Opposite Parity Research Articles

Enhanced effects of temporal variation of the fundamental constants in2Π1/2-term diatomic molecules:207Pb19F

The ${}^{207}$Pb${}^{19}$F molecule possesses a pair of closely spaced levels of opposite parity due to near cancellation of the omega-type doubling and magnetic hyperfine interaction energy shifts [Alphei et al., Phys. Rev. A 83, 040501 (2011)]. We calculate the dependence of the transition frequency between these levels on the fine-structure constant $\ensuremath{\alpha}$ and the ratio of the light quark masses to the quantum chromodynamics scale $({m}_{q}/{\ensuremath{\Lambda}}_{\mathrm{QCD}})$, and find large enhancement of the relative effects of the variation of these parameters. Note that the effect of $\ensuremath{\alpha}$ variation appears mainly due to the significant difference in the relativistic correction factors for the fine and hyperfine structure. We hence suggest the ${}^{207}$Pb${}^{19}$F molecule as a candidate system for investigating the possible temporal variation of the fundamental constants.

OPPOSITE PARITY FERMION MIXING AND BARYONS 1/2±

We develop a variant of K-matrix, which includes the effect of opposite parity fermions (OPF) mixing, and apply it for description of πN partial waves S11 and P11. OPF-mixing leads to appearance of negative energy poles in K-matrix and restoration of MacDowell symmetry, relating two partial waves. Joint analysis of PWA results for S11 and P11 confirms significance of this effect.

Upper bound estimate of character sums over Lehmer’s numbers

Let p be an odd prime. For each integer a with 1≤a≤p−1, it is clear that there exists one and only one a ¯ with 0≤ a ¯ ≤p−1 such that a⋅ a ¯ ≡1modp. Let denote the set of all integers 1≤a≤p−1, in which a and a ¯ are of opposite parity. The main purpose of this paper is using the analytic method and the properties of Kloosterman sums to study the estimate problem of the mean value ∑ a ∈ A χ(a), and give a sharp upper bound estimate for it, where χ denotes any non-principal even character modp.MSC:11L40.

Magneto-Stark effect of excitons as the origin of second harmonic generation in ZnO.

The magneto-Stark effect of excitons is demonstrated to be an efficient source of optical nonlinearity in hexagonal ZnO. Strong resonant second harmonic generation signals induced by an external magnetic field are observed in the spectral range of 2s and 2p excitons. The microscopic theoretical analysis shows that for excitons with a finite wave vector, exciton states of opposite parity are mixed by an effective odd parity electric field induced by the magnetic field despite its even parity. The field, spectral, and polarization dependencies of the second harmonic generation intensity validate the proposed mechanism. The observed phenomenon is not limited to a certain symmetry class and therefore must be effective in other semiconductors.

The de-clustering influence of aluminum ions on the emission features of Nd3+ ions in PbO–SiO2 glasses

Nd3+ doped lead alumino silicate glasses with varying concentration of Al2O3 (from 5 to 10mol%) have been synthesized. The IR and Raman spectral studies of these glasses have indicated that there is a gradual increase in the depolymerization of the glass network with increase in the concentration of Al2O3. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were recorded at room temperature. From these studies, the radiative parameters viz., spontaneous emission probability A, the total emission probability, the radiative lifetime τ, the fluorescent branching ratio β of different transitions originated from 4F3/2 level of Nd3+ ions have been evaluated. A clear increase in the quantum efficiency and luminescence emission of the two prominent NIR bands of Nd3+ ions viz., 4F3/2→4I11/2, 13/2, is observed with increase in the concentration of Al2O3. The increase has been attributed to the possible admixing of wavefunctions of opposite parities and due to the declusterization of Nd3+ ions by Al3+ ions in the glass network.

