首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
In this article, we study the $\frac{1} {2}^ -$ and $\frac{3} {2}^ -$ heavy and doubly heavy baryon states $\Sigma _Q \left( {\frac{1} {2}^ - } \right)$ , $\Xi '_Q \left( {\frac{1} {2}^ - } \right)$ , $\Omega _Q \left( {\frac{1} {2}^ - } \right)$ , $\Xi _{QQ} \left( {\frac{1} {2}^ - } \right)$ , $\Omega _{QQ} \left( {\frac{1} {2}^ - } \right)$ , $\Sigma _Q^* \left( {\frac{3} {2}^ - } \right)$ , $\Xi _Q^* \left( {\frac{3} {2}^ - } \right)$ , $\Omega _Q^* \left( {\frac{3} {2}^ - } \right)$ , $\Xi _{QQ}^* \left( {\frac{3} {2}^ - } \right)$ and $\Omega _{QQ}^* \left( {\frac{3} {2}^ - } \right)$ by subtracting the contributions from the corresponding $\frac{1} {2}^ +$ and $\frac{3} {2}^ +$ heavy and doubly heavy baryon states with the QCD sum rules in a systematic way, and make reasonable predictions for their masses.  相似文献   

2.
A full ligand-field energy matrix diagonalization treatment for 3d 1 ions in tetragonal symmetry is developed on the basis of the two spin?Corbit coupling parameter model, and the contributions of the spin?Corbit coupling of the ligand ions to the optical and electron paramagnetic resonance spectra are included. Spin Hamiltonian parameters of the tetragonal ${\rm V}^{4+}$ center in $\hbox{K}_2\hbox{SO}_4 {-} \hbox{Na}_2\hbox{SO}_4{-}\hbox{ZnSO}_4$ glass are calculated from the complete energy matrix diagonalization and the perturbation theory methods. The results calculated by both methods are not only close to each other but also in good agreement with the experimental values. Furthermore, the compressed defect structure of the ${\rm (VO_6)^{8-}}$ cluster is discussed.  相似文献   

3.
Induced effects in the photodetached electron spectra from a diatomic negative ion (H $_2^-$ ) near a hard surface are investigated. A z-polarized laser is used to knock off electrons from H $_2^-$ in the vicinity of a hard surface. Theoretical imaging method is used to derive a generalized modulation function for the total photodetachment cross-section, which describes invisible oscillation. It is found that the hard surface strongly affects the detached electron flux as well as total photodetachment cross-section. There exists strong dependence on the distance of H $_{2}^{-}$ from the hard surface and also on the separation of atomic centres of H $_2^-$ . Unlike the detached electron flux, no visible oscillations are noted in the photodetachment cross-section.  相似文献   

4.
The theoretical calculations indicated that the monoclinic low-temperature phase of silver telluride $(\upbeta \hbox {-Ag}_{2}\hbox {Te})$ is a new binary topological insulator with highly anisotropic single Dirac cone surface. We obtained $\upbeta \hbox {-Ag}_{2}\hbox {Te}$ crystal ingots containing few grains by the Bridgman method. We also deposited thin films of tellurium, $\hbox {Ag}_{5}\hbox {Te}_{3}\hbox { and }(\hbox {Te+Ag}_{5}\hbox {Te}_{3})$ by thermal evaporation method. The Raman spectra of $\upbeta \hbox {-Ag}_{2}\hbox {Te}$ , tellurium and $\hbox {Ag}_{5}\hbox {Te}_{3}$ were measured at three excitation wave lengths: 633, 515 and 488 nm. The Raman active modes of $\upbeta \hbox {-Ag}_{2}\hbox {Te}$ , tellurium and $\hbox {Ag}_{5}\hbox {Te}_{3}$ are situated at frequencies below 300  $\hbox {cm}^{-1}$ while vibrations of other phases appear at higher frequencies.  相似文献   

5.
Complex perovskite oxide ferroelectric thin films are of great technological interest because of their high dielectric constant and large tunability. In this paper, we report the structural and electrical properties of Sr \(_{3}\) Pb \(_{6}\) Ce \(_{2}\) Ti \(_{12}\) O \(_{36}\) (SPCTO) thin films grown by pulsed laser deposition. The role of oxygen pressure and substrate temperature on the microstructure, dielectric properties and leakage current mechanism of SPCTO thin films was investigated. Strong oxygen partial pressure dependence on the microcrystalline properties and leakage current conduction mechanism was observed. Both Raman spectra and C-V characteristics show a ferroelectric phase rather than paraelectric phase for the deposited thin films. Investigations on the leakage current showed that SPCTO thin films deposited at different oxygen pressure have different dominant conduction mechanism at various electric fields. The low field conduction mechanism is governed by Ohmic and space charge limited conduction mechanisms, whereas at high fields, the conduction process is dominated by Schottky emission mechanism. The dielectric constant as well as the tunability is found to increase with increase in the crystallite size.  相似文献   

