Nuclei Mode Research Articles

Finite amplitude method on the deformed relativistic Hartree-Bogoliubov theory in continuum: The isoscalar giant monopole resonance in exotic nuclei

Finite amplitude method based on the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc-FAM) is developed and applied to study isoscalar giant monopole resonance in exotic nuclei. Validation of the numerical implementation is examined for $^{208}\textrm{Pb}$. The isoscalar giant monopole resonances for even-even calcium isotopes from $^{40}\textrm{Ca}$ to the last bound neutron-rich nucleus $^{80}\textrm{Ca}$ are calculated, and a good agreement with the available experimental centroid energies is obtained for $^{40-48}\textrm{Ca}$. For the exotic calcium isotopes, e.g., $^{68}\textrm{Ca}$ and $^{80}\textrm{Ca}$, the DRHBc-FAM calculated results are closer to the energy weighted sum rule than the calculations on the harmonic oscillator basis, which highlights the advantages of DRHBc-FAM in describing giant resonances for exotic nuclei. In order to explore the soft monopole mode in the exotic nuclei, the giant monopole resonance for the deformed exotic nucleus $^{200}\textrm{Nd}$ is investigated, where the prolate shape and the oblate shape coexist. A soft monopole mode near 6.0 MeV is found in the prolate case, and another one near 4.5 MeV is found in the oblate case. The transition density of the soft monopole mode shows in phase or out-of-phase vibrations near the surface region, which is generated by quadrupole vibrations.

Angular momentum effects on the decay modes of hot compound nuclei formed in 86Kr+134,138Ba reactions

The dependence of decay modes of hot compound nuclei formed in [Formula: see text]Kr[Formula: see text]Ba reactions on the angular momentum has been analyzed using the dynamical cluster-decay model. This has been done by analyzing the change of fragmentation potential, preformation probability, penetrability and cross-section as a function of the fragment mass number at various values of the angular momentum. The evaporation residue cross-section calculated using dynamical cluster-decay model has been compared with the measured one for the channels: [Formula: see text], [Formula: see text], [Formula: see text] for the decay of [Formula: see text]U[Formula: see text] and [Formula: see text] for [Formula: see text]U[Formula: see text]. The summed up fragment cross-sections for the light particles, intermediate mass fragments and fission fragments as a function of angular momentum have been studied which gives an idea for the change of reaction mechanism with angular momentum. The charge distribution of the fission fragment cross-section shows an odd–even staggering, i.e., the probability of even-Z fission fragments is relatively higher than others. The mass distributions obtained within the dynamical cluster-decay model for the decay of [Formula: see text]U[Formula: see text] are in conformity with mass distributions determined by means of the double kinetic-energy technique in literature. The position of the most probable channel has been found to be fixed to a constant atomic number instead of mass number.

Influence of moments of inertia on transverse wobbling mode in odd-mass nuclei

The reported transverse wobbling band in odd-mass $^{105}$Pd has been reinvestigated by the triaxial particle rotor model. Employing different parameter sets of moment of inertia (MOI), several calculated results could be in good agreement with the experimental data, which show distinct modes of rotational excitation, respectively. These modes are sensitive to the ratio between the MOI at intermediate and short axis. With the increase of this ratio, a wobble about the short axis of the total angular momentum is gradually changed to a wobble about the intermediate axis. In addition, it is exhibited that precession and tunneling are two aspects of the quantum wobbling motion. The tunneling aspect dominates in the yrare states of $^{105}$Pd. The present results in $^{105}$Pd show the complexity of the transverse wobbling mode.

Studies on the decay modes of superheavy nuclei with Z = 120

A study on the competition between alpha-decay and spontaneous fission (SF) of the Z = 120 isotopes with 283 ≤ A ≤ 350 is performed in this paper. The alpha-decay half-lives are evaluated using the modified generalized liquid drop model (MGLDM). The SF half-lives are calculated within the shell-effect-dependent formula. It is found that the dominant decay mode of 294,295,297,298,301-304,308120 is alpha-decay and the half-lives fall within the experimental limit (>1 μs). Then the decay properties of the alpha-decay chain of 294,295,297,298,301-304,308120 are predicted within the MGLDM and the shell-effect-dependent formula. These predictions are helpful for searching and identifying the new elements in future. Finally, the possibility of the cluster radioactivity of the Z = 120 isotopes is discussed within the MGLDM. By analyzing the competition between the cluster radioactivity and alpha-decay, it is found that the possibility of the cluster radioactivity is much smaller than the corresponding alpha-decay.

