Cluster Emission Research Articles

Improved nucleus–nucleus folding potential with a repulsive core due to the change of intrinsic kinetic energy

The change in the internal kinetic energy (KE) of two interacting nuclei grows by increasing their density overlap. We investigated to what extent the double-folding potential based on the density dependent M3Y nucleon–nucleon interaction can be improved by considering this repulsive KE. We adopted the α-decay of , the 24Ne decay of 232U, and the fusion cross section as examples of reactions involving density redistribution. We performed the α and cluster decay calculations based on solving the Schrödinger equation to find the wavefunction and the penetration probability. Upon normalizing the calculated KE by applying the Bohr–Sommerfeld quantization condition, the necessary missed pocket is physically developed in the internal region of the total folding potential. The folding potential improved by considering the pivotal repulsive KE reduced the uncertainty inherent in the decay calculations at small internuclear distances. The calculated fusion cross section is substantially improved and its steep falloff at sub-barrier energies is reasonably reproduced.

Yield characteristics of cherry tomato cultivated with and without shading screen at different irrigation levels

ABSTRACT The use of shading screen in vegetable crops sensitive to the radiation excess, associated with the effective water use via irrigation, allows for yield gains. This study aimed to evaluate the yield characteristics of cherry tomato cultivated with and without shading screen and different irrigation levels. A randomized block design was used, in a 4 x 2 factorial arrangement, with four irrigation levels (140 %, 160 %, 180 % and 200 % of the reference evapotranspiration - ETo) and two cherry tomato hybrids (Wanda and Dolcetto). The irrigation level corresponding to 200 % of the ETo provided the highest values for number of flowers and clusters formed, number of fruits per plant and fruit diameter. The Wanda hybrid was more fruitful, with a higher emission of clusters, while Dolcetto was more floriferous. The use of shade screen for cultivating cherry tomato provides an increase in the yield characteristics, if compared to the cultivation in open areas.

Emission and Emissive Mechanism of Nonaromatic Oxygen Clusters.

Nonaromatic luminophores without remarkable conjugates have aroused great attention. Their emission mechanism, however, remains an open question. Meanwhile, previous studies generally focus on aliphatic amine and/or carbonyl-containing systems; those with merely oxygen moieties (i.e., ether, hydroxyl) are scarcely touched. Recently, the clustering-triggered emission (CTE) mechanism is proposed to rationalize the emission of nonconventional luminophores, according to which compounds bearing purely oxygen moieties can also be emissive. To check this conjecture, herein, both nonaromatic compound of xylitol and polymers of PEG and F127 are studied, which are found to be emissive in concentrated solutions and solids. Furthermore, cryogenic-persistent phosphorescence of the compounds and even persistent room temperature phosphorescence of xylitol crystals are observed. Additionally, their potential application as Fe3+ sensors is demonstrated. These results not only verify the rationality of the CTE mechanism but also suggest the possibility to discover and design new luminophores according to it.

Interaction of anionic tin clusters Snn−, n = 7 − 75 with electrons – polyanion production and cluster decay

Size-selected monoanionic tin clusters Snn−, n = 7 − 75, are stored simultaneously with electrons in a Penning trap to produce poly-anionic clusters by electron attachment. In addition to doubly and triply charged clusters with the size of the precursors, fragments such as Sn−n−7, Sn−n−10 or Snn−15 are observed in the lower size range (n ≲ 50). The latter come along with the clusters Sn−10 and Sn−15, probably due to fission of doubly charged clusters as in the case of the group-14 neighbor-element lead [Konig et al., Phys. Rev. Lett. 120, 163001 (2018)]. Furthermore, prominent doubly charged products Sn2−n−15 seem to be produced by break-off of neutral decamers, a feature not yet observed for any other dianionic cluster. In addition, while almost no monomer evaporation is observed for singly charged clusters, this process does occur for doubly charged ones.

