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1.	Biemont, E, et al. (författare) Experimental lifetime determination in neutral praseodymium (Pr I) and neodymium (Nd I) 2004 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:7, s. 1381-1389 Tidskriftsartikel (refereegranskat)abstract Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 18 even-parity levels of Pr I and 15 odd-parity levels of Nd I. The new results are compared with the few experimental data available in the literature and good agreement is found. However, fragmentary knowledge of the spectra prevents reliable calculation of branching fractions and calls for additional laboratory efforts in order to provide the astrophysicists with reliable transition probabilities needed for investigating the magnetic fields in chemically peculiar stars.
2.	Biemont, E, et al. (författare) Lifetime measurements and calculations in LaI 2004 Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 30:2, s. 157-162 Tidskriftsartikel (refereegranskat)abstract Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 20 odd-parity levels of La I belonging to the configurations 5d(2)6p, 5d6s6p and 4f5d6s. The new results are compared with the few experimental data available in the literature and with theoretical calculations including configuration interaction effects. The agreement theory-experiment is generally satisfying but discrepancies are observed for some levels emphasizing the difficulty to get a reliable theoretical model in such a heavy and complex neutral element.
3.	Biemont, E, et al. (författare) Lifetime measurements and calculations in singly ionized ytterbium 2002 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 35:22, s. 4743-4749 Tidskriftsartikel (refereegranskat)abstract New radiative lifetimes, measured by time-resolved laser-induced fluorescence spectroscopy, are reported for five Rydberg states of singly ionized ytterbium. Free Yb+ ions were produced in a laser-induced plasma. The experimental results have been compared with HFR calculations, taking core-polarization effects into account, and a good agreement (within 25%) between theory and experiment is observed for four levels. HFR results are also proposed for np (n less than or equal to 7) and nf (n less than or equal to 8) Rydberg states and compared with available data.
4.	Biemont, E, et al. (författare) Lifetimes along perturbed Rydberg series in neutral thallium 2005 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 38:19, s. 3547-3558 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of 15 Tl I levels belonging to the 6s(2)ns(2)S(1/2) (n = 7-14) and 6s(2)nd(2)D(3/2) Rydberg series (n = 6-12) have been measured using a time-resolved laser-induced fluorescence technique. All the measured levels have been excited from the ground state 6s(2)6p(2)P(1/2)(0) (odd parity) with a single-step excitation process. The general perturbation of the ns series by the 6s6p(2) configuration and the corresponding modification of the lifetimes are adequately reproduced by a theoretical model including core-polarization effects and combined with a least-squares fit to the observed energy levels. The general behaviour of the lifetime values for the 6s(2)np odd levels along the Rydberg series is also well reproduced. The use of the multiconfiguration quantum defect theory has allowed us to obtain lifetime values along the 6s(2)ns(2)S(1/2) series up to levels with n = 31.
5.	Biemont, E, et al. (författare) Radiative lifetime measurements and oscillator strength determination for transitions in singly ionized praseodymium (Pr II) 2003 Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 27:1, s. 33-41 Tidskriftsartikel (refereegranskat)abstract New radiative lifetimes for 20 levels of Pr II have been measured using the time-resolved laser-induced fluorescence (LIF) technique. The combination of these experimental values with theoretical branching fractions (BF) obtained with the pseudo-relativistic Hartree-Fock (HFR) approach has allowed us to determine oscillator strengths and transition probabilities for about 150 lines appearing in the spectral region between 369.9 and 741.2 nm. A detailed discussion of our new results and comparisons with previous data are also given in the present paper.
6.	Blackwell-Whitehead, R J, et al. (författare) Experimental oscillator strengths for the spectrum of neutral manganese 2005 Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 361:4, s. 1281-1286 Tidskriftsartikel (refereegranskat)abstract We report laboratory measurements of oscillator strengths for 44 transitions in the Mn T spectrum covering the wavelength range 209-2780 nm. Nine energy level lifetimes have been measured using time resolved laser-induced fluorescence (LIF). The lifetimes have been combined with branching fractions measured by Fourier transform spectroscopy to obtain absolute oscillator strengths. In total, 24 of these oscillator strengths are measured for the first time, including transitions in the previously unobserved infrared region above 2.0 mu m.
