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We present a review of the formalism and give some of the applications of polarization potentials in heavy ion scattering, placing special attention on the contributions of Prof. Mahir Hussein to the field. In particular, we discuss Feshbach’s formalism and show its applications to the case of coupling to rotational and vibrational states, in both the quantum mechanical and semiclassical cases.

The deexcitation of the primary hot fragments, produced in the breakup of an excited nuclear source, during their propagation under the influence of their mutual Coulomb repulsion is studied in the framework of a recently developed hybrid model. The latter is based on the Statistical Multifragmentation Model (SMM), describing the prompt breakup of the source, whereas the particle emission from the hot fragments, that decay while traveling away from each other, is treated by the Weisskopf-Ewing evaporation model. Since this treatment provides an event by event description of the process, in which the classical trajectories of the fragments are followed using molecular dynamics techniques, it allows one to study observables such as two-particle correlations and infer the extent to which the corresponding observables may provide information on the multifragment production mechanisms. Our results suggest that the framework on which these treatments are based may be considerably constrained by such analyses. They imply that information obtained from these model calculations may provide feedback to the theory of nuclear interferometry. In particular, our results do not support the hypothesis that the total momentum of the selected pair of particles used in the two-particle correlations remains constant during the post-breakup dynamics. Furthermore, the correlations may be appreciably affected by this fact. We also found that neutron deficient fragments should hold information more closely related to the breakup region than neutron rich ones, as they are produced in much earlier stages of the post breakup dynamics than the latter.

Considering an entropy-based division of energy transferred into heat and work, we develop an alternative theoretical framework for the thermodynamic analysis of two-level systems. When comparing these results with those obtained using the standard definitions of these quantities, we observe the appearance of a different term of work, which represents the energy cost of rotating the Bloch vector in the presence of the external field that defines the local Hamiltonian. Additionally, we obtain explicit expressions for the temperature, the heat capacity, and the internal entropy production of the system in both paradigms. In order to illustrate our findings we study, from both perspectives, matter-radiation interaction processes for two different systems.

An explicit expression for the temperature of an open two-level quantum system is obtained as a function of local properties, under the hypothesis of weak interaction with the environment. This temperature is defined for both equilibrium and out-of-equilibrium states, and coincides with the environment temperature if the system reaches thermal equilibrium with a heat reservoir. Additionally, we show that within this theoretical framework the total entropy production can be partitioned into two contributions: one due to heat transfer, and another, associated to internal irreversibilities, related to the loss of internal coherence by the qubit. The positiveness of the heat capacity is established, as well as its consistency with the well known results at thermal equilibrium. We apply these concepts to two different systems, and show that they behave in analogous ways as their classical counterparts.

We explore the energy cost of the information loss resulting from the passage of an initial density operator to a reduced one. We use the concept of entanglement temperature in order to obtain a lower bound for the energy change associated with this operation. We determine the minimal energy required for the case of the information losses associated with the trace over the space coordinates of a two-dimensional quantum walk.

Bacterial quorum sensing is the communication that takes place between bacteria as they secrete certain molecules into the intercellular medium that later get absorbed by the secreting cells themselves and by others. Depending on cell density, this uptake has the potential to alter gene expression and thereby affect global properties of the community. We consider the case of multiple bacterial species coexisting, referring to each one of them as a genotype and adopting the usual denomination of the molecules they collectively secrete as public goods. A crucial problem in this setting is characterizing the coevolution of genotypes as some of them secrete public goods (and pay the associated metabolic costs) while others do not but may nevertheless benefit from the available public goods. We introduce a network model to describe genotype interaction and evolution when genotype fitness depends on the production and uptake of public goods. The model comprises a random graph to summarize the possible evolutionary pathways the genotypes may take as they interact genetically with one another, and a system of coupled differential equations to characterize the behavior of genotype abundance in time. We study some simple variations of the model analytically and more complex variations computationally. Our results point to a simple trade-off affecting the long-term survival of those genotypes that do produce public goods. This trade-off involves, on the producer side, the impact of producing and that of absorbing the public good. On the non-producer side, it involves the impact of absorbing the public good as well, now compounded by the molecular compatibility between the producer and the non-producer. Depending on how these factors turn out, producers may or may not survive., Comment: Figure fonts are corrected in this version

We explore the notion of generated entropy in open quantum systems. We focus on the study of the discrete-time quantum walk on the line, from the entropy production perspective. We argue that the evolution of the coin can be modeled as an open two-level system that exchanges energy with the lattice at some effective temperature that depends on the initial state. The entropy balance shows that there is a positive entropy production during the evolution, in accordance with the second law of thermodynamics.

