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We present new results of temperature dependence of photoluminescence spectra carried out on poly-p-phenylene vinylene (PPV) and on PPV composite films with single-walled carbon nanotubes. By performing studies at different temperatures (87 and 300 K), we show that a distribution of conjugated PPV segments is needed to interpret experimental data. At the microscopic scale, such a distribution corresponds to the morphological picture of poorly packed short chain segments and well-packed ordered long chain segments. Within this scheme, a new interpretation emerges for explaining the specific behavior of the photoluminescence bands. In particular, the two most intense components of the photoluminescence spectra of PPV thermally converted at 300 °C (2.23 and 2.43 eV at 300 K) change drastically their relative intensity when the observation temperature decreases. This effect is interpreted as due to the inhibition of charge migration to longer segments and to radiative recombination occurring mainly on n=5 conjugated segments. [ABSTRACT FROM AUTHOR]

High-resolution laser excitation spectroscopy has been used to record the à 2E-X 2A1 electronic transition of SrCH3 in a laser ablation/molecular jet source. Transitions arising from the K′=1←K″=0, K′=0←K″=1, and K′=2←K″=1 subbands have been observed and assigned. The data were modeled with 2E and 2A1 symmetric top Hamiltonian matrices in a Hund’s case (a) basis, using a least squares fitting program. Rotational and fine structure parameters for the à 2E state were determined. A comparison of the spin-orbit energy separation in the à 2E state to other strontium containing free radicals showed that the Jahn-Teller effect is negligible. The spin-rotation constants for the à 2E state were calculated using the pure precession model and were found to be in good agreement with the experimentally determined parameters. These calculations suggest that the à 2E state of SrCH3 is not entirely of p orbital character. The rotational constants were used to estimate the structural parameters of SrCH3 in the à 2E state. The strontium-carbon bond length was found to decrease by ∼0.006 Å, and the hydrogen-carbon-hydrogen bond angle opened by ∼0.8° compared to the X 2A1 state, similar to the geometry changes observed for CaCH3. [ABSTRACT FROM AUTHOR]

A spectroscopic analysis is performed on Er[sup 3+] (4f[sup 11]) ions doped in NaBi(WO[sub 4])[sub 2] (NBWO) in order to assess this material for its potential as a near-infrared laser. The Judd–Ofelt model is applied to the room-temperature absorption intensities of Er[sup 3+] (4f[sup 11]) in NBWO to obtain the three phenomenological intensity parameters: Ω[sub 2]=5.50×10[sup -20] cm[sup 2], Ω[sub 4]=1.00×10[sup -20] cm[sup 2], and Ω[sub 6]=0.71×10[sup -20] cm[sup 2]. The intensity parameters are then used to determine the radiative decay rates (emission probabilities), radiative lifetimes, and branching ratios for the Er[sup 3+] transitions from the excited state multiplet manifolds to the lower lying manifold states. Using the radiative decay rates for the Er[sup 3+] (4f[sup 11]) transitions between the corresponding excited states and the lower lying states, the radiative lifetimes of eight excited states of Er[sup 3+] are determined in this host. Using the measured room temperature fluorescence lifetime of approximately 4.75 ms and the radiative lifetime of 5.63 ms as predicted by the Judd–Ofelt model for the [sup 4]I[sub 13/2]→[sup 4]I[sub 15/2] (1.52 μm) transition of Er[sup 3+] in NBWO the quantum efficiency is determined to be approximately 84% for this laser material. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

40Li 2 O-4MO-55B 2 O 3 : 1Nd 2 O 3 , where MO Nb 2 O 5 , MoO 3 and WO 3 glasses were prepared by conventional melt quenching technique; the photoluminescence spectra (excited at 800 nm) of these glasses were recorded at room temperature. These glasses exhibited the emission bands ascribed to 4 F 3/2 → 4 I 9/2, 11/2, 13/2 transitions. The radiative transition probability (A T ) of emission transitions was characterized as a function of linear combination of Judd-Ofelt (J-O) parameters (Ωλ , λ = 2, 4 and 6) which are used to derive radiative properties of the fluorescent levels. Branching ratio (β R ) was enlightened in terms of the spectroscopic ratio (Ω 4⁄ Ω 6 )⋅ Interpretation of the data shows that these glasses have the favorable local structure for Nd 3+ ions to emit laser transition 4 F 3/2 → 4 I 11/2 (∼1060 nm) as Ω 6 > Ω 4 . Spontaneous emission probability (A), the radiative life time (τ R ) and stimulated emission cross-section (σ E ) of the present glasses were determined. [ABSTRACT FROM AUTHOR]

We observed the spectra within the wavelength range of 910-990 nm of emission of the corona discharge in supercritical helium gas at 6-11 K. This spectral range contains the molecular bands of the He* excimer radiative transitions ( c Σ ⇒ a Σ) between the electron-vibrational-rotational levels of the c Σ and the a Σ triplet states. We have determined the populations of the rotational levels (quantity of molecules in the given excited state among the excited molecules of the discharge) of the c Σ excited state from experimental values of the intensity of the respective electron-vibrational-rotational lines. The calculated population distribution is nonmonotonous. The population of the level with the rotation quantum number K′ = 18 (the level number) is higher than those of the levels with the other K′ values. [ABSTRACT FROM AUTHOR]

