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We studied supramolecular chirality induced by circularly polarized light. Photoresponsive azopolymers form a helical intermolecular network. Furthermore, studies on photochemical materials using optical vortex light will also attract attention in the future. In contrast to circularly polarized light carrying spin angular momentum, an optical vortex with a spiral wave front and carrying orbital angular momentum may impart torque upon irradiated materials. In this review, we summarize a few examples, and then theoretically and computationally deduce the differences in spin angular momentum and orbital angular momentum depending on molecular orientation not on, but in, polymer films. UV-vis absorption and circular dichroism (CD) spectra are consequences of electric dipole transition and magnetic dipole transition, respectively. However, the basic effect of vortex light is postulated to originate from quadrupole transition. Therefore, we explored the simulated CD spectra of azo dyes with the aid of conventional density functional theory (DFT) calculations and preliminary theoretical discussions of the transition of CD. Either linearly or circularly polarized UV light causes the trans–cis photoisomerization of azo dyes, leading to anisotropic and/or helically organized methyl orange, respectively, which may be detectable by CD spectroscopy after some technical treatments. Our preliminary theoretical results may be useful for future experiments on the irradiation of UV light under vortex.

We investigate the electromagnetic transitions of the singly charmed baryons with spin 3/2, based on a pion mean-field approach, also known as the chiral quark-soliton model, taking into account the rotational $1/N_c$ corrections and the effects of flavor SU(3) symmetry breaking. We examine the valence- and sea-quark contributions to the electromagnetic transition form factors and find that the quadrupole form factors of the sea-quark contributions dominate over those of the valence-quark ones in the smaller $Q^2$ region, whereas the sea quarks only provide marginal contributions to the magnetic dipole transition form factors of the baryon sextet with spin 3/2. The effects of the flavor SU(3) symmetry breaking are in general very small except for the forbidden transition $\Xi_c^0\gamma\to \Xi_c^{*0}$ by $U$-spin symmetry. We also discuss the widths of the radiative decays for the baryon sextet with spin 3/2, comparing the present results with those from other works., Comment: 22 pages. 9 figures

Realizing a high luminescence dissymmetry factor ( g lum ) is a paramount yet challenging issue in the research field of circularly polarized luminescence (CPL). Here, we reported a novel set of organic conjugated systems with twisted intramolecular charge transfer (TICT) characteristics based on conjugated o -carborane-binaphthyl dyads composing of binaphthyl units as chiral electron donors and o -carborane units as achiral electron acceptors, demonstrating intense CPL with large g lum values. Interestingly, single-crystalline o -1 exhibited a high-level brightness and a large g lum factor as high as +0.13, whereas single-crystalline o -2 processed a relatively low brightness with a decreased g lum value to -0.04. The significant diversity of CPL-active properties was triggered by the selective introduction of o -carborane units onto the binaphthyl units. Benefiting from the large magnetic dipole transition moments in TICT states, the CPL activity of TICT o -carborane-based materials exhibited amplified circular polarization. This study provides an efficient molecular engineering strategy for the rational design and development of highly efficient CPL-active materials.

An extension of the Judd-Ofelt theory, a theoretical model to the field of Luminescence intensity ratio method in phosphor thermometry has been presented, that enables a calculation of thermometric figures of merit: sensitivity, maximum sensitivity and temperature resolution, by the Judd-Ofelt intensity parameters. The model is applicable for 7 out of 14 lanthanides, and as a testing ground for the model's adequacy, Y2O3 doped with three different Eu3+ concentrations had been chosen. PL spectra were recorded up to 480 °C and photoluminescence and thermometric properties have been obtained. Conventionally estimated thermometric figures of merit have been compared to those obtained by a Judd-Ofelt thermometric model, with a good matching. Consequently, a novel method for calculation of magnetic dipole strength of the mixed induced electric dipole and magnetic dipole transition has been developed. Additionally, an interactive application software has been developed for the quick evaluation of the sensitivity and temperature resolution from Judd-Ofelt intensity parameters. © 2019 Elsevier B.V.

Intrinsically chiral double stapled ortho-oligo phenylene ethynylenes (o-OPEs) 1 show g(lum) values up to 5.5 x 10(-2), the second highest value ever observed for a simple organic molecule (SOM). DFT calculations of molecular spectra and properties encompassing electric and magnetic dipole transition moments account for these observations.