6.
Chemiluminescence experiments have been performed to assess the state of current $\mathrm{CO}_{2}^{*}$ kinetics modeling. The difficulty with modeling $\mathrm{CO}_{2}^{*}$ lies in its broad emission spectrum, making it a challenge to isolate it from background emission of species such as CH? and CH2O?. Experiments were performed in a mixture of 0.0005H2+0.01N2O+0.03CO+0.9595Ar in an attempt to isolate $\mathrm{CO}_{2}^{*}$ emission. Temperatures ranged from 1654 K to 2221 K at two average pressures, 1.4 and 10.4 atm. The unique time histories of the various chemiluminescence species in the unconventional mixture employed at these conditions allow for easy identification of the $\mathrm{CO}_{2}^{*}$ concentration. Two different wavelengths to capture $\mathrm{CO}_{2}^{*}$ were used; one optical filter was centered at 415 nm and the other at 458 nm. The use of these two different wavelengths was done to verify that broadband $\mathrm{CO}_{2}^{*}$ was in fact being captured, and not emission from other species such as CH? and CH2O?. As a baseline for time history and peak magnitude comparison, OH? emission was captured at 307 nm simultaneously with the two $\mathrm{CO}_{2}^{*}$ filters. The results from the two $\mathrm{CO}_{2}^{*}$ filters were consistent with each other, implying that indeed the same species (i.e., $\mathrm{CO}_{2}^{*}$ ) was being measured at both wavelengths. A first-generation kinetics model for $\mathrm{CO}_{2}^{*}$ and CH2O? was developed, since no comprehensively validated one exists to date. CH2O? and CH? were ruled out as being present in the experiments at any measurable level, based on calculations and comparisons with the data. Agreement with the $\mathrm{CO}_{2}^{*}$ model was only fair, which necessitates future improvements for a better understanding of $\mathrm{CO}_{2}^{*}$ chemiluminescence as well as the kinetics of the ground state species.  相似文献   

7.
$\hbox {In}_{2}\hbox {S}_{3}$ thin films have been elaborated onto glass substrate by SILAR method at room temperature using different immersion time in the solution of cation and anion and fixing the rinsing time. The film composition, morphology and structure were investigated using energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM) and X-ray diffraction techniques. Optical properties, such transmission and band gap have been also analyzed. The effects of annealing on the morphological structure thin films are also described. The x-rays diffraction spectra indicated that the formed compounds are $\upbeta $ - $\hbox {In}_{2}\hbox {S}_{3}$ polycrystalline thin films with $\hbox {In}_{6}\hbox {S}_{7 }$ as second phase in sample S1 and sample S2 and no another phase in sample 3. SEM revealed homogeneous and relatively uniform films and EDAX shows sample 3 with S/In=1.44. For sample 1 and sample 2, we noted an increase of band gap when rinsing time increases.  相似文献   

8.
Isomeric decays in116, 118, 120Sn and119, 120Sb have been studied by measurements of delayedγ-rays following reactions of 26–40 MeV7Li ions on Cd targets. A 6.3 μs isomer of \((vh_{11/2} ^n )^{10 + } \) character in120Sn is reported. The experimental variation inB(E2, 10+ → 8+) between \(vh_{11/2} ^n \) states in116, 118, 120, 128, 130Sn is compared with the expected dependence on vh11/2 subshell occupation number. Isomerism in Sb nuclei is also discussed, and a known high-spin isomer in119Sb is assigned the same seniority-three configuration \((\pi d_{5/2} vh_{11/2} ^n )^{25/2 + } \) as a well-established 340 μs isomer in117Sb.  相似文献   

