Search

We have reported the level energies and radiative transition (E1, E2 and M1) parameters, such as wavelengths, transition rates, oscillator strengths and line strengths for some levels over the ionization limit of Ne III (oxygen-like). The calculations have been performed using the general-purpose relativistic atomic structure package (GRASP) based on the fully relativistic multiconfiguration Dirac-Fock (MCDF) method. The results obtained have been compared with the available theoretical and experimental values in the literature.

The radiative transition form factors of the pseudoscalar mesons π, η, η′ and the vector mesons ρ, ω, φ are restudied with π–η–η′ and ρ–ω–φ in the tri-meson-mixing pattern, which is described by tri-mixing matrices in the light-cone constituent quark model. The experimental transition decay widths are better reproduced with tri-meson mixing than previous results in a two-mixing-angle scenario of only two-meson η–η′ mixing and ω–φ mixing.

Fluorescence measurements have been an established mainstay of photosynthesis experiments for many decades. Because in the photosynthesis literature the basics of excited states and their fates are not usually described, we have presented here an easily understandable text for biology students in the style of a chapter in a text book. In this review we give an educational overview of fundamental physical principles of fluorescence, with emphasis on the temporal response of emission. Escape from the excited state of a molecule is a dynamic event, and the fluorescence emission is in direct kinetic competition with several other pathways of de-excitation. It is essentially through a kinetic competition between all the pathways of de-excitation that we gain information about the fluorescent sample on the molecular scale. A simple probability allegory is presented that illustrates the basic ideas that are important for understanding and interpreting most fluorescence experiments. We also briefly point out challenges that confront the experimenter when interpreting time-resolved fluorescence responses.

Numerical modeling of dynamical processes in semiconductor lasers with external delayed optical feedback has been performed on the basis of the rate equations taking into account the quantum fluctuations of radiative transition rates. It has been shown that the nature of the optoelectronic signal as a function of pump current is determined by the magnitude of the optoelectronic coupling and corresponds to the behavior of the autocorrelation function of the radiation. It has been found that the radiation coherence decreases substantially with strong optical feedback. Experimental measurements confirming the theoretical results have been performed.

Laboratory formation of four isomers of C5H2 molecule is reported and detection of the ring-chain isomer (isomer 1) of C5H2 in cosmic objects has been suggested. For identification of a molecule in cosmic objects, one of the required input data is EinsteinA-coefficients (radiative transition probabilities) for the molecule. Here, we report EinsteinA-coefficients for electric dipole transitions in the ring-chain isomer of C5H2 among the rotational levels of the ground electronic and ground vibrational states up to 21 cm−1.

The vacancy transfer probabilities of K to L1, L2 and L3 shell were measured with a new method. The L X-ray yields of targets excited by 59.5 keV incident photons, i.e., above the K edge of elements, were detected with a high-resolution Si(Li) detector. For comparison with the experimental results, theoretical calculations were made using data available on radiative and radiationless transitions. The radiative transition values of these elements were taken from the relativistic Hartree-Slater model, those of the radiationless transitions from the Dirac-Hartree-Slater model. The measured values were found to be in good agreement with theoretical ones. The hKLi (i = 1, 2, 3) values were calculated by measuring the L1x, L2x and L3x X-ray production cross-sections.

A study of $\chi_{b}$ meson production at LHCb is performed on proton-proton collision data, corresponding to 3.0fb$^{-1}$ of integrated luminosity collected at centre-of-mass energies $\sqrt{s}=7$ and 8TeV. The fraction of $\Upsilon(nS)$ mesons originating from $\chi_{b}$ decays is measured as a function of the $\Upsilon$ transverse momentum in the rapidity range $2.0 < y^{\Upsilon} < 4.5$. The radiative transition of the $\chi_{b}(3P)$ meson to $\Upsilon(3S)$ is observed for the first time. The $\chi_{b1}(3P)$ mass is determined to be $$m(\chi_{b1}(3P)) = 10\,511.3 \pm 1.7 \pm 2.5 MeV/c^2,$$ where the first uncertainty is statistical and the second is systematic.

Transition energies, oscillator strengths and transition probability values for radiative transitions have been calculated for the highly ionised atoms of Si isoelectronic sequence from Mn11+ to Kr22+ for the singly excited states up to principal quantum number n = 7. Time-dependent coupled Hartree-Fock (TDCHF) theory has been used to estimate such transition properties. Most of the results for the oscillator strengths and transition probabilities are new. Transition energies agree reasonably well with available spectroscopic values.