The mass spectra of charmonium are investigated using a Coulomb plus linear (Cornell) potential. Gaussian wave function in position space as well as in momentum space are employed to calculate the expectation value of potential and kinetic energy respectively. Various experimental states ($X(4660)(5^{3}S_{1})$, $X(3872)(2^{3}P_{1})$, $X(3900)(2^{1}P_{1})$, $X(3915)(2^{3}P_{0})$ and $X(4274)(3^{3}P_{1})$ etc.) are assigned as charmonium states. We also study the Regge trajectories, pseudoscalar and vector decay constants, the Electric and Magnetic dipole transition rates and the annihilation decay width for charmonium states.

International audience; Series of alkali metal ion co-doped with Eu3+ activated GdPO4 phosphors were synthesized by the conventional solid state method. Structural parameters were confirmed by the X-ray Rietveld refinement method. All the compounds are crystallized in the monazite phase with space group (P121/n1, No.14). Morphology and functional group analysis were performed on scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Room temperature photoluminescence (PL) spectroscopic results reveal that, on Eu3+ ion doping in the GdPO4 host matrix, the magnetic dipole transition (5D0 → 7F1) at 581 nm responsible for orange light, dominates the red emission with respect to the electric dipole transition (5D0 → 7F2) at 620 nm. It was found that the emission intensity increased up to 9 mol% of Eu3+ and then quenched due to multipolar interactions. Further, co-doping with Li+, Na+ and K+ ion in to Eu3+ activated GdPO4 phosphor led to an enhancement in luminescence intensity by reducing the parity restriction of electric dipole transitions as a consequence of suitable local distortion of the crystal field surrounding the Eu3+ activator ion. The results of Judd–Ofelt theory and radiative parameters suggest that these phosphors have a short lifetime, good quantum efficiency, excellent color purity compared to other reported Eu3+ doped phosphors. These results illustrate the mechanistic effect of alkali metal ions doping on luminescent properties of rare earth ion doped GdPO4 phosphors and help in optimization of their luminescent properties according to the practical requirements in optoelectronic and biomedical applications.

Rare earths (Europium, cerium)-doped CdS nanofilms are prepared using the growth technique chemical bath deposition (CBD) at the reservoir temperature of 70±2°C varying the synthesis time in a wide range. For the rare earths doped CdS nanofilms the synthesis time was ranged from 80 to 135 min. The rare earths molar concentration was in the range 0.0≤x≤3.47, which was determined by energy dispersive X-ray spectroscopy (EDS). The X-ray diffraction (XRD) analysis reveals that CdS nanofilms showed the zinc blende (ZB) crystalline phase. The nanocrystal size was ranged from 2.67 to 2.35 nm for the CdS and 1.84-2.33 nm for rare earth-doped CdS that were determined by the Debye-Scherrer equation from ZB (111) direction and it was confirmed by transmission electron microscopy (TEM). The doped CdS exhibits a direct band gap that diminishes with the increase of the synthesis time, from 2.50 to 2.42 eV, which was obtained by transmittance. The room-temperature photoluminescence of CdS presents the band-to-band transition at 431 nm, which is associated with quantum confinement because the grain size is less than its Bohr exciton radius and a dominant band at 523 nm, which is called the optical signature of interstitial oxygen. Eu3+-doped CdS photoluminescence shows the dominant radiative peak at 576 nm that is associated to the intra-4f radiative transition of Eu3+ ions, which corresponds to the magnetic dipole transition, (5D0→7F1). For the Ce3+-doped CdS the dominant radiative transitions are clearly redshifted. Additionally, other radiative peaks associated at structural defects are observed. The passivation of the CdS by rare earths was approximately of two orders of magnitude obtaining better results with cerium.

