Cluster Emission Research Articles

Pauli blocking effects in nα -nucleus-induced fusion reactions

The hindrances in the $n\ensuremath{\alpha}$-nucleus-induced fusion reactions at deep subbarrier energies are investigated by using the coupled-channels model. Inspired by the microscopic Pauli-blocking effects of $\ensuremath{\alpha}$-cluster decay in radioactive nuclei, a Pauli blocking potential is constructed in the $n\ensuremath{\alpha}$-nucleus-induced fusion reactions by using a single folding procedure, in which the $n\ensuremath{\alpha}$ nuclei are assumed to be consisted of $\ensuremath{\alpha}$ particles. A shallow pocket is formed in the inner part of the potential between two colliding nuclei as compared to the one obtained from the double-folding potential with standard Michigan-3-Yukawa effective nucleon-nucleon interaction. The experimental fusion cross sections are described well for fusion systems $^{12}\mathrm{C}+^{198}\mathrm{Pt}$, $^{16}\mathrm{O}+^{208}\mathrm{Pb}$, $^{12}\mathrm{C}+^{30}\mathrm{Si}$, $^{24}\mathrm{Mg}+^{30}\mathrm{Si}$, and $^{28}\mathrm{Si}+^{30}\mathrm{Si}$. At deep subbarrier energies, it is found that this shallow pocket potential reduces the partial fusion cross sections and shields the contributions of high-angular-momentum partial waves to fusion cross sections. In addition, a detailed comparison of fusion processes with different projectiles $^{12}\mathrm{C}$, $^{24}\mathrm{Mg}$, and $^{28}\mathrm{Si}$ on the same target $^{30}\mathrm{Si}$ shows the hindrance effect is stronger for heavier projectiles.

Radioactive Decay of Rutherfordium

Rutherfordium is the synthetic and unstable element. It undergoes different radioactive decays such as alpha decay, beta decay, proton decay and spontaneous fission. In the present work, we have studied the competition between different decay modes such as alpha decay, beta decay, cluster decay, proton decay and spontaneous fission of Rutherfordium. By studying the competition between different decay modes, we have identified the dominant decay modes for different isotopes of mass number range 238 < A < 340. The variation of half-lives with mass number corresponds different decay modes are graphically represented. The energy released during different decay modes is also represented as a function of mass number. The calculated half-lives are compared with that of the other models available in the literature. To validate the present work, we have also compared values produced by the present method with that of the experiments.

Clusters decay half-live of various heavy deformed nuclei with mass numbers in the range 221 ≤ A ≤ 242

Decay half-live of several clusters between 14C and 34Si emitted from various heavy deformed nuclei with mass numbers in the range 221 ≤ A ≤ 242 are calculated using nuclear Woods-Saxon (VN(r, θ)), Coulomb (VC(r, θ)) and rotational (Vl(r)) potentials considering deformation for both daughter and cluster and spherical configuration for them. Half-live of these decays are also obtained using a semi-empirical formula. Obtained results considering deformation are compared with the half-live of spherical configuration, results of a semi-empirical formula as well as the available experimental data. The comparison indicates that the calculated half-lives considering deformation are better agreed with the experimental data than the results of spherical configuration and the out put of semi-empirical formula. Also, The obtained results using deformation is better confirmed the Geiger-Nuttall low of alpha decay, especially for emission of light clusters as expected.

Photofragmentation Patterns of Cobalt Oxide Cations ConOm+ (n = 5-9, m = 4-13): From Oxygen-Deficient to Oxygen-Rich Species.

Cobalt oxide clusters, ConOm+ (5 ≤ n ≤ 9 and 4 ≤ m ≤ 13), are produced by laser vaporization and studied by time-of-flight mass spectrometry. Specific stoichiometries are mass separated and photofragmented using 355 nm laser light. The preferred fragmentation channels of m = n-1, m = n-2, and m ≥ n species are investigated. Loss of oxygen molecules is the favorable dissociation channel of m ≥ n clusters. While ConOn-2+ clusters decay via the loss of a Co atom, the photofragmentation behavior of ConOn-1+ species interestingly can be divided into two regimes: the n ≤ 6 clusters tend to lose an oxygen atom, but for n > 6 they favorably dissociate via the loss of a cobalt atom. The geometric structures of selected m = n - 2 species are studied using density functional theory calculations. Dissociation energies for different evaporation channels are calculated and thermodynamically favorable channels are found to correspond to the experimental observations.