A short review of theoretical and experimental studies concerning the photo‐excited florescence and Raman scattering of light for a substance in a space containing small material bodies is presented. Calculations of the radiative‐transition probability for atoms (molecules) in the vicinity of bodies with a size much smaller than the light wavelength are performed. The probabilities of the single‐photon and double‐photon transitions are shown to increase by factors of 9 and 81 in the vicinity of a nanosize sphere with dielectric constant |ɛ|\≫ 1. The probability of a radiative transition in the vicinity of the vertex of a conic needle bearing up against a plane (both with |ɛ|≫ 1) increases by factors of (λ/Rin)2 and (λ/Rin)4 for single‐photon and double‐photon transitions, respectively (Rin is the curvature radius for the needle vertex). This theoretical result is suggested as an explanation of the effect of increasing the radiation process intensity in the experiments carried out in the studies cited below.

Several physical, optical absorption and photoluminescence properties of Eu3+-doped ZnF2–PbO–TeO2 glasses have been studied. From the measured intensities of various absorption bands of these glasses the Judd–Ofelt parameters Ω2, Ω4 and Ω6 have been computed. The Judd–Ofelt theory has been applied to characterize the photoluminescence spectra of these glasses. From this theory, various radiative properties, such as transition probability, A, branching ratio, βr, and emission cross-section, σEP, for various emission levels of these glasses, have been determined and reported. © 1998 Chapman & Hall.

Nonequivalent Er3+ sites in LiNbO3 crystals have been evidenced by low-temperature optical absorption measurements. The radiative transition rates for the 4 S 3/2, 4 F 9/2, 4 I 9/2, 4 I 11/2, and 4 I 13/2 levels have been evaluated by the Judd-Ofelt method, and the contribution of multiphonon relaxation to the decay of excited states has been estimated. The quantum efficiency of the 4 I 11/2 level has been estimated to be 6% only, thus the excitation of levels lower than 4 S 3/2 is expected to populate efficiently the 4 I 13/2 level.

We have obtained accurate values for the radiative lifetimes of the 2p 3d1D0 and 2p 3d3P2o levels in NII by the cascade-free beam-foil-laser spectroscopy method. Our results are τ(2p 3d1D0)=0.346±0.012 ns and τ(2p 3d3P2o)=0.457±0.020 ns. Comparison of these results with experimental and recent theoretical lifetimes reported previously is also made.

On the bais of two programs, calculations are carried out for energies, probabilities of radiative transitions and nonradiative decays, and lifetimes of levels of two-electron systems 2l.4l′. The results of the two calculations are compared for a wide range of Z. Possible channels of radiative transitions and nonradiative decays are discussed. Their relative contribution to the total probability is evaluated. This evaluation is compared with data obtained by calculations, on the basis of which a conclusion is made about the contribution of correlation and relativistic effects. The Z-dependences are investigated for each of the parameters under consideration. A comparison is made with the results of other calculations.

When the collisional dynamics of two states under consideration for a radiative transition is different, the polarization and population relaxations in gas phase at low pressure are governed by four-, instead of three-, coupled Bloch-type equations. The general transient solutions of these four-coupled equations are solved by using the Laplace transformation technique. It has been found that an additional exponential term appears because of the effect. This is also responsible for the non-exponential character in the decay signal of a transient microwave pulse experiment, besides other factors reported earlier.

Energies and structures of 1s2snl 4 L and 1s2pnl' 4 L core-excited levels in lithium-like NV are calculated. Wavelengths, transition probabilities and radiative lifetimes are reported and compared with available experimental data. It is suggested that the 1s2p4d 4 P 0,4 D 0 levels are nearly degenerate in NV and have not been resolved experimentally. Several new assignments for observed lines are proposed.

The natural radiative lifetime of the 3s 4p 1P1 level of neutral magnesium was measured by pulsed level-crossing spectroscopy at the short excitation wavelength of 202.6 nm. We obtained tau = 13.4(5) ns for this state, strongly deviating from a previous beam-foil result, but in good agreement with a multi-configuration Hartree-Fock calculation. A discussion of the applicability of the pulsed Hanle effect method is given.

Radiative lifetimes are reported for 33 levels of Ti I. The longer-lived (τ>100 ns) levels show a systematic difference from previously reported values. The new results reduce the uncertainty in absolute normalisation of the Oxford relativef-values to less then 2.5%.