The high resolution infrared spectra of the 32 S 16 O 18 O molecule were recorded with a Bruker IFS 120 HR Fourier transform interferometer for the first time in the region of 1800–2800 cm −1 where the bands 2 ν 1 , ν 1 + ν 3 , and 2 ν 3 are located. About 3970, 2960 and 3450 transitions were assigned in the experimental spectra with the maximum values of quantum numbers J max . / K a max . equal to 59/20, 68/25, and 43/18 to the bands 2 ν 1 , ν 1 + ν 3 , and 2 ν 3 , respectively. The subsequent weighted fit of experimentally assigned transitions was made with the Hamiltonian model which takes into account the resonance interactions between the studied vibrational states. As the result, a set of 39 fitted parameters was obtained which reproduces the initial 3213 ro-vibrational energy values obtained from the assigned transitions with the d rms = 2.4 × 10 − 4 cm − 1 . [ABSTRACT FROM AUTHOR]

We report laboratory measurements of H 2 O-broadening coefficients of O 2 absorption lines in the A-band near 13,000 cm −1 . For this, four spectra of oxygen gas mixed with water vapor were recorded with a high resolution Fourier transform spectrometer for total pressures ranging from 125 to 175 Torr at 323 K, and a fifth at 175 Torr and 365 K. Broadening coefficients of 39 transitions (up to J ″ = 21 ) were retrieved from the measured spectra through fits using Galatry line profiles. Values at room temperature (296 K) were then extrapolated and compared with previous determinations in the A-band and millimeter waves region. This enables to resolve some controversial issues related to the inconsistencies between these studies. Finally, comparing our results with the line broadening coefficients by dry air confirms that H 2 O-broadenings of oxygen lines are, on average, 10% larger than those by dry air. [ABSTRACT FROM AUTHOR]

The Er3+:YPO 4 crystals co-doped with different concentrations of Yb3+ (7.5 at.% and 11.5 at.%) were successfully grown by high-temperature solution method with Pb 2 P 2 O 7 as cosolvent. Crystal growth, structures and spectroscopic characterizations, including polarized absorption spectra, polarized fluorescence spectra and lifetime, were systematically explored and compared. The absorption FWHM at around 975 nm is 17.1 nm for σ- polarizations and 12.0 nm for π- polarizations, which makes Er3+/Yb3+:YPO 4 crystal suitable for effective pumping by InGaAs laser diode. Based on J-O theory, the spectroscopic parameters, including J-O intensity, oscillator strength, line strength, fluorescence branching ratios, spontaneous transition rates and radiative lifetime were calculated systematically. Furthermore, four intense emission peaks at around 1505, 1537, 1561 and 1586 nm can be observed in the polarized fluorescence spectra. Theoretically, different frequencies interactions between these wavelengths may be used for the application of generating radiation in the range of 2.9–10.2 THz. The results show that Er3+/Yb3+:YPO 4 crystal may be a potential laser material of 1.5–1.6 μm. [Display omitted] • The Er3+/Yb3+:YPO 4 crystal was grown successfully from Pb 2 P 2 O 7 solution. • Spectral parameters of Er3+ ions were calculated in detail based on J-O theory. • Intense multi-wavelength emissions can be observed in the range of 1.5–1.6 μm. [ABSTRACT FROM AUTHOR]

The previously published photoluminescence spectra of bulk germanium single crystals with orientations (100), (110), and (111) under different biaxial tensile strains have been investigated using the differential method proposed by the author for the analysis of luminescence spectra of semiconductors. An increase in the strain for all these orientations of the single crystals leads to a shift in the maxima of the differential spectra in the region of direct radiative transitions toward lower photon energies due to the narrowing of the germanium direct band gap. At the same time, the positions of the maxima of the differential spectra in the region of indirect radiative transitions remain almost unchanged. This indicates that the germanium indirect band gap does not depend on the tensile strains, at least for their values of ∼0.2-0.3%. [ABSTRACT FROM AUTHOR]

Abstract: The low-lying electronic states (X 2Π, a 4Π, b 4Σ−, B 2Π, 12Φ, A 2Δ and B′2Σ+) of the NS molecule are computed at the AV5Z/CASSCF/MRCI+Q+DK level of theory. The potential energy curves are presented for these states; the corresponding spectroscopic constants are reported. Electronic transition moment functions, Einstein coefficients, Franck–Condon factors and radiative lifetimes for the B 2Π–X 2Π, B′2Σ+–X 2Π and A 2Δ–X 2Π system have been calculated. The F–C factors of the B 2Π are in good agreement with the corresponding RKR data. The B′2Σ+ state possesses a barrier in the potential energy curve, located at about 2.16Å. The height of the barrier is predicted to be 7890cm−1. [Copyright &y& Elsevier]

