Fusion Evaporation Research Articles

Characterization and In vitro Dissolution Assessment of Pitavastatin-polyvinyl Pyrrolidone and Kollicoat®IR Solid Dispersions Prepared by Solvent Evaporation and Fusion Methodologies

Pitavastatin (PTV) is a potent lipid lowering drug that acts on hepatocytes by blocking the 3-hydroxy-3- methylglutaryl-CoA reductase enzyme. As a Biopharmaceutical Classification System (BCS) Class II drug, PTV possesses very low water solubility; hence, poor bioavailability leads to poor drug delivery to the target organ. The study aims to develop various PTV solid dispersion (SD) formulations and to investigate the release profile of PTV SD systems. Different PTV physical mixing and SD formulations were prepared using polyvinylpyrrolidone (Kollidon®90F) and Kollicoat®IR hydrophilic polymers by fusion and solvent evaporation approaches. The efficacy of the formulations was evaluated by in vitro PTV release studies. Subsequently, the characterization of SD formulations was performed using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The in vitro release studies confirmed that all the developed formulations showed a comparatively better release percentage (75.31–98.45%) than the pure PTV (61.76%) after 60 min. Additionally, the outcomes showed that raising the concentration of both polymers improved PTV's ability to dissolve. In comparison to physical mixing formulations, SD formulations made using fusion and solvent evaporation processes performed better during dissolution. The TGA, DSC, and FTIR studies confirmed that the tested SD formulations (1:2, 1:3 ratios) were stable at high temperatures with a reduction in crystallinity and no notable interaction between the drug and polymers. The SEM analysis showed that the PTV was evenly spread out in the carriers and that the crystal-like structure of the PTV had changed into an amorphous form. Bangladesh Pharmaceutical Journal 27(1): 37-50, 2024 (January)

Formulation and Evaluation of Oral Dispersible Tablet of Poorly Water-Soluble Drug ‘Glimepiride’ by Using Solubility Enhancement Technique

The present study is regarding Glimepiride (GMP) is poorly water-soluble drug. According to the BCS, Glimepiride undergoes Class II - High Permeability and Low Solubility. The objective of the research project is to enhance the solubility of Glimepiride by using solubility enhancement techniques. The endeavor is to improve its solubility by using super disintegrating agent to enhance the ability of disintegration of Oro dispersible tablet. To enhance of solubility of GMP, our select the method i.e. solid dispersion technique because Solid dispersion is an effective way of improving the dissolution rate of poorly water-soluble drugs and hence its bioavailability. The polymers used were PEG 4000 and PEG 6000 for prepared solid dispersions in different ratio by two method i.e. Fusion and solvent evaporation method. The solvent evaporation method is better result of drug for enhancement of solubility. Oral dispersible tablet of Glimepiride was prepared by direct compression method. ODTs of glimepiride by using different super disintegrants such as sodium starch glycolate, cross povidone and croscarmellose sodium. Further, post evaluation parameters like Shape and Color of Tablets, Thickness, hardness, friability, weight variation, Uniformity of Drug Content, In vitro Dissolution Rate Studies and In-vitro disintegration time were also evaluated and the results were discussed.

A Radio-Frequency Ion Trap System for the Multi-Reflection Time-of-Flight Mass Spectrometer at SHANS and Its Offline Commissioning

To precisely measure atomic masses and select neutron-deficient isotopes produced by fusion evaporation reactions, an MRTOF-MS (multi-reflection time-of-flight mass spectrometer) at the SHANS (Spectrometer for Heavy Atom and Nuclear Structure) is being developed. One of the key parts, an RF ion trap system with the aim to provide brilliant ion pulses with a low energy spread and narrow pulse width for ion preparation prior to injection into the MRTOF mass analyzer, has been constructed and commissioned offline successfully. The principle, construction details and test results are reported. Pulsed beams of 39K1+, 85,87Rb1+ and 133Cs1+ ions have been tested and the amplitudes and frequencies of the RF signals, DC voltages, helium gas pressure and time parameters have been scanned. The corresponding time spreads have reached 0.252 µs, 0.394 µs and 0.450 µs, respectively.