Emission of charged particles from laser-induced germanium ecton, vacuum spark, and vacuum arc

The highly resolved temporal evolution of laser-induced micro-explosions on a germanium surface is studied in a triode configuration for various gate charge levels and cathode currents. Electron emission from individual spots is directly imaged with a luminescence screen, showing that the opening angle of the source is about 30°. Electron bunches of several nanocoulombs per pulse in a time interval of about 150 ns are directly extracted to the anode without vacuum breakdown in the cathodic gap. When breakdown occurs, a remarkable change in the arc behavior of a threshold gap potential of around 1 kV is observed, which hints at two different evaporation mechanisms that depend on the cathodic fall of an individual spot. Therefore, for voltages well above the threshold, a fast gate discharge is observed within the first 100–200 ns, followed by fundamental plasma oscillations and an electron emission of several μC per pulse from the plasma boundary. Additionally, highly efficient emission of germanium ion clusters occurs, evidencing a stable twofold electron multiplication in the plasma, with a charge of several μC per pulse below the threshold.

Deep XMM–Newton observations of the most distant SPT-SZ galaxy cluster

ABSTRACT We present results from a 577 ks XMM–Newton observation of SPT-CL J0459–4947, the most distant cluster detected in the South Pole Telescope 2500 square degree (SPT-SZ) survey, and currently the most distant cluster discovered through its Sunyaev–Zel’dovich effect. The data confirm the cluster’s high redshift, z = 1.71 ± 0.02, in agreement with earlier, less precise optical/IR photometric estimates. From the gas density profile, we estimate a characteristic mass of $M_{500}=(1.8\pm 0.2)\times 10^{14}\, {\rm M}_{\odot }$; cluster emission is detected above the background to a radius of $\sim \!2.2\, r_{500}$, or approximately the virial radius. The intracluster gas is characterized by an emission-weighted average temperature of 7.2 ± 0.3 keV and metallicity with respect to Solar of $Z/\, Z_{\odot }=0.37\pm 0.08$. For the first time at such high redshift, this deep data set provides a measurement of metallicity outside the cluster centre; at radii $r\gt 0.3\, r_{500}$, we find $Z/\, Z_{\odot }=0.33\pm 0.17$ in good agreement with precise measurements at similar radii in the most nearby clusters, supporting an early enrichment scenario in which the bulk of the cluster gas is enriched to a universal metallicity prior to cluster formation, with little to no evolution thereafter. The leverage provided by the high redshift of this cluster tightens by a factor of 2 constraints on evolving metallicity models, when combined with previous measurements at lower redshifts.

Cluster radioactivity of neutron-deficient nuclei in trans-tin region

The possibility of cluster radioactivity (CR) of the neutron-deficient nuclei in the trans-tin region is explored by using the effective liquid drop model (ELDM), generalized liquid drop model (GLDM), and several sets of analytic formulas. It is found that the minimal half-lives are at Nd = 50 (Nd is the neutron number of the daughter nucleus) for the same kind cluster emission because of the Q value (released energy) shell effect at Nd = 50. Meanwhile, it is shown that the half-lives of α-like (Ae = 4n, Ze = Ne. Ze and Ne are the charge number and neutron number of the emitted cluster, respectively.) cluster emissions leading to the isotopes with Zd = 50 (Zd is the proton number of the daughter nucleus) are easier to measure than those of non-α-like (Ae = 4n + 2) cases due to the large Q values in α-like cluster emission processes. Finally, some α-like CR half-lives of the Nd = 50 nuclei and their neighbours are predicted, which are useful for searching for the new CR in future experiments.

Formation region of emitted α and heavier particles inside radioactive nuclei

We investigate the formation distance (R0) from the center of the radioactive parent nucleus at which the emitted cluster is most probably formed. The calculations are performed microscopically starting with the solution to the time-independent Schrödinger wave equation for the cluster-core system, using nuclear potentials based on the Skyrme-SLy4 nucleon-nucleon interactions and folding Coulomb potential, to determine the incident and transmitted wave functions of the system. Our results show that the emitted cluster is mostly formed in the pre-surface region of the nucleus, under the effect of Pauli blocking from the saturated core density. The deeper α-formation distance inside the nucleus allows less preformation probability and indicates a more stable nucleus for a longer half-life. Furthermore, the α-particle tends to be formed at a slightly deeper region inside the nuclei, with larger isospin asymmetry, and in the closed shell nuclei. Regarding the heavy clusters, we observed that the formation distance of the emitted clusters heavier than α-particle increased via increasing the isospin asymmetry of the formed cluster rather than by increasing its mass number. The partial half-life of a certain cluster-decay mode increased with increase of either the mass number or the isospin asymmetry of the emitted cluster.