Competition between weak and α -decay modes in superheavy nuclei

The competition between $\ensuremath{\alpha}$- and ${\ensuremath{\beta}}^{+}/\text{EC}$-decay modes is studied systematically in nuclei along the $\ensuremath{\alpha}$-decay chains following the synthesis of superheavy nuclei with $Z=119$ and $Z=120$. A microscopic approach based on deformed self-consistent Hartree-Fock mean-field calculations with Skyrme forces and pairing correlations is used to describe the ${\ensuremath{\beta}}^{+}$ and electron capture weak decays, whereas the $\ensuremath{\alpha}$ decay is estimated from existing phenomenological expressions. It is shown that $\ensuremath{\alpha}$ decay is in most cases the dominant decay mode, but interesting instances are identified where the half-lives are comparable, opening the possibility of new pathways towards more neutron-rich nuclei in this region.

Particle emissions of a heavy-duty engine fueled with polyoxymethylene dimethyl ethers (OME)

OME as sustainable alternative diesel fuel burns without the agglomeration of soot particles which is the case for fossil and paraffinic diesel fuels. Nuclei mode particles are mainly of a volatile nature and do not survive exhaust aftertreatment.

Investigation of decay modes of superheavy nuclei

Investigation of decay modes of superheavy nuclei

Accretion mode and jet collimation in active galactic nuclei

AbstractIn this article, we summarize our recent progress in observational studies of jet collimation in active galactic nuclei. We focus on the investigation of a relation between the properties of the collimation zone and the AGN accretion mode, recently proposed by Boccardi, B., Perucho, M., Casadio, C. et al., 2021, A&A, 647, A67. We also discuss the efforts made by our team to increase the still limited number of sources that can be imaged on sufficiently small spatial scales to probe such zone, and we present first results for new candidates.

Decay modes of superheavy nuclei using a modified generalized liquid drop model and a mass-inertia-dependent approach for spontaneous fission

A modified generalized liquid drop model with the proximity 77 parametrization is used for studying the alpha decay of superheavy nuclei in the range $104\ensuremath{\le}Z\ensuremath{\le}118$. The spontaneous fission (SF) half-lives are computed using a new formula which depends on the shells effect (${E}_{\mathrm{shell}}$) and the mass inertia (${I}_{\mathrm{rigid}}$). The modes of decay are predicted by comparing ${T}_{1/2}^{\ensuremath{\alpha}}$ with ${T}_{1/2}^{\mathrm{SF}}$ and are compared with the experimental observations. These studies may induce further investigations in the superheavy region.

Impacts of the Variations of Aerosols Components and Relative Humidity on the Visibility and Particles Size Distribution of the Desert Atmosphere