7.	Blagoev, KB, et al. (författare) Radiative lifetimes of Zn I, II excited states 2004 Ingår i: Physica Scripta. - 0031-8949. ; 69:6, s. 433-440 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of excited states of Zn I (3d(10)4sns S-3(1), n = 6-8; 3d(10) 4snd D-3, n = 4-7) and Zn II (3d(10) 4p P-2(1/2.3/2), 4d D-2(3/2,5/2), 3d(10)5S S-2(1/2)) have been measured using a time-resolved laser-induced fluorescence technique. Single- or two-step excitation of atoms and ions produced by laser ablation was employed. The experimental radiative lifetimes have been compared with theoretical results obtained within a multiconfigurational relativistic Hartree-Fock approach taking core-polarization effects into account.
8.	Dai, Zhenwen, et al. (författare) Time-resolved laser-induced fluorescence measurements of Rydberg states in LuI and comparison with theory 2003 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 36:3, s. 479-487 Tidskriftsartikel (refereegranskat)abstract Time-resolved laser-induced fluorescence measurements have been performed for ten odd Rydberg states of neutral lutetium, belonging to the 6s(2)(S-1)np(n = 8-9) and 6 s(2)(S-1)nf (n = 5-8) series. For 6S(2)(S-1)8p and 6s(2)(S-1)7f, the experimental lifetimes corresponding to the two J values within the doublet differ substantially. Comparison with theoretical values, calculated with extensive configuration interaction and core-polarization effects included, shows that the experimental trends are adequately reproduced both for np (n = 8-9) and nf (n = 5-8) states.
9.	Fang, AP, et al. (författare) Theoretical study of electromagnetically induced transparency in Er3+: YAlO3 crystal 2003 Ingår i: Physica B: Condensed Matter. - 0921-4526. ; 328:3-4, s. 204-210 Tidskriftsartikel (refereegranskat)abstract By using the density matrix theory of interaction between light and matter, and relevant parameter calculations of the relaxation rate, the dipole matrix elements and the ion density for a three-level ladder model, we have discussed theoretically the possibility to realize electromagnetically induced transparency (EIT) in Er3+:YA1O(3) crystal. (C) 2002 Elsevier Science B.V. All rights reserved.
10.	Fivet, V, et al. (författare) Radiative lifetimes and transition probabilities in TaI 2006 Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 37:1, s. 29-35 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of 14 odd-parity Ta I levels, belonging to the 5d(3)6s6p and 5d(4)6p configurations in the energy range from 30 664 to 45 256 cm(-1). have been measured using the time-resolved laser-induced fluorescence technique. Extensive calculations, taking configuration interactions and corepolarisation effects into account, are able to reproduce in a satisfying way the available experimental results but suffer from the rather fragmentary knowledge of the level structure of this atom. New transition probabilities are deduced for a set of strong lines depopulating the levels investigated experimentally in the present work.
11.	Fivet, V., et al. (författare) Transition probabilities and lifetimes for atoms and ions from the sixth row of the periodic table and the database DESIRE 2007 Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 156, s. 250-254 Tidskriftsartikel (refereegranskat)abstract We have started a systematic investigation of the radiative properties of the elements of the sixth row of the periodic table. Using a combination of experimental radiative lifetimes obtained with the time-resolved laser-induced fluorescence (LIF) technique and of theoretical branching fractions (BF) calculated with a HFR approach taking configuration interaction and core-polarization effects into account, transition probabilities have been deduced for a number of transitions of astrophysical interest. So far results have been obtained for the elements Ta, Re, Os, Ir, Tl or An or their ions. The results obtained are stored in the database DatabasE for the SIxth Row Elements (DESIRE), an extension of the database DREAM, which will be progressively created on a web site of the University of Mons-Hainaut in Belgium. In the present paper, some emphasis is put on the procedures followed to obtain the new results but also on the difficulties associated with their determination. (c) 2006 Elsevier B.V. All rights reserved.
12.	Fivet, V., et al. (författare) Transition probabilities and lifetimes in gold (Au I and Au II) 2006 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:17, s. 3587-3598 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of three odd-parity levels of neutral gold (Au I) and one odd-parity level of singly ionized gold (Au II), measured using the time-resolved laser-induced fluorescence technique, have allowed the testing of the reliability of a relativistic Hartree-Fock model of the atomic structure taking configuration interaction and core-polarization effects into account. The importance of the inclusion of the latter effects in the calculations is emphasized. The laser-induced fluorescence lifetimes, combined with the theoretical branching fractions, have allowed us to deduce oscillator strengths for six 5d(9)6s(2)-5d(9)6s6p and 5d(10)6s-5d(9)6s6p transitions of Au I and for sixty-three 5d(9)6s-5d(9)6p, 5d(9)6p-5d(9)7s and 5d(10)-5d(9)6p UV transitions of Au II.
