Transition Lifetimes Research Articles

Transition probabilities and lifetimes in singly ionized rhenium

Transition probabilities and radiative lifetimes have been obtained for 45 transitions of Re ii using a combination of radiative lifetime values obtained with the laser-induced fluorescence technique (seven levels) and theoretical branching fractions. This new set of results, concerning ultraviolet and visible lines, will be useful in the future for investigating the composition of chemically peculiar stars.

Spectral properties of Eu 3+: ZnO–B 2O 3–SiO 2 glasses

Studies on the vibronic spectral analysis of Eu 3+ ions doped in zinc borosilicate glass have been performed in order to correlate them with the local environment of the dopant ion in this host matrix on the basis of the Fourier Transform infrared (FT-IR) spectroscopy. It is noticed that the Eu 3+ ions are bonded to the bridging and non-bridging oxygens of BO 3, BO 4 and SiO 4 structural units. The Stark splittings exhibited especially by the emission transitions: D 0 → F 1 7 , D 0 5 → F 2 7 and their intensity ratio (EMIR) could indicate that the Eu 3+ ions are taking the sites, which lack inversion symmetry. Judd–Ofelt intensity (Ω λ , λ=2, 4, 6) parameters have been obtained from the measured absorption spectra of Eu 3+: Zinc borosilicate glass and these intensity defining factors are used in the computation of the emission transition probabilities, radiative rates, braching ratios and radiative lifetimes of the fluorescence transitions. Decay curves of the emission transitions ( D 0 5 → F 0 , 1 , 2 , 3 , 4 7 ) were measured and their lifetimes have been estimated. Besides this, Optical band gap energies ( E Opt) have also been evaluated from the base glass absorption spectrum and the values are found to be 4.82 and 4.60 eV for direct and indirect band gaps, respectively.

Theoretical Transition Probabilities and Lifetimes

The beam-foil method and the computation of oscillator strengths with correlated wave functions both had their beginning in the late 1960s. The stimulating interplay between theory and experiment will be reviewed. With the power of todays computers, great progress has been made in computation. The current state of spectrum calculations using the multiconfiguration Hartree–Fock method will be described and the importance of relativistic effects mentioned.

The Milano electron antineutrino mass experiment

We report the final results of the Milano experiment, carried out in order to measure the electron antineutrino mass from the study of the 187 Re beta decay end-point. We used ten microcalorimeters of AgReO 4 with a total mass of 2.17 mg and a total activity of 1.17 Hz. We collected 6.2⋅10 6 events above 700 eV. The limit on the antineutrino mass achieved is m ν 187 Re transition energy and lifetime.

Transition Probabilities for Hydrogen-Like Atoms

E1, M1, E2, M2, E3, and M3 transition probabilities for hydrogen-like atoms are calculated with point-nucleus Dirac eigenfunctions for Z=1–118 and up to large quantum numbers l=25 and n=26, increasing existing data more than a thousandfold. A critical evaluation of the accuracy shows a higher reliability with respect to previous works. Tables for hydrogen containing a subset of the results are given explicitly, listing the states involved in each transition, wavelength, term energies, statistical weights, transition probabilities, oscillator strengths, and line strengths. The complete results, including 1 863 574 distinct transition probabilities, lifetimes, and branching fractions are available at http://www.fisica.unam.mx/research/tables/spectra/1el

Raman coherence beats from the entangled state involving polarized excitons in single quantum dots

The optically induced and detected entangled state involving an exciton Zeeman doublet with entanglement entropy as high as $\ensuremath{\sim}0.7$ was created using picosecond lasers in single $\mathrm{GaAs}$ quantum dots. The temporal evolution of the nonradiative Raman coherence between two exciton states was directly resolved in quantum beats measured in the homodyne detected differential transmission experiment. The Raman coherence time, $66\ifmmode\pm\else\textpm\fi{}15\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$, was determined from the decay of the envelope of the quantum beats, and was found to be limited by the lifetimes of the exciton transitions, $50\ifmmode\pm\else\textpm\fi{}3\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$.

Radiative transition quantum efficiency of 2H 11/2 and 4S 3/2 states of trivalent erbium ion in oxyfluoride tellurite glass

The optical transition intensity parameters of erbium ion in oxyfluoride tellurite glass were derived by fitting the absorption spectrum according to Judd–Ofelt theory. With the obtained parameters the radiative transition rates, branching ratios and lifetimes of different states in Er 3+ doped oxyfluoride tellurite glass were calculated. Temperature dependences of the emission spectrum and the lifetime of 2H 11/2, 4S 3/2 were measured within the temperature range from 108 to 315 K. The method for calculating the radiative transition quantum efficiency of the 2H 11/2 and 4S 3/2 states, which are in thermal equilibrium, was discussed. The quantum efficiencies of the 2H 11/2 and 4S 3/2 states of Er 3+ in oxyfluoride tellurite glass were calculated.

