The Experts below are selected from a list of 15105 Experts worldwide ranked by ideXlab platform
Emile Biemont - One of the best experts on this subject based on the ideXlab platform.
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Radiative Lifetime measurements and calculations of odd parity highly excited levels in ba i
Physical Review A, 2010Co-Authors: Wei Zhang, Emile Biemont, Pascal Quinet, P Palmeri, Shan DuAbstract: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{sup -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.
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improved atomic data for iridium atom ir i and ion ir ii and the solar content of iridium
Journal of Quantitative Spectroscopy & Radiative Transfer, 2007Co-Authors: Sune Svanberg, Emile Biemont, Pascal Quinet, P PalmeriAbstract:From a combination of Radiative Lifetime measurements, performed with a time-resolved laser-induced fluorescence technique, for nine odd-parity levels of Ir I and four odd-parity levels of Ir II and branching fraction calculations, extended sets of transition probabilities have been derived for transitions of astrophysical interest. The new results are compared with the few experimental data available in the literature and a good agreement is found. They extend considerably the previous sets of transition probabilities available in the literature. Implications of the new results regarding the solar content of iridium are briefly discussed.
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Radiative Lifetimes branching fractions and oscillator strengths in pd i and the solar palladium abundance
Astronomy and Astrophysics, 2006Co-Authors: Zhiwei Sun, Emile Biemont, Pascal Quinet, P Palmeri, Zhenwen Dai, Z K JiangAbstract:Transition probabilities have been derived for 20 5s−5p transitions of Pd I from a combination of Radiative Lifetime measurements for 6 odd-parity levels with time-resolved laser-induced fluorescence spectroscopy and of branching fraction determination using a hollow cathode discharge lamp. Additional oscillator strengths for 18 transitions have been determined from measured Lifetimes and theoretical branching fractions obtained from configuration interaction calculations with core-polarization effects included. These new results have allowed us to refine the palladium abundance in the solar photosphere: APd = 1.66 ± 0.04, in the usual logarithmic scale, a result in close agreement with the meteoritic value.
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Radiative Lifetime and transition probabilities in cdi and cdii
Physical Review A, 2004Co-Authors: Huailiang Xu, K Blagoev, G Malcheva, V Pentchev, Emile Biemont, Monsterrat Ortiz, J Campos, Sune Svanberg, Anders Persson, R. MayoAbstract:Radiative Lifetimes of 11 levels belonging to the 5s5p P-1(1)o 5snd D-3(1,2) (n=6-9) and 5sns S-3(1) (n=7,8) series of Cd I, and of 5 levels of Cd II (i.e., 4d(10)5p P-2(1/2.3/2)o, 4d(10)6s S-2(1/2), and 4d(10)5d D-2(3/2,5/2)) have been measured using the time-resolved laser-induced fluorescence technique. Free neutral and singly ionized cadmium atoms have been generated by laser ablation. Single- or two-step excitation processes were considered to populate the levels under study. Branching fractions of Cd II transitions have been measured by laser-induced breakdown spectroscopy. Transition probabilities and oscillator strengths for Cd I and Cd II spectral lines originating from the above states as well as from the 4d(9)5 s(22)D(3/2,5/2) states of Cd II have been deduced by combining the experimental Lifetimes and theoretical branching fractions obtained in multiconfigurational relativistic Hartree-Fock calculations taking core-polarization effects into account. (Less)
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Radiative Lifetime measurements and transition probability calculations in lanthanide ions
Journal of Alloys and Compounds, 2002Co-Authors: Emile Biemont, Pascal Quinet, P Palmeri, Zhongshan Li, Zhiguo Zhang, Sune SvanbergAbstract:We have undertaken a systematic investigation of spectroscopic properties of lanthanide ions (Z=57-71). Using time-resolved laser-induced fluorescence following one- or two-photon excitations, a large number of Radiative Lifetimes have been measured at the Lund Laser Centre for singly, doubly and trebly ionized atoms. These new measurements have been used for testing theoretical calculations performed within the framework of a relativistic Hartree-Fock approach taking core-polarization effects into account. Using the experimental Lifetimes (when available) and the theoretical branching fractions, a large number of transition probabilities, most of them of astrophysical interest, have been deduced and are stored in a new database (DREAM). Up to now, the results obtained concern the following ions: La2+, Ce2+, Ce2+, Pr2+, Ho2+, Er2+, Tm2+, Tm2+, Yb2+, Yb2+, Yb2+, Lu2+ and Lu2+. (C) 2002 Elsevier Science B.V. All rights reserved. (Less)
M I Kupchenko - One of the best experts on this subject based on the ideXlab platform.
