Natural Radiative Lifetimes Research Articles

The determination of radiative lifetime for some Eu I levels by time-resolved laser-induced fluorescence spectroscopy

Natural radiative lifetimes for 15 excited levels of Eu I were measured using time-resolved laser-induced fluorescence (TR-LIF) technique in a laser-induced europium plasma. The levels are in the energy range from 35612.47 to 50040 cm−1. The lifetimes range from 9.4 to 436 ns with the uncertainties within ten percent. To our best knowledge, 11 lifetimes of Eu I are reported for the first time.

Experimental radiative lifetimes, branching fractions, and oscillator strengths of some levels in Tm III

Natural radiative lifetimes for five even-parity levels of Tm III were measured by time-resolved laser-induced fluorescence method. The branching fraction measurements were performed based on the emission spectra of a hollow cathode lamp. By combining the measured branching fractions and the lifetime values reported in this work and in literature, experimental transition probabilities and oscillator strengths for 11 transitions were derived for the first time.

PhotochemCAD 3: Diverse Modules for Photophysical Calculations with Multiple Spectral Databases.

The PhotochemCAD program, developed over 30years, is described comprehensively with focus on features of the most recent version (PhotochemCAD 3). The program is equipped with a streamlined user interface and provisions for handling multiple spectral databases. Eight modules enable calculations to be performed on the basis of the spectra in the databases. The calculational modules provide results concerning properties of individual compounds (oscillator strength, transition dipole moment, natural radiative lifetime), interactions of multiple compounds (Förster energy transfer, Dexter energy transfer, analysis of energy transfer among an array of chromophores) and composition of mixtures (multicomponent analysis). Synthetic spectra (blackbody radiator, Gaussian and Lorentzian curves, delta functions) also can be generated. For comparison and calculation, synthetic and experimental spectra can be shifted along both coordinate axes and combined by addition, subtraction and use of multiplicative factors. The core databases (described in the companion paper) have been expanded to 339 compounds for which absorption spectra (including molar absorption coefficient, ε), fluorescence spectra (including fluorescence quantum yield, Φf ) and references to the primary literature have been included where available (552 spectra altogether). A database of 31 solar spectra also is included. Each calculational module is described along with illustrative examples.

Experimental branching fractions, transition probabilities and oscillator strengths of some levels in Ba I

Branching fractions (BFs) of Ba I for 108 lines including 96 lines from 33 odd-parity levels with the configurations 5dnp (n = 6, 7, 8), 6snp (n = 7, 8, 11, 12), 6snf (n = 5, 6, 11, 16) and 5d4f, as well as 12 lines from 5 even-parity levels with the configurations 6snd (n = 7, 9, 12) and 5d6d were measured using a high-resolution grating spectrometer with a hollow-cathode lamp. By combining the data of natural radiative lifetimes published in literature, the transition probabilities and oscillator strengths for these lines were also deduced, and the achieved results are in fair agreements with the previous ones.

Radiative lifetime measurements of some Gd I levels by time-resolved laser spectroscopy

Natural radiative lifetimes for 27 excited levels of Gd I in the energy range from 28215.140 to 43963.900cm−1 were measured using time-resolved laser-induced fluorescence (TR-LIF) technique in an atom beam produced by laser-induced plasma. All the lifetimes obtained in this paper range from 8.4 to 833ns with the uncertainties within ten percent. A comparison with a few previously reported values was performed and good agreement between them was achieved. To our best knowledge, 18 lifetimes of Gd I are reported for the first time.

Optical spectroscopy of Sm3+ doped Na2O–ZnO–La2O3–TeO2 glasses

Telluride glasses with the composition xSm2O3–(7−x)La2O3–3Na2O–25ZnO–65TeO2 (where x=0.1, 1, 2, 5 and 7mol%) were obtained by the melt quenching technique. Electronic absorption and fluorescence spectra as well as fluorescence dynamics of the Sm3+-doped title glasses are presented and analysed in detail. A Judd–Ofelt intensity analysis of the absorption spectrum at 300K has been applied for determination of Ωλ parameters (Ω2=3.10, Ω4=3.80, Ω6=1.61×10−20cm2) which in turn have been used for calculations of the radiative transition probabilities (AT), the natural (radiative) lifetimes (τR) of the 4G5/2 level of Sm3+, the fluorescence branching ratios (β) and the emission cross-sections (σem). The τR value of the 4G5/2 level amount to 1546μs and is slightly higher than the measured decay time of 1306μs. With the increasing of Sm2O3 concentration from 0.1 to 7.0mol% the experimental lifetime of the fluorescent level decreases from 1306 to 41μs. An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The optical achieved results indicate that the investigated glasses are potentially applicable as an orange and/or red laser host.