Spectroscopic study of floating zone technique-grown Nd3+-doped CaMoO4

Optical spectroscopy studies of Nd 3+ -doped scheelite calcium molybdate (CaMeO 4 ) single crystal grown by a floating zone-like technique was performed using Judd-Ofelt analysis, besides luminescence data and lifetime measurements in the visible and near infrared domains. The excited state absorption in cross section units of this material was measured by two different methods for all expected infrared emission. By using calculated intensity parameters Ω t (t = 2, 4, 6), it were determined branching ratios, emission cross-sections, and lifetimes for all related transitions. The observed single excited state absorption calibrated in absorption cross-section units was found too small to disturb the laser efficiency in the 1030-1100 nm spectral range. A comparison of main spectroscopic parameters of this material with those of other Nd 3+ -doped crystals is presented.

Structural phase transition and fluorescence lifetime of amorphous chalcogenide alloys doped with rare-earths

Lifetime of excited electronic states inside the 4f configuration of rare-earth elements embedded in covalent chalcogenide glasses turns out to be sensitive to medium-range structural phase transition of the host glasses. We have measured lifetimes of 1.6 μm emission originating from Pr 3+: ( 3F 3, 3F 4) → 3H 4 transition in amorphous Ge–Sb–Se alloys. The longest lifetime is measured at around the mean coordination number of ∼2.67, which arises coincidently from structural changes of the host glasses from two-dimensional layers to three-dimensional networks.

Theory of luminescent emission in nanocrystal ZnS:Mn with an extra electron

We consider the effect of an extra electron injected into a doped quantum dot $ZnS:Mn^{2+}$. The Coulomb interaction and the exchange interaction between the extra electron and the states of the Mn ion will mix the wavefunctions, split the impurity energy levels, break the previous selection rules and change the transition probabilities. Using this model of an extra electron in the doped quantum dot, we calculated the energy and the wavefunctions, the luminescence probability and the transition lifetime and compare with the experiments. Our calculation shows that two orders of magnitudes of lifetime shortening can occur in the transition $^4T_1-^6A_1$ when an extra electron is present.

Picosecond excitonic luminescence in ZnO and other wide-gap semiconductors

Radiative lifetimes of free-atom transitions, scaled by ω3 for comparison at 368nm, are not faster than about 6.9ns. BaF2 core-valence luminescence, scaled in the same way from 220 to 368nm, corresponds to 4.1ns. In contrast, excitonic transitions in wide-gap semiconductors display subnanosecond radiative lifetimes, and in particular ZnO has radiative lifetimes measured at 50–300ps for Do,X and 400–900ps for free excitons. The “giant oscillator strength” corresponding to these lifetimes can be explained by theories developed initially for defect-bound excitons, then quantum wells, and nanoparticles. An exciton is a coherent array of N dipoles, where N is the number of sites covered by coherent translational motion of the exciton. This is not essentially a phenomenon of multiple excitons, but applies as well to single-exciton decay. It differs in that regard from the more familiar Dicke giant dipole of N coherently excited atoms lacking translational periodicity. The phenomenon suggests possibilities for achieving ultrafast scintillators and high light yield.

Extension of the molecular quantum defect orbital methodology to the calculation of intensities and lifetimes for vibronic transitions within electronic Rydberg series of NO

AbstractExpressions relating explicitly the radiative lifetimes of vibronic states to the electronic transition moment and the absorption oscillator strengths for spin‐allowed transitions have been developed for the first time within the molecular quantum defect orbital (MQDO) methodology. Application to the intensities of the γ(A2Σ+ ← X2Π), ε(D2Σ+ ← X2Π), and (D2Σ+ ← A2Σ+) bands of NO, which are known to be of relevance in atmospheric studies, has been made. The MQDO results are in excellent accord with the measurements available in the literature. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004

Salient Features of Electric and Magnetic Multipole Transition Probabilities of Hydrogen-Like Systems

Several aspects of E1, M1, E2, M2, E3 and M3 transition probabilities, lifetimes and branching fractions for hydrogen-like atoms evaluated with point-nucleus Dirac eigenfunctions for Z = 1–118 are discussed.

Radiative transition probabilities, lifetimes and dipole moments for the vibrational levels of the X1Sigma+ ground state of 39K85Rb.

Using a potential energy curve (based primarily on the RKR potential of Amiot and Verges [J. Chem. Phys. 112, 7068 (2000)]) and a dipole moment function (based primarily on ab initio calculations of Park et al. [Chem. Phys. 257, 135 (2000)]), we have calculated radiative transition probabilities (Einstein A coefficients), radiative lifetimes, and dipole moment expectation values involving all vibrational levels (for several rotational quantum numbers) of the X1Sigma+ ground state of 39K85Rb. We observe that the radiative lifetimes of vibrationally excited levels, in particular, are approximately 10(3)-10(6) seconds, far too long to be significant in most ultracold experiments involving 39K85Rb or its isotopomers. Comparison with other molecules (LiH and HF) suggests that simple scaling (A approximately mu2nu3 approximately tau(-1)) will predict similarly long lifetimes for many other heteronuclear molecules, e.g., RbCs.