Nuclear surface energy coefficients in cluster decay

The influence of different nuclear surface energy coefficients of the proximity potential in cluster decay of heavy, unstable radioactive nuclei is studied using a fission model by incorporating the preformation probability as the penetration probability of the overlapping region. An expression for preformation probability is fitted for preformation values, for which best matching is noted between calculated and experimental half-lives and is used in further calculations of cluster decay of superheavy elements. Half-lives for heavy cluster emission such as Ar, Ca, Ti, Cr, Fe, Co, Ni, Zn, Ga, Ge and Se, from superheavy nuclei with mass number in the range $ 252 \leq A \leq 294$ are predicted using the fitted expression for preformation probability. Predicted half-lives of heavy particle decay of superheavy nuclei compare well with the other prediction for a few clusters. Alpha decay being the predominant decay mode of heavy and superheavy nuclei, half-lives of heavy and superheavy nuclei are also calculated. Calculated half-lives of alpha decay for superheavy nuclei better reproduce the experimental values.

Dust in galaxy clusters: Modeling at millimeter wavelengths and impact on Planck cluster cosmology

We have examined dust emission in galaxy clusters at millimeter wavelengths using the Planck 857 GHz map to constrain the model based on Herschel observations that was used in studies for the Cosmic ORigins Explorer (CORE) mission concept. By stacking the emission from Planck-detected clusters, we estimated the normalization of the infrared luminosity versus mass relation and constrained the spatial profile of the dust emission. We used this newly constrained model to simulate clusters that we inject into Planck frequency maps. The comparison between clusters extracted using these gas+dust simulations and the basic gas-only simulations allows us to assess the impact of cluster dust emission on Planck results. In particular, we determined the impact on cluster parameter recovery (size, flux) and on Planck cluster cosmology results (survey completeness, determination of cosmological parameters). We show that dust emission has a negligible effect on the recovery of individual cluster parameters for the Planck mission, but that it impacts the cluster catalog completeness, reducing the number of detections in the redshift range [0.3–0.8] by up to ∼9%. Correcting for this incompleteness in the cosmological analysis has a negligible effect on cosmological parameter measurements: in particular, it does not ease the tension between Planck cluster and primary cosmic microwave background cosmologies.

First results from the IllustrisTNG simulations: radio haloes and magnetic fields

We introduce the IllustrisTNG project, a new suite of cosmological magnetohydrodynamical simulations performed with the moving-mesh code AREPO employing an updated Illustris galaxy formation model. Here we focus on the general properties of magnetic fields and the diffuse radio emission in galaxy clusters. Magnetic fields are prevalent in galaxies, and their build-up is closely linked to structure formation. We find that structure formation amplifies the initial seed fields ($10^{-14}$ comoving Gauss) to the values observed in low-redshift galaxies ($1-10\,\mu{\rm G}$). The magnetic field topology is closely connected to galaxy morphology such that irregular fields are hosted by early-type galaxies, while large-scale, ordered fields are present in disc galaxies. Using two simple models for the energy distribution of relativistic electrons we predict the diffuse radio emission of $280$ clusters with a baryonic mass resolution of $1.1\times 10^{7}\,{\rm M_{\odot}}$, and generate mock observations for VLA, LOFAR, ASKAP and SKA. Our simulated clusters show extended radio emission, whose detectability correlates with their virial mass. We reproduce the observed scaling relations between total radio power and X-ray emission, $M_{500}$, and the Sunyaev-Zel'dovich $Y_{\rm 500}$ parameter. The radio emission surface brightness profiles of our most massive clusters are in reasonable agreement with VLA measurements of Coma and Perseus. Finally, we discuss the fraction of detected extended radio haloes as a function of virial mass and source count functions for different instruments. Overall our results agree encouragingly well with observations, but a refined analysis requires a more sophisticated treatment of relativistic particles in large-scale galaxy formation simulations.