9.
Soft X-ray absorption (XAS) and emission (XES) spectroscopies were applied to determine valence states of manganese ions in nanostructured powder of half-doped \(\hbox {La}_{0.5}\hbox {Ca}_{0.5}\hbox {MnO}_{3}\) manganite obtained by milling in a ball mill. XAS spectra were measured both in surface-sensitivity total electron-yield and in bulk-sensitivity total fluorescence-yield modes. O K\(_{\upalpha }\) XES and O 1s XAS spectra characterized the occupied and unoccupied partial O 2p densities of states are compared with band-structure calculations made using the TB-LMTO-ASA codes. Experimental Mn 2p, Ca 2p, and La 3\(d\) XAS spectra are compared with results of crystal field atomic multiplet calculations. For the nanostructured system of \(\hbox {La}_{0.5}\hbox {Ca}_{0.5}\hbox {MnO}_{3}\), concentrations of Mn\(^{4+}\) ions are found to be increased with increasing the time of milling.  相似文献   

10.
Monoclinic H-type Nb $_{2}$ O $_{5}$ powders subjected to Q-switched laser pulses in water were characterized by X-ray/electron diffraction and optical spectroscopy to have a significant optical property change with accompanied transformation into orthorhombic T-, pseudohexagonal TT-type and an amorphous phase. The T-Nb $_{2}$ O $_{5}$ nanoparticles were (100), (010), (001) and ( $\overline{2} $ 01) faceted and commonly in oriented intergrowth with TT-type or amorphized domains retaining the polymerized block units of the relic H-type. Such multiple-phase nanoparticles were hydrogenated and densified to modify Raman and FTIR bands and to show visible absorptions corresponding to a broad minimum band gap of 2.3–2.8 eV for potential opto-catalytic and electrochromic applications.  相似文献   

11.
We construct a \(U_q\bigl (\mathfrak {s}\mathfrak {o}(2n+1)\bigr )\)-equivariant local star product on the complex sphere \(\mathbb {S}^{2n}\) as a non-Levi conjugacy class \(SO(2n+1)/SO(2n)\).  相似文献   

12.
Excitation functions for \(\alpha \)-induced reactions on natural vanadium were measured in the energy range up to 20 MeV. The stacked-foil activation technique was used. The experimental results were compared with the theoretical calculations using EMPIRE-3.1, EMPIRE-3.2.2 and TENDL 2015, and with earlier experimental results. Thick target yields were calculated for the production of \(^{54}\hbox {Mn}\) and for the associated impurity \(^{52}\hbox {Mn}\).  相似文献   

13.
We extend from \(B^0 - \overline {B^0 } to T^0 - \overline {T^0 } \) the study of neutral pseudoscalar mesons with respect to mixing and CP violation. The possibility of a quite large top quark mass necessitates a more careful computation of the box diagram amplitude. Our result is that, while in \(B^0 - \overline {B^0 } \) systems CP violation is expected to be very small (~10?6) and mixing quite large (10–20% or more), precisely the opposite occurs for \( T^0 - \overline {T^0 } \) . In particular, CP violation in the \( T_u^0 - \overline {T_u^0 } \) system could be of the same order of magnitude as in the \(K^0 - \overline {K^0 } \) system (~10?3) while the mixing is totally negligible.  相似文献   

14.
The basic operator ordering regarding to coordinate-momentum operator is discussed by virtue of the technique of integration within $\mathfrak{Q}$ -ordering (all Q are on the left of all P) and $\mathfrak{P}$ -ordering (all P are on the left of all Q). We derive new operator-ordering identities about $\mathfrak{Q}$ -ordering , $\mathfrak{P}$ -ordering and Weyl-ordering of both single-mode and two-mode squeezing operators. Its application in combinatorics is pointed out.  相似文献   

15.
The process p $ \bar{{p}}$ $ \rightarrow$ $ \Lambda_{c}^{+}$ $ \bar{{\Lambda}}_{c}^{-}$ is investigated within the handbag approach. It is shown to lowest order of perturbative QCD that, under the assumption of restricted parton virtualities and transverse momenta, the dominant dynamical mechanism, characterized by the partonic subprocess u $ \bar{{u}}$ $ \rightarrow$ c $ \bar{{c}}$ , factorizes in the sense that only the subprocess contains highly virtual partons, namely a gluon, while the hadronic matrix elements embody only soft scales and can be parameterized in terms of helicity flip and non-flip generalized parton distributions. Modelling the latter functions by overlaps of light-cone wave functions for the involved baryons we are able to predict cross-sections and spin correlation parameters for the process of interest.  相似文献   