Radiative lifetime measurements for some levels in Mn I and Ni I by time-resolved laser spectroscopy

Natural radiative lifetimes for 32 excited levels of Mn I and for 17 excited levels of Ni I were measured using time-resolved laser-induced fluorescence (TR-LIF) spectroscopy in laser-induced plasma. The energy regions are from 45,754.27 to 54,950.81cm−1 for Mn I and from 28,578.018 to 50,851.199cm−1 for Ni I. The uncertainties of all lifetime results are within 10%. To our best knowledge, 26 lifetime results of Mn I and 9 lifetime results of Ni I are reported for the first time.

Optical properties of Sm3+-doped Y2Te4O11

Spectroscopic properties of Sm3+-doped Y2Te4O11 micro-crystals were studied in the 6000–18,500cm−1 spectral range. Vibrational, electronic absorption, fluorescence and excitation spectra as well as fluorescence dynamics of the Sm3+-doped title micro-crystals are presented and analyzed in detail. A Judd–Ofelt intensity analysis of the absorption spectrum at 300K has been applied for determination of Ωλ parameters which in turn have been used for calculations of the radiative transition probability factor (A), the fluorescence branching ratios (β), the natural (radiative) lifetime of the 4G(4)5/2 level of Sm3+ and the emission cross-section (σem). An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The achieved results indicate that the investigated samples are potentially applicable as a 605 and 652nm laser host as well as an orange phosphor.

The absorption and fluorescence emission spectra of meso-tetra(aryl)porphyrin dications with weak and strong carboxylic acids: a comparative study

The absorption and emission spectra, natural radiative lifetime, radiative rate constant (kr) and the non-radiative one (knr) of the dications of a series of meso-tetra(aryl)porphyrins with CF3COOH and HCOOH were studied and compared.

Ultrafast non-local control of spontaneous emission.

The radiative interaction of solid-state emitters with cavity fields is the basis of semiconductor microcavity lasers and cavity quantum electrodynamics (CQED) systems. Its control in real time would open new avenues for the generation of non-classical light states, the control of entanglement and the modulation of lasers. However, unlike atomic CQED or circuit quantum electrodynamics, the real-time control of radiative processes has not yet been achieved in semiconductors because of the ultrafast timescales involved. Here we propose an ultrafast non-local moulding of the vacuum field in a coupled-cavity system as an approach to the control of radiative processes and demonstrate the dynamic control of the spontaneous emission (SE) of quantum dots (QDs) in a photonic crystal (PhC) cavity on a ∼ 200 ps timescale, much faster than their natural SE lifetimes.

A study of optical properties of Sm3+ ions in α-Na3Y(VO4)2 single crystals

Single crystals of α-Sm3+:Na3Y(VO4)2 have been grown by the flux growth method. The absorption (300K) fluorescence (4.2 and 300K) and excitation (7 and 300K) spectra as well as the fluorescence dynamics of the Sm3+-doped title crystals are presented and analyzed in detail. The energy transfer between Sm3+–Sm3+ as well as from VO43− to Sm3+ were studied in detail. A Judd–Ofelt intensity analysis of the absorption (300K) spectrum has been applied for determination of Ωλ parameters which in turn have been used in calculation of the radiative transition probability factor (A), fluorescence branching ratios (β), natural (radiative) lifetime of the 4G(4)5/2 level of Sm3+ and emission cross-section (σem). For the first time very large lifetimes of the Sm3+ fluorescence level have been observed.

稀土原子与离子的自然辐射寿命测量

稀土原子与离子的自然辐射寿命测量

Theoretical study of potential energy curves, spectroscopic constants, and radiative lifetimes of low-lying states in an SeO molecule

The low-lying potential energy curves of the SeO molecule are computed by means of an ab initio multireference configuration interaction technique, taking into account relativistic (scalar plus spin—orbit coupling) effects. The spectroscopic constants of Ω states for X3Σ−, a1Δ, b1Σ+, A3Π, A′3Δ, and A″ 3Σ+ states are obtained, and they are in good accordance with available experimental values. The Franck—Condon factors and transition dipole moments to the ground state are computed, and the natural radiative lifetimes of low-lying Ω states are theoretically obtained. Comparisons of the natural lifetimes of Ω states with previous experimental results and those of isovalent TeO molecule are made.

Silica sol–gel glasses incorporating dual-luminescent Yb quinolinolato complex: processing, emission and photosensitising properties of the ‘antenna’ ligand

The [Yb(5,7ClQ)(2)(H5,7ClQ)(2)Cl] (1) complex, that exhibits dual-luminescence in the visible (ligand-centered) and in the NIR (Yb-centered), has been incorporated into a silica sol-gel glass obtaining 1-doped glassy material which is optically transparent and homogeneous and with good mechanical properties. The doped sol-gel glass can be considered a "solid state solution" and photophysical studies demonstrate that the emissive properties of the dopant complex are preserved in the silica matrix. Observed NIR decay times fall in the μs range and are likely limited by "second-sphere" matrix interactions. The ligand-to-metal energy transfer mechanism occurs on ultrafast timescale and involves ligand triplet states. The sensitization efficiency of the antenna quinolinolato ligand toward Yb(3+) is estimated to be as high as ~80%. The Yb natural radiative lifetime observed for 1 in MeCN-EtOH solution (τ(rad) = 438 μs) is the shortest reported so far for ytterbium complexes.