Bulk and neutron–proton asymmetry coefficients of the semi-empirical mass formula tuned to ground state mass excess of AME2020 and/or FRDM(2012)

Davidson et al. has extended Seeger’s mass formula to non-zero excitation energies by introducing temperature-dependent coefficients in the liquid drop energy part of the semi-empirical mass formula, but did not consider the nuclear shape and shell effects. The semi-empirical mass formula of Davidson et al. is applicable for nuclear temperatures less than or equal to 4 MeV. The mass excess calculated using this mass formula with/without nuclear shape and shell effects does not reproduce the ground state mass excesses of the new atomic mass evaluation data AME2020 and/or FRDM(2012) with its coefficients at zero temperature. So, the coefficients of the semi-empirical mass formula with nuclear shape and shell effects are required to be tuned to reproduce the ground state mass excess of all the nuclei available in the recent atomic mass evaluation data AME2020 and/or FRDM(2012). The bulk and neutron–proton asymmetry coefficients of the semi-empirical mass formula of Davidson et al., including the nuclear shape and shell effects, have been tuned to reproduce the mass excess data for all known 9420 nuclei which include all the nuclei of AME2020 (Z = 1-118 and A = 1-295) and of FRDM(2012) (Z = 8-136 and A = 16-339, except 3456 nuclei which are also available in the AME2020 data) at zero temperature. The tuned bulk and neutron–proton asymmetry coefficients reproduce the ground state mass excess of the new atomic mass evaluation data AME2020 and/or FRDM(2012) within a difference of less than 1 MeV and can be used for the applications/investigations in the areas of physics where high energies are experienced or nuclei involved are in excited states, e.g., fusion–evaporation and fusion–fission processes in heavy-ion reactions. The mass excess calculated for the excited states of nuclei is compared with the excited state mass excess of the NUBASE2020 evaluation data and is in good agreement with it.

Correlation of intrinsic fusion barriers and evaporation residue cross-sections of SHEs

Correlation of intrinsic fusion barriers and evaporation residue cross-sections of SHEs

Coexistence of single-particle and collective excitation in Ni61

The high spin states in 61 Ni have been studied using the fusion evaporation reaction, Ti( $^{14}$C,3n) $^{61}$Ni at an incident beam energy of 40 MeV. A Compton suppressed multi-HPGe detector setup, consisting of six Clover detectors and three single crystal HPGe detectors was used to detect the de-exciting $\gamma$ rays from the excited states. The level scheme has been extended up to an excitation energy of 12.8 MeV and a tentative J$_{\pi}$ = 35/2$^+$ . The low-lying negative parity levels are found to be generated by single particle excitation within the f p shell and also excitations to the g$_{9/2}$ orbitals as explained well with shell model calculations using the GXPF1Br+V M U (modified) interaction. Two rotational structure of regular E2 sequences with small to moderate axial deformation have been established at higher excitation energy. Most interestingly, two sequences of M1 transitions are reported for the first time and described as magnetic rotational bands. The shears mechanism for both the bands can be described satisfactorily by the geometrical model. The shell model calculation involving the cross shell excitation beyond the fp shell well reproduce the M1 and E2 sequences. The shell model predicted B(M1) values for the magnetic rotational band B1 show the decreasing trend with spin as expected with closing of the shears.

Stability-Enhanced Ternary Solid Dispersions of Glyburide: Effect of Preparation Method on Physicochemical Properties.