This paper investigates the Impact of relative humidity, varying the concentrations of water-soluble aerosol particle concentrations (WASO), Mineral Nuclei Mode Aerosols Particle Concentration (MINN), mineral accumulation mode, nonspherical (MIAN) aerosol particles concentrations and Mineral Coarse Mode Aerosols Particle Concentration (MICN) on the visibility and particles size distribution of desert aerosols based on microphysical properties of desert aerosols. The microphysical properties (the extinction coefficients, volume mix ratios, dry mode radii and wet mode radii) were extracted from Optical Properties of Aerosols and Clouds (OPAC 4.0) at eight relative humidities, RHs (00 to 99%) and at the spectral visible range of 0.4-0.8mm, the concentrations were varied to obtain five different models for each above-mentioned component. Regression analysis of some standard equations were used to determine the Angstrom exponent (α), the turbidity coefficient (β), the curvature (α2), humidification factor (), the mean exponent of aerosol growth curve (µ) and the mean exponent of aerosol size distributions (n). The values of angstrom exponent (α) were observed to be less than 1 throughout the five models at all RHs for the four studied components, and this signifies the dominance of coarse mode particles over fine mode particles. But the magnitude of the angstrom exponent (α) fluctuates all through the studied components except for WASO which increased with the increase in RH across the models and this also signifies the dominance of coarse mode particles with some traces of fine mode particles. The investigation also revealed that the curvature (α2) has both monomodal (negative signs) and bimodal (positive signs) types of distributions all through the five models and this also signifies the dominance of coarse mode particles with some traces of fine mode particles across the individual models for all the studied components. it was also found that the visibility decreased with the increase in RH and increased with the increase in wavelength. The investigation further revealed that the turbidity coefficient (β) fluctuates with the increase in RH and the particles concentrations, and this might be due to major coagulation and sedimentation. The analysis further found that there is a direct inverse power relation between the humidification factor and the mean exponent of aerosols size distribution with the mean exponent of aerosols growth curve. It was also found that as the magnitude of µ increased for MIAN, MINN and MICN, the effective hygroscopic growth decreased. For WASO, it was found that as the magnitude of µ decreased, the effective hygroscopic growth increased with the increase in particles concentrations and RH. The decreased in the magnitude of µ for WASO might be due to the fact that as we increase the non-hygroscopic particles, we decrease the deliquescence. The mean exponent of aerosol size distribution (n) being less than 3 shows foggy condition of the desert atmosphere the four investigated components and five studied models.

New insights into sub-barrier fusion of 28Si + 100Mo

Fusion cross sections of the 28Si + 100Mo system have been measured near and below the Coulomb barrier by detecting the evaporation residues at forward angles. The excitation function has an overall smoother trend than what obtained in a previous experiment, and a large discrepancy is found for the lowest-energy region, where we observe a tendency of the S factor to develop a maximum, which would be a clear indication of hindrance. The results have been compared with the theoretical prediction of coupled-channels calculations using a Woods–Saxon nuclear potential, and including the low-energy excitation modes of both nuclei. Good agreement with data is found by including, in the coupling scheme, the three lowest members of the ground state rotational band of the oblate deformed 28Si, and two-phonons of the strong quadrupole vibration of 100Mo. The additional coupling, in a schematic way, of the two-neutron pick-up between ground states (Q-value = +4.86 MeV) has a minor effect on calculated cross sections, and does not essentially improve the data fit. The excitation function of 28Si + 100Mo has been compared with that of (1) the heavier system 60Ni + 100Mo having analogous features, and (2) several near-by 28Si, 32S + Zr, Mo systems with various nuclear structures and transfer Q-values. The role of quadrupole and octupole excitation modes, as well as of transfer channels, in affecting the fusion dynamics, are clarified to some extent. Systematic measurements of fusion barrier distributions and CC calculations properly including transfer couplings, are necessary, in order to shed full light on the influence of the various coupled channels on the fusion cross sections.

Size distribution and chemical characteristics of particles from crop residue open burning in North China

Crop residue open burning is an important emission source of ambient particles in China. This study analyzed the particle emission characteristics of crop residue open burning through combustion experiments with a novel open combustion simulation device using three typical crop straws in north China (corn, wheat, and rice). Particle samples size ranging from 0.006–9.890 µm were collected by an Electrical Low Pressure Impactor plus, a high size-resolution instrument capable of dividing particles into 14 size stages. The size distributions of organic carbon (OC), elemental carbon (EC), water-soluble ions, and elements were analyzed, and source chemical profiles were constructed for PM0.1, PM1, PM2.5, and PM10. The number concentration of particles was concentrated in the Aiken nuclei mode (0.006–0.054 µm), accounting for 75% of the total number, whereas the mass concentration was concentrated in the accumulation mode (0.054–0.949 µm), accounting for 85.43% of the mass loading. OC, EC, Cl−, and K(include total K and water-soluble K) were the major chemical components of the particles, whose mass percentage distributions differed from those of other components. These five main components exhibited a bell-shaped size distribution in the 0.006–9.890 µm range, whereas the other components exhibited a U-shaped distribution. Among the chemical profiles for PM0.1–PM10, OC was the most important component at 10–30%, followed by EC at 2%–8%. The proportions of K+, Cl−, and K varied substantially in different experimental groups, ranging from 0–15%, and K+ and Cl− were significantly correlated (r = 0.878, α = 0.000).

