Dipole Transition Probabilities Research Articles

Spectroscopic parameters, vibrational levels, transition dipole moments and transition probabilities of the 9 low-lying states of the NCl+ cation

This work calculates the potential energy curves of 9 Λ-S and 28Ω states of the NCl+ cation. The technique employed is the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction approach with the Davidson correction. The Λ-S states are X2Π, 12Σ+, 14Π, 14Σ+, 14Σ−, 24Π, 14Δ, 16Σ+, and 16Π, which are yielded from the first two dissociation channels of NCl+ cation. The Ω states are generated from these Λ-S states. The 14Π, 14Δ, 16Σ+, and 16Π states are inverted with the spin-orbit coupling effect included. The 14Σ+, 16Σ+, and 16Π states are very weakly bound, whose well depths are only several-hundredcm−1. One avoided crossing of PECs occurs between the 12Σ+ and 22Σ+ states. To improve the quality of potential energy curves, core-valence correlation and scalar relativistic corrections are included. The potential energies are extrapolated to the complete basis set limit. The spectroscopic parameters and vibrational levels are calculated. The transition dipole moments are computed. The Franck-Condon factors, Einstein coefficients, and radiative lifetimes of many transitions are determined. The spectroscopic approaches are proposed for observing these states according to the transition probabilities. The spin-orbit coupling effect on the spectroscopic and vibrational properties is evaluated. The spectroscopic parameters, vibrational levels, transition dipole moments, as well as transition probabilities reported in this paper could be considered to be very reliable.

Photonic Effects for Magnetic Dipole Transitions.

The radiative transition probability is a fundamental property for optical transitions. Extensive research, theoretical and experimental, has been conducted to establish the relation between the photonic environment and electric dipole (ED) transition probabilities. Recent work shows that the nanocrystal (NC)-cavity model accurately describes the influence of the refractive index n on ED transition rates for emitters in NCs. For magnetic dipole (MD) transitions, theory predicts a simple n3 dependence. However, experimental evidence is sparse and difficult to obtain. Here we report Eu3+-(with distinct ED+MD transitions) and Gd3+-(MD transitions) doped β-NaYF4 NC model systems to probe the influence of n on ED and MD transition probabilities through luminescence lifetime and ED/MD intensity ratio measurements. The results provide strong experimental evidence for an n3 dependence of MD transition probabilities. This insight is important for understanding and controlling the variation of spectral distribution in emission spectra by photonic effects.

Theoretical investigation on forbidden transition properties of fine-structure splitting in 2D state for K-like ions with **Project supported by the National Natural Science Foundation of China (Grant Nos. 91436103, 91536102, and 91336211), the Research Programme of National University of Defense Technology, China (Grant No. JC15-0203), and the Strategic Priority Research Programme of the Chinese Academy of Sciences (Grant No. XDB21030300).

Excitation energies, magnetic dipole, and electric quadrupole transition probabilities of the transition in the potassium-like (K-like) sequence with are investigated by using the multi-configuration Dirac–Hartree–Fock (MCDHF) method. The contributions of the electron correlations, Breit interaction, and the leading-order quantum electrodynamic (QED) effects on the transition properties are analyzed. The present results are interested in the laboratory tokamak and the astronomical observations. Furthermore, the feasibility of these ions for the highly charged ion (HCI) clocks is discussed. Considering the wavelength of lasers and manipulation process of the atomic clocks, Cu10+ and Zn11+ are recommended as promising candidates with achievable quality factors at the 1015 level.

Optical characterizations and Judd-Ofelt analysis of Dy3+ doped borosilicate glasses

Preparation of various concentrations of Dy3+ doped borosilicate glasses using melt quenching technique and their optical characterizations are presented. Based on the measured optical spectra, Judd-Ofelt approach is used to determine the optical parameters such as oscillator strengths, optical intensity parameters and transition lifetime. The impact of the total angular momentum on the transition lifetime is theoretically investigated. The lifetime decreases as the angular momentum increases until J=7/2, for the atomic terms FJ6, then its value increases at higher values of angular momentum. The same behavior occurs for the HJ6 states, but longer lifetime starts at J=11/2 to J=13/2. The free ion collision strengths and cross sections are evaluated to asses an interpretation of the presented radiative results. The cross sections show a decrease trend with the J-increasing while the collision strengths show the opposite behavior. Calculated data of electric dipole transition probabilities and branching ratio of several transitions of Dy3+ are reported.