Limited aqueous solubility and subsequent poor absorption and low bioavailability are the main challenges in oral drug delivery. Solid dispersion is a widely used formulation strategy to overcome this problem. Despite their efficiency, drug crystallization tendency and poor physical stability limited their commercial use. To overcome this defect, ternary solid dispersions of glyburide: sodium lauryl sulfate (SLS) and polyethylene glycol 4000 (PEG), were developed using the fusion (F) and solvent evaporation (SE) techniques and subsequently evaluated and compared. Physicochemical and dissolution properties of the prepared ternary solid dispersions were evaluated using differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), and dissolution test. Flow properties were also assessed using Carr's index and Hausner's ratio. The physical stability of the formulations was evaluated initially and after 12 months by comparing dissolution properties. Formulations prepared by both methods similarly showed significant improvements in dissolution efficiency and mean dissolution time compared to the pure drug. However, formulations that were prepared by SE showed a greater dissolution rate during the initial phase of dissolution. Also, after a 12-month follow-up, no significant change was observed in the mentioned parameters. The results of the infrared spectroscopy indicated that there was no chemical interaction between the drug and the polymer. The absence of endotherms related to the pure drug from thermograms of the prepared formulations could be indicative of reduced crystallinity or the gradual dissolving of the drug in the molten polymer. Moreover, formulations prepared by the SE technique revealed superior flowability and compressibility in comparison with the pure drug and physical mixture (ANOVA, P < 0.05). Efficient ternary solid dispersions of glyburide were successfully prepared by F and SE methods. Solid dispersions prepared by SE, in addition to increasing the dissolution properties and the possibility of improving the bioavailability of the drug, showed acceptable long-term physical stability with remarkably improved flowability and compressibility features.

Nuclear Data Sheets for A=245

Available information pertaining to the nuclear structure of ground and excited states for all known nuclei with mass numbers A=245 have been compiled and evaluated. The adopted level and decay schemes, as well as the detailed nuclear properties and configuration assignments based on experimental data, are presented for these nuclides. When there are insufficient data, expected values from systematics of nuclear properties and/or theoretical calculations are utilized. Unexpected or discrepant experimental results are also noted. Since the last evaluation, new rotational bands in 245Pu have been observed to high spin from transfer reaction 244Pu(209Bi, 208Biγ) by 2014Ho16. While in 245Am, the 249Bk α decay measurements by 2013Ah03 added a new rotational band based on π3/2[521] configuration. The 245Pu β− decay scheme is basically what was proposed in the late 60's and 47 γ rays have still not been placed. In 245Cm, precise alpha energies and intensities were measured by 2015Ah03 in 249Cf α decay. Their reported alpha energies of the main α group were about 2 keV lower than in the previous evaluation. The spin and parity of the g.s. of 245Es is still ambiguous as more detailed information on the decay is needed. With the production of 249No via fusion evaporation reaction by groups in Dubna and GSI, it's alpha decay was studied and some properties of the daughter 245Fm were published and included in this evalaution. Information on the other nuclides is scarce and not much has been investigated since the last evaluation. A summary and compilation of the discovery of the various nuclides in this mass region is given in: 2013Fr02 (245Pu, 245Am, 245Cm, 245Bk, 245Cf), 2011Me01 (245Es), and 2013Th02 (245Md, 245Fm).

Lithium–lithium fusion evaporation research

AbstractIn this study we have explored6Li + 7Li fusion evaporation reactions cross sections dependencies on both nuclear level density and various spin combination effects. The reaction cross section was calculated in the energy range of 0.1–16 MeV projectile of6Li on the fixed target of7Li. The excited compound nucleus (13C) can decay into various channels, and its decay rate in any given channel is proportional to the available phase space, i.e., the corresponding level density of it which is explained in the present study. In the present study, LISE++, PACE4, NRV and GEMINI codes were used to determine cross section of evaporation residues cross sections of13C.

Nuclear structure studies in mirror nuclei

The nuclear structure of the A=31 and A=47 mirror couples produced by two fusion evaporation reactions has been elaborated, utilizing the Doppler-shift attenuation method. Excited states in 31P and 31S were populated using the 1p and 1n exit channels, respectively, of the reaction 20Ne + 12C, while in 47Cr and 47V couple excited states were populated based on 28Si + 28Si reaction, as products of 2αn and 2αp exit channels. The A=31 mirror couple was studied utilizing Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro with GASP multidetector array and for A=47 one - with the EUROBALL array using XTU Tandem also in Legnaro. In both cases the lifetime measurements in mirror couples at the same experiment open possibilities for investigations of isospin symmetry. Determined B(E1) strengths in the mirror nuclei 31P and 31S allow to extract the isoscalar component, which can reach up to 24% of the isovector one. The B(E1) values can be modeled by the Equation of motion method. In the case of A=47 mirror couple, the quadrupole moments can be described by shell-model calculations.