Collective rotational bands were observed for the first time in neutron-rich odd–odd [Formula: see text]La by means of [Formula: see text]-[Formula: see text]-[Formula: see text] and [Formula: see text]-[Formula: see text]-[Formula: see text]-[Formula: see text] coincidence measurements of prompt fission [Formula: see text] rays from [Formula: see text]Cf using multi-detector array Gammasphere. Similarity between the yrast band of [Formula: see text]La and those of neighboring [Formula: see text]La, [Formula: see text]Ce was found and interpreted as quasiparticle excitations. PES calculations suggested triaxial deformation for the ground state of 142La. Considerable triaxial and near zero octupole deformations were deduced for the yrast band of [Formula: see text]La by the TRS model calculations. The band-crossing observed in the yrast band of [Formula: see text]La was interpreted to be caused by alignment of the (h[Formula: see text])2 proton pair, and the crossing frequency was best reproduced by the TRS calculations taking into account triaxial deformations. In contrast to the interpretations for the band crossing of [Formula: see text]La, alignments of the (i[Formula: see text])2 neutron pair were found to be responsible for the band-crossing of the yrast band in the neighboring even-N [Formula: see text]La, and triaxial degree of freedom was found to play a more significant role than octupole deformations in the nucleus, although its [Formula: see text] values deduced are large.

We study, from a thermodynamic perspective, the equilibrium states of a qubit interacting with an arbitrary environment of dimension N>>2. We show that even in presence of memory about the initial state, in some cases the qubit can be considered in a thermal state characterized by an entanglement Hamiltonian, which encodes the effects of the environment, and an initial-state- dependent entanglement temperature that measures the degree of entanglement generated between the system and its environment. Geometrical aspects of the thermal states are studied, and the results are confirmed for the concrete case of the Quantum Walk on the Line., 3 figures

We use an improved version of the semiclassical method described in Refs. [1,2,3] to evaluate fusion cross sections in collisions of weakly bound nuclei. This version takes into account the static effects of the low breakup threshold, uses better bin states in the discretization of the continuum and avoids the excitation of closed channels. The population of these channels is a consequence of the violation of energy conservation, which is inherent in the semiclassical method. The method is employed to evaluate complete fusion and total fusion cross section in collisions of the weakly bound 6,7Li projectiles with 159Tb and 197Au targets, for which data is available. The overall agreement between theory and experiment is fairly good., 12 pages, 3 figures

We carefully compare the one-dimensional WKB barrier tunneling model, and the one-channel Sch\"odinger equation with a complex optical potential calculation of heavy-ion fusion, for a light and a heavy system. It is found that the major difference between the two approaches occurs around the critical energy, above which the effective potential for the grazing angular momentum ceases to exhibit a pocket. The value of this critical energy is shown to be strongly dependent on the nuclear potential at short distances, on the inside region of the Coulomb barrier, and this dependence is much more important for heavy systems. Therefore the nuclear fusion process is expected to provide information on the nuclear potential in this inner region. We compare calculations with available data to show that the results are consistent with this expectation., Comment: 12 pages, 7 figures

The genetic material of a eukaryotic cell (one whose nucleus and other organelles, including mitochondria, are enclosed within membranes) comprises both nuclear DNA (ncDNA) and mitochondrial DNA (mtDNA). These differ markedly in several aspects but nevertheless must encode proteins that are compatible with one another for the proper functioning of the organism. Here, we introduce a network model of the hypothetical coevolution of the two most common modes of cellular division for reproduction: by mitosis (supporting asexual reproduction) and by meiosis (supporting sexual reproduction). Our model is based on a random hypergraph, with two nodes for each possible genotype, each encompassing both ncDNA and mtDNA. One of the nodes is necessarily generated by mitosis occurring at a parent genotype, the other by meiosis occurring at two parent genotypes. A genotype's fitness depends on the compatibility of its ncDNA and mtDNA. The model has two probability parameters, $p$ and $r$, the former accounting for the diversification of ncDNA during meiosis, the latter for the diversification of mtDNA accompanying both meiosis and mitosis. Another parameter, $\ensuremath{\lambda}$, is used to regulate the relative rate at which mitosis- and meiosis-generated genotypes are produced. We have found that, even though $p$ and $r$ do affect the existence of evolutionary pathways in the network, the crucial parameter regulating the coexistence of the two modes of cellular division is $\ensuremath{\lambda}$. Depending on genotype size, $\ensuremath{\lambda}$ can be valued so that either mode of cellular division prevails. Our study is closely related to a recent hypothesis that brings mitochondria to the center stage and views the appearance of cellular division by meiosis, as opposed to division by mitosis, as an evolutionary strategy for boosting ncDNA diversification to keep up with that of mtDNA. Our results indicate that this may well have been the case, thus lending support to the first hypothesis in the field to take into account the role of such ubiquitous and essential organelles as mitochondria.