Experimental and numerical investigations into effects of urea-water solution injection on tailpipe particulate matter emissions

Selective catalytic reduction (SCR) is currently the most effective method to control NOx emissions for heavy-duty vehicles. However, urea-water solution injection may lead to increase of particulate matter (PM) emissions. In this study, PM emissions caused by urea-water solution injection from a China VI heavy-duty vehicle under real-world driving conditions is investigated experimentally. Average PM number emissions increase by over 200 % due to urea-water solution injection. Inlet temperature and space velocity are found to be significant factors. Droplet depletion model is developed for analyzing the contribution of urea decomposition by-products. Results suggest that secondary-breakup-based particles is major contributor to particles formation instead of primary-breakup-based. About 20 % of secondary-breakup-based particles are nuclei mode particles and 80 % are accumulation mode particles. The main component of the secondary-breakup-based particles is cyanuric acid and ammelide.

Theoretical studies on α decays of even-even nuclei with the improved square-well cluster model

<p indent=0mm>α decay is one of the main decay modes of some unstable nuclei. It provides rich information on nuclear structures and is crucial for the experimental identification of new nuclides and new elements in heavy and superheavy regions. It is important to develop theoretical models for α-decay researches. Gamow, Gurney, and Condon proposed the first theoretical model to explain α decay within the framework of quantum tunneling in 1928, which is the first application of quantum mechanics in the subatomic systems. After that, several new theoretical models are proposed to get a better understanding of α decay. They provide preliminary descriptions of α decays in medium-mass and heavy nuclei. Square-well cluster model is an important model for α decay studies. It has several valuable advantages and gives a good description of the experimental α-decay half-lives of some even-even nuclei. It assumes that the effective potential between α cluster and daughter nucleus is given by the square well + the Coulomb potential at the surface. The Pauli blocking between α cluster and daughter nucleus is simulated by the Wildermuth condition, which prevents the α cluster from occupying the orbits inside the daughter nucleus. The theoretical α-decay half-lives are given by the WKB approximation. One of the shortcomings of the square-well cluster model is that different α-emitters are assumed to have exactly the same potential-well depth, which is disfavored by, e.g., the double-folding model and is an oversimplification of realistic effective potentials. In this work, we improve the square-well cluster model by taking into consideration that the depth of the square well depends on the mass number and the proton number. Such an improvement preserves, at the same time, many important merits of the original square-well cluster model. The Pauli blocking effect is simulated by the Wildermuth condition. The theoretical α-decay half-lives are calculated by the WKB approximation. The free parameters in the improved square-well cluster model are determined by fitting the experimental α-decay half-lives of the medium-mass, heavy, and superheavy even-even nuclei, respectively. We then study systematically α decays of even-even nuclei in different mass regions. The logarithmic hindrance factors and root-mean-square deviations between the experimental and theoretical results are calculated. We find that the theoretical α-decay half-lives given by the improved square-well cluster model are in better agreement with the experimental data than those given by the square-well cluster model. There are more theoretical data points agreeing with the experimental data within a factor of 1.5 in the improved square-well cluster model than the squared-well cluster model. For instance, the theoretical α-decay half-life of ²⁸⁸Fl is about three times the experimental data in the square-well cluster model, but only deviates from the experimental data by 3% in the improved square-well cluster model. This shows the advantages of the improved square-well cluster model by introducing the mass-number and proton-number dependence of the square-well depth. These results could be useful for experimental and theoretical studies of α decays.