A method is proposed for processing of thermostimulated luminescence (TSL) curve in the presence of thermostimulated conductivity (TSC) in which no assumption is made as to the smallness of dnc/dt (nc is the conduction electron concentration). Results of the theory are applied to study of ZnS∶Ag, Al and ZnS∶Cu single crystals, in which elementary traps are revealed, and their activation energy and the value of the frequency factor determined. For ZnS∶Cu the radiative transition recombination section is calculated.

Emission spectrum of pure AgCl crystals at room temperature after ruby laser excitation was measured. The emission consists of a continuous fluorescence band with the maximum at about 460 nm which is at sufficiently high excitation intensities covered with characteristic line structure emission. The appearance of continous emission at this temperature was in accordance with experimental results explained by the increase of the radiative transition probability in AgCl crystals.

A universal, semi-empirical procedure is proposed for including polarization of the core by the outer electrons of an atom in calculations of radiative transition probabilities based on the S-matrix approach. A calculation was carried out of dipole transition probabilities between low lying configurations of sodium-like ions for nuclear charges Z = 16 to 40 and for aluminum-like ions with nuclear charges Z = 21 to 40.

Total cross sections for radiative muon capture into inner shells of light atoms are evaluated.

Autoionization levels 1s 2s2 2p2, 1s 2p4 and 1s 2s 2p3 of B-like ions were theoretically investigated for Z= 5–100. Calculation was made using perturbation theory over 1/Z. Relativistic corrections were taken into account in limits of Breit operator. Behaviour of radiative transition probabilityA, autoionization rate Γ and level lifetime τ was considered fromZ = 5 up toZ = 100 in detail for configurations 1s 2s2 2p2, 1s 2p4 withJ = 1/2.

The recent failures of the quark model and the vector-dominance model to explain the radiative transitions V → P + γ are analysed. Within the quark model several partial solutions exhibiting the octet dominance for the electromagnetic current are noticed. A genuineSU3 solution is also proposed relying on theω-ϕ current mixing. The VDM difficulties seem to be solvable only by introducing higher vector mesons.

We have developed a method to determineL-subshell ionization cross sections and report here on the first measurements of electron inducedL-subshell cross sections for target elements (29≦Z≦79) at electron bombarding energies between 50≦E0≦200 keV. The method involves the detection of characteristic X rays by means of a high resolution flat crystal spectrometer of known reflectivity and is based on the correlation of measured X ray intensities, Auger- and Coster-Kronig yields and radiative transition probabilities with theL-subshell cross section.

The modified surface delta interaction (MSDI) is used as the effective two-nucleon residual interaction in extensive shell-model calculations forA=10–15 nuclei; a He-4 core andj-j coupled extra-core nucleon configurations of the formP3/2 n P1/2 m (1d5/2,2s1/2)1 are employed. Level energies and wave functions for low-lying non-normal parity states are first obtained from a simultaneous fit to experimental energies over the entire 10–15 mass range. The wave functions are next tested by comparing predicted nuclear properties with experimental data: single-nucleon spectroscopic factors, beta decay lifetimes,M1 andE2 radiative transition widths as well asE1 andM2 radiative widths are calculated. In general good agreement between experiment and theory is obtained.

High resolution Si(Li)-Si(Li) and Si(Li)-Ge(Li) detector arrangements have been used to studyL x-ray spectra in coincidence withL-shell internal conversion electrons, gamma rays, andK x-rays emitted in249Cf decay. TheL1 subshell fluorescence and Coster-Kronig yields determined forZ=96 from these spectra are ω1=0.25±0.06,f12≦0.10, andf13=0.69 ±0.08. The presence of theL1-L3 radiative transition is also further confirmed in this work.

The systematics of the excitation energies of the non-normal parity states of the scandium isotopes are interpreted in terms of the formation of a quartet of 1f7/2 nucleons. Calculation of theB(E2) value for a typical radiative transition between non-normal parity states in43Sc, using this model, shows that the transition must involve more than the single quartet formed in the 1f7/2 shell; that is, that core polarization is an important factor in determining theB(E2) value.

Spectral investigation of Tm3+ in thulium nitrate has been carried out. For the first time, the second derivative spectrum of this complex has been recorded. The results of a least squares fit of the energy levels and oscillator strengths of the bands are reported in terms of interaction parameters and Judd-Ofelt parameters. Radiative transition probabilities for fluorescence levels3P0,1I6,1D2 and1G4 of Tm3+ in thulium nitrate are estimated.

Spectra of γ-rays following thermal neutron capture in128Te have been measured. Partial cross section for the radiative transitions to eight129Te levels with ln=1 have been determined. The experimental data are in a very good quantitative agreement with the theory of direct capture by Lane and Lynn.