International audience; Herein, we report on the theoretical-experimental analysis of the two photon absorption and circular dichroism spectra of 1-(2-pyridyl)-4-methoxy-carbo[6]helicene derivative (P6). The primary outcomes of our investigation on this particular helicene derivative with a donor-acceptor motif on one end led to two important conclusions (1) the lengthening of the π-electron delocalization within the helical core of P6 predominantly increases the contribution of the magnetic dipole transition moment to the two-photon circular dichroism (TPCD) signal; and (2) the electric quadrupole transition moment contribution to the TPCD signal is enhanced by the intramolecular charge transfer (ICT) produced by the donor-acceptor combination on one end of the molecule. To corroborate our results, we performed a comparative theoretical analysis of the effect of the energy gap and ICT on TPCD on a series of P6-like helicenes with different donor-acceptor combinations. Two-photon absorption and TPCD spectra were obtained using the double L-scan technique over a broad spectral range (400-900 nm) using 90 fs pulses at a low repetition rate (2-50 Hz) produced by an amplified femtosecond system. The theoretical simulations were calculated using time dependent density functional theory at the CAM-B3LYP/6-311++G(d,p) level of theory.

The presence of anomalous chirality in a roll of graphitic carbon sheets has been recognized since the discovery of carbon nanotubes, which are becoming available in higher quantities through the isolation of chiral single-wall congeners with high purity. Exploration of the properties arising from cylinder chirality is expected to expand the scope of tubular entities in the future. By studying molecular fragments of helical carbon nanotubes, we herein reveal interesting properties that arise from this chirality. The chirality of nanoscale cylinders resulted in chirality of larger dimensions in the form of a double-helix assembly. Cylinder chirality in solution gave rise to a large dissymmetry factor of metal-free entities in circular polarized luminescence. Theoretical investigations revealed the pivotal role of cylindrical shapes in enhancing magnetic dipole transition moments to yield extreme rotatory strength. Unique effects of cylinder chirality in this study may prompt the development of tubular entities, for instance, toward chiroptical applications.

We observe a dramatic difference in optical line shapes of a $^4\text{He}$ Bose-Einstein condensate and a $^3\text{He}$ degenerate Fermi gas by measuring the 1557-nm $2~^3S-2~^1S$ magnetic dipole transition ($8~\text{Hz}$ natural linewidth) in an optical dipole trap. The $15~\text{kHz}$ FWHM condensate line shape is only broadened by mean field interactions, whereas the degenerate Fermi gas line shape is broadened to $75~\text{kHz}$ FWHM due to the effect of Pauli exclusion on the spatial and momentum distributions. The asymmetric optical line shapes are observed in excellent agreement with line shape models for the quantum degenerate gases. For $^4$He a triplet-singlet s-wave scattering length $a=+50(10)_{\text{stat}}(43)_{\text{syst}}~a_0$ is extracted. The high spectral resolution reveals a doublet in the absorption spectrum of the BEC, and this effect is understood by the presence of a weak optical lattice in which a degeneracy of the lattice recoil and the spectroscopy photon recoil leads to Bragg-like scattering., Comment: 5 pages, 4 figures, 5 pages supplemental information

Relativistic configuration interaction calculations with the inclusion of the Breit interaction, quantum electrodynamics and finite nuclear mass corrections have been carried out in the extended optimal level scheme using multiconfiguration Dirac-Fock wavefunctions on the forbidden transition probabilities for the 2p 4 ground state configuration of the oxygen isoelectronic sequence for 8 ⩽ Z ⩽ 42. Electric quadrupole and magnetic dipole transition probabilities are reported for transitions between several of these levels. Our results are compared with those from other theories and experiments. Our energy levels are in better agreement with experiment than other theories.

The use of calculations of the rotational strengths of normal modes in order to determine the absolute configuration (AC) of a molecule, by comparing a calculated vibrational circular dichroism (VCD) spectrum to an experimental one, can be made much more reliable when the vibrational modes are classified as either robust or non-robust. The robust modes are the ones with a robust sign of the rotational strength in the sense that it will not change by small perturbations in either experiment or calculation. The signs of non-robust modes may change. Clearly only robust modes should be used to establish the AC. We recommend that programs which calculate VCD spectra should provide, per normal mode, information that indicates the robustness of a mode, and therefore its usefulness for the AC determination. Such information consists of the angle ξ between the electric and magnetic dipole transition moments, and the magnitudes of these dipole transition moments. © 2009 the Owner Societies.