Confirmation of Giant Pairing Vibration evidence in $$^{\mathrm {12,13}}$$C($$^{\mathrm {18}}$$O,$$^{\mathrm {16}}$$O)$$^{\mathrm {14,15}}$$C reactions at 275 MeV

The Giant Pairing Vibration (GPV) is a correlated two-nucleon excitation mode in atomic nuclei predicted long time ago. It is expected to be excited in two-nucleon transfer reactions, similarly to the pairing vibrations feeding the ground states of even-even nuclei near shell-closure. Recent experiments have provided evidence for this mode in $$^{\mathrm {14}}$$ C and $$^{\mathrm {15}}$$ C nuclei populated via $$^{\mathrm {12}}$$ C, $$^{\mathrm {13}}$$ C( $$^{\mathrm {18}}$$ O, $$^{\mathrm {16}}$$ O) $$^{\mathrm {14}}$$ C, $$^{\mathrm {15}}$$ C two-neutron transfer reactions at 84 MeV beam energy. In the present paper, new data show the persistence of the same structures in the energy spectra of $$^{\mathrm {14}}$$ C and $$^{\mathrm {15}}$$ C populated by the same reactions at a higher bombarding energy of 275 MeV. The extracted centroid, width, spin-parity and transition probability fully agree with the previous observation thus giving a robust confirmation that the GPV mode is populated in such transfer reactions.

Systematics of the mass-asymmetric fission of excited nuclei from 176Os to 206Pb

The competition between the dominant mass-asymmetric and rarer narrow mass-symmetric fission modes in actinide nuclei are controlled by deformed and spherical shell effects. The low energy fission of 80180Hg was recently observed to be strongly mass-asymmetric, indicating that despite spherical shell gaps in fragments around 4090Zr, the system does not fission mass-symmetrically. Several theoretical approaches have been used to explain this unexpected result.To investigate the underlying mechanism, systematic measurements of fission mass distributions for isotopes of Os, Pt, Hg and Pb, formed in fusion reactions with p, 12C, 32S, 40,48Ca projectiles, have been made for excitation energies above the fission saddle-point (Eeff⁎) between 2.8 and 28.2 MeV. Evidence for mass-asymmetric fission is widespread, manifested as flat topped mass distributions or significant deviations from a single Gaussian shape. The systematic trends seen cannot be attributed to quasifission. Comparing two-Gaussian fits at a wide range of E⁎, it is concluded that the fit centroids reflect the low energy character of mass-asymmetric fission in the sub-lead region.Quantitative comparisons were made with microscopic calculations by Scamps and Simenel (2019) [33] of fission mass-asymmetries attributed to the influence of shell gaps in both neutrons (N=52, 56 for compact octuple deformations) and protons (Z=34 and Z=42, 44, 46 with large quadrupole deformations). For the predominant fission mode in the calculations, having one elongated and one compact fragment, the results are in extremely good agreement with all experimental values. This provides strong support for both the calculations, and the exploration of mass-asymmetric fission systematics through heavy ion fusion reactions. The total kinetic energy distributions for 176Pt and 180Pt do not show any evidence of a low TKE mass-symmetric fission mode, as had been reported for 178Pt by Tsekhanovich et al. (2019) [39].

Cluster radioactivity of superheavy nuclei 290–310120 using different proximity functions

The present work used eight different proximity functions in the modified liquid drop model [MGLDM] to study the cluster and alpha decay half-lives in the superheavy nuclei Z = 120. The values produced by the present work are compared with experiments. We have explored the proximity function is suitable in MGLDM for the cluster and alpha radioactivity of superheavy nuclei. The present work is useful in the study of decay modes of superheavy nuclei Z = 120.

Competition between decay modes of superheavy nuclei 281−310Og

In this work, we have made an attempt to study the cluster-decay half-lives and alpha-decay half-lives of the superheavy nuclei [Formula: see text]Og by considering the temperature-dependent (TD) and also temperature-independent (TID) proximity potential model. The evaluated half-lives were compared with that of the experiments. To predict the decay modes, we have compared the cluster-decay half-lives and alpha-decay half-lives with that of spontaneous fission half-lives. This work also predicts the decay chains of the superheavy nuclei [Formula: see text]Og and finds an importance in the synthesis of further isotopes of superheavy element Oganesson.