13.	Lundqvist, Martin, et al. (författare) Improved oscillator strengths and wavelengths in Hf II, with applications to stellar elemental abundances 2006 Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 450:1, s. 115-407 Tidskriftsartikel (refereegranskat)abstract Aims. We present new and improved radiative lifetimes for eight levels in HfI and 18 levels in HfII, along with oscillator strengths and wavelengths for 195 transitions in HfII. With these data we determine the abundance of hafnium in two chemically peculiar stars: the hot-Am star HR 3383 and the HgMn star chi Lupi, and discuss the implications of the new data to the hafnium abundance for the Sun and the metal-poor galactic halo stars CS 22892-052 and CS 31082-001. Methods. The oscillator strengths are derived by combining radiative lifetimes measured with the laser induced fluorescence technique and branching fractions determined from intensity calibrated Fourier transform spectra. The hafnium abundance in the two sharp-lined peculair stars is determined by comparison of spectra obtained from instruments onboard the Hubble Space Telescope with synthetic spectra, while the abundance of hafnium in the solar photosphere and the metal-poor halo stars is discussed in terms of rescaling previous investigations using the new g f values. Results. The abundance enhancement of hafnium has been determined in HR 3383 to be +1.7 dex and that for chi Lupi A is +1.3 dex. In the course of the analysis we have also determined an abundance enhancement for molybdenum in HR 3383 to be +1.2 dex, which is similar to that known for. Lupi A. The abundances in the metal-poor halo stars CS 31082-001 and CS 22892-052 were rescaled to log epsilon(Hf) = -0.75 and -0.82 respectively, with smaller 1 sigma uncertainty. This has the effect of improving the theoretical fits of r-process nucleosynthesis to abundance data for heavy elements. The change of g f values also implies that the hafnium abundance in the solar photosphere should be reduced by up to 0.2 dex, thereby inducing a discrepancy with the meteoritic hafnium abundance.
14.	Malcheva, G, et al. (författare) Radiative lifetimes and transition probabilities of astrophysical interest in ZrII 2006 Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 367:2, s. 754-762 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of 16 odd levels belonging to the 4d(2)5p configuration of Zr II have been measured using a time-resolved laser-induced fluorescence technique with a single-step excitation process either from the ground state or from metastable levels belonging to the 4d(2)5s and 4d(3) configurations. For 12 levels, there were no previous results available. The new experimental results and the lifetime values available in the literature have allowed to test a theoretical relativistic Hartree-Fock (HFR) model including core-polarization effects and to deduce transition probabilities for 242 transitions of astrophysical interest in the range 187.8-535.0 nm.
15.	Mayo, R., et al. (författare) Radiative lifetimes of Zr III excited levels 2006 Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 40:2, s. 169-173 Tidskriftsartikel (refereegranskat)abstract We report on radiative lifetimes of 4d5p excited states of Zr III produced in a laser produced plasma. The ions were populated either in the ground state or in metastable states, and the number of ions is strongly dependent on the application of an external magnetic field, which is shown to be very important when using the time-resolved laser-induced fluorescence technique for lifetime measurements in highly charged ions. The experimental lifetime results fall in the region 1-2 ns with statistical uncertainties less than 7%. The experimental values were compared with multi-configuration Hartree-Fock calculations showing an agreement within 12-20%. The experimental values are systematically higher than the theoretical ones.
16.	Moncorge, R, et al. (författare) Linear and non-linear spectroscopy of Ho3+-doped YVO4 and LuVO4 2005 Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 17:42, s. 6751-6762 Tidskriftsartikel (refereegranskat)abstract Rare-earth-doped crystals can be attractive materials for quantum information processing, because of the long coherence times that can be expected, in particular, from non-Kramers ions. In this paper, Ho3+-doped yttrium and lutetium vanadate single crystals have been investigated using linear and coherent optical spectroscopy. For Ho3+:YVO4, the crystal-field levels of the I-5(8), F-5, F-5(4) and S-5(2) multiplets have been determined and compared with crystal-field level calculations. This allowed us to unambiguously assign most of the observed transitions, although some results suggest that the site symmetry of the Ho3+ ion could deviate from D-2d. Similar conclusions were reached for Ho3+:LuVO4. Hole burning measurements indicate that the coherence time of the I-5(8)-F-5(5) optical transitions is rather short in both compounds (around 40 ns). Assuming that the coherence is limited by spin interactions, this is accounted for by the high nuclear moment of the nearby vanadium ions, since the large crystal-field level splittings of the I-5(8) and F-5(5) multiplets do not favour a large enhanced nuclear Zeeman effect.