Enhancement of red emission intensity of Ca9Y(VO4)7:Eu3+ phosphor via Bi co-doping for the application to white LEDs

The present investigation aims at the luminescence properties of Ca9Y(VO4)7:Eu3+, Bi3+ red phosphor materials. The red emission at 613 nm originating from 5D0–7F2 transition of Eu3+ in Ca9Y(VO4)7 is enhanced strongly with Bi3+–V5+ couple as the sensitizer, under excitation either into the 5L6 state or the 5D2 state. The energy transfer from Bi3+–V5+ to Eu3+ is discussed. For a fixed Eu3+ concentration, there is an optimal Bi3+ concentration with 15 mol%, at which the maximum luminescence intensity of Eu3+ is achieved. The red emission of Ca9Y(VO4)7:0.8Eu3+, 0.15Bi3+ (under 395 nm and 465 nm excitations) is stronger than that of commercial Y2O3:Eu3+ phosphor (under 395 nm and 467 nm excitations). Based on the ratios of the red emission at 613 nm to orange one at 592 nm, it is considered that the symmetry of Eu3+ site decreases with doping of Bi3+, leading to more opposite parity components. Lifetime and diffuse reflection spectra measurements indicate that the red emission enhancement is due to the enhanced transition probabilities from the ground state to 5L6 and 5D2 states of Eu3+ in the distorted crystal field. Therefore the present material is a promising red-emitting phosphor for white-light diodes with near-ultraviolet/blue GaN-based chips.

Defect solitons in parity-time symmetric optical lattices with self-defocusing nonlinearity

The existence and stability of defect solitons in parity-time (PT) symmetric optical lattices with self-defocusing nonlinearity are reported. It is found that various solitons can exist in different gaps for different defects. All of the solitons have real and imaginary parts of opposite parities. For positive defects, fundamental and multipole solitons can exist stably in the semi-infinite gap and the first gap, respectively. For zero or negative defects, fundamental and multipole solitons can exist stably in the first gap and the second gap, respectively. For solitons with positive and negative defects, there exists a cutoff point of the propagation constant above which the defect solitons vanish. The relation with the cutoff point and the depth of PT potentials is studied. The influence of the imaginary part of the PT-symmetric potentials on soliton stability is given.

Resonances Interference Effects on 233, 235U Nuclei

Abstract The asymmetry effects (as forward – backward (FB), left – right (LR) and parity non conservation (PNC)) observed in the fission induced by thermal and resonant neutrons on 233, 235 U nuclei in the frame of the formalism of mixing states of compound nucleus with the same spin and opposite parities were explained. In this work new P resonance parameters from FB and LR effects in order to explain the observed asymmetries and PNC effect have been derived. The present study demonstrates by using the multilevel Breit – Wigner formalism that the resonance states observed in FB and LR measurements are just a result of multilevel interference between S resonances. Only new P resonances, not indicated in nuclear data atlases for neutron resonance parameters, are enough to describe the asymmetry effects.

Influence of Al declustering on the photoluminescent properties of Pr3 + ions in PbO–SiO2 glasses

Pr3+ doped lead alumino silicate glasses with varying concentrations of Al2O3 (from 5 to 10mol%) have been synthesized. The IR and Raman spectral studies of these glasses have indicated that there is a gradual increase in the depolymerization of the glass network with an increase in the concentration of Al2O3. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were recorded at room temperature. The luminescence spectra of these glasses have exhibited the bands due to 3P0→3F2, 3F3, 3H6, 3H4,3H5 transitions. From these spectra, the radiative parameters viz., spontaneous emission probability A, the total emission probability AT, the radiative lifetime τ, the fluorescent branching ratio β of different transitions that originated from the 3P0 level of Pr3+ ions have been evaluated. A considerable enhancement in the luminescence emission, especially in the red region corresponding to 3P0→3H6, 3F2 transitions has been observed. The increase has been attributed to the possible admixing of wavefunctions of opposite parities and due to the declusterization of Pr3+ ions by Al3+ ions in the glass network. The branching ratio β has been observed to be the highest for the transition 3P0→3F2 and it is found to be ~50% for the glass mixed with 10mol% of Al2O3. The CIE color coordinates for three glasses have been evaluated and found to be in the bright red region.