Investigations of the synthesis of the superheavy element Z=122

We have identified the most probable projectile-target combination by studying the fusion cross section, evaporation residue cross section, compound nucleus formation probability (${P}_{\mathrm{CN}}$), and survival probability (${P}_{\mathrm{Surv}}$) of different projectile target combinations to synthesize the superheavy element $Z=122$. The selected most probable projectile-target combinations to synthesize the superheavy element $Z=122$ are $\mathrm{Cr}+\mathrm{Cf}$, $\mathrm{Fe}+\mathrm{Cm}$, $\mathrm{Se}+\mathrm{Ra}$, and $\mathrm{As}+\mathrm{Ac}$. Superheavy nuclei may decay through the different decay modes such as spontaneous fission, ternary fission, and cluster decay. We have also studied the half-lives of spontaneous fission, ternary fission, and cluster decay of the predicted nuclei for $Z=122$ and compared with that of alpha decay. This enables us to study the competition between spontaneous fission, ternary fission, cluster decay, and alpha decay in the superheavy nuclei of $Z=122$. The comparision of half lives for different decay modes reveals that alpha decay is having smaller half lives than the other studied decay modes. A detail study of branching ratio of alpha decay with respect to other decay modes also confirms that alpha decay is most dominant decay mode for the isotopes superheavy nuclei $^{307--314}122$ and hence these nuclei can be detected through the alpha decay mode only. We hope that our predictions may be guide for the future experiments in the synthesis of more isotopes of superheavy nuclei $\mathrm{Z}=122$.

Orbital Decay of Globular Clusters in the Galaxy with Little Dark Matter

Abstract Recently, van Dokkum et al. presented an important discovery of an ultra-diffuse galaxy, NGC1052-DF2, with a dark matter content significantly less than predicted from its stellar mass alone. The analysis relies on measured radial velocities of 10 globular clusters (GCs), of estimated individual masses of a few ×106 M ⊙. This is about 1% of the inferred mass of NGC1052-DF2 of 2 × 108 M ⊙ within a half-light radius, R e = 2.2 kpc. The large relative mass and the old age of these objects imply that they might be susceptible to orbital decay by dynamical friction. Using analytic estimates and N-body simulations of an isolated system matching the inferred mass profile of NGC1052-DF2, we show that the orbits of the most massive GCs should already have decayed on a timescale of a few Gyrs. These findings should help in constraining mass profile and formation scenarios of NGC1052-DF2.

Optimization of acoustic emission parameters to discriminate failure modes in glass–epoxy composite laminates using pattern recognition

In this article, to overcome the challenges encountered during the discrimination of various failure modes in post impacted/indented glass-fiber-reinforced plastic, techniques like pattern recognition method and advanced signal processing were employed. The significant acoustic emission parameters such as amplitude, rise time, counts, energy, duration, and peak frequency that are acquired during compression after impact test are considered as inputs to cluster validity index and for various clustering techniques such as k-means, fuzzy C-means, and Kohonen’s self-organizing map. The acoustic emission count–frequency and amplitude–frequency have no overlapping, whereas other combinations of acoustic emission parameters result in overlapping with four clusters. The clustering techniques are validated by discrete wavelet transform of acoustic emission signals. The discrete wavelet transform was performed on the clustered acoustic emission signals to identify the percentage of energy and frequency content of each level which correlates the different failure modes. The results infer that k-means, fuzzy C-means clustering, and Kohonen’s self-organizing map are 94.5%, 97.1%, and 98.6% reliability, respectively, clearly suggesting Kohonen’s self-organizing map as the most appropriate technique for the classification of acoustic emission signature.

Enhanced monopole transition strength from the cluster decay of 13C

The inelastic excitations and cluster decay of $^{13}$C have been measured using the reaction, $^9$Be($^{13}$C,$^{13}$C* $\rightarrow$ $^9$Be + $\alpha$ )$^9$Be. We observe strong excitation to the 14.3-MeV (1/2$^-$) resonant state from the cluster-decay channel, leading to an enhanced monopole matrix element of (6.3 $\pm$ 0.6) fm$^2$. This large cluster-related monopole strength is a clear indication of the cluster-structure domination of this state and is consistent with the recent prediction of the orthogonality condition model (OCM). It would be interesting to further explore the three-center molecular rotational band that is initiated from the observed band-head.