17.	Palmeri, P., et al. (författare) Radiative lifetime measurements and semi-empirical transition probability calculations in neutral rhenium 2006 Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 74:3, s. 297-303 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of 11 odd-parity levels of neutral rhenium (Re I) were measured using time-resolved laser-induced fluorescence techniques. For ten levels, there were no previous results available. The new results have been used to assess the accuracy of calculations with a Hartree-Fock-plus-relativistic-corrections model that takes configuration interaction and core-polarization effects into account and they have allowed the deduction of reliable semi-empirical transition probabilities for 81 Re I lines.
18.	Quinet, P, et al. (författare) Transition probabilities and lifetimes in neutral and singly ionized osmium and the Solar osmium abundance 2006 Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 448:3, s. 93-1207 Tidskriftsartikel (refereegranskat)abstract Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 12 levels of Os I and for 9 levels of Os II. For 9 levels of Os I and 4 levels of Os II, there were no previous experimental data available. From a comparison with new theoretical calculations, taking configuration interactions and core-polarization effects into account, it has been possible to deduce oscillator strengths for 129 transitions of Os I and 137 transitions of Os II of astrophysical interest appearing in the wavelength range 180.0-870.0 nm. These results have allowed us to revise the abundance of osmium in the solar photosphere (log epsilon(Os) = 1.25 +/- 0.11). The newly derived oscillator strengths have been applied as well to derive the osmium abundance in the carbon-rich metal-poor star HD 187861.
19.	Xu, Huailiang, et al. (författare) Dynamics of visible-to-ultraviolet upconversion in YAlO3: 1% Er3 2003 Ingår i: Chemical Physics. - 0301-0104. ; 287:1-2, s. 155-159 Tidskriftsartikel (refereegranskat)abstract The dynamics of visible-to-ultraviolet upconversion in YAlO3: 1% Er3+ crystal has been investigated using the time-resolved laser spectroscopy when the sample was excited into the S-4(3/2) multiplets. It is found that the upconverted luminescence is produced by energy-transfer upconversion or by excited-state absorption depending on the excitation wavelength. The dependence of upconverted luminescence on pump power is presented, and the relative intensities of upconverted luminescence were accounted for by Judd-Ofelt theory. (C) 2002 Elsevier Science B.V. All rights reserved.
20.	Xu, Huailiang, et al. (författare) Hyperfine structure and homogeneous broadening in Pr3+: KY(WO4)(2) 2004 Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 70:21 Tidskriftsartikel (refereegranskat)abstract As part of a search for suitable materials for coherent quantum operations, relaxation times and hyperfine structure of the D-1(2)(1)-H-3(4)(1) transition in Pr3+:KY(WO4)(2) (0.29 at. %) at 4 K have been obtained using photon-echo and spectral hole burning techniques. The homogeneous linewidth and the effect of excitation-induced dephasing were measured using two-pulse photon-echo techniques. Linewidths of 23.4+/-1.0 and 17.6+/-0.9 kHz were obtained in the absence and presence of an external magnetic field of about 9 mT. The radiative lifetime (T-1) of the D-1(2) state was measured to be 43+/-2 mus using time-resolved laser-induced fluorescence and three-pulse photon-echo measurements. The transmission hole spectra were measured and directly yielded the quadrupole level splitting in the D-1(2) (3.77+/-0.03 and 4.58+/-0.04 MHz) and H-3(4) (17.1+/-0.1 and 33.2+/-0.3 MHz) states. The spectral hole lifetime due to population redistribution between the ground-state nuclear levels was also determined to be 70+/-10 ms. A strong dipole-dipole interaction observed in this crystal opens for potential applications in quantum computing schemes for performing quantum logic operations, but the short dephasing time makes it less useful in data storage applications.
21.	Xu, Huailiang, et al. (författare) Improved atomic data for iridium atom (Ir I) and ion (Ir II) and the solar content of iridium 2007 Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073. ; 104, s. 52-70 Tidskriftsartikel (refereegranskat)abstract 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.