International audience; Herein we report on the theoretical-experimental analysis of the one- and two-photon absorption and circular dichroism spectra of two intrinsically chiral aromatic molecules - hexahelicene derivatives - with helical chirality and intramolecular charge transfer (ICT). The primary outcomes of our investigation demonstrate that the TPA cross-section and the amplitude of the TPCD signal of this type of helicenes are strongly affected by the strength of the ICT and the nature of the extension of the electronic delocalization, i.e. beyond (EXO-ICT) or within (ENDO-ICT) the helicene core. These results were corroborated through the comparative theoretical analysis of the corresponding contributions of the magnetic dipole transition moment and the electric quadrupole transition moment to the TPA rotatory strength on a series of five similar helicene derivatives with different molecular electron delocalization disposition.Two-photon absorption (TPA) and two-photon circular dichroism (TPCD) spectra were obtained using the double L-scan technique over a broad spectral range (400 nm - 900 nm) using 90 fs pulses at a low repetition rate (2-50 Hz) produced by an amplified femtosecond system. The theoretical simulations were performed using modern analytical response theory within the Time-Dependent Density Functional Theory (TD-DFT) approach using B3LYP and CAM-B3LYP, and the aug-cc-pVDZ and 6-311++G(d,p) basis sets.

Novel Sm(III) complexes were synthesized by the reaction of hexafluoroacetylacetonato (hfa) and triphenylphosphine oxide (TPPO), 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen). Emission bands were observed at “deep-red” region and were attributed to f–f transitions. The branching ratio (electric-dipole transitions 644 nm vs. magnetic dipole transition 598 nm) of the Sm(hfa) 3 (TPPO) 2 was much larger than that of Sm(hfa) 3 (bpy) 2 , Sm(hfa) 3 (phen) 2 . Those emission properties are due to coordination number and asymmetrical structures of novel Sm(III) complexes.

We have demonstrated that second harmonic generation (SHG) can be obtained from centrosymmetric crystals of a racemic mixture of chiral molecules. Circular polarization of the fundamental wave is a prerequisite to obtain selectivity in the interaction of the fundamental wave with one of the enantiomers in the racemic mixture, furnishing a distortion of the centrosymmetry. An explanation is presented to show that this SHG originates from a transition that is both allowed for the electric dipole and the magnetic dipole, resulting in a correction term in the hyperpolarizability, β. This correction to β is similar to the correction of the polarizability, better known as the optical activity. Therefore, the phenomenon described in this paper is refered to as the optical activity in the hyperpolarizability and can be represented by eehχ(2)(−2ω;ω,ω):E(2ω).E(ω).H(ω). Furthermore, theory and preliminary experimental evidence are presented for the existence of a eehχ(2) (−2ω;ω,ω): rmH(2ω).E(ω).E(ω) effect. In this case SHG from centrosymmetric crystals of a racemic mixture is the result of a linear polarized incident beam and a nonvanishing radiating magnetic dipole transition.

We calculate optical near fields generated by a periodically structured 50-nm-wide slit array of a 50-nm-thick gold film with a finite difference time domain method. Efficiencies of the electric quadrupole (E2) and magnetic dipole (M1) transitions, which are associated with the space derivative of the excitation light field, are evaluated for the calculated optical fields. The E2 transition efficiency is largely enhanced in the case where the polarization of the incident light is perpendicular to the slit direction, while such an enhancement is not expected for the M1 transition for this polarization. The large enhancement of the E2 transition efficiency originates not only from the field enhancement but also from its localization near the slit edge. The slit period dependence of the enhancement of the E2 transition efficiency suggests the enhancement to be affected by surface plasmon resonance. In the case where the polarization of the incident light is parallel to the slit, a small enhancement is obtain...

We present the atomic parity violation measurements made in Cs vapour using a pump-probe scheme. After pulsed excitation of the 6S-7S forbidden transition in the presence of a longitudinal electric field, a laser beam resonant with one of the 7S-6P transitions stimulates the 7S atom emission for a duration of 20 ns. The polarisation of the amplified probe beam is analysed. A seven-fold signature allows discrimination of the parity violating linear dichroism, and real-time calibration by a similar, known, parity conserving linear dichroism. The zero-field linear dichroism signal due to the magnetic dipole transition moment is observed for the first time, and used for in-situ determination of the electric field. The result, ImE1^{pv}= (-808+/- 21) 10^{-14} ea\_{0}, is in perfect agreement with the corresponding, more precise measurement obtained by the Boulder group. A transverse field configuration with large probe amplification could bring atomic parity violation measurements to the 0.1% accuracy level., "conference PAVI 06, Milos, Greece, May 2006"