Radiative lifetime measurements of some Eu I and Eu II levels by time-resolved laser spectroscopy

Natural radiative lifetimes of nine odd-parity highly excited levels in Eu I and eleven even-parity levels in Eu II have been measured by time-resolved laser-induced fluorescence technique in laser-produced plasma. The lifetime values measured in this paper are in the range from 7.1 to 1520 ns. When they are compared with the previous measurements, good agreement was achieved.

Photophysical Properties of 9,10-Disubstituted Anthracene Derivatives in Solution and Films

We have carried out absorption, time-resolved fluorescence, and fluorescence quantum yield measurements of four new soluble anthracene derivatives. They show natural radiative lifetimes in the range of 2.5-4.4 ns, which is 5-10 times shorter than those reported for unsubstituted anthracene. The 9,10-bis(phenylethynyl)anthracene (BPEA) derivatives show the largest fluorescence transition dipoles, which is attributed to extended π-conjugation between anthracene and phenyls through acetylene linkages. Spin-cast films of the BPEA derivatives show strong fluorescence quenching by weakly emitting low energy excitations, which is attributed to excimer-like traps. Quenching is significantly reduced when bulky dendrons are attached so that they give maximum coverage of the emitting chromophore and prevent their aggregation. The results show that anthracene derivatives can be developed into efficient solution-processable fluorescent emitters for the blue and green spectral regions.

Lifetime measurements of odd-parity high-excitation levels of Sm ii by time-resolved laser spectroscopy

Natural radiative lifetimes of 53 odd-parity highly excited levels of singly ionized samarium in the energy range 26 599.08–36 107.66 cm −1 have been measured by the time-resolved laserinduced fluorescence technique in an ionic plume produced by laser ablation. The fundamental frequency and second harmonic of a dye laser have been adopted as the tunable exciting source (308–650 nm), and a fast detection system has been used to record fluorescence signals. The lifetime values obtained in this paper are in the range 10.5–271 ns. A good agreement between the present results and the previously published values was achieved. This work will be useful for investigating the composition of chemically peculiar stars.

Radiative lifetime measurements of highly excited even-parity levels of Eu i

Natural radiative lifetime measurements have been performed for 186 even-parity highly excited levels of neutral europium in the energy range from 27852.90 to 45106.83 cm -1 using a time-resolved laser-induced fluorescence technique in a laser-produced plasma. This work is the largest-scale laboratory study to date of Eu I radiative lifetimes using modern methods. The lifetime values measured in this paper are in the range from 17.0 to 3569 ns. Comparison with previous data reveals a good level of agreement. Unique J-values of the 43438.19- and 43637.11-cm -1 levels have been assigned. The present work will be useful for extending the set of oscillator strengths available for Eu I.

Radiative lifetime measurements of odd-parity moderately excited levels belonging to J = 4, 5, 6 and 7 series in Sm I

Natural radiative lifetimes of 64 odd-parity moderately excited levels of neutral samarium in the energy range from 21 243.3 to 34 723.16 cm−1 have been measured by the time-resolved laser-induced fluorescence (LIF) technique in an atomic beam produced by laser ablation. Lifetime values in the range from 11.8 to 550.1 ns are obtained. A comparison with a few previously reported values is performed and good agreement between them has been achieved. The measured results in this paper are useful for determination of the oscillator strengths of transitions in Sm I.

Radiative-lifetime measurements and calculations of odd-parity highly excited levels in Ba i

Natural radiative lifetime measurements have been performed for $70$ odd-parity highly excited levels of neutral barium in the energy range from $308$ $15.512$ to $417$ $59.93$ cm${}^{\ensuremath{-}1}$ by a time-resolved laser-induced fluorescence technique in a laser-produced plasma. The lifetime values measured in this paper are in the range from $11.3$ to $901$ ns. They are compared with the published lifetimes of four levels. Two of them are in good agreement, whereas for the other two our measurements are slightly longer than the published data. The reasons for the discrepancies are discussed. Comparisons with theoretical results of the Hartree-Fock method with relativistic corrections illustrate the difficulties associated with the use of Cowan's codes for obtaining accurate branching fractions for transitions depopulating highly excited levels along the Rydberg series of heavy neutral elements. This work will be useful to extend the set of oscillator strengths available in Ba i.