22.	Xu, Huailiang, et al. (författare) Lifetime measurements in neutral and singly ionized vanadium 2006 Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 23:12, s. 2597-2600 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of ten odd-parity levels of V I belonging to the 3d(3)4s4p and 3d(4)4p configurations and of 11 odd-parity levels of V II belonging to the 3d(3)4p configuration are reported. The lifetimes were measured with use of single-step excitation and time-resolved fluorescence spectroscopy. The neutral and singly ionized vanadium atoms were produced in a laser-induced vanadium plasma. (c) 2006 Optical Society of America.
23.	Xu, Huailiang, et al. (författare) Lifetime measurements in neutral erbium using time-resolved laser spectroscopy 2003 Ingår i: Physica Scripta. - 0031-8949. ; 67:1, s. 64-67 Tidskriftsartikel (refereegranskat)abstract Natural radiative lifetimes, measured by time-resolved laser-induced fluorescence spectroscopy, are reported for eighteen levels of neutral erbium belonging to the odd-parity 4f(12)6s6p, 4f(11)5d6s(2), 4f(11)5d(2)6s and 4f(11)5d6s7s configurations in the wavenumber range from 26 237 to 42 154 cm(-1). Free erbium atoms were produced in a laser-induced plasma. Stimulated Brillouin scattering (SBS) techniques were employed to produce laser pulses as short as 1 ns for the excitation of short-lived levels, and special care was taken to avoid flight-out-of-view effects on the long lifetime measurements.
24.	Xu, Huailiang, et al. (författare) Lifetime measurements in TmI, TmII, and TmIII by time-resolved laser spectroscopy 2003 Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 23:3, s. 323-326 Tidskriftsartikel (refereegranskat)abstract Natural radiative lifetimes of eight levels in Tin I (4f(13)5d6p and 4f(12)5d682 configurations), two levels in Tin 11 (4f(12)5d6s configuration) and three levels in Tm III (4f(12)5d configuration) have been measured by using time-resolved laser spectroscopy. Free thulium atoms, as well as singly and doubly ionized ions, were obtained in a laser-induced thulium plasma and the investigated states were selectively populated by a single-step excitation process With a tunable narrow-band laser pulse.
25.	Xu, Huailiang, et al. (författare) Radiative lifetime and transition probabilities in CdI and CdII 2004 Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 70:4 Tidskriftsartikel (refereegranskat)abstract 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.
26.	Xu, Huailiang, et al. (författare) Radiative lifetime measurements in ErII by time-resolved laser spectroscopy 2003 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36:9, s. 1771-1781 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of 30 excited states of Er 11, ranging in energy from 25 592 to 36 148 cm(-1), have been measured by means of a time-resolved laser-induced fluorescence (LIF) technique. Free, singly ionized erbium ions were produced in a laser-induced plasma. A tunable laser, with 1 ns duration pulse, was employed to selectively excite the Er+ ions. The lifetime values were evaluated from the transient LIF signals recorded by a fast detection system. A comparison of the new results with previously published values is given. HFR calculations, including core-polarization contributions, are found to be in reasonable agreement with experiment, but the present calculations clearly indicate that further laboratory and theoretical work is urgently needed, particularly for the low lying odd configurations of this complex ion.
27.	Xu, Huailiang, et al. (författare) Radiative lifetime measurements of even-parity levels of singly ionized erbium 2004 Ingår i: Chinese Physics Letters. - 1741-3540. ; 21:9, s. 1720-1722 Tidskriftsartikel (refereegranskat)abstract Radiative lifetime measurements were performed by time-resolved laser-induced fluorescence (LIF) technique for eight even-parity levels of the astrophysically important ion Er+ over the energy range from 33753 to 55317 cm(-1). Free erbium ions were generated by a laser-induced plasma. A narrow bandwidth UV laser pulse (1 ns) was employed to populate selectively the short-lived upper levels, and the lifetime value were evaluated from the time-resolved fluorescence signals. The lifetimes reported fall in the range of 3-35ns with the experimental accuracy 5-8%.
28.	Xu, Huailiang, et al. (författare) Radiative lifetimes in Ce I and Ce II 2003 Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 23:2, s. 233-236 Tidskriftsartikel (refereegranskat)abstract New radiative lifetime measurements based on time-resolved laser-induced fluorescence techniques are reported for 18 even-parity levels belonging to the 4f5d(2)6p and 4f(2)5d(2) configurations of Ce I and 6 even-parity levels belonging to the 5d(2)6s, 4f5d6p, and 4f6s6p configurations of Ce II. Free neutral and singly ionized cerium atoms were produced by laser ablation. The Ce I and Ce II levels range in energy from 26.54.5 to 29 102 cm(-1). and 42573 to 48 152 cm(-1) respectively.