A systematic experimental study of pre-compound emission in $$\alpha $$-particle induced reactions on odd mass nuclei A = 103–123

The compound and pre-compound emission processes have been established as two main competing de-excitation modes of an excited nucleus by-dint-of evaporation and emission of light fast particles in low energy $$\alpha $$ -induced reactions, respectively. An existence of the plenty experimental data on above established processes for a wide range of mass nuclei coerces to drive for some systematic trends in such reactions with excitation energy and mass number (A). Present work is an attempt to develop a systematics on the pre-compound emission process by analysing consistent experimental cross-section data of $$\alpha $$ -particle induced reactions on odd Z and odd A isotopic target nuclei viz., $$^{103}$$ Rh, $$^{107}$$ Ag, $$^{109}$$ Ag, $$^{113}$$ In, $$^{115}$$ In, $$^{121}$$ Sb, and $$^{123}$$ Sb, respectively. The analysis of data indicates sarcastic deviation in the experimental cross-section data with respect to calculations performed by the statistical Monte-Carlo code pace4 beyond the peak region. Such deviation becomes more prominent towards tail portion of excitation functions, which is regarded as a significant contribution of the pre-compound emission process. Observed energy dependent uniformity of such deviation for all studied reactions gives a clue for existing some systematics on concerning process with atomic mass number (A). Present study is an extension of previous work [Eur. Phys. J. A 54, 205 (2018)], but rather in more precise way for nearby isotopic target mass nuclei $$^{107}$$ Ag, $$^{109}$$ Ag, $$^{113}$$ In, $$^{115}$$ In, $$^{121}$$ Sb, and $$^{123}$$ Sb, respectively, where role of the Coulomb barrier V $$_b$$ and target deformation is found to be significantly important in the systematic decay of excited nuclei through emission of light fast particles in pre-compound process with mass number (A).

Progress of experimental studies on two-proton emission

<p indent=0mm>Radioactivity is one of the most significant characteristics of unstable nuclei, the familiar modes including α, β, γ decay and fission. Two-proton (2p) emission is an exotic radioactivity mode of nuclei in the proton drip-line area, which is very significant for studying the structure, mass and correlation between proton pair of extremely proton-rich nuclei and one of the frontiers in radioactive ion beam physics. In this article, progress of experimental studies on two-proton emission was briefly reviewed. Several experimental measurement methods were introduced. The identification method for the mechanism of two-proton emission was discussed. Two-proton emission was predicted to be existed in extremely proton-rich nuclei in 1960. For 2p emission from the ground state of a nucleus with long half-life, it was observed for the first time in 2002 due to the difficulty in the production of a candidate. Only few decay events were observed for the four proton drip-line nuclei with a long half-life ground state. For the detection of 2p emission process, the in-flight decay, implantation decay and optical time projection chamber (OTPC) plus CCD method are the three main experimental methods. The in-flight decay method is suitable for the candidate with very short half-life and almost inapplicable for the candidate with a half-life longer than 1 μs. The implantation decay method is suitable for the candidate with long half-life, especially for β-delayed decay nuclei. In this case, the measured decay signal will be very clear with low background due to the separation recording of the implantation and decay events. The OTPC plus CCD method could record a picture of 2p emission process directly for the candidate. Generally, there are three mechanisms for proton-rich nuclei to emit two protons: (1) ²He cluster emission; (2) three-body emission; (3) sequential emission. The ²He cluster emission is basically two protons constrained by the pair correlation into a quasi-bound singlet, i.e., ¹S₀ configuration. Such a quasi-bound state can only exist for very short time and then becomes separated after penetrating through the Coulomb barrier. Usually, the two-proton relative momentum and the opening angle distributions are used to identify the mechanism of 2p emission in experimental investigations. However, this method can only distinguish it being ²He cluster emission or not. For the three-body and sequential emissions, the key difference is the emission time between the two protons. The proton-proton momentum correlation function (also called HBT) method is a widely used analysis technique in nuclear physics, which can extract the emission time of a particle. It has been demonstrated that the three-body and sequential emissions could be distinguished by using the HBT method. The difficulty in the study of exotic radioactivity is the low production rate of the unstable nuclei in the drip-line area. The high-intensity heavy-ion accelerator facility (HIAF) under construction in China has an advantage of high beam intensity, the most frontier work in the field of exotic radioactivity for nuclei around the drip-line could be performed on it by adopting the superior detection technique and investigation method.