The scattering of identical nuclei at low energies exhibits conspicuous Mott oscillations which can be used to investigate the presence of components in the predominantly Coulomb interaction arising from several physical effects. It is found that at a certain critical value of the Sommerfeld parameter the Mott oscillations disappear and the cross section becomes quite flat. We call this effect Transverse Isotropy (TI). The critical value of the Sommerfeld parameter at which TI sets in is found to be $\eta_{c} = \sqrt{3s +2}$, where $s$ is the spin of the nuclei participating in the scattering. No TI is found in the Mott scattering of identical Fermionic nuclei. The critical center of mass energy corresponding to $\eta_c$ is found to be $E_c$ = 0.40 MeV for $\alpha + \alpha$ (s = 0) , 1.2 MeV for $^{6}$Li + $^{6}$LI (s = 1) and 7.1 MeV for $^{10}$B + $^{10}$B (s = 3). We further found that the inclusion of the nuclear interaction induces a significant modification in the TI. We suggest measurements at these sub-barrier energies for the purpose of extracting useful information about the nuclear interaction between light heavy ions. We also suggest extending the study of the TI to the scattering of identical atomic ions., Comment: 9 pages, one figure, To be published in a special issue of Few Body Systems, "Weakly Bound Exotic Nuclei: Challenges for structure and reactions". This special issue is dedicated to the proceedings of a Workshop on Weakly-Bound Exotic Nuclei,Sunday, May 24 - Saturday, May 30, 2015 Natal, RN - Brazi

In this Report we give a balanced account of the experimental and theoretical advances acquired over the last decade in the field of near-barrier fusion reactions induced by weakly bound stable and unstable nuclei. The elastic scattering and breakup reactions of these systems are also extensively reviewed as they play an important role in the fusion process. We review several theoretical tools used in the description of the data. The concepts of Complete Fusion (CF), Incomplete Fusion (ICF) and Total Fusion (TF), which is the sum of CF and ICF, are discussed and recent work on the calculation of these quantities is reviewed. The Continuum Discretized Coupled Channels (CDCC) method and its semiclassical version are described in detail and their limitations are pointed out. More importantly, we describe the salient features of the conclusions reached from the more than 40 measurements made, over a decade, of near-barrier fusion, elastic scattering and breakup reactions, and confront these data with the CDCC or other methods appropriate for these processes at the energy regime in question.

Numerical semiclassical calculations are carried out to study the angular distribution of deuterons from the p,d pickup reaction of 25 MeV protons incident on the nucleus $^{156}\mathrm{Gd}$ and also its proton elastic scattering. It is found that, due to the rapid fall of the real optical potential in the vicinity of the target nucleus, the classical trajectories are very sensitive to the proton impact parameters. A selection of 276,983 trajectories is used for protons with impact parameters ${b}_{\mathrm{p}}$ satisfying $7.23018\phantom{\rule{0.16em}{0ex}}\mathrm{fm}\ensuremath{\le}{b}_{\mathrm{p}}\ensuremath{\le}10\phantom{\rule{0.16em}{0ex}}\mathrm{fm}$ with steps of ${10}^{\ensuremath{-}5}\phantom{\rule{0.16em}{0ex}}\mathrm{fm}$. Using the imaginary part of the optical potential for protons, a simple quantum approach is constructed to evaluate the probability of a surviving proton throughout its path. In addition, a simple three-body quantum approach is developed to calculate the probability of a neutron transfer by a surviving proton at closest approach. The formed deuteron is then allowed to start its trajectory while keeping its identity until detected. Throughout this journey, the deuteron trajectory is under the influence of its Coulomb and real optical potential, while its absorption is determined by the imaginary optical potential component. Within estimated uncertainties, the resulting theoretical angular distribution achieves a comparable fit with experimental results for the angular momentum transfer $\mathrm{L}=0$ compared to other theoretical models, and concludes that the strong p,d cross sections are due to the dominant ${\mathrm{s}}_{1/2}$ component of the Nilsson ${\frac{1}{2}}^{+}[400]$ level in $^{155}\mathrm{Gd}$.

