Narrow Results

Molecular orbital (MO) calculations of more than 60 porphyrinic π conjugated structures have been performed within the framework of the Pariser–Parr–Pople approximation. The results of a series of compounds are introduced and summarized in order to show how they vary depending on the systematic change in molecular structure. These are shown schematically or itemized. Our results are compared with the spectra of the corresponding known compounds and with the MO results reported by previous workers, if available. In addition, the results have continually been compared, where possible, with those of tetraazaporphyrin or phthalocyanine systems. In naphthalene- or anthracene-fused compounds, these molecule-centered orbitals often appear, and these are indicated using either triangles or circles in figures if they appear between HOMO – 3 and LUMO + 3 orbitals.

Our theoretical approach to deal with the excitonic problem is the potential model. The considered terms are the Coulomb and quadratic ones and the energy eigenvalues are obtained. This is an interesting problem as it contains both confining and non-confining terms and has no exact analytical solutions. We consider the case of the vanishing magnetic field. Numerical results are reported in terms of the Wigner parameter. Our approach might be used for some desired materials as well.

Representative strained values of effective mass and potential of charge carriers in indium arsenide (InAs) quantum dots have been used as input to the complete orthonormal set approach of an effective-mass, single-band, and constant-potential model for the calculation of the ground state energy levels. Even with the avoidance of the diagonalization of the strain Hamiltonian matrix, the single-band-model-calculated ground state energy levels are reasonably refined by the use of representative strained values of potential and effective mass.

In this work, a variational method is used to examine the problems relevant to the free polaron energy spectrum in a wurtzite Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N triangle quantum well structure. The numerical calculations for the ground state energy, transition energy and polaron energy shifts as the functions of well-width $d$ and composition $x$ are carried out by considering the anisotropies of the parameters, such as the optical phonon frequency, dielectric constant and electron effective mass, as well as their observed changes with coordinate $z$ in this system. The research results show that the polaron energy shift caused by the electron–optical phonon interaction is large, and leads to an obvious energy decrease in the Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N triangular quantum well structure. The contribution of the confined phonon is found to increase with the increasing of the well-width and composition $x$, while that of the half space phonon is observed to decrease with the increasing of the well-width and composition $x$. The total contribution of the phonon increases with the increasing composition $x$, while a minimum is found to occur to the total contribution of the phonon during the decreasing process with the well-width. As the $d$ increases, the free polaron energies and transition energies decrease. Meanwhile, with the increasing of the composition $x$, the energy and transition energy are found to be increased. In the Al${}_y$Ga${}_{1-y}$N/Al${}_x$Ga${}_{1-x}$N triangular quantum well structure, the trends of the free polaron energy, transition energy and polaron energy shifts with the well-width and composition $x$ are found to be similar to those in the GaN/Al${}_x$Ga${}_{1-x}$N square quantum well structure. However, the corresponding values in the triangular quantum well structure are obviously greater than those in the square quantum well structure.

In this research, the ground state gamma ray bands of even ^114-124Cd isotopes are calculated using interacting boson model (IBM-1). The theoretical energy levels for Z = 48, N = 66–76 up to spin-parity 8⁺ have been obtained by using PHINT computer program. The values of the parameters in the IBM-1 Hamiltonian yield the best fit to the experimental energy spectrum. The calculated results of the ground state energy band are compared to the previous experimental results and the obtained theoretical calculations in IBM-1 are in good agreement with the experimental energy level.

The low-lying collective properties of ¹⁰²Pd, ¹⁰⁶Cd, ¹²⁴Te and ¹²⁸Xe nuclei have been established. The relation between gamma-energy over spin E_γ/I as a function of spin I has been drawn to determine the properties of these nuclei in the ground states band. The combined vibrator-γ-soft energy equation was used to calculate the energy of the ground states band for the above nuclei, and it was compared with the calculated energy by using the U(5)–O(6) of the IBM-1. The calculation of the combined equation and the IBM-1 is in good agreement with the measured and other calculated values.