A gas-filled recoil separator, SHANS2, at the China Accelerator Facility for Superheavy Elements

A gas-filled recoil separator, SHANS2 (Spectrometer for Heavy Atoms and Nuclear Structure-2), with five magnets arranged in a Qv-D-Qh-Qv-D configuration is constructed at the China Accelerator Facility for Superheavy Elements (CAFE2) of the Institute of Modern Physics (IMP) in Lanzhou. It is dedicated to the study of the heavy nuclei produced in heavy-ion-induced fusion evaporation reactions, especially to the experiments on the superheavy elements with cross-sections lower than 1 pb. The maximum magnetic rigidity of the main dipole magnet is designed to be 2.5 T m. The detailed design of the SHANS2 and the results of several test experiments are presented.

Francium ion source with novel methods of target heating and beam characterization.

We have developed a novel ion source and beam diagnostic system for the production and detection of radioactive francium (Fr) isotopes. The Fr ions are produced using a fusion-evaporation reaction at the RIKEN Nishina Center, Japan. The installation of an infrared heater has enabled a precise and rapid control of the target temperature, and the newly developed diagnostic system allows for a quantitative characterization of the extracted ion beam. With the new system, an analysis of the Fr208-211 isotopes has been performed. Additionally, the flux of Fr210 ions has been estimated as 6.7 × 106s-1 corresponding to an extraction efficiency of 24.5% and a beam purity of 1.6 × 10-5.

Progress on the magnetic rotation in the nuclei of &amp;lt;italic&amp;gt;A&amp;lt;/italic&amp;gt;~60 and &amp;lt;italic&amp;gt;A&amp;lt;/italic&amp;gt;~80 mass regions