Reduced Transition Probabilities for the Gamma Decay of the 7.8eV Isomer in ^{229}Th.

The reduced magnetic dipole and electric quadrupole transition probabilities for the radiative decay of the ^{229}Th 7.8 eV isomer to the ground state are predicted within a detailed nuclear-structure model approach. We show that the presence and decay of this isomer can only be accounted for by the Coriolis mixing emerging from a remarkably fine interplay between the coherent quadrupole-octupole motion of the nuclear core and the single-nucleon motion within a reflection-asymmetric deformed potential. We find that the magnetic dipole transition probability which determines the radiative lifetime of the isomer is considerably smaller than presently estimated. The so-far disregarded electric quadrupole component may have non-negligible contributions to the internal conversion channel. These findings support new directions in the experimental search of the ^{229}Th transition frequency for the development of a future nuclear frequency standard.

Transition moments between excited electronic states from the Hermitian formulation of the coupled cluster quadratic response function.

We introduce a new method for the computation of the transition moments between the excited electronic states based on the expectation value formalism of the coupled cluster theory [B. Jeziorski and R. Moszynski, Int. J. Quantum Chem. 48, 161 (1993)]. The working expressions of the new method solely employ the coupled cluster operator T and an auxiliary operator S that is expressed as a finite commutator expansion in terms of T and T†. In the approximation adopted in the present paper, the cluster expansion is limited to single, double, and linear triple excitations. The computed dipole transition probabilities for the singlet-singlet and triplet-triplet transitions in alkali earth atoms agree well with the available theoretical and experimental data. In contrast to the existing coupled cluster response theory, the matrix elements obtained by using our approach satisfy the Hermitian symmetry even if the excitations in the cluster operator are truncated, but the operator S is exact. The Hermitian symmetry is slightly broken if the commutator series for the operator S are truncated. As a part of the numerical evidence for the new method, we report calculations of the transition moments between the excited triplet states which have not yet been reported in the literature within the coupled cluster theory. Slater-type basis sets constructed according to the correlation-consistency principle are used in our calculations.

The Hulthén Potential Model for Hydrogen Atoms in Debye Plasma

In this paper, the well-known Hulthen potential is used for describing the plasma screening effect on a hydrogen atom embedded in weakly coupled plasma. As the radial Schrodinger equation with Hulthen potential gives analytical solutions, the energy levels and wave functions are obtained in a closed form. Structural properties such as dipole polarizability, transition probability, and oscillator strength are calculated easily using the corresponding analytical formulas. Moreover, the analytic solutions of the Hulthen potential enable us to obtain many other observables reliably. Asymptotic iteration method solutions of the Hulthen potential for different screening parameters are considered to calculate the transition energies, oscillator strength, and transition probability values for a few dipole allowed states of hydrogen atom embedded in weakly coupled plasma. Use of the Hulthen potential to determine the screening effects on hydrogen atom embedded in weakly coupled plasma would be useful for modeling Debye plasma in investigations of the atomic structure and collisions in the plasma physics field.

Understanding the complexation of Eu3 + with potential ligands used for preferential separation of lanthanides and actinides in various stages of nuclear fuel cycle: A luminescence investigation

A systematic photoluminescence based investigation was carried out to understand the complexation of Eu3+ with different ligands (TBP: tri-n-butyl phosphate, DHOA: di-n-hexyl octanamide, Cyanex 923: tri-n-alkyl phosphine oxide and Cyanex 272: Bis (2,4,4 trimethyl) pentyl phosphinic acid) used for preferential separation of lanthanides and actinides in various stages of nuclear fuel cycle. In case of TBP and DHOA complexes, 3 ligand molecules coordinated in monodentate fashion and 3 nitrate ion in bidentate fashion to Eu3+ to satisfy the 9 coordination of Eu. In case of Cyanex 923 and Cyanex 272 complexes, 3 ligand molecules, 3 nitrate ion and 3 water molecules coordinated to Eu3+ in monodentate fashion. The Eu complexes of TBP and DHOA were found to have D3h local symmetry while that for Cyanex 923 and Cyanex 272 were C3h. Judd–Ofelt analysis of these systems revealed that the covalency of EuO bond followed the trend DHOA>TBP>Cyanex 272>Cyanex 923. Different photophysical properties like radiative and non-radiative life time, branching ratio for different transitions, magnetic and electric dipole moment transition probabilities and quantum efficiency were also evaluated and compared for these systems. The magnetic dipole transition probability was found to be almost independent of ligand field perturbation while electric dipole transition probability for 5D0-7F2 transition was found to be hypersensitive with ligand field with a trend DHOA>TBP>Cyanex 272>Cyanex 923.

