Quadrupole Oscillator Strengths Research Articles

Exploring quadrupole oscillator strength of impurity doped quantum dots controlled by Gaussian white noise

Present study explores the effect of Gaussian white noise on quadrupole oscillator strength (QOS) of impurity doped quantum dot (QD). In view of this QOS profiles have been monitored as various relevant physical parameters vary over a range with and without noise. Two distinct pathways viz. additive and multiplicative have been conceived for the entrance of noise to the system. The QOS profiles exhibit rather regular behavior in absence of noise and in presence of additive noise in similar ways. However, multiplicative noise appears to be successful in bringing about important aspects like maximization, minimization and saturation in the QOS profiles and also for production of large QOS. The outcomes of the study are expected to have substantial impact on nonlinear optical properties of opto-electronic devices comprising of QD where noise plays some active role.

Asymptotic oscillator strength at the critical charge

A conjecture concerning the asymptotic behavior of the outermost orbital in atomic configurations with a single electron outside an N-electron closed shell, in the limit Z→N, was proposed on the basis of an investigation of the asymptotic behavior of the corresponding quantum defect: If the outermost atomic orbital is of type nℓ, then in the limit specified above it approaches an (infinitely diffuse) hydrogenic orbital of the form (n-nℓ)ℓ, where nℓ is the number of occupied subshells with angular momentum quantum number ℓ. The consequences of this conjecture concerning the corresponding asymptotic behavior of dipole and quadrupole oscillator strengths are formulated and explored. Reasonably convincing agreement is established for several transitions in the isoelectronic sequences of He, the alkali atoms, B, Al and Cu. Some apparent violations of the presently proposed asymptotic values of the oscillator strengths are pointed out.

Dipole and quadrupole polarizabilities and oscillator strengths of spherical quantum dot

In this study, the energy eigenvalues and eigenfunctions of the ground and excited states of a spherical quantum dot are calculated by using the Quantum Genetic algorithm (QGA) and Hartree-Fock Roothaan (HFR) method. Based on the calculated energies and wave functions, the static and dynamic dipole polarizabilities, the quadrupole polarizability, dipole and quadrupole oscillator strengths of spherical quantum dot are carried out as a function of dot size and the confining potential as perturbative. The results show that dot size and confining potential have a great influence on the polarizability and oscillator strength. It is found that the polarizability increases due to the spatial confinement effect in the strong confinement region. In the weak confinement region, the polarizability increases again until it reaches the saturation value. In addition, the peak positions of the dipole and quadrupole oscillator strengths shift toward smaller dot radii with the increases of the potential well depth.

Benchmarking Atomic Data for Astrophysics: Be-like Ions between B ii and Ne vii

Large-scale self-consistent multiconfiguration Dirac--Hartree--Fock and relativistic configuration interaction calculations are reported for the $n \leq 6$ levels in Be-like ions from B II to Ne VII. Effects from electron correlation are taken into account by means of large expansions in terms of a basis of configuration state functions, and a complete and accurate data set of excitation energies, lifetimes, wavelengths, and electric dipole, magnetic dipole, electric quadrupole, and magnetic quadrupole line strengths, transition rates, and oscillator strengths for these levels is provided for each ion. Comparisons are made with available experimental and theoretical results. The uncertainty of excitation energies is assessed to be 0.01\% on average, which makes it possible to find and rule out misidentifications and aid new line identifications involving high-lying levels in astrophysical spectra. The complete data set is also useful for modeling and diagnosing astrophysical plasmas.

Enhancement of the quadrupole interaction of an atom with the guided light of an ultrathin optical fiber

We investigate the electric quadrupole interaction of an alkali-metal atom with guided light in the fundamental and higher-order modes of a vacuum-clad ultrathin optical fiber. We calculate the quadrupole Rabi frequency, the quadrupole oscillator strength, and their enhancement factors. In the example of a rubidium-87 atom, we study the dependencies of the quadrupole Rabi frequency on the quantum numbers of the transition, the mode type, the phase circulation direction, the propagation direction, the orientation of the quantization axis, the position of the atom, and the fiber radius. We find that the root-mean-square (rms) quadrupole Rabi frequency reduces quickly but the quadrupole oscillator strength varies slowly with increasing radial distance. We show that the enhancement factors of the rms Rabi frequency and the oscillator strength do not depend on any characteristics of the internal atomic states except for the atomic transition frequency. The enhancement factor of the oscillator strength can be significant even when the atom is far away from the fiber. We show that, in the case where the atom is positioned on the fiber surface, the oscillator strength for the quasicircularly polarized fundamental mode HE$_{11}$ has a local minimum at the fiber radius $a\simeq 107$ nm, and is larger than that for quasicircularly polarized higher-order hybrid modes, TE modes, and TM modes in the region $a<498.2$ nm.