High-resolution spectroscopic study of the C 0+ and D 1 Rydberg states of KrXe and of the X 1/2 and A1 3/2 states of KrXe+

The electronic spectrum of the C 0+, D 1←X 0+ transitions of KrXe has been studied at high resolution in the vicinity of the Kr(1S0)+Xe 6p[5/2]2 dissociation limit by resonance-enhanced (1+1′) two-photon ionization spectroscopy. The rotational structure of 13 bands, 5 and 8 of which correspond to transitions to levels of 0+ and 1 symmetry, respectively, were observed in the spectra of several isotopomers. The hyperfine structure in the spectrum of the Ω=1 levels of 84Kr129Xe was determined. The five transitions to levels of 0+ symmetry form a regular progression of bands characterized by a regular rotational structure and corresponding to high vibrational levels (with v=16–20) of the C 0+ state. The C 0+ state is found to possess significant X 1/2, A1 3/2 and A2 1/2 ion-core character in combination with an excited electron of 6pσ, 6pπ and 6sσ character, respectively, and to correlate adiabatically to the Kr(1S0)+Xe6s[1/2]1o dissociation limit. The transition to the eight levels of Ω=1 symmetry form a very irregular progression both as far as spectral positions and intensities are concerned. Rotational levels of f-symmetry, accessed via Q-branch transitions, are weakly predissociated by a repulsive level associated with the Kr(1S0)+Xe6s[1/2]0o limit. A local perturbation in the rotational structure of the fourth level of Ω=1 symmetry enabled the identification of a so far unobserved predissociative level of Ω=1 or Ω=2 symmetry with band center near 77318.5cm−1. The determination of the band centers, rotational constants and isotopic shifts of the Ω=1 levels led to the conclusion that the level structure is affected by homogeneous perturbations and that at least two electronic states of Ω=1 symmetry contribute to the spectrum of KrXe in this spectral region. Modelling the observed rovibronic structure using a coupling model involving low vibrational levels of a weakly bound Ω=1 state associated with the Kr(1S0)+Xe6s[1/2]1o dissociation limit and high vibrational levels of a more strongly bound state associated with the Kr(1S0)+Xe 6p[5/2]2 dissociation limit enabled us to reproduce the observed values of the rotational constants, vibronic positions and intensity distribution in a qualitatively satisfactory manner. However, the model failed to account for the observed isotopic shifts. Rotationally resolved photoelectron spectra of the KrXe+ X 1/2←KrXe C 0+ and KrXe+ A1 3/2←KrXe C 0+ ionizing transitions were recorded from selected rotational levels of selected isotopomers of KrXe. The rotational levels of the X 1/2 state of KrXe+ group as pairs of levels of opposite parity and have a spin-rotation coupling constant γ of approximately −2B, as a consequence of pure precession. The rotational level structure of the low-lying electronic states of KrXe+ thus appears to form the same patterns as the corresponding states of ArXe+.

Total angular momentum waves for scalar, vector, and tensor fields

Most calculations in cosmological perturbation theorydecompose those perturbations into plane waves (Fourier modes). However, for some calculations, particularly those involving observations performed on a spherical sky, a decomposition into waves of fixed total angular momentum (TAM) may be more appropriate. Here we introduce TAM waves, solutions of fixed total angular momentum to the Helmholtz equation, for three-dimensional scalar, vector, and tensor fields. The vector TAM waves of given total angular momentum can be decomposed further into a set of three basis functions of fixed orbital angular momentum (OAM), a set of fixed helicity, or a basis consisting of a longitudinal (L) and two transverse (E and B) TAM waves. The symmetric traceless rank-2 tensor TAM waves can be similarly decomposed into a basis of fixed OAM or fixed helicity, or a basis that consists of a longitudinal (L), two vector (VE and VB, of opposite parity), and two tensor (TE and TB, of opposite parity) waves. We show how all of the vector and tensor TAM waves can be obtained by applying derivative operators to scalar TAM waves. This operator approach then allows one to decompose a vector field into three covariant scalar fields for the L, E, and B components and symmetric-traceless-tensor fields into five covariant scalar fields for the L, VE, VB, TE, and TB components. We provide projections of the vector and tensor TAM waves onto vector and tensor spherical harmonics. We provide calculational detail to facilitate the assimilation of this formalism into cosmological calculations. As an example, we calculate the power spectra of the deflection angle for gravitational lensing by density perturbations and by gravitational waves. We comment on an alternative approach to CMB fluctuations based on TAM waves. Our work may have applications elsewhere in field theory and in general relativity.

