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Within the macroscopic approach, investigation of different decay modes such as alpha-decay, cluster-decay (¹²C to ⁴⁰Ca), heavy particle radioactivity (HPR) (⁵⁸Ni to ⁸⁵Rb), and spontaneous fission (SF) half-lives are investigated in detail in the superheavy element (SHE), Z = 119. The decay energies, penetration probability, and different decay half-lives in the isotopes of synthesized superheavy nuclei (SHN) ^290–303119 are evaluated. Both ¹²C and ⁴⁰Ar cluster emissions reveal shorter half-lives when compared to other cluster emissions. Furthermore, ⁸⁵Rb heavy particle emission from the SHN ^290–303119 discloses shorter half-lives compared to other heavy particle emissions. From the comparison of different decay half-lives, it is observed that ⁸⁵Rb HPR is dominant in the region ^290–299119, alpha-decay is dominant for the ^300–302119, and SF half-lives are predominant in ³⁰³119 nuclei. Hence, the prediction of decay modes and decay path in the SHE, Z = 119 are helpful in the identification of experimentally synthesized SHE.

The paper proposes a novel cosmological model based on a two-field scenario, where the two fields are independently coupled with a specific invariant, based on cubic contractions of the Riemann tensor. After obtaining the modified Friedmann equations and the specific Klein–Gordon relations, the investigation studies the corresponding physical features by adopting the linear stability theory in a quintom scenario case where the coupling functions and potential energies have an exponential behavior. The corresponding investigation revealed a high complexity of the phase space structure, with various stationary points which can explain different aspects in the evolution of our Universe, the matter dominated epoch, and the late time accelerated stage. The present model can represent a viable solution to the dark energy problem due to the high complexity of the phase space and the existence of the scaling solutions.

In this work, we present a theoretical investigation of the structural and optoelectronic properties of Ga_xIn_1-xBi_yP_1-y quaternary alloys lattice-matched to InP using the full-potential linearized augmented plane wave approach based on the functional theory of density. The local density approximation (LDA) and the generalized gradient approximation of Wu–Cohen (WC-GGA) have been used for calculating the structural properties of Ga_xIn_1-xBi_yP_1-y quaternaries. The lattice matching condition and the range of (x, y) concentrations for which the quaternary alloys are lattice-matched to InP substrate were determined. It is found that the calculated lattice constants of Ga_xIn_1-xBi_yP_1-y for all selected concentrations (x, y) are about 5.9 Å, which are in good agreement with the experimental value of the lattice constant of InP (5.869 Å). The electronic property calculations are executed via EV-GGA and TB-mBJ approximations. The calculated band structures show that Ga_xIn_1-xBi_yP_1-y quaternaries have semiconductor character and exhibit a direct band gap, for all selected concentrations (x, y). In addition, the optical properties were calculated and discussed in detail. And also, the optical band gaps of quaternaries were determined using Tauc's method. We observed that the Ga_xIn_1-xBi_yP_1-y quaternaries cover the wavelength ranging from 0.911 to 2.456 µm while maintaining a lattice match to the InP substrate. The obtained results reveal that these quaternaries are suitable candidates for telecommunication applications.

Measurements of the L-shell X-ray emission of fluorine-like europium ions (Eu⁵⁴⁺) were made under controlled laboratory conditions on the EBIT-I electron beam ion trap at Livermore using an X-ray calorimeter, extending such measurements to the middle of the rare earth elements. Comparing the calorimeter spectra with atomic data from the flexible atomic code, we have identified and analyzed several prominent n = 3 → n = 2 transitions, including one two-electron, one-photon core changing transition and one electric quadrupole transition. We find that the measured energies are typically up to several eV higher than predicted.

Galperin introduced an interesting method to learn the digits of π by counting the collisions of two billiard balls and a hard wall. This paper studies two quantum versions of the Galperin billiards. It is shown that the digits of π can be observed in the phase shifts of the quantum models.