The structure and spectroscopic properties of the ground and the lowest excited electronic states of the alkali hydride cation NaH+ have been investigated using an ab initio approach. In this approach, a nonempirical pseudopotential for the Na+ core has been used and a core-core and a core-valence correlation corrections have been added. The adiabatic potential energy curves and the molecular spectroscopic constants for numerous electronic states of 2Σ+, 2Π, and 2Δ symmetries, dissociating up to Na (4 d) + H+ and Na+ + H (3 d), have been calculated. As no experimental data are available, we discuss our results by comparing with the available theoretical calculations. A satisfying agreement has been found for the ground state with previous works. However, a clear disagreement between this study and the model potential work of Magnier (Magnier, J. Phys. Chem. A 2005, 109, 5411) has been observed for several excited states. Numerous avoided crossings between electronic states of 2Σ+ and 2Π symmetries have been found and analysed. They are related to the interaction between the potential energy curves and to the charge transfer process between the two ionic systems Na+H and NaH+. Furthermore, we provide an extensive set of data concerning the transition dipole moments from X2Σ+ and the 22Σ+ states to higher excited states of 2Σ+ and 2Π symmetries. Finally, the adiabatic potential energy curves of the ground (X2Σ+) and the first (22Σ+) excited states and the transition dipole moments between these states are used to evaluate the radiative lifetimes for the vibrational levels of the 22∑+ state for the first time. In addition to the bound-bound contribution, the bound-free term has been evaluated and added to the total radiative lifetime. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports new assignments of rovibrational transitions of 12CH4 bands in the range 4600–4887 cm−1 which is usually referred to as a part of the 2μm methane transparency window. Several experimental data sources for methane line positions and intensities were combined for this analysis. Three long path Fourier transform spectra newly recorded in Reims with 1603m absorption path length and pressures of 1, 7 and 34hPa for samples of natural abundance CH4 provided new measurements of 12CH4 lines. Older spectra for 13CH4 (90% purity) from JPL with 73m absorption path length were used to identify the corresponding lines. Most of the lines in this region belong to the Octad system of 12CH4. The new spectra allowed us to assign 1014 new line positions and to measure 1095 line intensities in the cold bands of the Octad. These new line positions and intensities were added to the global fit of Hamiltonian and dipole moment parameters of the Ground State, Dyad, Pentad and Octad systems. This leads to a noticeable improvement of the theoretical description in this methane transparency window and a better global prediction of the methane spectrum. [Copyright &y& Elsevier]

Abstract: The optical absorption spectra of yttrium aluminum garnet (YAG) crystals doped with Nd3+ ions with different concentrations (0.6at%, 1.0at%, 1.2at%) at the temperature range from 300K to 500K have been measured. The calculated Judd–Ofelt (JO) parameters Ω t (t=2, 4, 6) based on the spectra have been used to predict the radiative transition probabilities, branching ratios and radiative lifetimes of the transitions from 4F3/2 level to the lower levels (4I13/2, 4I11/2, 4I9/2) at each concentration and temperature. The three JO parameters Ω t (t=2, 4, 6), according to the calculation, decrease with the increasing doped concentration at each temperature. The JO parameters Ω 2 and Ω 4 increase, while the parameter Ω 6 decreases with the increasing temperature at each concentration. The branching ratios and radiative transition probabilities of the transitions from the 4F3/2 level to 4I13/2 and 4I11/2 levels decrease, while the transition from the 4F3/2 level to 4I9/2 level increases with the increasing temperature. The obtained results at each concentration and temperature are discussed. [Copyright &y& Elsevier]

The semimicroscopic algebraic cluster model (SACM) is applied to the systems 12C + α -> 160, 14C + α -> 180, 160 + α-> 20Ne, 18C + α -» 22Ne, and 20Ne + α -* 24Mg. The spectrum and some £2 values are fitted to experiment. Further E2 transition values as well as Ε1 and M1 transitions are calculated and compared to experiment. In addition, we list the spectroscopic factors of the states listed. These factors are predictions of the model and are of interest in current astrophysical studies. [ABSTRACT FROM AUTHOR]

Excited states have been identified in the very neutron-deficient Ζ = 58 nucleus 123Ce. This is the most neutron-deficient odd-A cerium isotope in which excited states have been identified. The states have been unambiguously assigned to 123Ce by detecting de-excitation γ rays in coincidence with evaporated charged particles and neutrons. Three rotational bands, each consisting of at least eight E2 transitions, have been observed. The bands have tentatively been assigned to be based on neutrons in g7/2 and h11/2 Orbitals. Two of the bands have been assigned to be signature partners, although no interband transitions have been observed. The aligned angular momenta of the bands have been studied in comparison with neighboring nuclei and with the results of Woods-Saxon cranking calculations. Observation of the deformation-dependent n{h11/2 quasiparticle alignment at 0.36 MeV/h in each of the bands suggests a quadrupole deformation of ß2 0.3, in good agreement with theoretical predictions for the suggested possible configuration assignments. [ABSTRACT FROM AUTHOR]