We investigate correlations in the fragment momentum distribution due to the propagation of fragments under the influence of their mutual Coulomb field, after the breakup of an excited nuclear source.The magnitude of the effects on the nuclear temperatures obtained from such distributions is estimated with the help of a simple approach in which a charged fragment interacts with a homogeneous charged sphere. The resuslts are used to correct the temperatures obtained from the asymptotic momentum distributions of fragments produced by a Monte-Carlo simulation in which the system's configuration at breakup is provided by the canonical version of the Statistical Multifragmentation Model. In a separate calculation, the dynamics of this many-particle charged system is followed in a molecular dynamics calculation until the fragments are far away from the breakup volume. The results suggest that, although the magnitude of the corrections is similar in both models, many-particle correlations present in the second approach are non-negligible and should be taken into account in order to minimize ambiguities in such studies., 7 pages, 4 figures

New level schemes of 112,114,115,116,117,118Pd are established by means of γ – γ – γ , γ – γ – γ – γ and γ – γ ( θ ) measurements of prompt fission γ rays from 252Cf using the Gammasphere multi-detector array. Spins/parities were assigned to levels based on γ – γ angular correlation measurements, level systematics and decay patterns. In the even-N isotopes 112,114,116Pd, two sets of odd-parity bands were identified and extended with spins measured in each band. The odd-parity bands with large level staggerings were interpreted as disturbed chirality with less pronounced triaxial deformations in the Pd isotopes than observed in the chiral symmetry breaking 110,112Ru with maximum triaxiality. Onset of wobbling motion was identified from the sign of the signature splitting in the γ band of even–even 114Pd, and probably also in 116Pd, as first seen in the N = 68 isotone 112Ru. Maximal triaxiality in Ru and Pd isotopes is found to be reached for N = 68 , 112Ru and 114Pd, 4 neutrons more than predicted in the theoretical calculations. The new data and TRS calculations allowed a systematic study of the band crossings in the even-N 112,114,116Pd and odd-N 115,117Pd isotopes. Now we find a new overall, more complex shape evolution than previously proposed from triaxial prolate in 110Pd via triaxial oblate in 112Pd to nearly oblate in 114,116Pd with a large change of the triaxial deformation parameter γ toward nearly oblate in the ( π g 9 / 2 ) 2 alignment in 114,115,116,117,118Pd, and triaxial-prolate–triaxial-oblate shape coexisting bands in 115Pd.

International audience; The cross sections of elastic scattering and fusion of identical heavy ions with arbitrary spin, s are derived. Applications to several light heavy ions at near-barrier energies are made. It is found that the transverse isotropy; namely, the flat angular distribution which sets in at a critical value of the energy, becomes less pronounced with higher values of the spin. The oscillations in energy in the fusion cross section was found to go as 1/(2s+1). A similar factor is found in the angle-oscillating term in the elastic-scattering cross section.

The properties of the kinetic energy spectra of light isotopes produced in the breakup of a nuclear source and during the deexcitation of its products are examined. The initial stage, at which the hot fragments are created, is modeled by the Statistical Multifragmentation Model, whereas the Weisskopf-Ewing evaporation treatment is adopted to describe the subsequent fragment deexcita- tion, as they follow their classical trajectories dictated by the Coulomb repulsion among them. The energy spectra obtained are compared to available experimental data. The influence of the fusion cross-section entering into the evaporation treatment is investigated and its influence on the qual- itative aspects of the energy spectra turns out to be small. Although these aspects can be fairly well described by the model, the underlying physics associated with the quantitative discrepancies remains to be understood., Comment: 7 pages, 4 figures

The definition of entanglement temperature for the quantum walk on the line is extended to $N$-cycles, which are more amenable to a physical implementation. We show that, for these systems, there is a linear connection between the thermalization time and the mixing time, and also that these characteristic times become insensitive to the system size when $N$ is larger than a few units