Calculation of parity nonconservation in xenon and mercury

We use configuration interaction technique to calculate parity non-conservation (PNC) in metastable Xe and Hg [proposal of the experiment in L. Bougas et al, Phys. Rev. Lett. 108, 210801 (2012)]. Both, nuclear spin-independent and nuclear spin-dependent (dominated by the nuclear anapole moment) parts of the amplitude are considered. The amplitudes are strongly enhanced by proximity of the states of opposite parity.

A note on the diophantine equation (a n − 1)(b n − 1) = x 2

Let a, b be fixed positive integers such that a ≠ b, min(a, b) > 1, ν(a−1) and ν(b − 1) have opposite parity, where ν(a − 1) and ν(b − 1) denote the highest powers of 2 dividing a − 1 and b − 1 respectively. In this paper, all positive integer solutions (x, n) of the equation (an − 1)(bn − 1) = x2 are determined.

Dynamical correlation effects in the transition probability: A study for the atoms Li to Ar

Explicitly correlated wave functions constructed as a Jastrow correlation factor times a model function have been obtained for the ground and the first excited state of opposite parity of the atoms Li to Ar. Single and restricted multi-configuration model functions are employed. Line strength, oscillator strength and transition probabilities have been obtained. An analysis of the different correlation mechanisms considered, single particle excitations and dynamical correlations, on these quantities is carried out. All calculations have been done by using Variational Monte Carlo, except when no Jastrow is involved where calculations have been performed using the Optimized Effective Potential method.

Multiple anisotropic collisions for advection–diffusion Lattice Boltzmann schemes

This paper develops a symmetrized framework for the analysis of the anisotropic advection–diffusion Lattice Boltzmann schemes. Two main approaches build the anisotropic diffusion coefficients either from the anisotropic anti-symmetric collision matrix or from the anisotropic symmetric equilibrium distribution. We combine and extend existing approaches for all commonly used velocity sets, prescribe most general equilibrium and build the diffusion and numerical-diffusion forms, then derive and compare solvability conditions, examine available anisotropy and stable velocity magnitudes in the presence of advection. Besides the deterioration of accuracy, the numerical diffusion dictates the stable velocity range. Three techniques are proposed for its elimination: (i) velocity-dependent relaxation entries; (ii) their combination with the coordinate-link equilibrium correction; and (iii) equilibrium correction for all links. Two first techniques are also available for the minimal (coordinate) velocity sets. Even then, the two-relaxation-times model with the isotropic rates often gains in effective stability and accuracy. The key point is that the symmetric collision mode does not modify the modeled diffusion tensor but it controls the effective accuracy and stability, via eigenvalue combinations of the opposite parity eigenmodes. We propose to reduce the eigenvalue spectrum by properly combining different anisotropic collision elements. The stability role of the symmetric, multiple-relaxation-times component, is further investigated with the exact von Neumann stability analysis developed in diffusion-dominant limit.