We calculate reduced B(E2) and B{M\) electromagnetic transition strengths within and between K bands in support of a recently proposed model for the structure of heavy nuclei. Previously, only spectra and a rough indication of the largest B(E2) strengths were reported. The present more detailed calculations should aid the experimental identification of the predicted 0+, 1+, and 2+ bands and, in particular, act to confirm or refute the suggestion that the model 0+ and 2+ bands correspond to the well known and widespread beta and gamma bands. Furthermore they pinpoint transitions that can indicate the presence of a so-far elusive 1+ band by feeding relatively strongly into or out of it. Some of these transitions may already have been measured in 230Th, 232Th, and 238U. [ABSTRACT FROM AUTHOR]

Abstract: Different concentrations of Ho3+-doped lead borate titanate aluminum fluoride (LBTAFHo) glasses with chemical composition of PbO–H3BO3–TiO2–AlF3–Ho2O3 were prepared by the melt quenching method. The spectral properties were investigated using the absorption, emission and decay measurements. The experimental oscillator strengths were calculated from the area under the absorption bands. Applying Judd–Ofelt theory, the intensity parameters (Ω λ=2, 4, 6) were calculated, by the least square fit approach from which the radiative transition rates, luminescence branching ratios and radiative decay times were determined. The photoluminescence spectra revealed the quenching of luminescence intensity beyond 1.0mol% of Ho3+ ion concentration. To investigate the luminescence potentiality of 5F4→5I8 emission level, the effective bandwidth and the stimulated emission cross-section were determined. The quenching in experimental decay time is attributed to the resonance energy transfer among the excited Ho3+ ions. [Copyright &y& Elsevier]

We calculate the full spectrum, as observed today, of the cosmological gravitational waves generated within a model based on loop quantum cosmology, in which the corrections to the dynamical equations describing the evolution of the universe during the semiclassical regime are of the inverse-volume type. It is assumed that the universe, after the transition to the classical regime, undergoes a period of inflation driven by a scalar field with a chaotic-type potential. Our analysis shows that, for certain conditions, loop quantum effects leave a clear signature on the spectrum, namely, an overproduction of low-frequency gravitational waves. One of the aims of our work is to show that loop quantum cosmology models can be tested and that, more generally, preinfiationary physical processes leave their imprint in gravitational-wave spectra and can also be tested. [ABSTRACT FROM AUTHOR]

We present a simulation model for a stream of photon counts that can be detected in fluorescence fluctuation spectroscopy systems from diffusing molecules undergoing spontaneous transitions between radiative and nonradiative states. Using our model, we can obtain various characteristics of a random stream of photon counts which allows us to test fluorescence fluctuation spectroscopy methods and to predict the results of full-scale experiments. [ABSTRACT FROM AUTHOR]

Energy levels, Auger decay and radiative transition rates of the doubly-excited 1 s3 l3 l′ states for Be-like neon are calculated using relativistic Multiconfiguration Dirac-Fock (MCDF) method. Electron correlation and relaxation effects are taken into account. The magnitude of Auger rates for the 35 doubly-excited states and their decay channels are discussed. Present calculated values are in agreement with the latest experimental electron spectra as well as other theoretical results. [ABSTRACT FROM AUTHOR]

Abstract: The internal bremsstrahlung (IB) spectrum accompanying the β-decay of the first forbidden β-transitions of 169Er and 170Tm is studied. The IB was measured using a scintillation γ-spectrometer. It was analyzed by the variable width peeling-off-method, and then corrected by applying the proper corrections. The analyzed and corrected IB spectrum was compared with those calculated according to the original theories of Knipp and Uhlenbeck (1936) as well as of Bloch (1936) (KUB), the coulomb corrected theory of Nilsson (1956), Lewis and Ford (1957), and detour transitions of Ford and Martin (1969). Also, a new trial was carried out by applying the shape correction factor C 1 of the first forbidden β-transition suggested by Konopinski and Uhlenbeck (1935, 1941) on the Fermi β-decay theory to the calculated IB based on Nilsson''s theory. It is called modified KUB (M.KUB). The experimental results are in a good agreement with the theoretical calculations of forbidden β-transition of Ford and Martin (1969), and M.KUB. It is observed that the Coloumb contribution into IB spectrum is larger for lower β-endpoint energies in case of the sources of same Coulomb charge (Z) and different β-endpoint energies. [Copyright &y& Elsevier]

Abstract: Tm3+-doped and Tm3+/Yb3+-codoped TeO2–ZnO–Bi2O3 (TZB) glasses are prepared by melt-quenching method. The Judd-Ofelt intensity parameters (Ω t t =2, 4, 6), radiative transition rate, and radiative lifetime of Tm3+ are calculated based on the absorption spectra. The 1.8μm emission of the samples is investigated under 980nm laser excitation. The absorption, emission cross-sections, and gain coefficient of Tm3+:3F4 → 3H6 are calculated. The energy transfer processes of Yb3+–Yb3+ and Yb3+–Tm3+ are analyzed, the results show that the Yb3+ ions can transfer their energy to Tm3+ ions with large energy transfer coefficient, and a maximum efficiency of 79%. [Copyright &y& Elsevier]