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spectroscopy and continuous wave diode pumped laser action of yb 3 yvo 4
Optics Letters, 2004Co-Authors: V E Kisel, N V Kuleshov, A E Troshin, N A Tolstik, V G Shcherbitsky, V N Matrosov, T A Matrosova, M I KupchenkoAbstract:The growth, spectroscopic properties, and laser performance of Yb:YVO4 crystal with laser diode pumping are reported. A peak absorption cross section of 7.4×10-20 cm2 at 985 nm, a Radiative Lifetime of 0.25 ms, and a stimulated-emission cross section of 1.25×10-20 cm2 at 1008 nm for π polarization were determined for the Yb3+ ions in YVO4. Continuous-wave laser action of Yb:YVO4 at 1020–1027 nm was demonstrated with an output power of 610 mW and a slope efficiency of 49%.
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spectroscopy and continuous wave diode pumped laser action of yb3 yvo4
Optics Letters, 2004Co-Authors: V E Kisel, N V Kuleshov, A E Troshin, N A Tolstik, V G Shcherbitsky, V N Matrosov, T A Matrosova, M I KupchenkoAbstract:The growth, spectroscopic properties, and laser performance of Yb:YVO4 crystal with laser diode pumping are reported. A peak absorption cross section of 7.4×10-20 cm2 at 985 nm, a Radiative Lifetime of 0.25 ms, and a stimulated-emission cross section of 1.25×10-20 cm2 at 1008 nm for π polarization were determined for the Yb3+ ions in YVO4. Continuous-wave laser action of Yb:YVO4 at 1020–1027 nm was demonstrated with an output power of 610 mW and a slope efficiency of 49%.
Uri Banin - One of the best experts on this subject based on the ideXlab platform.
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universal role of discrete acoustic phonons in the low temperature optical emission of colloidal quantum dots
Physical Review Letters, 2009Co-Authors: Dan Oron, Andries Meijerink, Assaf Aharoni, Celso De Mello Donega, Jos Van Rijssel, Uri BaninAbstract:Multiple energy scales contribute to the Radiative properties of colloidal quantum dots, including magnetic interactions, crystal field splitting, Pauli exclusion, and phonons. Identification of the exact physical mechanism which couples first to the dark ground state of colloidal quantum dots, inducing a significant reduction in the Radiative Lifetime at low temperatures, has thus been under significant debate. Here we present measurements of this phenomenon on a variety of materials as well as on colloidal heterostructures. These show unambiguously that the dominant mechanism is coupling of the ground state to a confined acoustic phonon, and that this mechanism is universal.
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multiexcitons in type ii colloidal semiconductor quantum dots
Physical Review B, 2007Co-Authors: Dan Oron, Miri Kazes, Uri BaninAbstract:The spectroscopy and dynamics of multiple excitations on colloidal type-II $\mathrm{Cd}\mathrm{Te}∕\mathrm{Cd}\mathrm{Se}$ core-shell quantum dots (QDs) are explored via quasi-cw multiexciton spectroscopy. The charge separation induced by the band offset redshifts the exciton emission and increases the Radiative Lifetime. In addition, we observe a significant modification of multiexciton properties compared with core-only or type-I QDs. In particular, the Auger recombination Lifetimes are significantly increased, up to a nanosecond time scale. While in type-I QDs the Auger Lifetime scales with the volume, we find for type-II QDs a scaling law that introduces a linear dependence also on the Radiative Lifetime. We observe a blueshift of the biexciton emission and extract biexciton repulsion of up to $30\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ in type-II QDs. This is assigned to the dominance of the Coulomb repulsion as the positive and negative charges become spatially separated, which overwhelms the correlation binding term. Higher electronic excited states can remain type I even when the lowest transition is already type II, resulting in a different size dependence of the triexciton emission. Finally, we discuss the possibilities of ``multiexciton band gap engineering'' using colloidal type-II QDs.
V E Kisel - One of the best experts on this subject based on the ideXlab platform.
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spectroscopy and continuous wave diode pumped laser action of yb 3 yvo 4
Optics Letters, 2004Co-Authors: V E Kisel, N V Kuleshov, A E Troshin, N A Tolstik, V G Shcherbitsky, V N Matrosov, T A Matrosova, M I KupchenkoAbstract:The growth, spectroscopic properties, and laser performance of Yb:YVO4 crystal with laser diode pumping are reported. A peak absorption cross section of 7.4×10-20 cm2 at 985 nm, a Radiative Lifetime of 0.25 ms, and a stimulated-emission cross section of 1.25×10-20 cm2 at 1008 nm for π polarization were determined for the Yb3+ ions in YVO4. Continuous-wave laser action of Yb:YVO4 at 1020–1027 nm was demonstrated with an output power of 610 mW and a slope efficiency of 49%.