Exciton-polaritons in cuprous oxide: Theory and comparison with experiment

The observation of giant Rydberg excitons in cuprous oxide $\left(\mathrm{Cu_{2}O}\right)$ up to a principal quantum number of $n=25$ by T.~Kazimierczuk \emph{et al.} [Nature \textbf{514}, 343, (2014)] inevitably raises the question whether these quasi-particles must be described within a multi-polariton framework since excitons and photons are always coupled in the solid. In this paper we present the theory of exciton-polaritons in $\mathrm{Cu_{2}O}$. To this end we extend the Hamiltonian which includes the complete valence band structure, the exchange interaction, and the central-cell corrections effects, and which has been recently deduced by F.~Schweiner \emph{et al.} [Phys.~Rev.~B \textbf{95}, 195201, (2017)], for finite values of the exciton momentum $\hbar K$. We derive formulas to calculate not only dipole but also quadrupole oscillator strengths when using the complete basis of F.~Schweiner \emph{et al.}. Very complex polariton spectra for the three orientations of $\boldsymbol{K}$ along the axes $[001]$, $[110]$, and $[111]$ of high symmetry are obtained and a strong mixing of exciton states is reported. The main focus is on the $1S$ ortho exciton-polariton, for which pronounced polariton effects have been measured in experiments. We set up a $5\times 5$ matrix model, which accounts for both the polariton effect and the $K$-dependent splitting, and which allows treating the anisotropic polariton dispersion for any direction of $\boldsymbol{K}$. We especially discuss the dispersions for $\boldsymbol{K}$ being oriented in the planes perpendicular to $[1\bar{1}0]$ and $[111]$, for which experimental transmission spectra have been measured. Furthermore, we compare our results with experimental values of the $K$-dependent splitting, the group velocity, and the oscillator strengths of this exciton-polariton.

Calculations for energies, transition rates, and lifetimes in Al-like Kr XXIV

Using the second-order many-body perturbation theory (MBPT) method, a complete and accurate data set of excitation energies, lifetimes, wavelengths, and electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) line strengths, transition rates, and oscillator strengths for the lowest 880 levels arising from the 3l3 (0≤l≤2), 3l24l′ (0≤l≤2, 0≤l′≤3), 3s25l (0≤l≤4), 3p25l (0≤l≤1), and 3s3p5l (0≤l≤4) configurations in Al-like Kr XXIV is provided. Comparisons are made with available experimental and theoretical results. Our calculated energies are expected to be accurate enough to facilitate identifications of observed lines involving the n=4,5 levels. The complete data set is also useful for modeling and diagnosing fusion plasma.

Oscillator strengths for 1s2 1S0–1s2p 3P1,2 transitions in helium-like carbon, nitrogen and oxygen including the effects of a finite nuclear mass

We have calculated the electric dipole (E1) and magnetic quadrupole (M2) oscillator strengths and spontaneous decay rates for the spin-changing transitions of helium-like C v, N vi and O vii. We added the effects of the finite nuclear mass and the anomalous magnetic moment of the electron including an extra term derived by Pachucki. For the E1 calculations we used the Breit approximation and pseudostate expansions to perform the perturbation sums over intermediate states in both the length and velocity gauge as a check on numerical accuracy and the validity of the transition operators. There is some cancellation in the corrections for the nuclear mass and the electron anomaly so that if one is included the other should not be ignored

EXTENDED RELATIVISTIC CONFIGURATION INTERACTION AND MANY-BODY PERTURBATION CALCULATIONS OF SPECTROSCOPIC DATA FOR THE N ≤ 6 CONFIGURATIONS IN Ne-LIKE IONS BETWEEN Cr xv AND Kr xxvii

ABSTRACT Level energies, wavelengths, electric dipole, magnetic dipole, electric quadrupole, and magnetic quadrupole transition rates, oscillator strengths, and line strengths from combined relativistic configuration interaction and many-body perturbation calculations are reported for the 201 fine-structure states of the , , , , , , and configurations in all Ne-like ions between Cr xv and Kr xxvii. Calculated level energies and transition data are compared with experiments from the National Institute of Standards and Technology (NIST) and CHIANTI databases, and other recent benchmark calculations. The mean energy difference with the NIST experiments is only 0.05%. The present calculations significantly increase the amount of accurate spectroscopic data for the n &gt; 3 states in a number of Ne-like ions of astrophysical interest. A complete data set should be helpful for analyzing new observations from solar and other astrophysical sources, and is also likely to be useful for modeling and diagnosing a variety of plasmas, including astronomical and fusion plasma.