Abstract: In this research we prepared Zn2SiO4:Eu3+ phosphor nanopowders using a combination of sol–gel and combustion synthesis with the aim to examine the influence of synthesis conditions on the optical properties of the phosphor. As combustion fuels we used polyethylene glycol (PEG) with different average molecular weights, and the combustion was performed in two ways—in a microwave oven and a conventional furnace. Optical properties were examined by photoluminescence spectroscopy and spectra of all samples showed intense red emission, typical for f–f electronic transitions of the Eu3+ ions. Emission decays exhibited classical one exponential behavior at longer times and nonlinear nature at short times, with average lifetimes varied from 0.49 to 0.71ms between samples. Judd–Ofelt theory was applied to experimental data for the quantitative determination of optical parameters such as Ω 2,4 Judd–Ofelt parameters, radiative and nonradiative transition rates and emission quantum efficiency. Calculated parameters vary moderately between samples prepared with different PEGs and combusted in different manner. [Copyright &y& Elsevier]

Abstract: The spectroscopic properties of tellurite glasses of composition (in mol%) TNKNd: (70− x)TeO2–15Nb2O5–15K2O–xNd2O3 (x =0.1, 1.0, 1.5, 2.0 and 2.5) and TNLNd10: 69TeO2–15Nb2O5–15Li2O–1.0Nd2O3 and lithium metaborate glass of composition LBNNd10: 89LiBO2–10Nb2O5–1.0Nd2O3 have been investigated using absorption and emission spectra and decay curve analysis. An energy level analysis has been carried out considering the experimental energy positions of the absorption and emission bands, using the free-ion Hamiltonian model. The spectral intensities have been calculated by using the Judd–Ofelt theory and in turn the radiative properties such as radiative transition probabilities, emission cross-sections, branching ratios and radiative lifetimes have been estimated. The decay curves at the lower concentrations are exponential while they show a non-exponential behavior at higher concentrations (⩾1.0mol%) due to energy transfer processes. The effective lifetimes for the 4F3/2 level are found to decrease with increase in Nd2O3 concentration for all the glasses under investigation. The non-exponential decay curves have been well-fitted to the Yokota–Tanimoto model with S =6, indicating that the nature of energy transfer is of dipole–dipole type and energy migration also plays an important role. The results obtained have been compared with Nd3+-doped phosphate, fluorophosphate, lead borate, tellurite, germanate and silicate glasses and Nd3+-doped YAG ceramic and Ca2Nb2O7 crystals. [Copyright &y& Elsevier]

Abstract: This article reports the effect of mixed alkalis on the optical absorption and emission spectra of Sm3+ and Dy3+ doped chloroborate glass matrices of the compositions 69.5B2O3 xLiCl(30− x)NaCl0.5R2O3 and 69.5B2O3 xLiCl(30− x)KCl0.5R2O3 (where R=Sm and Dy and x =5, 10, 15, 20 and 25). Using Judd–Ofelt theory, the spectral intensities and Judd–Ofelt intensity parameters (Ω 2, Ω 4 and Ω 6) were obtained from the measured absorption bands of the spectra. Using these intensity parameters, total radiative transition probabilities (A T), radiative lifetimes (τ R), branching ratios (β) and peak emission cross-sections (σ P) were obtained for the two rare earth ions in these two glass matrices. Variation of these parameters with x in the glass matrix has been discussed. It is found that for Sm3+ ion, the transition, 4G5/2 → 6H9/2 shows highest emission cross-section and is maximum at x =10mol% in lithium–sodium and at x =20mol% in lithium–potassium glass matrices. For Dy3+ ion, the transition, 4F9/2 → 6H13/2 shows highest emission cross-section and is maximum at x =20mol% in lithium–sodium and at x =10mol% in lithium–potassium glass matrix. [Copyright &y& Elsevier]

We report on preliminary results from the experiment performed at Legnaro National Laboratories aiming at the investigation of the shape evolution of the 88Mo nucleus. The GDR spectra obtained for two data sets measured at 48Ti beam energy of 300 and 450 MeV corresponding to 3 and 3.8 MeV temperatures, respectively, are presented. The low energy component in GDR strength functions, similar to the theoretical predictions of LSD model, possibly indicates the presence of Jacobi shape transition. [ABSTRACT FROM AUTHOR]

We study the spectral evolution of 13 short-duration gamma-ray bursts (GRBs) detected by the Gamma Burst Monitor onboard Fermi. We study spectra resolved in time at the level of 2-512 ms in the 8 keV-35 MeV energy range. We find a strong correlation between the observed peak energy and the flux within individual short GRBs. The slope of the correlation for individual bursts ranges between ∼0.4 and ∼1. There is no correlation between the low-energy spectral index and the peak energy or the flux. Our results show that in our 13 short GRBs, evolves in time tracking the flux. This behaviour is similar to what found in the population of long GRBs and it is in agreement with the evidence that long GRBs and (the still few) short GRBs with measured redshifts follow the same rest-frame - correlation. Its origin is most likely to be found in the radiative mechanism that has to be the same in both classes of GRBs. [ABSTRACT FROM AUTHOR]