Photonuclear reactions are important tools in the understanding of the nucleus. These reactions are also interesting for realizing the element creation processes in stellar environment. The use of bremsstrahlung photons generated from clinic linear accelerator is practical for performing these type of reactions. In this study, the bremsstrahlung photons with endpoint energy of 18MeV have been used for activating gallium target material. After irradiation, the transition energies and half-lives associated with the decay of ${}^{68}\mathrm{\text{Ga}}$, ${}^{70}\mathrm{\text{Ga}}$ and ${}^{72}\mathrm{\text{Ga}}$ isotopes have been determined The values obtained for half-life of ${}^{68}\mathrm{\text{Ga}}$, ${}^{70}\mathrm{\text{Ga}}$ and ${}^{72}\mathrm{\text{Ga}}$ isotopes are $67.5\pm 0.9$min, $21.1\pm 0.9$min and $13.8\pm 0.4$h, respectively. It has been seen that the values are consistent with the present literature values. In addition, the new measurements of gamma-ray energies for transition energies have been obtained comparable to the literature values with good uncertainties.

Photon induced reactions are called as photonuclear reactions and used in many research fields of nuclear science and nuclear physics. The photonuclear data are used in many nuclear applications such as radiation shielding and protection, radiation transport analyses, reactor core design, activation analysis and nuclear waste transmutation. In the past, many studies had been devoted to extract photonuclear data covering the isotopic chart. However, there is still lack of existing data. In the present study, we have performed photonuclear reactions on erbium (Er) target by using clinical electron linear accelerators (cLINAC). By using measured residual activity of photonuclear reaction products of Er nuclei, we have determined the half-life of ${}^{161}$Er nucleus and transition energies of ${}^{161}$Ho nucleus. Also, new measurements on gamma-ray energies of the products have been determined accurately. Furthermore, this study shows that repurposed cLINAC with limited budget can contribute to the global nuclear science knowledge.

Interacting Boson Model (IBM -1) has been used to study the energy levels and $B(E2)$ transition rates in Ba–Dy ($N=92$) isotones. A simplified Hamiltonian is used which is written in the creation and annihilation form and for each nucleus, by fitting the selected experimental energy levels and $B(E2)$ transition rates with the calculated ones to get the best model parameters. Using the (IBM) Hamiltonian with an intrinsic state formalism, the potential energy surfaces (PES) for even–even Ba–Dy nuclei have been obtained and the contour plot of PES show that the shape phase transitions from spherical $U(5)$ to deformed shape $SU(3)$ has been determined for the ${}^{148}\mathrm{\text{Ba}}$, while ${}^{150}$Ce, ${}^{152}$Nd, ${}^{154}$Sm, ${}^{156}$Gd and ${}^{158}$Dy nuclei are deformed and have rotational-like characters. The behavior of energy and $B(E2)$ ratios in the ground state band are examined.

The energies of the ground, $\beta$ and $\gamma$ bands as well as the associated $B(E2)$ values have been calculated using interacting boson model (IBM). We have developed a new method called “new empirical equation” for each even–even rare-earth Er–Os for $N=100$. Also, the relation of the gamma energy over spin as a function of the spin $(I)$ (E-GOS) has been drawn. The ratio between the energies of the $(I+2)$ and $(I)$ states as a function of $I$ has been drawn to determine the property of the ground-state band, these curves indicated that these isotopes have a rotational property SU(3), with the $X(5)$ property for ${}^{176}$Os isotopes. The contour plots of the potential energy surface for Er–Os for $N=100$ are studied using the simplified form of interacting boson model with an intrinsic coherent state. The critical points have been determined for ${}^{176}$Os isotopes. The behaviors of energy and $B(E2)$ ratios in the ground-state band are examined.

