naive expectation based on the vibrational picture of independent β and γ excitations. This relation is supported by experimental data on deformed nuclei, and suggests a re-examination of the traditional understanding of these basic collective modes and their inter-relationships.

The Coulomb excitation of a very neutron-rich nucleus 32Mg to its 2+ state was studied using an unstable nuclear beam of 32Mg at 49.2 MeV/u with a 208Pb target. The B(E2) value of 454±78 e2fm4 was extracted by a coupled channel analysis. The value is in good agreement with recent predictions. It confirms a large deformation for 32Mg suggested by the low excitation energy of the 2+ state, and points to the vanishing of the N = 20 shell gap.

The distribution of rotational energy spacings for low-spin yrast states in over two thousand pairs of deformed rare-earth even-even nuclei are studied to determine key factors that correlate with the moments of inertia. Nuclei with near identical [ital P] values ([ital P]=[ital N][sub [ital p]]N[sub [ital n]]/[[ital N][sub [ital p]]+[ital N][sub [ital n]]] where [ital N][sub [ital p]] and [ital N][sub [ital n]] are the numbers of valence protons and valence neutrons) are more than an order of magnitude more likely to show near identical bands than nuclei with different [ital P] values. This is, by far, the highest correlation found: no other variable is even 20% as effective. The statistical significance of these large [ital P] enhancements and the special relation between [ital P] and ground-state mean-field structures is confirmed by a complementary analysis of negative parity near identical bands, which show no [ital P] enhancement at all.

The structure of $^{122}\mathrm{Cd}$ was studied through the decay of $^{122}\mathrm{Ag}$ by \ensuremath{\gamma}-\ensuremath{\gamma} coincidences, \ensuremath{\gamma}-ray angular correlations, and \ensuremath{\beta}-\ensuremath{\gamma}-\ensuremath{\gamma} fast electronic scintillation timing (FEST) measurements. The phonon and intruder structure of the ${0}^{+}$ states is discussed. The energy systematics of the low-lying levels in the Cd isotopes exhibits two distinct patterns, one minimizing at midshell, one somewhat later.

We show that δVpn values in the rare earth region show peaks, reminiscent of the spikes at N = Z in light nuclei, but occurring at Nval ∼ Zval. These peaks, evident for both even and odd Z values, are interpreted in terms of large spatial overlaps of respective proton and neutron wave functions whose Nilsson quantum numbers are related by δK[δN,δnz,δΛ] = 0[110[. That is, the wave functions differ only by a single oscillator quantum in the z-direction. The implications of this for the development of collectivity and deformation in heavy nuclei, and the locus of this development, are discussed.

It is shown that the remarkable nearly-universal anharmonic vibrator behavior recently discovered for yrast states in collective non-rotational nuclei is naturally reproduced by the IBA. The results shed light on the microscopic basis for the IBA.

Extremely high statistics \ensuremath{\gamma}-\ensuremath{\gamma} coincidence data for $^{168}\mathrm{Er}$ have been recorded following thermal neutron capture on $^{167}\mathrm{Er}$. The results alter considerably recent experimental and theoretical work on $^{168}\mathrm{Er}$ and affect conclusions concerning the quality of the K quantum number in the neutron resonance region: earlier claims that K remains good and that this energy region is nonchaotic are shown to be based in part on band assignments that need to be seriously reexamined.

The transient-field-perturbed angular correlation technique was used with Coulomb excitation in inverse kinematics to perform a systematic measurement of the $g$ factors of the first excited ${2}_{1}^{+}$ states in the stable even-$A$ isotopes $^{96\ensuremath{-}104}\mathrm{Ru}$. The measurements have been made relative to one another under matched kinematic conditions and include a measurement of $g({2}_{1}^{+})=+0.47(3)$ in $^{96}\mathrm{Ru}$.

The energies of [Formula: see text] states in even-even nuclei from Dy to W are shown to be linear in the P-factor and can be described using the same slope prescription for all these nuclei. Deviations are found for Os and Pt isotopes with Np. The results for N>104 give evidence for a more complex structural evolution beyond midneutron shell.

The 2-tracked empirical correlation between B (E2; 2 1 + → 0 1 + ) and E(4 1 + )/E(2 1 + ) values is shown to exemplify the different ways yrast transition rates and energy levels sample collectivity. Model calculations for transitional nuclei show that this correlation provides a simple new signature to distinguish the two principal classes of nuclear shape transitions.

The lifetimes of the lowest ${3}^{\mathrm{\ensuremath{-}}}$ and ${1}^{\mathrm{\ensuremath{-}}}$ states in $^{148\mathrm{\ensuremath{-}}152}\mathrm{Sm}$ have been determined employing the gamma-ray-induced Doppler broadening technique. The B(E1;${3}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${2}^{+}$) transition rates are compared to the corresponding B(E1;${1}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${0}^{+}$) values and interpreted in the framework of the interacting boson approximation sdf model. The qualitative behavior of these absolute transition rates can be understood in a simple physical picture by considering only the one-body part in the E1 transition operator. A more complex form including two-body terms is needed to explain simultaneously all available experimental data related to these levels.

Level lifetimes were measured for the first time for the neutron-rich isotope $^{78}\mathrm{Ge}$ by the fast electronic scintillation timing technique and B(E2) values were extracted. The energies of the low-lying states and the B(E2) values between the ${0}^{+}$ and ${2}^{+}$ states disclose a rapidly changing structure near N=40, followed by a stabilization, with $^{74\mathrm{\ensuremath{-}}78}\mathrm{Ge}$ best understood as asymmetric rotors.

Excited states in $^{192}\mathrm{Pt}$ and $^{194}\mathrm{Pt}$ have been studied with high-energy resolution, in the ($p,t$) reaction, by using the Q3D magnetic spectrograph at the Munich MP tandem accelerator. Outgoing tritons were recorded at laboratory angles sensitive to the unique shape of the $L=0$ angular distribution. Sets of previously unknown ${0}^{+}$ states were identified up to an energy of $~3 \mathrm{MeV}$. The ${0}^{+}$ states in $^{192,194}\mathrm{Pt}$ are discussed in the context of the evolution of intruder states and shape coexistence in the light Pt isotopes.

Mass measurements of neutron-rich Cd and Ag isotopes were performed with the Penning trap mass spectrometer ISOLTRAP. The masses of ${}^{112,114\ensuremath{-}124}$Ag and ${}^{114,120,122\ensuremath{-}124,126,128}$Cd, determined with relative uncertainties between $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ and $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$, resulted in significant corrections and improvements of the mass surface. In particular, the mass of $^{124}\mathrm{Ag}$ was previously unknown. In addition, other masses that had to be inferred from $Q$ values of nuclear decays and reactions have now been measured directly. The analysis includes various mass differences, namely the two-neutron separation energies, the applicability of the Garvey-Kelson relations, double differences of masses $\ensuremath{\delta}{V}_{\mathit{pn}}$, which give empirical proton-neutron interaction strengths, as well as a comparison with recent microscopic calculations. The $\ensuremath{\delta}{V}_{\mathit{pn}}$ results reveal that for even-even nuclides around $^{132}\mathrm{Sn}$ the trends are similar to those in the $^{208}\mathrm{Pb}$ region.