<p indent="0mm">Nuclear collective rotation, which involves coherent contributions from many nucleons, has been well known for a long time. It is ascribed as a consequence of deformation and gives rise to regular rotational bands, which are characterized by strong electric quadrupole (<italic>E</italic>2) transitions. Studies of the rotational bands in nuclei have been in the forefront of nuclear structure physics and have led to many interesting phenomena including the backbending, superdeformed bands, and chiral doublet bands. In 1990s, a new type of rotational-like sequences, which have strong <italic>M</italic>1 transitions and weak or vanishing <italic>E</italic>2 transitions, have been discovered in weakly deformed or near-spherical nuclei and attracted a lot of interests. This new type of rotational structure cannot be understood in terms of conventional rotation of deformed nuclei but has been successfully interpreted in terms of the shears mechanism. In this interpretation, nuclear orientation is specified by the current distribution rather than the deformation. The magnetic dipole vector arises from proton particles (holes) and neutron holes (particles) in high-<italic>j</italic> orbitals, and rotates around the total angular momentum vector. In the subsequent experimental studies, the magnetic rotation phenomenon were found in the <italic>A</italic>~60, <italic>A</italic>~80, <italic>A</italic>~110, <italic>A</italic>~140, and <italic>A</italic>~190 mass regions. Here, we report the studies of magnetic rotation in the <italic>A</italic>~80 and <italic>A</italic>~60 mass regions. The high-spin structures of⁷⁵As, ⁷⁹Se and ⁶²Cu were respectively populated via ⁷⁰Zn(⁹Be, 1p3n)⁷⁵As, ⁸²Se(α, α3n)⁷⁹Se and ⁵⁴Cr(¹²C, 1p3n)⁶²Cu heavy ion fusion–evaporation reactions. The dipole bands were established for the first time in these three nuclei. The properties of these dipole bands are investigated in terms of the self-consistent tilted axis cranking covariant density functional theory. In the calculation for ⁷⁵As, ⁷⁹Se and ⁶²Cu, the valence nucleon configurations of π[(1g_9/2)¹(1f_5/2)⁻²]<x content-type="symbol">Ä</x>υ[(1g_9/2)⁵(fp)⁻³], <sc>π[(1g_9/2)¹(fp)⁵]</sc><x content-type="symbol">Ä</x>υ[(1g_9/2)⁵] and π[(f_7/2)⁻¹(p_3/2f_5/2)²]<x content-type="symbol">Ä</x>υ[(g_9/2)¹(p_3/2f_5/2)⁴] are used, respectively. The calculated energy spectra reasonably reproduce the experimental excitation energies of ⁷⁵As, ⁷⁹Se, and ⁶²Cu. The evolutions of deformation parameters <italic>β</italic> and <italic>γ</italic> of these dipole bands driven by increasing rotational frequency are discussed. In contrast to the relatively large triaxial deformation of the dipole bands in ⁷⁵As and ⁶²Cu, the dipole band of ⁷⁹Se has a relatively axially symmetric and small prolate deformation. With the increase of rotational frequency, the <italic>β </italic>deformations for ⁷⁵As, ⁷⁹Se and⁶²Cu behave in a similar way, i.e., a smooth decrease in <italic>β</italic>. Meanwhile, both <italic>γ</italic> values of ⁷⁵As and ⁶²Cu show a smoothly increasing tendency. Based on the examination of the composition of the proton and neutron angular momentum vectors <italic>J</italic>_π and <italic>J</italic>_υ as well as the total angular momentum <italic>J</italic>_tot=<italic>J</italic>_π+<italic>J</italic>_υ at both the bandhead and the maximum rotational frequency, the dipole bands in ⁷⁵As and ⁷⁹Se can be interpreted as novel stapler bands, where the valence nucleons in (1g_9/2) orbital rather than the collective core are responsible for the closing of the stapler of angular momentum. Although not firmly confirmed in experiments, the dipole structure in ⁶²Cu may be a candidate of magnetic rotational bands. To unambiguously confirm this, further experimental investigations are strongly desirable.

Systematic analysis of the decay of Fl*287,288,290,292 formed in the complete fusion reactions Pu239,240,242,244+Ca48 including Skyrme forces

The fusion evaporation residue cross sections for the decay of the compound nuclear system $^{287,288,290,292}\mathrm{Fl}^{*}$ via $2n$- to $5n$-decay channels, synthesized in $^{239,240,242,244}\mathrm{Pu}+^{48}\mathrm{Ca}$, are studied using the dynamical cluster-decay model (DCM), including quadrupole deformations ${\ensuremath{\beta}}_{2i}$ for compact hot orientations ${\ensuremath{\theta}}_{i}$ at various excitation energies ${E}^{*}=32.5$ to 52.6 MeV. For the nucleus-nucleus interaction potentials, we have employed the Skyrme energy density functional based on the semiclassical extended Thomas-Fermi approach under frozen density approximation. Here, within the DCM, the Skyrme forces used are SLy4, ${\mathrm{SkM}}^{*}$, and, KDE0(v1). The DCM makes use of a single parameter, the neck-length parameter $\mathrm{\ensuremath{\Delta}}R$ that takes different values for different processes at a given temperature and provides an excellent fit to the measured data, independently of the choice of Skyrme force used. We make predictions of probable fusion-fission and quasifission mass regions of fragments and then calculate the evaporation residue cross sections ${\ensuremath{\sigma}}_{\mathrm{ER}}$ for experimentally unobserved neutron channels. Further, the product ${P}_{\mathrm{CN}}{P}_{\mathrm{surv}}$ of compound nucleus (CN) fusion probability ${P}_{\mathrm{CN}}$ and survival probability ${P}_{\mathrm{surv}}$ is calculated to determine the reduced evaporation residue cross section ${\ensuremath{\sigma}}_{\mathrm{ER}}/{\ensuremath{\sigma}}_{\mathrm{fusion}}$, denoted as ${\ensuremath{\sigma}}_{\mathrm{ER}}^{\mathrm{reduced}}$, and we have seen that ${P}_{\mathrm{surv}}$ is the main dominant factor in the product ${P}_{\mathrm{CN}}{P}_{\mathrm{surv}}$. To this end, we have analyzed the effects of mass asymmetry and isospin effect of target nucleus on the ${\ensuremath{\sigma}}_{\mathrm{ER}}$ and have found that the ${\ensuremath{\sigma}}_{\mathrm{ER}}$ for the production of superheavy element ${\mathrm{Fl}}^{*}$ increases slowly with increasing neutron number of the target nucleus. We have also searched for all possible target-projectile combinations forming the hot compound nucleus ${\mathrm{Fl}}^{*}$ at the excitation energy ${E}^{*}$ for compact-hot configurations and have also calculated the fusion evaporation residue cross sections for the proposed new reactions synthesizing Fl.