ON THE POSSIBILITY TO DETECT ACTS OF CLUSTER DECAY OF ATOMIC NUCLEI BY THE METHODS OF NOISE DIAGNOSTIC

Cluster decay, as a special type of radioactive decay, up to date, is widely investigated. Nevertheless, until now, this activity is restricted: from one side by the possibilities of theoretical analysis, where some success is obtained for light nuclei only; and from another side only by experiments for nuclei defragmentation in searching for fission on magic nuclei. However, standard methods of radiometry and statistical analysis have not yet been applied. Such possibility can be realized by searching for acts of cluster decay as a rare event on an array of alpha-decay acts of actinides, which are recorded by industrial ionization fission chambers. The scheme of the experiment is discussed, which consists in the registration of every act of alpha-decay, against the background of which it is possible to detect the presence of nuclear clusters based on isotopes of 12,14С, 20О, and others, which can be formed in the decay of 234,235U. The requirements for electronics and the background conditions for such an experiment are discussed in detail.

Cluster decay half-lives and preformation probabilities

An improved semi-analytic approach to the barrier penetration probability is developed in the frame work of the Wentzel-Kramers-Brillouin (WKB) approximation. It is used to calculate decay half-lives and preformation probabilities for a set of 304 cluster emitters in the range 87 ≤ Z ≤ 96 and a set of 390 α-emitters in the range 52 ≤ Z ≤ 120. For cluster decay, the validity of our approach is tested against Coulomb and proximity potential model (CPPM) by comparing decay half-lives and barrier penetration probabilities. Our results are found to be in a good agreement with CPPM calculations and with the available experimental data. In case of α-decay, our calculations are tested against the experimental data and also a very good agreement is achieved. In both cases, results are also compared with calculations of some other well known universal decay laws that are used in many recent studies. Our approach shows a better agreement with experimental data than most of the other models. Our study is extended to calculate the assault frequency and preformation probability of the cluster inside the parent nucleus. A strong correlation is obtained for all these parameters with each other. Neutron shell closures are found to be more important in the cluster decay process than proton shell closure. It is also noted that the odd–even staggering behavior dominates the decay processes involving the emission of clusters with odd neutron number.

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.

Dynamical aspects of Ti48+Fe58,Ni58→Cd*106,Sn*106 reactions at energies near the Coulomb barrier

The study of the heavy-ion reactions at the near- and sub-barrier regimes gives immense information about the nuclear structure and the involved reaction dynamics. It has been observed that a slight difference in the nuclear structure may lead to a significant change in the sub-barrier fusion excitation functions. The studies of different trends of excitation functions below the Coulomb barrier region due to dissimilar structures of the nuclei, which are involved in the reaction, are available in literature. To understand the role of different structures and dynamics involved in such reactions, an investigation of $^{48}\mathrm{Ti}$-induced reactions on $^{58}\mathrm{Fe}$ and $^{58}\mathrm{Ni}$ forming $^{106}\mathrm{Cd}^{*}$ and $^{106}\mathrm{Sn}^{*}$ compound nuclei (CN), respectively, has been made at similar ${E}_{\mathrm{c}.\mathrm{m}.}/{V}_{b}$ values within the framework of the dynamical cluster decay model (DCM). The difference in the structure between the nuclei is quite notable with $^{58}\mathrm{Ni}$ and $^{106}\mathrm{Sn}^{*}$ having a proton shell closure ($Z=28$ and 50, respectively). Within the DCM, the experimental fusion evaporation cross sections are reproduced using deformed configurations effects included up to quadruple deformations (${\ensuremath{\beta}}_{2i}$) for two nuclei having optimum orientations ${\ensuremath{\theta}}^{\mathrm{opt}.}$. The fusion evaporation data at near- and sub-barriers has been explained through the calculated enhanced $\mathrm{\ensuremath{\Sigma}}{P}_{0}$ values of the decaying channels in the case of $^{106}\mathrm{Cd}^{*}$ in comparison to $^{106}\mathrm{Sn}^{*}$. Moreover, it is observed that the quantum tunneling of the fragments is less hindered in the case of $^{106}\mathrm{Cd}^{*}$ as compared to $^{106}\mathrm{Sn}^{*}$ at the lower values of ${E}_{\mathrm{c}.\mathrm{m}.}/{V}_{b}$, i.e., having less barrier modification ($\mathrm{\ensuremath{\Delta}}{V}_{B}$) in the case of the former. The role of magicity has been further explored with the plotted values of the ratio of fusion cross sections (${\ensuremath{\sigma}}_{\mathrm{fus}}$) of CN $^{106}\mathrm{Sn}^{*}$ and $^{112}\mathrm{Xe}^{*}$ (formed in the reaction with both the projectile $^{58}\mathrm{Ni}$ and target $^{54}\mathrm{Fe}$ having proton and neutron magicity, respectively) with respect to $^{106}\mathrm{Cd}^{*}$, which are highly suppressed in the case of the latter in comparison to the former, particularly, below the Coulomb barrier.