Effect of phase modifiers TBP and iso-decanol on the extraction and complexation of Eu3+ with CMPO

ABSTRACTThe effect of tri-n-butyl phosphate (TBP) and iso-decanol as phase modifiers on the complexation of Eu3+ with octyl-phenyl N,N-diisobutyl carbamoyl methyl phosphine oxide (CMPO) was studied. On an increase of iso-decanol the extraction efficiency of Eu3+ decreases. The metal–ligand stoichiometry was found to be 1:3. The Eu complex of CMPO–TBP was more symmetric compared to CMPO–iso-decanol. The Eu3+ complex exhibited D3h and C3h symmetry for 30% and 5% iso-decanol, while that for TBP was C6v. The radiative, non-radiative life time, electric and magnetic dipole transition probabilities, branching ratio, quantum efficiency etc. were evaluated. The covalency between Eu3+ and CMPO is as follows: CMPO–TBP < CMPO-5% iso-decanol < CMPO-30% iso-decanol.

Analysis of the free ion spectrum of Er3+(Er IV)

The vacuum spark spectrum of erbium is observed in the wavelength region 705–2460 Å where transitions between the low-lying configurations , , and take place. Predictions of energy levels and electric dipole transition probabilities by means of the Cowan codes served for a complete revised analysis of the spectrum. The identification of 591 spectral lines as transitions mostly between low levels of these four configurations led to the determination of 120 energy levels. Radial parameters obtained in least-squares fits of both parities are compared with ab initio Hartree–Fock integrals including relativistic corrections. The mean error of the fits are respectively 41 cm−1 for 38 known levels of the odd parity configurations + and 49 cm−1 for 82 known levels of the even configurations + .

An exacting transition probability measurement - a direct test of atomic many-body theories.

A new protocol for measuring the branching fraction of hydrogenic atoms with only statistically limited uncertainty is proposed and demonstrated for the decay of the P3/2 level of the barium ion, with precision below 0.5%. Heavy hydrogenic atoms like the barium ion are test beds for fundamental physics such as atomic parity violation and they also hold the key to understanding nucleo-synthesis in stars. To draw definitive conclusion about possible physics beyond the standard model by measuring atomic parity violation in the barium ion it is necessary to measure the dipole transition probabilities of low-lying excited states with a precision better than 1%. Furthermore, enhancing our understanding of the barium puzzle in barium stars requires branching fraction data for proper modelling of nucleo-synthesis. Our measurements are the first to provide a direct test of quantum many-body calculations on the barium ion with a precision below one percent and more importantly with no known systematic uncertainties. The unique measurement protocol proposed here can be easily extended to any decay with more than two channels and hence paves the way for measuring the branching fractions of other hydrogenic atoms with no significant systematic uncertainties.

Infrared to ultraviolet optical response for armchair-edge silicene nanoribbons

We investigate the infrared to ultraviolet optical response for perfect armchair-edge silicene nanoribbons (N-ASiNRs) with N atomic chains under the irradiation of an external electromagnetic field at low temperatures, in the method of dipole-transition theorem for semiconductors. The electronic structure for N-ASiNRs has been manifested from the tight-binding calculations to two distinct families, that is the semiconducting one for $$N=3l$$ or $$3l+1$$ (l is a positive integer) and metallic one for $$N=3l+2$$ . The dipole-transition probabilities from the valence subbands to the smaller indexed conduction ones for semiconducting 9-/10- and metallic 11-ASiNRs have been demonstrated to be continuously increasing, while those to the larger indexed conduction subbands are firstly increasing and then decreasing. Both the semiconducting 9-/10- and metallic 11-ASiNRs have been found to have a wide (from 0.50 to 3.20 eV) absorption spectrum, refractive index, and extinction coefficient at the vicinity of K-point. The optical response for semiconducting 9-/10-ASiNRs is observed to be from the transitions between the valence and conduction subbands with the same and/or different indices, while that for metallic 11-ASiNR may be originated from the different indexed valence and conduction subbands. The obtained results are believed to be of importance in the design of the silicene-based nano-optoelectronic devices.