Progress on production cross-sections of unknown nuclei in fusion evaporation reactions and multinucleon transfer reactions

The progresses on production cross-sections of unknown nuclei in fusion evaporation (FE) reactions and multinucleon transfer (MNT) reactions are reviewed. The synthesis of the superheavy nuclei (SHN) with [Formula: see text], 119, 120, 121, and 122 in FE reactions is presented. As a promising pathway to produce neutron-rich nuclei, the MNT reactions near the Coulomb barrier are applied to investigate the generation of neutron-rich heavy nuclei and the transuranium nuclei. The predicted production cross-sections of unknown neutron-rich nuclei in MNT reactions are summarized. We make a comparison of the radioactive beam-induced FE reactions and MNT process for producing the predicted double magic nuclei [Formula: see text]Fl, which provides a possible pathway to approach the island of stability.

On the time-scale of quasifission and Coulomb fission

The Coulomb fission may take place in a reaction if the maximum Coulomb excitation energy transfer exceeds the fission barrier of either the projectile or the target nucleus. This condition is satisfied in all the reactions used for the earlier blocking measurements of fission time-scale except for the reaction \(^{208}\hbox {Pb}~+\) natural Ge crystal, where the time-scale is below the measurement limit of the blocking technique \(<1\) as. Inclusion of Coulomb fission in the data analysis of the blocking experiments leads us to interpret the measured time-scales longer than a few attoseconds (as) (about 1–2.2 as) due to slow Coulomb fission and those shorter than 1 as, as due to quasifission and fast Coulomb fission. Consequently, this finding resolves the critical discrepancies between the fission time-scales measured using the nuclear and blocking techniques. This, in turn, validates the fact that the quasifission and fast Coulomb fission time-scales are indeed of the order of zeptosecond (zs) in accordance with the nuclear experiments and theories. The present results thus provide an essential input to the understanding of the fusion evaporation reaction during the formation of heavy elements.

Evidence for prolate-oblate shape coexistence in the odd- ABr383573 nucleus

The excited states in $^{73}\mathrm{Br}$ nucleus have been investigated through the fusion evaporation reaction $^{50}\mathrm{Cr}(^{28}\mathrm{Si}$, $\ensuremath{\alpha}p)^{73}\mathrm{Br}$ at a beam energy of 90 MeV using the Indian National Gamma Array. The $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidence technique has been used to add eight new $\ensuremath{\gamma}$-ray transitions in the level scheme. The mixing ratio of $\mathrm{\ensuremath{\Delta}}I=0$ (mixed with $E2$ and $M1$) transitions have been determined using angular distribution and ${R}_{\mathrm{DCO}}$-polarization measurement. The half-life of the ${9/2}^{+}$ isomeric state has been measured to be ${\ensuremath{\tau}}_{1/2}=52(2)$ ns from the variation in the intensity of delayed $\ensuremath{\gamma}$-ray transition as a function of coincidence time window. The two state mixing model calculations were performed to obtain the mixing amplitude, and mixing interaction of two different configurations of $^{73}\mathrm{Br}$. The calculated mixing amplitudes along with the deformations of two different configurations provide the monopole transition strength ${\ensuremath{\rho}}^{2}(E0)$ for Se, Br, and Kr isotopes in a semiempirical approach. These results support a prolate-oblate shape coexistence in the odd-$A\phantom{\rule{4pt}{0ex}}^{73}\mathrm{Br}$ nucleus. The observed structural properties have been discussed in terms of projected shell model calculations.