Oscillator strengths and radiative decay rates for spin-changing S–P transitions in helium: finite nuclear mass effects

We have calculated the electric dipole (E1) and magnetic quadrupole (M2) oscillator strengths and spontaneous decay rates for 24 spin-changing transitions of atomic helium. We included the effects of the finite nuclear mass and the anomalous magnetic moment of the electron augmented by the recently derived Pachucki term. The specific transitions for 4He are and with and for For the E1 calculations we used the Breit approximation and pseudostate expansions to perform the perturbation sums over intermediate states in both the length and velocity gauge as a check on both numerical accuracy and validity of the transition operators. The corrections for the nuclear mass and the electron anomaly tend to cancel, indicating that if one is included, then so should be the other. The tables give mass- and anomaly-dependent coefficients permitting the easy generation of results for the other isotopes of helium.

Quadrupole Oscillator Strengths of Helium Interacting with Debye Potentials

The influence of Debye potentials on the quadrupole oscillator strengths of helium atom is investigated using highly correlated wave functions within a framework of a variational method. The quadrupole oscillator strengths for the 1,3S–1,3D, 1,3P–1,3P and 1,3D–1,3D transitions of He for various screening parameters are reported for the first time in the literature. In free atomic case, our calculated results are in good agreement with the available results.

Relativistic Quadrupole Polarizability for the Ground State of Hydrogen-Like Ions

The static quadrupole polarizabilities for hydrogen-like ions from Z = 1 to Z = 100 in the 1S1/2 ground state are calculated to high precision by solving the Dirac equation using the B-spline Galerkin method. The results are consistent with the expression of Kaneko [J. Phys. B 10 (1977) 3347] at low Z. The quadrupole oscillator strength sum Σnf(2)gn is computed to be zero to a very high degree of precision.

Oscillator strengths of the transitions in a spherically confined hydrogen atom

Dipole and quadrupole oscillator strengths have been calculated for the series of transitions nl → n′l′ (n ⩽ 5) in a hydrogen atom confined in the centre of a sphere with impenetrable walls. The non-monotonic dependence of the oscillator strengths on the radius of confinement has been discussed through their general forms obtained with a properly chosen radial wavefunction. It was qualitatively ascribed to variation of the radial electron density distributions of the states involved in the transitions. The effect of the confinement on the use of the dipole approximation has been studied, introducing a correction through the octupole term as well as performing the calculation with the full form of the interaction term.

Electric quadrupole oscillator strengths of helium

AbstractUsing a set of explicitly correlated trial wave functions that describe the three lowest singlet and triplet states of the helium atom with symmetry S, P, and D, we calculate the electric quadrupole oscillator strengths for all possible 1S‐1D, 1P‐1P, 1D‐1D, 3S‐3D, 3P‐3P, and 3D‐3D transitions and compare their accuracy to our earlier calculations of the electric dipole oscillator strengths. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008

Quadrupole oscillator strengths for thehelium isoelectronic sequence: n 1S-m 1D,n 3S-m 3D, n 1P-m 1P, andn 3P-m 3P transitions with n

Quadrupole oscillator strengths (QOS) for He and the isoelectronic ions from Li+to Ne8+ are reported for all possible n 1S-m 1D,n 3S-m 3D, n 1P-m 1P and n 3P-m 3Ptransitions involving states with m <7 and n <7. The calculations are basedupon explicitly correlated wavefunctions that lead to variational energiesonly nano-Hartrees above the best literature values. The results extendsignificantly both the accuracy and range of the QOSsavailable for two-electron atomic species.