Gamma-ray emission from high Galactic latitude globular clusters

We analyse 8 years of PASS 8 Fermi-LAT data, in the 60 MeV - 300 GeV energy range, from 30 high Galactic latitude globular clusters. Six of these globular clusters are detected with a TS > 25, with NGC 6254 being detected as gamma-ray bright for the first time. The most significant detection is of the well-known globular cluster 47 Tuc, and we produce a refined spectral fit for this object with a log parabola model. NGC 6093, NGC 6752 and NGC 6254 are fitted with hard, flat power law models, NGC 7078 is best fitted with a soft power law and NGC 6218 is best fitted with a hard, broken power law. This variety of spectral models suggests that there is a variety of gamma-ray source types within globular clusters, in addition to the traditional millisecond pulsar interpretation. We identify a correspondence between diffuse X-ray emission in globular cluster cores and gamma-ray emission. This connection suggests that gamma-ray emission in globular clusters could also arise from unresolved X-ray sources or a relativistic electron population, perhaps generated by the millisecond pulsars. X-ray observations of further gamma-ray bright globular clusters would allow a functional relationship to be determined between diffuse X-ray and gamma-ray emission.

Alpha and cluster decay half-lives in Tungsten isotopes: A microscopic analysis

Alpha and cluster decay half-lives of Tungsten (W) isotopes in the range between 2p drip line and beta stability line are studied. The sensitivity of different Skyrme parametrizations in predicting the alpha decay and probable cluster decay modes from W isotopes have been analysed. The half-lives are calculated using Universal Decay Law (UDL). Predicted half-lives are compared with Effective Liquid Drop Model (ELDM) and also with available experimental values. The use of harmonic oscillator (HO) and transformed harmonic oscillator (THO) basis do not produce much differences in the results. The study also revealed the role of neutron shell closure in cluster decay process.

Systematic studies of α and heavy-cluster emissions from superheavy nuclei

The probabilities of \ensuremath{\alpha} decay and heavy-cluster decay in the superheavy region are investigated. The preformation probabilities for \ensuremath{\alpha} and cluster emissions are evaluated with a new formula which depends on the $Q$ value of the decay. The formula shows a better agreement with the experimentally extracted cluster preformation probabilities in the heavy region. The \ensuremath{\alpha} half-lives using our model are compared with the experimental results and it is found that the present model can be employed successfully to predict \ensuremath{\alpha} half-lives in the superheavy region. The probable heavy-cluster radioactivity from superheavy nuclei is also studied using the same model. A comparison of the heavy-cluster half-lives using the present model, the half-lives given by Poenaru et al. [Eur. Phys. J. A 54, 14 (2018)] (analytical superasymmetric fission) and Zhang et al. [Phys. Rev. C 97, 014318 (2018)] are performed. The agreement between these three formalisms is evident from the study. A further study on the competition between \ensuremath{\alpha} decay and heavy-cluster radioactivity leading to $^{208}\mathrm{Pb}$ is performed. The study suggests that heavy-cluster radioactivity may be comparable to or even dominant over \ensuremath{\alpha} decay for some of the isotopes with $Z\ensuremath{\ge}118$. The study shows that the present model can be used effectively to obtain the \ensuremath{\alpha} as well as the heavier cluster decay half-lives in the superheavy region.

Ion energy spectra directly measured in the interaction volume of intense laser pulses with clustered plasma

The use of gas cluster media as a target for an intense femtosecond laser pulses is considered to be uniquely convenient approach for the development of a compact versatile pulsed source of ionizing radiation. Also, one may consider cluster media as a nanolab to investigate fundamental issues of intense optical fields interaction with sub-wavelength scale structures. However, conventional diagnostic methods fail to register highly charged ion states from a cluster plasma because of strong recombination in the ambient gas. In the paper we introduce high-resolution X-ray spectroscopy method allowing to study energy spectra of highly charged ions created in the area of most intense laser radiation. The emission of CO2 clusters were analyzed in experiments with 60 fs 780 nm laser pulses of 1018 W/cm2 intensity. Theory and according X-ray spectra modeling allows to reveal the energy spectra and yield of highly charged oxygen ions. It was found that while the laser of fundamental frequency creates commonly expected monotonic ion energy spectrum, frequency doubled laser radiation initiates energy spectra featuring of distinctive quasi-monoenergetic peaks. The later would provide definite advantage in further development of laser-plasma based compact ion accelerators.