Timing characteristics of the R13089-100 photomultiplier tube coupled with 1.5" × 1.5" CeBr3 scintillators and its application in lifetime measurements

The fast-timing performance of the Hamamatsu Photomultiplier Tube (PMT) model R13089-100 is investigated using 1.5" × 1.5" CeBr3 scintillators. The time walk was measured using the Mirror-Symmetric Centroid Difference (MSCD) method for various PMT Bias voltages and CFD delays, to optimize the parameters for measurement of the lifetime of nuclear excited states via the γ-γ fast-timing technique. The 152Eu and 133Ba sources were used for investigation on timing characteristics. Lifetimes of 161 and 383 keV states of 133Cs from the decay of 133Ba radioactive source have been determined for different bias voltages of PMT and CFD delays, with two 1.5" × 1.5" CeBr3 detector setup. The lifetime of 1522 keV state of 209Po from the decay of 209At, produced from α induced fusion evaporation reaction, has also been determined. The results reported in the present paper show that the time resolution and time-walk characteristics of the Hamamatsu PMT R13089-100 can be improved in low-energy region using higher PMT bias voltage and shorter CFD delay.

High-spin states of $$^{204}$$At: isomeric states and shears band structure

High-spin states of neutron-deficient trans-lead nucleus \(^{204}\hbox {At}\) were populated up to \(\sim 8\,\mathrm{MeV}\) excitation through the \(^{12}\hbox {C} + ^{197}\hbox {Au}\) fusion evaporation reaction. Decay of the associated levels through prompt and delayed \(\gamma \)-ray emissions were studied to evaluate the underlying nuclear structure. The level scheme, which was partly known, was extended further. An isomeric \(16^+\) level with observed mean lifetime \(\tau =52 \pm 5\, \mathrm{ns}\), was established from our measurements. Attempts were made to interpret the excited states based on multi quasiparticle and hole structures involving \(2f_{5/2}\), \(1h_{9/2}\), and \(1i_{13/2}\) shell model states, along with moderate core excitation. Magnetic dipole band structure over the spin parity range: \(16^+\)–\(23^+\) was confirmed and evaluated in more detail, including the missing cross-over E2 transitions. Band-crossing along the shears band was observed and compared with the evidence of similar phenomena in the neighbouring \(^{202}\hbox {Bi}\), \(^{205}\hbox {Rn}\) isotones and the \(^{203}\hbox {At}\) isotope. Based on comparison of the measured B(M1)/B(E2) values for transitions along the band with the semiclassical model based estimates, the shears band of \(^{204}\hbox {At}\) was established along with the level scheme.

Lifetime measurements in the tungsten isotopes W176,178,180

Lifetimes of yrast states in the rare-earth midshell isotopes $^{176,178,180}\mathrm{W}$ have been measured with fast-timing methods using the Cologne iron-free Orange spectrometer and the Cologne HORUS spectrometer and with the recoil distance Doppler shift method using the Cologne coincidence plunger setup. Different fusion evaporation reactions have been used to populated excited states in the investigated nuclei. Lifetimes of the ${2}_{1}^{+}$, ${4}_{1}^{+}$, ${6}_{1}^{+}$, and ${8}_{1}^{+}$ yrast states were measured in all three tungsten isotopes and in addition the lifetime of the ${10}_{1}^{+}$ state was measured in $^{176}\mathrm{W}$. Quadrupole deformation parameters, reduced transition probabilities, and ${\text{B}}_{4/2}$ ratios are extracted and discussed in the context of interacting boson model 1 calculations. The results with newly determined signatures largely confirm the investigated tungsten isotopes to be deformed prolate rotors.