Clustering effects in the exit channels of C13,12+C12 reactions within the collective clusterization mechanism of the dynamical cluster decay model

From the past few years, increasing experimental evidence has shown that clusters (multiple of $\ensuremath{\alpha}$ particles) of intermediate mass are emitted with quite large cross sections at forward angles in heavy-ion reactions. In the present work a theoretical investigation has been made to explore the role of $\ensuremath{\alpha}$-clustering in $^{13,12}\mathrm{C}+^{12}\mathrm{C}$ reactions populating $^{25,24}\mathrm{Mg}^{*}$ compound nuclei (CN), which results in the enhanced cross sections of intermediate mass fragments (IMFs) within the collective clusterization framework of the dynamical cluster decay model (DCM). With in the formalism the experimental cross sections are reproduced using the spherical as well as deformed configurations effects included up to quadruple deformations (${\ensuremath{\beta}}_{2i}$) for two nuclei having optimum orientations ${\ensuremath{\theta}}^{\mathrm{opt}}$. The ratio of the calculated (fission-like) yields of each isotopic fragment $^{6,7}\mathrm{Li}, ^{7,8,9}\mathrm{Be}$ obtained in the two reactions has been compared with the experimental and statistical model predictions also. The DCM calculated result is in little better comparison to the statistical models due to the inclusion of structure effects in the calculations. In the present calculations, the dynamical yields count for the preformation probability (${P}_{0}$) of the IMFs within the collective clusterization process of DCM, before penetrating the scattering potential barrier. Quite interestingly, the calculated ratio of ${P}_{0}$ of the corresponding IMFs ${P}_{0(\mathrm{IMFs})}^{^{25}\mathrm{Mg}^{*}}/{P}_{0(\mathrm{IMFs})}^{^{24}\mathrm{Mg}^{*}}$ for the CN $^{25,24}\mathrm{Mg}^{*}$ shows the trend of ratio of experimental cross sections, i.e., ${\ensuremath{\sigma}}_{\mathrm{IMFs}}^{^{25}\mathrm{Mg}^{*}}/{\ensuremath{\sigma}}_{\mathrm{IMFs}}^{^{24}\mathrm{Mg}^{*}}$. It is found that $\ensuremath{\alpha}$-cluster structure of complimentary fragments of the IMFs under investigation plays quite a significant role in their decays.

α decay to a doubly magic core in the quartetting wave function approach

We present a microscopic calculation of $\alpha$-cluster formation in heavy nuclei $^{104}$Te ($\alpha$+$^{100}$Sn), $^{212}$Po ($\alpha$+$^{208}$Pb) and their neighbors $^{102}$Sn, $^{102}$Te, $^{210}$Pb and $^{210}$Po by using the quartetting wave function approach. Improving the local density approximation, the shell structure of the core nucleus is considered, and the center-of-mass (c.o.m.) effective potential for the quartet is obtained self-consistently from the shell model wavefunctions. The $\alpha$-cluster formation and decay probabilities are obtained by solving the bound-state of the c.o.m. motion of the quartet and the scattering state of the formed $\alpha$-cluster in the Gurvitz approach. Striking shell effects on the $\alpha$-cluster formation probabilities are analyzed for magic numbers 50, 82 and 126. The computed $\alpha$-decay half-lives of these special nuclei are compared with the newest experimental data.