16.
We provide the energy spectrum of an electron in a degenerately doped semiconductor of parabolic band. Knowing the energy spectrum, the density-of-states (DOS) functions are obtained, considering the Gaussian distribution of the potential energy of the impurity states, showing a band tail in them e.g., energy spectrum and density-of-states. Therefore, Fermi integrals (FIs) of DOS functions, having band tail, are developed by the exact theoretical calculations of the same. It is noticed that with heavy dopings in semiconductors, the total FI demonstrates complex functions, containing both real and imaginary terms of different FI functions. Their moduli possess an oscillatory function of \(\eta \) (reduced \(\hbox {Fermi energy} = E_{\mathrm{f}}/k_{\mathrm{B}}T\), \(k_{\mathrm{B}}\) is the Boltzmann constant and T is the absolute temperature) and \(\eta _{e}\) (impurity screening potential), having a series solutions of confluent hypergeometric functions, \(\Phi (a, b; z)\), superimposed with natural cosine functions of angle \(\theta \). The variation of \(\theta \) with respect to \(\eta \) indicated a resonance at \(\eta =1.5\). The oscillatory behaviour of FIs show the existence of ‘band-gaps’, both in the real as well as in the forbidden bands as new band gaps in the semiconductor.  相似文献   

17.
We present the properties of the C-parameter as an event-shape variable. We calculate the coupling constants in the perturbative and also in the non-perturbative parts of the QCD theory, using the dispersive as well as the shape function models. By fitting the corresponding theoretical predictions to our data, we find \(\alpha _{\mathrm {s}} (M_{Z^{0}})\) = 0.117 ± 0.014 and α 0(μ I ) = 0.491 ± 0.043 for dispersive model and \(\alpha _{\mathrm {s}} (M_{Z^{0}})\) = 0.124 ± 0.015 and λ 1 = 1.234 ± 0.052 for the shape function model. Our results are consistent with the world average value of \(\alpha _{\mathrm {s}} (M_{Z^{0}})\) = 0.118 ± 0.002. All these features are explained in the main text.  相似文献   

18.
We study the photodissociation of trapped $\mathrm{H}_{2}^{+}$ ions by 248?nm light from an excimer laser. Our results are in good agreement with calculated populations and photodissociation cross sections of the involved vibrational levels and yield a determination of the ion cloud radius. These data are used to obtain a reliable estimate of the efficiency of the resonance-enhanced multiphoton dissociation (REMPD) scheme in our $\mathrm{H}_{2}^{+}$ vibrational spectroscopy experiment. We go on to estimate the expected signal-to-noise ratio and discuss future improvements of the experimental setup.  相似文献   

19.
In this work, we present a study of the magneto transport properties in magnetic multilayered structure $\text{ Ni }_{81}\text{ Fe }_{19}\text{/Zr }$ Ni 81 Fe 19 /Zr . The magnetic $(\text{ Ni }_{81}\text{ Fe }_{19})$ ( Ni 81 Fe 19 ) and non magnetic (Zr) layer thickness $(\mathbf{t}_\mathbf{NiFe}, \mathbf{t}_\mathbf{zr})$ ( t NiFe , t zr ) effects on the magneto resistance (MR) are discussed theoretically in the framework of the Johnson–Camley semi classical approach based on the Boltzmann transport equation. A comparison between calculated and measured MR is obtained. The observed MR ratio oscillates for Zr layer thickness with an average period of 7Å. A generally weak $\text{ MR }(\text{ t }_{\mathrm{NiFe}})$ MR ( t NiFe ) ratio for fixed $\mathbf{t}_\mathbf{zr}$ t zr is obtained and it shows a maxima peak of the MR with a value of 1.8 % located at $\mathbf{t}_\mathbf{NiFe}= 80$ t NiFe = 80 Å.  相似文献   

20.
First-principle calculations on the structural, electronic, optical, elastic and thermal properties of the chalcopyrite \(\hbox {MgXAs}_{2}\) (\(\hbox {X}=\hbox {Si}, \hbox {Ge}\)) have been performed within the density functional theory (DFT) using the full-potential linearized augmented plane wave (FP-LAPW) method. The obtained equilibrium structural parameters are in good agreement with the available experimental data and theoretical results. The calculated band structures reveal a direct energy band gap for the interested compounds. The predicted band gaps using the modified Becke–Johnson (mBJ) exchange approximation are in fairly good agreement with the experimental data. The optical constants such as the dielectric function, refractive index, and the extinction coefficient are calculated and analysed. The independent elastic parameters namely, \(C_{11}\), \(C_{12}\), \(C_{13}\), \(C_{33}\), \(C_{44}\) and \(C_{66 }\) are evaluated. The effects of temperature and pressure on some macroscopic properties of \(\hbox {MgSiAs}_{2}\) and \(\hbox {MgGeAs}_{2}\) are predicted using the quasiharmonic Debye model in which the lattice vibrations are taken into account.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号