Third-order relativistic many-body calculations of energies and lifetimes of levels along the silver isoelectronic sequence

Energies of ${5l}_{j}(l=s,p,d,f,g)$ and ${4f}_{j}$ states in neutral Ag and Ag-like ions with nuclear charges $Z=48--100$ are calculated using relativistic many-body perturbation theory. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are calculated for the 17 possible ${5l}_{j}\ensuremath{-}{5l}_{{j}^{\ensuremath{'}}}^{\ensuremath{'}}$ and ${4f}_{j}\ensuremath{-}{5l}_{{j}^{\ensuremath{'}}}$ electric-dipole transitions. Third-order corrections to energies and dipole matrix elements are included for neutral Ag and for ions with $Z<~60.$ Second-order corrections are included for $Z>60.$ Comparisons are made with available experimental data for transition energies and lifetimes. Correlation energies and transition rates are shown graphically as functions of nuclear charge Z for selected cases. These calculations provide a theoretical benchmark for comparison with experiment and theory.

New limits from the Milano neutrino mass experiment with thermal microcalorimeters

In the Standard Model of electroweak interactions an important input parameter is still missing: the absolute value of the mass of one of the neutrinos. In this paper we report the final results of the Milano electron anti-neutrino mass experiment after having measured for about one year the beta spectrum of 187Re with 10AgReO4 microcalorimeters. We describe the experimental set-up, the detector performance and the measuring conditions. We present the updated limit on the electron anti-neutrino mass which is the most stringent so far obtained with thermal detectors. We also give the most precise estimates for the 187Re transition energy and lifetime.

Radiative transition probabilities and lifetimes for the band systems (1) [formula omitted] and (2) [formula omitted] of the isovalent molecules BeC, MgC, and CaC

Accurate potential energy curves, transition moments, spectroscopic constants, radiative transition probabilities, and lifetimes for the states X 3 Σ − , (1) 3 Π , and (2) 3 Σ − of BeC, MgC, and CaC are reported using high level calculations. Diagonal transitions dominate for the (2) 3 Σ − → X 3 Σ − system, with band origins falling at 745, 648, and 770 nm, and an intensity ratio of 6,3,1, respectively for BeC, MgC, and CaC. Radiative lifetimes for v ′=0 are equal to 0.48, 1.45, and 3.29 μs for the state (2) 3 Σ − , and equal to 13.57, 10.44, and 9.62 μs for the state (1) 3 Π for BeC, MgC, and CaC.

Photoluminescence characterization of GaInNAs/GaAs quantum well carrier dynamics

Variable temperature photoluminescence (PL) measurement of a thermal-annealed 6 nm GaInNAs/GaAs quantum well (QW) is carried out to understand its low-temperature carrier dynamic characteristics. It is found that the effect of carrier localization, which remained after a thermal anneal, is due possibly to a center characterized by a transition with activation energy of 13.7 meV below the e1 state. This result is deduced from fitting the integrated PL intensity versus the temperature data with a single-activation-energy model. A comparable value of 11 meV was also obtained between the low-energy (main localized state) and high-energy (e1 state) Gaussian functions used to fit the low-temperature PL spectrum. The localization effect in the thermal-annealed GaInNAs/GaAs QW is further confirmed by time-resolved PL measurements at 17 K, which showed emission-energy-dependent PL decay time characteristic for the low-energy regime (below 1.045 eV) and nearly constant decay time of about 0.14 ns at the high-energy regime, which corresponds to the e1−hh1 transition lifetime. The main localization center could form carrier traps that reduce the e1−hh1 PL transition efficiency.

Oxyfluoride tellurite glasses doped by erbium: thermal analysis, structural organization and spectral properties

The effects of fluorine substitution in zinc tellurite glass system doped with rare earths on the spectral properties of the Er 3+ ions are investigated. Differential thermal analysis, vibrational spectroscopies studies and in situ high-temperature X-ray diffraction measurements have been considered in term of fluorine influence. As a function of composition, we have principally measured optical absorption, spontaneous emission, and lifetime measurements. Judd–Ofelt intensity parameters of Er 3+ in these host glasses were determined and used to calculate radiative transition rates and lifetimes. The bulk composition variation and addition of fluoride compounds in tellurite glasses result among others, in broad emission spectra, improved emission lifetime and difference in relative band intensities compared to pure oxide glass.

A theoretical study of the radiative transition probabilities and lifetimes of the lowest quartet states of CaN

Accurate potential energy curves, dipole moment functions, dissociation energies and spectroscopic constants for three quartet electronic states (X 4Σ −, A 4Π and B 4Σ −) of the CaN molecule are reported with the multireference singles and doubles configuration interaction methodology. Also, are present radiative transition probabilities and lifetimes for the A 4Π–X 4Σ −, B 4Σ −–X 4Σ − and B 4Σ −–A 4Π band systems. The ground state (X 4Σ −) has an equilibrium distance equal to 4.410 a 0 and the dissociation energy is 0.85 eV. The A 4Π has a shorter equilibrium distance equal to 4.142 a 0 and the B 4Σ − has a much longer equilibrium distance, equal to 5.426 a 0. Radiative lifetimes for v ′=0 are predicted to be 27 000, 0.256 and 565 μs for the A 4Π–X 4Σ −, B 4Σ −–X 4Σ − and B 4Σ −–A 4Π band systems, respectively.