The ASACUSA collaboration at CERN has previously measured the optical transition frequencies of antiprotonic helium to a precision of <1 part in 108 by laser spectroscopy. We describe some recent theoretical and experimental developmental work carried out by our collaboration to further improve the experimental precision. Utilisant la spectroscopie laser, la collaboration ASACUSA au CERN a déjà mesuré les fréquences de transition optique de l'hélium antiprotonique à mieux qu'une partie dans 108. Nous décrivons des travaux récents, théoriques et expérimentaux, effectués par nos collaborateurs, afin d'améliorer la précision expérimentale. [ABSTRACT FROM AUTHOR]

new type host of germanate glass (GeO− BaO−BaF−GaO−LaO) codoped with TmO has been investigated for application as laser material. It possesses a large emission cross section with the value of 9.3×10 cm at 1.8 μm. Judd-Ofelt intensity parameters and radiative transition probability are calculated and analyzed by Judd-Ofelt theory and absorption spectra. The infrared emission spectra at 1.8 μm have been obtained by using a 794 nm laser diode as excitation resource. The emission intensity ratio of 1.8 (F→H) to 1.47 μm (H→F) increases, while the experimental lifetime of the Tm:H level decreases by increasing TmO concentration, which is attributed to the presence of a cross relaxation process. The most intensive emission at 1.8 μm is achieved from the germanate glass with the concentration of TmO reaches 1.0 wt%. The extended overlap integral method is used to calculate the microparameter of the energy transfer and the critical distance, which are derived to better understand the energy transfer process of thulium ions in the germanate glass responsible for emission at 1.8 μm. [ABSTRACT FROM AUTHOR]

Abstract: The paper introduces general considerations on structural properties of aromatic, antiaromatic and non-aromatic conjugated systems in terms of potential energy along bond length alternation and distortion coordinates, taking as examples benzene, cyclobutadiene and cyclooctatetraene. Pentalene, formally derived from cyclooctatetraene by cross linking, is also considered as a typical antiaromatic system. The main interest is concerned with [n]annulenes and model [n]annulene molecular systems, n ranging from 10 to 18. The rich variety of conformational and configurational isomers and of dynamical processes among them is described. Specific attention is devoted to bridged [10]- and [14]annulenes in the ground and lowest excited states as well as to s-indacene and biphenylene. Experimental data obtained from vibrational and electronic spectroscopies are discussed and compared with ab initio calculation results. Finally, porphyrin, tetraoxaporphyrin dication and diprotonated porphyrin are presented as annulene structures adopting planar/non-planar geometries depending on the steric hindrance in the inner macrocycle ring. Radiative and non-radiative relaxation processes from excited state levels have been observed by means of time-resolved fluorescence and femtosecond transient absorption spectroscopy. A short account is also given of porphycene, the structural isomer of porphyrin, and of porphycene properties. [ABSTRACT FROM AUTHOR]

Abstract: The pressure dependence of the peak positions and widths of the fluorescence lines corresponding to the 5D J →7F J electronic transitions in Sm2+-doped SrFCl crystals was measured at room temperature (RT) with a diamond anvil cell (DAC) and a high-pressure gas system, using silicone oil and gaseous helium as the pressure-transmitting medium, respectively. At RT and ambient pressure the electronic transitions 5D0→7F J (J= 0, 1, 2, 3) and 5D1→7F J (J=0, 1, 2) in Sm2+ ions yielded rather sharp spectral lines peaked at 14490, 14206, 13685, 13012cm−1 and 15823, 15533, 15012cm−1, respectively. At pressures up to 45kbar in the DAC all these peaks shifted linearly to lower energies at the rates −2.36, −2.10, −2.43, −2.22cm−1/kbar and −2.35, −2.33, −2.47cm−1/kbar. Under purely hydrostatic gas pressure up to 7kbar at RT the initial (normal pressure) widths of the 5D0→7F0, 5D0→7F1 and 5D1→7F0 lines having a Lorentzian profile (with corrected FWHM values of 1.55, 5.71 and 1.97cm−1) decreased linearly with increasing pressure at the rates −0.009(2), −0.077(3) and −0.034(2)cm−1/kbar, respectively. Possible mechanisms of the observed pressure effects are discussed. For further studies of linewidth variations with the pressure, gaseous helium as a best possible high-pressure medium is strongly recommended. [Copyright &y& Elsevier]

Abstract: Nd3+ doped fluorine containing zinc-aluminophosphate glasses have been prepared with alkali and alkaline earth content to understand the effect of network modifiers on radiative process. The physical and optical properties of these glasses have been evaluated. The Judd–Ofelt model for the intensity analysis of induced electric dipole transitions has been applied to the measured oscillator strengths of the absorption bands to determine the three phenomenological intensity parameters Ω 2, Ω 4 and Ω 6 for each glass. Using these parameters, transition probability (A), total transition probability (A T), branching ratios (β R) radiative life times (τ R) and integrated cross-section (σ a) for the stimulated emission have been theoretically calculated for certain excited Nd3+ fluorescent levels. From the obtained results the conclusion is made about the possibility of using these glasses as laser material. [Copyright &y& Elsevier]