A quasispecies is a set of interrelated genotypes that have reached a stationary state while evolving according to the usual Darwinian principles of selection and mutation. Quasispecies studies invariably assume that it is possible for any genotype to mutate into any other, but recent finds indicate that this assumption is not necessarily true. Here we revisit the traditional quasispecies theory by adopting a network structure to constrain the occurrence of mutations. Such structure is governed by a random-graph model, whose single parameter (a probability p) controls both the graph's density and the dynamics of mutation. We contribute two further modifications to the theory, one to account for the fact that different loci in a genotype may be differently susceptible to the occurrence of mutations, the other to allow for a more plausible description of the transition from adaptation to degeneracy of the quasispecies as p is increased. We give analytical and simulation results for the usual case of binary genotypes, assuming the fitness landscape in which a genotype's fitness decays exponentially with its Hamming distance to the wild type. These results support the theory's assertions regarding the adaptation of the quasispecies to the fitness landscape and also its possible demise as a function of p.

We demonstrate the close similarity of a generalized Fermi breakup model, in which densities of excited states are taken into account, to the microcanonical statistical multifragmentation model used to describe the desintegration of highly excited fragments of nuclear reactions., Comment: 19 pages, 2 figures

High-spin level schemes of 117,118,119,120,122 Cd are expanded by analyzing our high-statistics triple- and higher-fold coincidence events of prompt fission γ rays from 252 Cf at Gammasphere. Spin/parity assignments were made based on new γ – γ angular correlation measurements and level systematics in the neighboring isotopes. Stretch-aligned band structures observed in low-lying levels in 117,119,121 Cd are seen to weaken with increasing spins, with a quasi-rotational degree of freedom manifested at higher spins. The 5 − levels in even- N 118,120 Cd were tentatively interpreted as candidates of quadrupole–octupole (QOC) coupling. The model-independent spin versus ℏω curves for even- N and odd- N Cd isotopes imply quasi-rotational alignment of an h 11 / 2 neutron pair in the even- N Cd isotopes. The relative energies of the lowest 11 / 2 − , 9 / 2 − , 7 / 2 − , and 15 / 2 − levels in 117 Cd and 119 Cd suggest triaxial shapes based on Meyer-Ter-Vehn theory for these odd- N Cd nuclei. For the even- N Cd isotopes evidence of triaxiality may also be provided by the Shell Correction version of the Tilted Axis Cranking model (SCTAC).

Level schemes of even–even neutron-rich 88-92 Kr and 86 Se have been investigated by measuring triple-γ coincidence data from the spontaneous fission of 252 Cf with the Gammasphere detector array. The level scheme of 88 Kr has been extended up to 7169 keV state. Several new excited states with new transitions have been identified in 90,92 Kr and 86 Se . Spins and parities have been assigned to levels in these nuclei by following regional systematics and angular correlation measurements. The level structures of the N = 52, 54, Se , Kr , and Sr isotones are discussed.

The level scheme of odd-Z neutron-rich 141Cs (Z=55, N=86) was extended and expanded and that of 144Cs (N=89) was identified for the first time by means of γ–γ–γ coincidence measurements of prompt γ rays in the spontaneous fission of 252Cf with Gammasphere. Spin/parity was assigned to the levels based on angular correlations and level systematics in 141,143Cs. Parity doublets characteristic of both simplex quantum number s=+i and s=−i were proposed in 141Cs. The tests by using rotational frequency ratio ω−(I)/ω+(I) imply octupole vibrations in 141Cs and 143Cs. B(E1)/B(E2) values and electric dipole moments D0 were calculated for 141Cs, and re-determined for 143Cs. It was found that B(E1)/B(E2) values of 141Cs are simplex-dependent and the average value is one order of magnitude larger than that of 143Cs, and the deduced dipole moment D0 of 141Cs is considerably larger than that of 143Cs, and comparable to the N=86 isotone 142Ba. For 144Cs the yrast sequence looks like a well-deformed rotational band, but no octupole band structure was identified in this nucleus. The overall variations of D0 in 141,143,144Cs exhibit a pronounced drop of dipole moment with increasing neutron number in this odd-Z isotopic chain, which may be analogous in nature to the quenching of D0 observed in even–even 146Ba (Z=56, N=90) and 224Ra (Z=88, N=136), and to the drop of D0 in the odd-Z neutron-rich 147La (Z=57, N=90) reported by our collaboration.