Prediction of α -decay chains and cluster radioactivity of 121300–304 and 122302–306 isotopes using the double-folding potential

The $\ensuremath{\alpha}$- and cluster-decay half-lives for the two superheavy nuclei (SHN) with $Z=121$ and 122 have been calculated within the density-dependent cluster model. The $\ensuremath{\alpha}$-nucleus potential was constructed by employing the double-folding model with a realistic $NN$ interaction whose exchange part has a finite range. We considered five isotopes for each one of the two SHN, $Z=121$ and 122, and compared the calculated $\ensuremath{\alpha}$-decay half-lives with those obtained from three semiempirical formulas, namely, the Viola-Seaborg-Sobiczewski formula, the modified Brown formula, and the semiempirical formula based on fission theory. The calculated $\ensuremath{\alpha}$-decay half-lives are in good agreement with their counterparts. We studied the competition between $\ensuremath{\alpha}$-decay and spontaneous fission and predicted possible decay modes for the SHN $^{300--304}121$ and $^{302--306}122$. The cluster decays for $^{300}121$ and $^{302}122$ have been studied within the double folding model, the unified formula, the scaling law of Horoi, and the universal decay law (UDL). We found that the UDL model predicts the possibility of heavy cluster emission from $^{300}121$ and $^{302}122$. We found that the proton and neutron numbers in the emitted clusters and their residual daughter nuclei are magic or near to the magic numbers. We hope that the theoretical prediction of $\ensuremath{\alpha}$-decay chains and cluster radioactivity could be helpful for future investigation in this field.

COMPETITION BETWEEN LIGHT CLUSTER AND CONSTITUENT MULTINUCLEON EMISSION IN HEAVY-ION REACTIONS

Isoproduct competition. i.e. competition between cluster and multlnucleon emission leading to the same residual nucleus, emerges as a general, interesting and useful characteristic of nuclear reactions. Common properties and factors underlying the competition between pn and d as well as between p2n. dn and t evaporation are recognized and discussed. The application of the isoproduct-competition method in the delineation of the mechanisms involved in 7Li-lnduced reactions suggests that an additional mechanism, breakup-fusion, is involved even at very low energies. Finally, the competition associated with alpha emission In the 12C+16O reaction demonstrates a strong contribution from composite 4He emission which cannot be accounted far by either the systematica or standard statistical calculations.

Tunable white light emission in zinc phosphate glasses activated with [formula omitted] clusters and Sm3+

Zinc phosphate glasses, activated with Agmn+ clusters and Sm3+, were prepared by the conventional melt-quenching method. The X-ray diffraction patterns revealed that the samples remain amorphous for Ag and Sm3+ contents up to 3.0 and 1.0 mol%, respectively. The Raman and FTIR spectra showed that the main vibrational modes are associated with P–O bonds. The absorption coefficient spectrum of the Ag singly doped glass sample displayed a broad band centered at 318 nm, related to Agmn+ clusters, whereas those co-doped with Sm3+ showed, in addition to the Agmn+ cluster absorption, the well-known Sm3+ absorptions at 343, 360, 374, 401, 415, 438, 465 and 477 nm. The photoluminescence excitation spectrum of the Ag singly doped glass sample exhibited a broadband from 3 to 6 eV (207–413 nm), assigned to superposition of the Ag+: 4 d10 → 4d95s and Agmn+ cluster: S0 → S1 transitions, being the excitation into the Agmn+ clusters attractive for W-LEDs applications. The photoluminescence emission spectra of the Ag singly doped glass sample, upon Agmn+ cluster excitations at 340, 350 and 360 nm, displayed cold white light tonality, with (0.279, 0.300) CIE1931 chromaticity coordinates of 9453 K and bluish-white light tonality with (0.264, 0.276) and (0.259, 0.270) CIE1931 chromaticity coordinates and correlated color temperature values of 12901 and 14201 K, respectively. The global emission of the Ag and Sm3+ co-doped glass samples was, upon 340, 350 and 360 nm excitations, gradually tuned from the bluish and cold white region to the warm white one, as the Sm3+ content was increased, with correlated color temperatures in the 14201-2691 K range. The Sm.3+ emission bands, under excitations at 340 and 350 nm, were attained at expense of radiative and non-radiative energy transfer from the Agmn+ clusters, as revealed respectively by the sinks mounted on the Agmn+ cluster emission bands and the emission decay profile shortening in presence of Sm3+. Analysis of the Agmn+ cluster emission intensity and decay profiles, with the Dexter and Burstein models, showed that Agmn+ cluster cross-relaxation and/or non-radiative energy transfer to Sm3+ might be dominated by an electric quadrupole-quadrupole interaction.