In this work, first-principles calculations of Sr₃MgSi₂O₈ with Eu${}^{2+}$, Ca${}^{2+}$ and Ba${}^{2+}$ dopants have been performed. These results reveal that the Eu${}^{2+}$ ions prefer to substitute the Sr${}^{2+}$ in 8f site. In addition, Ca${}^{2+}$ and Ba${}^{2+}$ have been introduced into the crystal structure to generate complex cation environments in Sr₃MgSi₂O₈. Through the analysis of the crystal structure and electronic band structure, it can be found that the lattice size, band gap value along with the density of states of Sr₃MgSi₂O₈ could be changed and the coordination environments around the Eu${}^{2+}$ could be modulated through the Ca${}^{2+}$ or Ba${}^{2+}$ substituting for Sr${}^{2+}$. The Ca${}^{2+}$ doping would induce decreased crystal structure and band gap value between the VB and CB. Meanwhile, the Ba${}^{2+}$ doping would induce enlarged crystal structure and band gap value between the VB and CB. Especially, the bond length range of Eu${}^{2+}$ and O${}^{2-}$ could be expanded through the doping of Ca${}^{2+}$ or Ba${}^{2+}$. In summary, it can be concluded that the doped Ca${}^{2+}$ and Ba${}^{2+}$ in Sr₃MgSi₂O₈ could successfully modulate the coordination environment around the Eu${}^{2+}$ and thus lead to multiple light emissions of Eu${}^{2+}$.

The excited states of light neutron-rich isotopes were studied in the reactions of stopped pion absorption. The level structure of the superheavy hydrogen isotopes ^4–7H, heavy helium isotopes ^6,7He and lithium isotopes ^6-12Li were determined up to the excitation energy ∼ 30 MeV. For most nuclei results were obtained in several reaction channels. The wide range of excitation energies provided the possibilities to study isobar-analog states and cluster resonances. Our data are compared with theoretical and experimental results obtained up to now.

The excited states of heavy helium isotopes ^6,7He were studied in stopped pion absorption on ^10,11B nuclei. In three reaction channels ¹¹B(π⁻, dt)⁶He, ¹⁰B(π⁻, pt)⁶He and ¹⁰B(π⁻, dd)⁶He the ⁶He state with E_x = 3.5(3) MeV and Г = 3.1(4) MeV has been observed. At high excitations new levels of ⁶He have been found with E_x = 9.3(2) MeV, Г = 1.0(4) MeV, E_x = 22(1) MeV, Г = 2.7(1.4) MeV and E_x = 27.0(8) MeV, Г = 2.5(1.1) MeV. Excitation spectrum of ⁷He has been studied in three reaction channels ¹¹B(π⁻, pt)⁷He, ¹¹B(π⁻, dd)⁷He and ¹⁰B(π⁻, pd)⁷He. For the first time in one experiment it was observed three low-lying narrow (Г<0.5 MeV) states with E_x = 3.1(1), 4.9(2) and 6.7(2) MeV. At high excitations new levels have been found with E_x = 19.8(3) MeV, Г = 1.5(3) MeV and E_x = 24.8(4) MeV, Г = 4.6(7) MeV.

Correlation measurements of the stopped π⁻-meson absorption reactions ¹⁰B(π⁻, dt)X and ¹¹B(π⁻, tt)X were carried out at low energy pion channel of LAMPF with the two-arm multilayer semiconductor spectrometer of charged particles. The analysis of twodimensional distributions (Dalitz' diagram) and the momentum distribution of the residual nucleus allowed to identify the process of pion absorption on the intranuclear lithium clusters 5,6Li and to get the evidence on the existence of the configurations ⁵Li + ⁵He_g.s and ⁶Li + ⁵He_g.s in the boron nuclei ^10,11B. The levels of ⁸Li^* isotope with the resonance parameters (E_x, Г): (8.7 ± 0.2, 1.9 ± 0.4) MeV and (10.1 ± 0.3, 4.0 ± 1.3) MeV were observed for the first time. These states break up with the triton emission: ⁸Li^* → t + ⁵He..