Abstract: In an earlier study [Flaud JM, Brizzi G, Carlotti M, Perrin A, Ridolfi M. MIPAS database: validation of HNO3 line parameters using MIPAS satellite measurements. Atmos Chem Phys 2006;6:1–12] the HNO3 line parameters in the HITRAN spectroscopic database have recently been revisited in the interval corresponding to the MIPAS spectral range. For the 11.3μm region these updates involve the line positions for the {ν 5, 2ν 9} bands, and the intensities. However, comparisons between observed spectra recorded by MIPAS and the calculated ones in the 600–950cm−1 region still show significant disagreements. The goal of the present paper is to solve some of these problems. Based on the analysis of N2-broadened HNO3 laboratory spectra recorded with a Fourier transform instrument, a new HNO3 database was generated, including the following improvements: (i) approximate parameters for the ν 5+ν 7−ν 7 and ν 5+ν 6−ν 6 hot bands have been added, and (ii) the intensities for the ν 6 and ν 8 bands have been updated. (iii) The air broadening and its temperature dependence, calculated using a semi-classical approach, have been added for each HNO3 transition. (iv) Finally, line-mixing effects have been pointed out, particularly in the ν 5+ν 9−ν 9 Q branch, and an approach correctly modeling the resulting spectral shape is proposed. [Copyright &y& Elsevier]

Angular intensity distributions for transition radiation excited by a beam of relativistic electrons in the emitter in the form of a dihedral angle are measured in the millimeter range. The angle is formed by the intersection of two conducting planes. The source of radiation is a microtron with an electron energy of 7.4 MeV. We analyze the effect of the magnitude of the dihedral angle of the emitter, the position of the electron transition point on the surface of the angle, and the direction of motion of electrons on the angular distribution of radiation intensity. It is shown that the spectral and angular distributions of radiation intensity in the dihedral angle substantially differ from analogous distributions for a particle intersecting a planar conducting surface. The possibility of using radiation to measure the energy, spatial position, and direction of motion of charges is considered. [ABSTRACT FROM AUTHOR]

The high-resolution spectrum of the D2S molecule registered with a Bruker IFS 120HR Fourier spectrometer in the range 2000–4200 cm–1 is analyzed. The spectroscopic parameters of the (110), (011), and (030) vibrational states are obtained. They reproduce rotational energy levels with the accuracy close to experimental one (a total of 737 rovibrational energies is considered corresponding to 2590 transitions up to Jmax = 21). [ABSTRACT FROM AUTHOR]

Abstract: Multireference singles and doubles configuration interaction calculations are performed to study the electronic structure and spectroscopic properties of SiC−. Potential energy curves and spectroscopic parameters of 21 low-lying doublets, quartets, and sextets within 6eV are determined. Two strong transitions, C2Π-X2Σ+ and D2Π-X2Σ+ with band origins around 22300 and 23550cm−1, respectively are predicted for the first time. The partial radiative lifetimes for these transitions are estimated. Dipole moments of some of the low-lying states are calculated by keeping the origin at the center of mass. The vertical and adiabatic electron affinities of SiC are also reported. [Copyright &y& Elsevier]

Abstract: Er3+:SrMoO4 crystal of high optical quality was grown by the Czochralski method. The room temperature polarized absorption and emission spectra together with the lifetime decay curve were measured. Based on the Judd–Ofelt theory, three intensity parameters, radiative transition rates, radiative lifetimes and fluorescent branching ratios, were obtained. Emission cross-section and gain cross-section around 1.54μm were also obtained. [Copyright &y& Elsevier]

Abstract: Applying the emission method, intensities of 60 spectral lines of neutral nitrogen (N I) belonging to 15 multiplets originating from 3s–np (n=3, 4, 5) transition arrays have been measured. A wall-stabilized arc, operated at atmospheric pressure in helium with some admixture of nitrogen was applied as the excitation source. From measured line intensities, relative line strengths within multiplets have been evaluated. For transitions with Δn=1 and 2, significantly larger discrepancies from LS coupling results are found if compared to transitions 3s–3p (Δn=0). The measured relative line strengths within 3s–3p multiplets are compared with older measurements, recent calculations and with the new data recommended by NIST. [Copyright &y& Elsevier]