Moments of the quadrupole oscillator strength distribution for O 2, N 2, CO, HF, HCl, N 2O, CO 2, OCS, CS 2 and C 2H 2: ab initio sum rule calculations

Anisotropic moments, S 2, m ( k), of quadrupole oscillator strength distributions (QOSDs) are calculated for O 2, N 2, CO, HF, HCl, N 2O, CO 2, OCS, CS 2 and C 2H 2. Sum rule methods are used with ground state multi-reference configuration interaction wave functions. These methods are found to be superior to propagator and pseudo-spectral methods used with finite basis sets for those moments that place emphasis on the high energy region of the spectrum. The QOSD moments, except S 2, m (− 1), do not seem to be overly sensitive to either basis set or electron correlation effects.

An ab initio quantum chemical study of vertically excited singlet states of pyrimidine

Ab initio calculations of a number of singlet electronic states of pyrimidine are presented. In addition to the ground 1A 1 state, ten valence excited states were studied: three 1A 1 and three 1B 2 states, which are ππ* excited states, and two 1B 1 and two 1A 2 states, which are nπ* excited. Rydberg states were encountered, but since these were irrelevant to the present study, the basis set employed was not designed to describe these states well, and their energy relative to the valence states will be incorrect. Such spurious states may perturb the valence states by accidental near-degeneracy, and care was taken to effectively remove them to prevent such perturbation. The calculation were performed by the CASSCF and MRCI methods, using a modest basis set (C, N: 3s3p1d; H: 2s; 116 basis functions) of ANO type. Energies, dipole and quadrupole moments, transition moments, and oscillator strengths are reported. All calculations were made using the experimental equilibrium geometry, and all excitation data are therefore vertical. The MRCI excitation energies, corrected for unlinked clusters, give results in good agreement with known experimental data. The error in the computed excitation energy is in no case larger than 0.4 eV. In some cases, alternative assignments of experimental energies are indicated.

Electric quadrupole allowed transitions of lanthanide ions in octahedral symmetry

The calculation of the electric quadrupole oscillator strength for a transition between the crystal field levels Γ′ and Γ″ of a lanthanide ion in octahedral symmetry is presented. The calculated values are < 10-12 in most cases, except for the (6F1/2)Γ6 ← Γ7(6H5/2) transition of Sm3+ in Cs2 NaSmCl6, where the value of 2·3 × 10-10 is in agreement with experiment at 300 K. The oscillator strength for the (3F3)Γ5 ← Γ1(3H4) transition of Pr3+ in PrCl3- 6 is 8·8 × 10-13, so that an observed zero phonon line close to the calculated wavenumber of this transition, but whose intensity is 1·7 × 104 times greater, does not correspond to it. Additional information from vibronic analysis, magnetic dipole and electronic Raman line strength calculations enable reassignments to be made for the 3F3 term of Pr3+.

The quadrupole polarizability and spectral moments of the quadrupole oscillator strength distribution of N2

We report the spectral moments for 0 ˇ- k ˇ- -6 of the quadrupole oscillator strength distribution (QOSD) of N2 as calculated in the polarization propagator formalism. The moments with k ˇ- -3 have not been calculated before. The choice of basis and of inclusion of correlation to the level of RPA are discussed. The accuracy of the calculated QOSD's is estimated from sum rules, completeness relations and origin dependence. We conclude that f-orbitals are an essential ingredient for the basis, and that correlation must be included in a balanced way. Vibrationally averaged spectral moments are reported. We calculate the quadrupole polarizability and its components, and find α2 = 76·54 a.u. (Hartree atomic units), in good agreement with other calculations.

MCHF oscillator strength and lifetime calculations in neutral calcium

The authors report extensive multiconfiguration Hartree-Fock (MCHF) calculations, taking into account valence correlation and core-relaxation effects, of energy levels, eigenvector compositions, electric dipole and quadrupole oscillator strengths involving the n1S(n=1-4), n1PO (n=1, 2), n1D(n=1-3) and n1FO(n=1, 2) states in Ca I. On the whole, the agreement between theory and observation has been improved by their set of MCHF results. The theoretical transition probabilities allow the evaluation of the lifetimes for the levels 4s4p, 4s5p 1PO; 4s4d, 4p2 1D and 3d4p, 4s4f 1FO which are compared with previous measurements. The differences between MCHF calculations for series perturbed by doubly-excited states in Ca and Sr are discussed. It is concluded that core-polarization effects are of about the same importance in the two atoms but that the effects on the 3d (Ca) and 4d (Sr) orbitals are such that the total core-polarization effects for series and perturbers are of the same magnitude in Sr while large differences exist in Ca.