Radiative rates for forbidden M1 and E2 transitions of astrophysical interest in doubly ionized iron-peak elements

Aims. Accurate and reliable atomic data for lowly ionized Fe-peak species (Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) are of paramount importance for analyzing the high-resolution astrophysical spectra currently available. The third spectra of several iron group elements have been observed in different galactic sources, such as Herbig-Haro objects in the Orion Nebula and stars like Eta Carinae. However, forbidden M1 and E2 transitions between low-lying metastable levels of doubly charged iron-peak ions have been investigated very little so far, and radiative rates for those lines remain sparse or nonexistent. We attempt to fill that gap and provide transition probabilities for the most important forbidden lines of all doubly ionized iron-peak elements. Methods. We carried out a systematic study of the electronic structure of doubly ionized Fe-peak species. The magnetic dipole (M1) and electric quadrupole (E2) transition probabilities were computed using the pseudo-relativistic Hartree-Fock (HFR) code of Cowan and the central Thomas-Fermi-Dirac-Amaldi potential approximation implemented in AUTOSTRUCTURE. This multiplatform approach allowed for consistency checks and intercomparison and has proven very useful in many previous works for estimating the uncertainties affecting the radiative data. Results. We present transition probabilities for the M1 and E2 forbidden lines depopulating the metastable even levels belonging to the 3dk and 3dk−14s configurations in Sc III (k = 1), Ti III (k = 2), V III (k = 3), Cr III (k = 4), Mn III (k = 5), Fe III (k = 6), Co III (k = 7), and Ni III (k = 8).

Electric dipole transition probabilities, oscillator strengths, and lifetimes for Co16+

The electric dipole transition probabilities, oscillator strengths, and lifetimes for Co16+ have been calculated within the weakest bound electron potential model (WBEPM) theory using experimental energy levels and theoretical expectation values of orbital radii corresponding to those energy levels under the assumption of the LS coupling scheme. In the calculations both multiplet and fine structure transitions are studied. The present results are consistent with earlier results given in the literature. Moreover, some transition probability and oscillator strength values not existing in the literature are reported for the first time.

Relativistic atomic structure calculations and electron impact excitations of Fe23+

Relativistic calculations using the multiconfiguration Dirac–Fock method for energy levels, oscillator strengths, and electronic dipole transition probabilities of Li-like iron (Fe23+) are presented. A configuration state list with the quantum numbers nl, where n=2–7 and l=s,p,d,f,g,h,i has been considered. Excitations up to three electrons and correlation contributions from higher orbitals up to 7l have been included. Contributions from core levels have been taken into account, EOL (extended optimal level) type calculations have been applied, and doubly excited levels are considered. The calculations have been executed by using the fully relativistic atomic structure package GRASP2K. The present calculations have been compared with the available experimental and theoretical sources, the comparisons show a good agreement between the present results of energy levels and oscillator strengths with the literature. In the second part of the present study, the atomic data (energy levels, and radiative parameters) have been used to calculate the excitation and deexcitation rates of allowed transitions by electron impact, as well as the population densities of some excited levels at different electron temperatures.

A systematic and detailed investigation of radiative rates for forbidden transitions of astrophysical interest in doubly ionized iron peak elements

AbstractWe carried out a systematic study of the electronic structure of doubly-ionized Fe-peak species, from Sc III to Ni III. The magnetic dipole (M1) and electric quadrupole (E2) transition probabilities were computed using the pseudo-relativistic Hartree-Fock (HFR) method and the central Thomas-Fermi-Dirac-Amaldi potential approximation implemented in the AUTOSTRUCTURE code. This multi-platform approach allowed for consistency checks and intercomparison and has proven very useful in many previous works for estimating the uncertainties affecting the radiative data.

Probing of the local environment and calculation of J.O. parameters for Eu3+ CMPO functionalized pillararene complexes by time resolved fluorescence spectroscopy

An attempt was made to understand the complexation of Eu3+ with structurally modified CMPO-functionalized pillararenes by luminescence spectroscopy. Formation of single species with different numbers of inner sphere water molecules was found to be present for all the complexes. On increasing spacer length between ligating moieties and supramolecular pillararenes, the stereo-chemical crowding around ligating oxygen decreased. Therefore, strong covalent metal–oxygen bond was formed which was reflected in the increasing trend of the computed Ω2 values (Judd–Offelt parameter): LI (4.66×10−20)<LII (6.82×10−20)<LIII (7.85×10−20). Deconvolution of each 5D0→7F1, 5D0→7F2 and 5D0→7F4 transitions into two peaks revealed that the most probable local symmetry around Eu3+ was C6/C6v. The radiative lifetime for the Eu complexes followed LI (4.09ms)>LII (3.19ms)>LIII (2.94ms) while the branching ratio values for all three complexes followed the same trend as β2>β4>β1. The other photo-physical constants like asymmetric factor, quantum efficiency, magnetic and electric dipole transition probabilities were also computed.