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spectroscopy and continuous wave diode pumped laser action of yb3 yvo4
Optics Letters, 2004Co-Authors: V E Kisel, N V Kuleshov, A E Troshin, N A Tolstik, V G Shcherbitsky, V N Matrosov, T A Matrosova, M I KupchenkoAbstract:The growth, spectroscopic properties, and laser performance of Yb:YVO4 crystal with laser diode pumping are reported. A peak absorption cross section of 7.4×10-20 cm2 at 985 nm, a Radiative Lifetime of 0.25 ms, and a stimulated-emission cross section of 1.25×10-20 cm2 at 1008 nm for π polarization were determined for the Yb3+ ions in YVO4. Continuous-wave laser action of Yb:YVO4 at 1020–1027 nm was demonstrated with an output power of 610 mW and a slope efficiency of 49%.
Pascal Quinet - One of the best experts on this subject based on the ideXlab platform.
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Radiative Lifetime measurements and calculations of odd parity highly excited levels in ba i
Physical Review A, 2010Co-Authors: Wei Zhang, Emile Biemont, Pascal Quinet, P Palmeri, Shan DuAbstract: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{sup -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.
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improved atomic data for iridium atom ir i and ion ir ii and the solar content of iridium
Journal of Quantitative Spectroscopy & Radiative Transfer, 2007Co-Authors: Sune Svanberg, Emile Biemont, Pascal Quinet, P PalmeriAbstract:From a combination of Radiative Lifetime measurements, performed with a time-resolved laser-induced fluorescence technique, for nine odd-parity levels of Ir I and four odd-parity levels of Ir II and branching fraction calculations, extended sets of transition probabilities have been derived for transitions of astrophysical interest. The new results are compared with the few experimental data available in the literature and a good agreement is found. They extend considerably the previous sets of transition probabilities available in the literature. Implications of the new results regarding the solar content of iridium are briefly discussed.
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Radiative Lifetimes branching fractions and oscillator strengths in pd i and the solar palladium abundance
Astronomy and Astrophysics, 2006Co-Authors: Zhiwei Sun, Emile Biemont, Pascal Quinet, P Palmeri, Zhenwen Dai, Z K JiangAbstract:Transition probabilities have been derived for 20 5s−5p transitions of Pd I from a combination of Radiative Lifetime measurements for 6 odd-parity levels with time-resolved laser-induced fluorescence spectroscopy and of branching fraction determination using a hollow cathode discharge lamp. Additional oscillator strengths for 18 transitions have been determined from measured Lifetimes and theoretical branching fractions obtained from configuration interaction calculations with core-polarization effects included. These new results have allowed us to refine the palladium abundance in the solar photosphere: APd = 1.66 ± 0.04, in the usual logarithmic scale, a result in close agreement with the meteoritic value.
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Radiative Lifetime measurements and transition probability calculations in lanthanide ions
Journal of Alloys and Compounds, 2002Co-Authors: Emile Biemont, Pascal Quinet, P Palmeri, Zhongshan Li, Zhiguo Zhang, Sune SvanbergAbstract:We have undertaken a systematic investigation of spectroscopic properties of lanthanide ions (Z=57-71). Using time-resolved laser-induced fluorescence following one- or two-photon excitations, a large number of Radiative Lifetimes have been measured at the Lund Laser Centre for singly, doubly and trebly ionized atoms. These new measurements have been used for testing theoretical calculations performed within the framework of a relativistic Hartree-Fock approach taking core-polarization effects into account. Using the experimental Lifetimes (when available) and the theoretical branching fractions, a large number of transition probabilities, most of them of astrophysical interest, have been deduced and are stored in a new database (DREAM). Up to now, the results obtained concern the following ions: La2+, Ce2+, Ce2+, Pr2+, Ho2+, Er2+, Tm2+, Tm2+, Yb2+, Yb2+, Yb2+, Lu2+ and Lu2+. (C) 2002 Elsevier Science B.V. All rights reserved. (Less)
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Radiative Lifetime measurements and transition probabilities of astrophysical interest in er iii
Monthly Notices of the Royal Astronomical Society, 2001Co-Authors: Emile Biemont, Pascal Quinet, P Palmeri, Zhongshan Li, Henripierre Garnir, Thierry Bastin, Zijing Zhang, V Lokhnygin, Sune SvanbergAbstract:Radiative Lifetimes of seven excited states of Er iii have been measured using time-resolved laser-induced fluorescence following two-photon excitation. Relativistic Hartree-Fock calculations taking core-polarization effects into account are found to be in excellent agreement with the experimental results. A large set of new calculated transition probabilities is presented for many transitions of astrophysical interest. These results will be useful for investigating the composition of chemically peculiar stars.