In this work, we carried out in-depth study of the structural, electronic, and optical properties of intrinsic, fluorine (F)- and chlorine (Cl)-doped SnO₂, using a pseudo-potential plane-wave scheme in the framework of the density functional theory. We found that the substitution of oxygen by F or Cl elements slightly modified the crystalline parameters without altering the stability of SnO₂ compounds. The doping of tin oxide by these two halogens is confirmed by the displacement of the Fermi level position to the conduction band. Consequently, the doped materials are strongly degenerated as illustrated by the Moss-Burstein shift: 2.310 and 2.332 eV for F:SnO₂ and Cl:SnO₂, respectively. On the other hand, the density of states and Mulliken population analysis show that the covalent character of Sn–O bond is maintained after doping, while Sn–X (X = F or Cl) bond reveals an ionic nature. In terms of optical properties after doping, intrinsic SnO₂ exhibits low absorption, while the doped ones are transparent in the visible range, making them more efficient in photovoltaic applications. Moreover, in the ultraviolet (UV) scale, pure and doped tin oxide compounds show better absorption, which may be beneficial for use in devices of protection against UV light and UV absorbers or sensors. Finally, the plasma frequencies of 28.22, 29.16, and 27.67 eV for pure, F-, and Cl-doped SnO₂, respectively, were obtained.

High-level electronic structure calculations were conducted for LiC molecule and compared to other theoretical results. The potential energy curves (PECs) for the 18 states originating from the first three dissociation channels of LiC molecule were calculated by the internally contracted multireference configuration interaction method. The spectral constants and vibrational energy levels are reported. The transition properties for the a²Π, b²Δ, c²Σ⁻, d²Σ⁺, and 2²Π states are discussed. In addition, the spin-orbit coupling effects were taken into account in the electronic transition d²Σ⁺–a²Π. The b²Δ and c²Σ⁻ states had radiative lifetimes of approximately 0.03–16.83 and 0.86–8.06 ms, respectively. The d²Σ⁺ and 2²Π states had radiative lifetimes of approximately 1.94–64.83 and 0.31–16.59 µs, respectively. Between these transitions, the emissions from the d²Σ⁺–a²Π, 2²Π–c²Σ⁻, 2²Π–b²Δ, and 2²Π–a²Π systems were strongest, while the emissions from the c²Σ⁻–a²Π, b²Δ–a²Π, and 2²Π–d²Σ⁺ systems were weaker. The d²Σ⁺ _1/2 state had radiative lifetimes of approximately 3.75–29.81 µs. Among the spontaneous emissions of the transitions generated by the d²Σ⁺ _1/2 state, the emissions from the d²Σ⁺ _1/2–a²Π_1/2 and d²Σ⁺ _1/2–a²Π_3/2 systems were relatively strong and easily observed experimentally. The radiative lifetime variation law with the rotational quantum number for the d²Σ⁺ _1/2 state at rotational quantum number J ≤ 70 and vibrational quantum number ν ≤ 15 is also presented in this paper. In addition, almost all the strong emissions of the transitions were distributed in the infrared region. It is expected that the results of this study will serve as a helpful reference for future experimental and theoretical studies.

Online learning environments have been used intensively during the COVID-19 pandemic and are frequently preferred alternative learning environments afterward. On the other hand, the lack of adequate learning applications for online environments negatively affects teaching. The main purpose of this research is to develop problem-based learning (PBL) activities for online learning environments within the scope of Physics course and to reveal the application processes. The study was carried out with 97 students in the fall semester of the 2020–2021 academic year. PBL applications were carried out in online learning environments with the interaction of online groups of 5–7 people through the Zoom program. A qualitative research approach and critical action research model were used in this research. The data were obtained with the help of rubric form, interview, peer assessment, peer group assessment, and documents and evaluated with content analysis and descriptive analysis. In the process of PBL activities in online learning environments, students took an active role as a part of their learning processes, interacted constantly with their peers, and demonstrated high-level success in their learning competencies by fulfilling their responsibilities. In online learning environments, there is a need for application examples where all students can demonstrate their process skills and student-centered assessment–evaluation applications that will determine the application outputs.