Structural and luminescence behavior of Sm3+ ions doped lead boro-telluro-phosphate glasses

The Sm3+ ions doped lead boro-telluro-phosphate glasses with the chemical composition 30H3O3+(20–x)PbO+15TeO2+10P2O5+10ZnO+15BaCO3+xSm2O3 (x=0.05, 0.1, 0.25, 0.5, 1.0 and 2.0 in wt%) have been prepared by a melt quenching technique and their structural and optical behavior were studied and reported. The physical properties like, refractive index, density and dielectric constant etc., have been estimated. FTIR and Raman spectral studies have been made to explore the presence of functional groups and various structural units in the prepared glasses. The formation of bridging and non-bridging oxygens of BO4, BO3, TeO3, TeO6 and PbO4 structural units have been investigated. From the absorption spectra, the direct (n=1/2), indirect (n=2) band gap, band tailing parameter (B) and Urbach energy (ΔE) values were estimated. The ionic nature of the metal–ligand bond in the title glasses has been discussed. The Judd–Ofelt intensity parameters (Ωλ,λ=2, 4, and 6), oscillator strength of ƒ−ƒ electric dipole transitions and transition probability (A) have been evaluated. The predicted radiative lifetime (τrad) and branching ratio (βR) values of the 4G5/2 excited level of the Sm3+ ions to the lower energy levels were determined and compared with the experimentally measured values. From the recorded fluorescence spectra, the strong transitions of Sm3+ ions 4G5/2→6H5/2 (565nm), 4G5/2→6H7/2 (602nm), 4G5/2→6H9/2 (648nm) and a weak transition, 4G5/2→6H11/2 (709nm) have been observed. The significant laser parameters like, gain bandwidth (σpE×λeff), optical gain (σpE×τrad) and stimulated emission cross-section (σpE) values were estimated for the 4G5/2→6HJ (J=5/2, 7/2, 9/2 and 11/2) emission transitions. The decay profile of the present glasses reveal the single exponential nature at small concentrations (≤0.25%) and non-exponential at higher concentrations (≥0.5%) due to cross-relaxation and non-radiative energy transfer processes and the same has been discussed using I–H model. The 0.5wt% of the Sm3+ ions doped lead boro-telluro-phosphate glasses exhibit reddish orange luminescence indicating its usefulness for the development of optical, display and LED devices.

Transition probabilities of neutral scandium

The electric dipole transition probabilities and the oscillator strengths of neutral scandium have been calculated using the quantum defect orbital theory and the Cowan code for the 3d4s2–3d4s4p, 3d24s–3d24p, and 3d4s2–4s24p transitions. In addition, a parametric analysis of the fine structure for the 3d4s2configuration of even parity is performed using Cowan code. The transition probabilities and the oscillator strengths obtained in this work are mostly in agreement with the data obtained from different theoretical works given in the literature. Moreover, transition probabilities for 24 levels of neutral scandium are given for the first time.

Luminescence investigation on Eu–pillar[5]arene-based diglycolamide (DGA) complexes: Nature of the complex, Judd–Ofelt calculations and effect of ligand structure

An attempt was made to understand the insight of complexation of Eu3+ ion with three different structurally modified pillar[5]arene-based diglycolamides (P5DGA) and a comparison was also made with their molecular identity, TODGA. 7F0-5D2, 5G2,3,4, 5L6 transitions were observed in the absorption profiles while 5D0-7F0,1,2,3,4 transitions for emission spectra. Number of water molecules present in the primary coordination sphere of Eu3+ and the number of species were calculated from the life time measurement of the complexes under investigation. From the splitting pattern of the luminescence spectra of Eu3+ complex the point group symmetry around Eu3+ was found to be C4v. Judd-Offelt parameters (Ωλ, λ=2,4) were calculated for the complexes and correlated with the covalency of metal ligand bonds and long range ordering, respectively. It was demonstrated that preorganization of ligating moieties on the platform of pillararenes favoured the covalency of the metal–ligand bond in diglycolamides. Different photo physical properties such as radiative and non radiative life time, magnetic and electric dipole transition probabilities, branching ratio values for different transitions, quantum efficiency were evaluated for all the Eu3+-diglycolamide complexes.