Abstract: Pressure broadened (1atm. N2) laboratory spectra of benzene vapor (in natural abundance) were recorded at 278, 298, and 323K, covering 600–6500cm−1. The spectra were recorded at a resolution of 0.112cm−1 using a commercial Fourier transform spectrometer. The pressure of each benzene vapor sample was measured using high-precision capacitance manometers, and a minimum of nine sample pressures were recorded for each temperature. The samples were introduced into a temperature-stabilized static cell (19.94(1)cm pathlength) that was hard-mounted into the spectrometer. From these data a fit composite spectrum was calculated for each temperature. The number density for the three composite spectra was normalized to 296K. The spectra give the absorption coefficient (cm2 molecule−1, naperian units) as a function of wavenumber. From these spectra integrated band intensities (cmmolecule−1 and atm−1 cm−2) for intervals corresponding to the stronger benzene bands were calculated and were compared with previously reported values. We discuss and quantify error sources and estimate our systematic (NIST Type-B) errors to be 3% for the stronger bands. The measured absorption coefficients and integrated band intensities are useful for remote sensing applications such as measurements of planetary atmospheres and assessment of the environmental impact of terrestrial oil fire emissions. [Copyright &y& Elsevier]

The potentiality of Photocurrent (PC) and Surface Photovoltage Spectrosocopy (SPS) analyses in the determination of the band gap of CdTe-based ternary alloys was investigated. Both methods can detect band-to-band and defect state-to-band transitions. The role played by the surface states in both experimental methods has been studied since it may significantly alter the results. The below-band gap energy levels have also been detected by PC and SPS and the different information that can be obtained in the two cases has been discussed. The results obtained by PC and SPS have been compared in order to extract the contribution of the surface and bulk states. [ABSTRACT FROM AUTHOR]

Abstract: Nd3+-doped NaLa(WO4)2 single crystal with a dimension of ∅20mm×40mm and a good optical quality was grown by Czochralski method. The polarized absorption spectra and emission spectra were measured at room temperature. The absorption cross-section and emission cross-section were presented. The Judd–Ofelt theory, extended to anisotropic system, has been applied to evaluate the intensity parameters Ω t (t =2,4,6), radiative transition rates A, radiative lifetimes τ R and fluorescent branching ratios β. The calculated radiative lifetime was compared with the experiment data for the 4F3/2 emitting level. All spectral features are strongly affected by an inhomogeneous broadening connected with the ‘disordered crystal’ character of the title compound. [Copyright &y& Elsevier]

Based on the analysis of the absorption spectra of Er-doped calcium-niobium-gallium garnet (Er:CNGG) crystals according to the Judd-Ofelt theory, the intensity parameters for these crystals are determined to be Θ2 = 3.43 × 10−20 cm2 Θ4 = 1.20 × 10−20 cm2, and Θ6 = 0.58 × 10−20 cm2. The parameters found are compared with the intensity parameters for other laser oxide crystals. Using these intensity parameters, the probabilities of radiative transitions between the energy levels of Er3+ ions in CNGG crystals and the luminescence branching ratios βJJ’ are calculated. From the measured lifetime of the 4 I 11/2 level of Er3+ ions (τ = 626 μs) and the probability of the radiative transition from this level ( A = 192 s−1), it is found that about 88% of the excitation energy in the Er:CNGG crystals is nonradiatively transferred from the 4 I 11/2 to the 4 I 13/2 level. It is suggested that an increase in the oscillator strength and in the line strength of the 4 I 15/2 → 2 H 11/2 transition of Er3+ in CNGG crystals, as well as an increase in the intensity parameter Θ2 with respect to the corresponding parameters for other garnet crystals are caused by the existence in CNGG crystals of Er3+ centers with the environment symmetry lower than D 2. [ABSTRACT FROM AUTHOR]

Abstract: We compare experimental spectra of radiative and semileptonic B decays with the predictions of a model based on soft-gluon resummation to next-to-next-to-leading order and on a ghost-less time-like coupling. We find a good agreement with photon spectra in the radiative decay and with hadron mass distributions in the semileptonic one: the extracted values for are in agreement with the current PDG average within at most two standard deviations. The agreement is instead less good for the electron spectra measured by BaBar and Belle in semileptonic decays for small electron energies (): our spectrum is harder. We also show that, in general, the inclusion of next-to-next-to-leading order effects is crucial for bringing the model closer to the data and that the non-power expansion introduced in the framework of analytic coupling studies does not accurately describe soft-gluon effects. [Copyright &y& Elsevier]

The polarized absorption and emission spectra of Pr3+ ions in NaY(MoO4)2 single crystal were investigated. The standard and modified Judd–Ofelt theory have been applied to the measured optical absorption intensities to determine the spectroscopic parameters, including the Judd–Oflet intensity parameters Ωt (t=2,4,6), the radiative transition rates, branching ratios, and emission cross-sections for various excited levels of Pr3+ ions. In samples with Pr3+ ions concentration of 2.00×1020 cm-3, the excitation of the 1 D 2 manifold decays non-radiatively by the electric dipole–dipole transfer between Pr3+ neighbors. The good spectroscopic properties show the possible application of the Pr3+ doped NaY(MoO4)2 crystal as a solid-state laser. [ABSTRACT FROM AUTHOR]

Cross sections for 13C(α,α′) reactions at Eα = 400 MeV have been measured to obtain the monopole and quadrupole transition strengths. The excitation strengths are compared with the shell-model predictions. It is suggested that the large monopole strengths observed for the $1/2^-_2$ and $1/2^-_3$ states in 13C are attributed to the cluster structure of those states. [ABSTRACT FROM AUTHOR]