We show that negative refraction with minimal absorption can be obtained by means of quantum interference effects similar to electromagnetically induced transparency. Coupling a magnetic dipole transition coherently with an electric dipole transition leads to electromagnetically induced chirality, which can provide negative refraction without requiring negative permeability, and also suppresses absorption. This technique allows negative refraction in the optical regime at densities where the magnetic susceptibility is still small and with refraction/absorption ratios that are orders of magnitude larger than those achievable previously. Furthermore, the value of the refractive index can be fine-tuned via external laser fields, which is essential for practical realization of sub-diffraction-limit imaging., 4 pages, 5 figures (shortened version, submitted to PRL)

We have used an electron beam ion trap to observe a visible line at 598.30(13) nm that corresponds to the 4d9 2D3/2–4d9 2D5/2 magnetic dipole transition within the ground state configuration of Xe9+. We have found no evidence to support the claim by others that a line near this position originates from Xe31+. The comparison of the measured wavelength with previous indirect experimental values, and the dependence of the line intensity on the electron beam energy, confirms the validity of the present identification. Our measured wavelength is in agreement with semiempirical Hartree-Fock calculations but shows a discrepancy with ab initio multiconfiguration Dirac-Fock calculations. We propose that the line may be useful as a diagnostic for extreme ultraviolet lithography light sources.

The generalized Gerasimov-Drell-Hearn sum rule $I^{GDH}_{\gamma^*d}(Q^2)$ for deuteron electrodisintegration $d(e,e')np$ as function of the squared four-momentum transfer $Q^2$ is evaluated by explicit integration. The calculation is based on a conventional nonrelativistic framework using a realistic $NN$-potential and including contributions from meson exchange currents, isobar configurations and leading order relativistic terms. Good convergence is achieved. The prominent feature is a deep negative minimum, $I_{\gamma^* d}^{GDH}=-9.5$ mb, at low $Q^2\approx 0.2$ fm$^{-2}$ which is almost exclusively driven by the nucleon isovector anomalous magnetic moment contribution to the magnetic dipole transition to the $^1S_0$-state. Above $Q^2=20$ fm$^{-2}$ the integral $I^{GDH}_{\gamma^*}(Q^2)$ approaches zero rapidly., Comment: 6 pages Revtex4, 4 figures

Among all 6S-7S Cs transition amplitudes, M 1 hf induced by the off-diagonal hyperfine interaction has recently become the most precisely known on theoretical grounds. Consequently, it is now possible to achieve 0.3% accuracy in the calibration of the parity violating amplitude E 1 pv using M 1 hf as a standard. For this reason we address here the problem of a precise interpretation of the signals involved in the calibration procedure, namely those providing the ratio of M 1 hf to the normal M 1 amplitude. We show that the interpretation of the data can no longer omit the quadrupole electric amplitude E 2 induced Parmi toutes les amplitudes de la transition 6S-7S du cesium, M 1 hf , induite par interaction hyperfine non diagonale, est recemment devenue celle que la theorie predit avec la plus grande precision. Il est desormais possible d'atteindre une precision de 0,3% sur l'etalonnage de l'amplitude violant la parite E 1 pv en l'utilisant comme etalon. D'ou la raison d'examiner ici le probleme de l'interpretation precise des signaux mis en jeu dans l'etalonnage, en particulier ceux qui fournissent le rapport entre M 1 hf et l'amplitude M 1 normale. Il n'est plus possible, pour cette interpretation, d'omettre l'amplitude quadripolaire electrique E 2 induite par interaction hyperfine non diagonale. En incluant E 2 , l'accord entre les determinations de M 1 hf /M 1 provenant d'experiences de types differents se trouve nettement ameliore. Apres reanalyse les donnees conduisent a M 1 hf /M 1 =(188,6±1,7)×10 −3 et E 2 /M 1 hf =(42±13)×10 −3 . Ce dernier resultat est compatible avec une evaluation theorique approchee de E 2 . En combinant le rapport empirique M 1 hf /β revise a la valeur theorique de M 1 hf parvient a une determination de la polarisabilite vectorielle Stark β=(27,17±0,35)a 0 3 en excellent accord avec la determination semi-empirique β se =(27,2±0,4)a 0 3