The High-Density Symmetry Energy in Heavy-Ion Collisions and Compact Stars

High-density nuclear symmetry energy is of crucial importance in astrophysics. Information on such energy has been obtained from mass–radius determinations of neutron stars (NSs), and in the future NS mergers will increasingly contribute. In the laboratory, the symmetry energy can be studied in heavy-ion collisions (HICs) at different incident energies over a large range, from very low to several times higher saturation density. Transport theory is necessary to extract the symmetry energy from the typically non-equilibrated nuclear collisions. In this contribution, we first review the transport approaches, their differences, and recent studies of their reliability. We then discuss several prominent observables, which have been used to determine the symmetry energy at high density: collective flow, light cluster emission, and particle production. It is finally argued that the results of the symmetry energy from microscopic many-body calculations, nuclear structure, nuclear reactions, and astrophysics begin to converge but still need considerable improvements in terms of accuracy.

Highly Luminescent Inks: Aggregation-Induced Emission of Copper-Iodine Hybrid Clusters.

Aggregation-induced emission (AIE) is an attractive phenomenon in which materials display strong luminescence in the aggregated solid states rather than in the conventional dissolved molecular states. However, highly luminescent inks based on AIE are hard to be obtained because of the difficulty in finely controlling the crystallinity of AIE materials at nanoscale. Herein, we report the preparation of highly luminescent inks via oil-in-water microemulsion induced aggregation of Cu-I hybrid clusters based on the highly soluble copper iodide-tris(3-methylphenyl)phosphine (Cu4 I4 (P-(m-Tol)3 )4 ) hybrid. Furthermore, we can synthesize a series of AIE inks with different light-emission colors to cover the whole visible spectrum range via a facile ligand exchange processes. The assemblies of Cu-I hybrid clusters with AIE characteristics will pave the way to fabricate low-cost highly luminescent inks.

Decay modes of superheavy nuclei Z = 124

It is important to study the different decay modes of superheavy nuclei such as spontaneous fission, ternary fission and cluster decay. We studied the spontaneous fission, ternary fission and cluster decay of predicted isotopes of superheavy nuclei [Formula: see text] and compared with that of alpha decay. This enables us to study the competition between spontaneous fission, ternary fission, cluster decay and alpha decay in the superheavy nuclei [Formula: see text]. We have studied the half-lives and decay constants of different decay modes. We have also studied the branching ratio of alpha decay with respect to other decay modes. This study reveals that alpha decay is the most dominant decay mode for the superheavy nuclei [Formula: see text] and hence these nuclei can be detected through the alpha decay mode only.

Hough-Transform-Based Cluster Identification and Modeling for V2V Channels Based on Measurements

In this paper, a recently conducted measurement campaign for vehicle-to-vehicle (V2V) propagation channel characterization is introduced. Two vehicles carrying a transmitter and a receiver, respectively, have been driven along an eight-lane road with heavy traffic. The measurement was conducted with 100 MHz signal bandwidth at a carrier frequency of 5.9 GHz. Channels are observed consisting of two kinds of channel components, i.e., time-evolving clusters and clutter paths. A novel approach based on Hough transform is proposed to identify the clusters. Based on the cluster identification results, channel characteristics in composite, intracluster, and time-variant levels are analyzed. The parameters investigated include the composite root-mean-square (RMS) delay spreads and power decay versus delay behaviors of clusters and clutter paths, cluster RMS delay spread, cluster RMS Doppler frequency spread, correlations of cluster parameters, and coherence time of parameters of interest. The statistics constitute an empirical stochastic clustered-delay-line channel model focusing on the wideband characteristics observed in the realistic time-variant V2V propagation scenario.

Secondary particle clusterization in carbon-carbon collision

In the present work, using the hadron clustering algorithm, we have determined the mass of π0 mesons with excellent accuracy by restoring data of the neutral particles which are produced in the collisions of carbons and propane. It has observed that the value of cut parameter for the clustering depends on the primary energies. We have studied hadron cluster’s and its particle multiplicities, longitudinal rapidity, transverse momentum and the temperature feature of cluster decay. In the central region of the interaction, there is a cluster with high temperature produced by the collision process.