Pseudo Jahn–Teller origin of bending instability of triatomic molecules

For several decades the bending of linear molecules in degenerate states has been assumed to be due to the Renner–Teller effect (RTE), whereas the pseudo Jahn–Teller effect (PJTE) has been completely ignored. But in a recent publication of ab initio calculations performed on a series of triatomics it was shown that the contribution of the PJTE to their bending instability is much larger than that of the RTE. This raised the question of whether the finding of the essential role of the PJTE in the instability is a particular case for the molecules studied or a general trend. The problem is important not only for rationalizing the experimental observations and ab initio calculations of such systems, but also for a correct interpretation of their spectra, as the PJTE, by admixing excited states of different symmetry (opposite parity) to the ground one, influences significantly their spectroscopic properties. To contribute to the solution of this problem we performed ab initio calculations of electronic structure and energy profiles of a group of triatomic systems including CH2+,H2O+,SiH2+,PH2, and HNF which have a Π twofold degenerate state in the linear configuration, but are bent in the equilibrium geometry. For them we formulated the combined RTE and PJTE problem and, by calculating ab initio the Renner–Teller vibronic coupling constant g and estimating the other parameters by fitting the PJTE equations to the ab initio calculated energy profiles, we show that in all the cases under consideration the PJTE contribution is significantly larger than that of the RTE. The parameters of the equilibrium geometry and electronic structure of these systems obtained in our calculations are in good agreement with those reported in other publications.

Pseudo Jahn-Teller Origin of Perovskite Multiferroics, Magnetic-Ferroelectric Crossover, and Magnetoelectric Effects: Thed0−d10Problem

The conditions of multiferroicity in d(n) perovskites are derived from the pseudo Jahn-Teller effect, due to which ferroelectric displacements are triggered by vibronic coupling between ground and excited electronic states of opposite parity but same spin multiplicity; it takes place for some specific d(n) configurations and spin states only. In combination with the high-spin-low-spin crossover effect this leads to a novel phenomenon, the magnetic-ferroelectric (multiferroics) crossover which predicts magnetoelectric effects with exciting functionalities including electric magnetization and demagnetization.

Hyperons Analogous to the Λ(1405)

The low mass of the $\Lambda(1405)$ hyperon with $j^P = 1/2^-$, which is higher than the ground state $\Lambda(1116)$ mass by 290 MeV, is difficult to understand in quark models. We analyze the hyperon spectrum in the bound state approach of the Skyrme model that successfully describes both the $\Lambda(1116)$ and the $\Lambda(1405)$. This model predicts that several hyperon resonances of the same spin but with opposite parity form parity doublets that have a mass difference of around 300 MeV, which is indeed realized in the observed hyperon spectrum. Furthermore, the existence of the $\Xi(1620)$ and the $\Xi(1690)$ of $j^P=1/2^-$ is predicted by this model. Comments on the $\Omega$ baryons and heavy quark baryons are made as well.

Non-yrast nuclear spectra in a model of coherent quadrupole-octupole motion

A model assuming coherent quadrupole-octupole vibrations and rotations is applied to describe non-yrast energy sequences with alternating parity in several even-even nuclei from different regions, namely $^{152,154}$Sm, $^{154,156,158}$Gd, $^{236}$U and $^{100}$Mo. Within the model scheme the yrast alternating-parity band is composed by the members of the ground-state band and the lowest negative-parity levels with odd angular momenta. The non-yrast alternating-parity sequences unite levels of $\beta$-bands with higher negative-parity levels. The model description reproduces the structure of the considered alternating-parity spectra together with the observed B(E1), B(E2) and B(E3) transition probabilities within and between the different level-sequences. B(E1) and B(E3) reduced probabilities for transitions connecting states with opposite parity in the non-yrast alternating-parity bands are predicted. The implemented study outlines the limits of the considered band-coupling scheme and provides estimations about the collective energy potential which governs the quadrupole-octupole properties of the considered nuclei.

Macroscopic amplification of electroweak effects in molecular Bose-Einstein condensates

We investigate the possible use of Bose-Einstein condensates of diatomic molecules to measure nuclear spin-dependent parity violation effects, outlining a detection method based on the internal Josephson effect between molecular states of opposite parity. When applied to molecular condensates, the fine experimental control achieved in atomic bosonic Josephson junctions could provide data on anapole moments and neutral weak couplings.