Cluster radioactivity within the collective fragmentation approach using different mass tables and related deformations

The cluster decay of radioactive nuclei with mass $$^{221}\hbox {Fr}{\le }\hbox {A}{\le }^{252}\hbox {Cf}$$ decaying to lead and near-lead daughters are investigated considering four different sets of binding energies given by Moller et al. (At Data Nucl Data Tables 59:185, 1995) (MN1995), Moller et al. (At Data Nucl Data Tables 109:1, 2016) (MS2016) and Wang et al. (Phys Rev C 81:044322, 2010) (NW2010) with corresponding deformation parameters and experimentally measured data in 2017 (EX2017) considering deformations of the MN1995, MS2016 and NW2010 formalisms. The calculations are carried out using the preformed cluster-decay model based on the collective clusterization approach, which is inherited from the quantum mechanical fragmentation theory. With the incorporation of quadrupole deformations along with optimum cold orientations, the fragmentation potential changes for different choices of binding energy data and hence the preformation probability ($${P}_{0}$$) of the clusters get accordingly modified. The calculated half-lives of the cluster decays find reasonable agreement with the experimental data using the MS2016 formalism. Applying MS2016, the prediction of half-lives of some competing clusters (not measured so far) from known parents is also made in the lead and near-lead region, which could possibly provide new edges for cluster-decay measurements. Further, the role of axial deformations ($$\beta _{2}$$–$$\beta _{4}$$) from various formalisms along with cold elongated configurations of decay products is analyzed in view of cluster emission from the radioactive nuclei considered. The fragmentation profile calculated using MN1995, MS2016 and NW2010 gets significantly influenced when $$\beta _{2}$$-deformations are replaced with $$\beta _{2}$$–$$\beta _{4}$$ deformations. Nearly $$32\%$$ of the clusters are not observed in the decay path using theoretical binding energies and deformation parameters of MN1995, which reduces to $$16\%$$ for MS2016 and $$7\%$$ for NW2010.

Cluster decay half-lives using modified generalized liquid drop model (MGLDM) with different pre-formation factors

Cluster decay from 212–240Pa, 219–245Np, 228–246Pu, 230–249Am, and 232–252Cm has been studied by including three different pre-formation factors that depend on cluster size, atomic number of cluster and daughter nuclei, and Q value in MGLDM, an approach developed by modifying GLDM with proximity 77 potential. In MGLDM, where Q value-dependent pre-formation factor is added, the standard deviation of logarithmic half-lives was found to be 0.83, and the experimental half-lives were successfully reproduced using MGLDM with cluster size-dependent, and atomic number of cluster and daughter nuclei-dependent pre-formation factor with a standard deviation of 0.58 and 0.63, respectively. The half-lives of heavy elements in trans-lead region emitting 22Ne, 24Ne, 26Mg, 28Mg, 32Si and 33Si clusters, which have not been experimentally determined so far, have been predicted by incorporating three types of pre-formation factors to MGLDM. As all the predicted half-lives are below 1030s and are within the experimentally measurable range, we hope that our present predictions would be helpful for future studies in this field.

The Comparative Study of S-V Model Between 3.5 and 28 GHz in Indoor and Outdoor Scenarios

The 3.5 GHz and 28 GHz bands are both very important for the fifth-generation (5 G) wireless communication system. To model their propagation characteristics and study their channel properties, we conduct measurements at these two bands in indoor and outdoor scenarios. The measured bandwidths at 3.5 and 28 GHz are 100 and 400 MHz, respectively. To make a fair comparison, the measurement results at 28 GHz are divided into four groups with bandwidths from 100 to 400 MHz. This is also helpful to study the effect of bandwidth on the channel properties, especially numbers of clusters and their growth rate. We choose the Saleh-Valenzuela (S-V) model to analyze the wireless channel. Its cluster-based property is very suitable to describe the power delay profiles (PDPs) in our measurement. To maintain the time continuity of multipath components (MPCs) during the clustering, we propose a new heuristic cluster algorithm. Based on the clustering results, we obtain the channel parameters, i.e., the number of clusters, inter-cluster interval, intra-cluster root mean square (RMS) delay spread, cluster decay factor, and ray decay factor. From the comparative study, we can find that the rays suffer a larger attenuation at 28 GHz than at 3.5 GHz. Increasing bandwidth can increase the ray decay factor. But the effects of frequency on the cluster decay rate are different in indoor and outdoor scenarios. The cluster decay rate is smaller at 28 GHz in the indoor scenario.