The task of providing leading indicators of catastrophic regime shifts in ecosystems is fundamental in order to design management protocols for those systems. Here we address the problem of lake eutrophication (that is, nutrient enrichment leading to algal blooms) using a simple spatial lake model. We discuss and compare different spatial and temporal early warning signals announcing the catastrophic transition of an oligotrophic lake to eutrophic conditions. In particular, we consider the spatial variance and its associated patchiness of eutrophic water regions. We found that spatial variance increases as the lake approaches the point of transition to a eutrophic state. We also analyze the spatial and temporal early warnings in terms of the amount of information required by each and their respective forewarning times. From the consideration of different remedial procedures that can be followed after these early signals we conclude that some of these indicators are not early enough to avert the undesired impending shift.

High-spin, even-parity bands in neutron-rich 108, 110, 112 Ru nuclei were reinvestigated and considerably expanded by measuring many-fold prompt γ-ray coincidence events following the spontaneous fission of 252 Cf with Gammasphere. Our high statistics data allow us to detect weaker transitions and bands not previously published. Also, gamma branching ratios, which are important for theory, are carefully measured from all levels. In 110 Ru , we find a doubling of levels for both ground and quasi-gamma bands above the 8+ levels. There are likely two-phonon quasi-gamma bands in 110, 112 Ru , as well as a bandhead level in 108 Ru . The odd–even spin energy band staggering observed in the quasi-gamma bands in 108, 110, 112 Ru and the doubling of levels in 110 Ru present a challenge to theory.

Two similar sets of odd-parity bands are observed in each of three even–even neighbors, 108, 110, 112 Ru , from a study of prompt spontaneous-fission gamma rays at Gammasphere. A careful study of the odd-parity levels of these nuclei shows evidence for the features of chiral doubling. Comparisons are made with reported other candidates for chiral doubling.

The high-spin level schemes of odd–odd 100Nb ( Z = 41 , N = 59 ) and 148La ( Z = 57 , N = 91 ) were identified from γ – γ – γ coincidence studies of prompt γ rays in the spontaneous fission of 252Cf with Gammasphere. Spin/parity assignments for the levels in these two nuclei were made based on the low-lying levels assigned in decay work, on the internal conversion coefficient (ICC) measurements and the level systematics of the neighboring isotopes. A K π = 1 + deformed ground-state band was identified in 100Nb. The onset of ground-state deformation in Nb isotopes is found to take place at N = 59 , in contrast to N = 60 for Sr ( Z = 38 ), Y ( Z = 39 ) and Zr ( Z = 40 ) isotopes. Unlike the observation in 99Nb, the N = 56 subshell closure seems to be no longer dominant in 100Nb. The bands observed in 148La are interpreted as aligned coupling of [ π h 11 / 2 υ h 9 / 2 ] low J to the deformed core rotor.

The yrast and near-yrast level scheme of light neutron-rich 143La ( Z = 57 , N = 86 ) is reinvestigated and expanded and that of 144La ( N = 87 ) is proposed for the first time by measuring prompt γ rays from the spontaneous fission of 252Cf at Gammasphere. Spins/parities are assigned to the lowest-lying levels of 143,144La based on the early studies of β − decay, and the assignments for high-spin levels of 143,144La are made by measuring internal conversion coefficients and following the level systematics of the neighboring heavier La isotopes and even–even Ba and Ce nuclei. The B ( E 1 ) / B ( E 2 ) ratios, energy displacements δ E ( I ) and rotational frequency ratios ω − ( I ) / ω + ( I ) of the new parity-doublets of 143,144La indicate that octupole deformations/correlations also develop in these nuclei. The band-crossings observed in a rotational frequency range of 0.31 to 0.34 MeV for the two even-parity bands in 143La but being absent in 144La are interpreted as due to alignment of a pair of i 13 / 2 neutrons in 143La.

Rotational bands in 108,110,112Ru have been investigated by means of γ – γ – γ and γ – γ ( θ ) coincidences of prompt γ rays emitted in the spontaneous fission of 252Cf. The positive parity bands are described by different versions of IBA, where 108Ru is best described as a γ-soft nucleus whereas 110,112Ru are more like rigid triaxial rotors. New Δ I = 1 negative parity doublet bands are found. In case of 110,112Ru, these are interpreted as soft chiral vibrations. Many of the experimental findings can be explained by microscopic calculations that combine the TAC mean-field with random phase approximation but a simple geometrical explanation is not apparent.