29.	Xu, Huailiang, et al. (författare) Radiative lifetimes of Cd I and Cd II excited states 2003 Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5449:1, s. 359-366 Konferensbidrag (refereegranskat)abstract Radiative lifetimes of 11 levels in Cd I belonging to the 5s5p 1po1 and 5snd 3D1,2(n=6-9) and 5sns 3S1 (n=7,8) series, and of 5 levels of Cd II belonging to the 4d105p 2po1/2,3/2, 4d106s 2S1/2, and 4d105d 2D3/2,5/2 configurations were measured using the time-resolved laser-induced fluorescence technique. Free neutral and singly ionized cadmium were generated by laser ablation. Single- or two-step excitation processes were used to populate the levels under study. Transition probabilities and oscillator strengths for Cd I and Cd II transitions were also deduced by combining the experimental lifetimes and theoretical branching fractions obtained in multiconfigurational relativistic Hartree-Fock calculations, taking core-polarisation effects into account
30.	Xu, Huailiang, et al. (författare) Radiative lifetimes of CdI and CdII excited states 2004 Ingår i: Proceedings of SPIE. ; 5449, s. 359-359 Konferensbidrag (refereegranskat)
31.	Xu, Huailiang, et al. (författare) Radiative lifetimes of doubly ionized terbium 2005 Ingår i: Chinese Physics Letters. - 1741-3540. ; 22:11, s. 2798-2800 Tidskriftsartikel (refereegranskat)abstract Radiative lifetimes of two short-lived levels (i.e. 4f(8) (F-7(6))6p(1/2) (6,1/2)(11/2,13/2)) in Tb II are measured by time-resolved laser-induced fluorescence (LIF) technique with a two-step excitation process. Free Tb III ions are produced in a laser-induced plasma. Lifetime values are evaluated with a deconvolution procedure of the time-resolved fluorescence signal with the temporal shape of second-step excitation pulse (about 1 ns). The lifetimes of the 4f(8) (F-7(6))6p(1/2) (6,1/2)(11/2) and 4f(8) (F-7(6))6p(1/2) (6, 1/2)(13/2) levels are determined to be 1.9 (2) and 2.0 (2) ns, respectively.
32.	Xu, Huailiang, et al. (författare) Radiative lifetimes of GdI and GdII 2003 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 36:3, s. 411-417 Tidskriftsartikel (refereegranskat)abstract Natural radiative lifetimes of 25 even-parity levels in Gd i (4f(7) 5d(2) 6p, 4f(7)5d6s6p and 4f(8)5d6s configurations) and 13 even-parity levels in Gd it (4f(7)5d6p and 4f(7)6s6p configurations) have been measured using the time-resolved laser-induced fluorescence technique in a laser-induced gadolinium plasma. The Gd I and Gd it levels range in energy from 26 866 to 36 395 cm(-1), and 25 960 to 42 746 cm(-1), respectively. In the measurements, stimulated Brillouin scattering techniques were employed to produce I ns laser pulses to enable accurate measurements of short-lived states. The uncertainty of the radiative lifetimes is, with a few exceptions. about +/-5%.
33.	Xu, Huailiang (författare) Radiative Properties of Rare Earth Elements - Free and Bound in Crystals 2004 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract This thesis is devoted to fundamental aspects, and to spectroscopic applications of radiative properties in free atoms and ions, as well as in ions doped into crystals. Using the time-resolved laser-induced fluorescence technique, measurements of radiative lifetimes for rare earth elements have been performed in neutral Pr, Nd, Tm, and in singly ionized Sm, Er, Nd, Tm, Yb, as well as in doubly ionized Tm and Tb ions. Free atom and ions were produced by laser ablation. This technique was also applied to Mn I and Cd I, II. The excitation schemes include single-step and two-step processes. The levels range in energy from 18000 up to 98000 cm-1 and the lifetimes fall in the range between 1.5 to 200 ns. Data were compared to theoretical results obtained in relativistic Hartree-Fock calculations taking core-polarization effects into account. Radiative lifetimes of trivalent RE ions doped into several host crystals, including YAG and YAlO3, have been measured at room temperature. Upconversion emissions in the green, blue, violet, and ultraviolet ranges were observed. The upconversion mechanisms were studied by making use of time-resolved luminescence spectroscopy. It appears that, depending on the excitation energy, the upconversion luminescence is dominant due to either energy-transfer upconversion or excited state absorption when the samples were excited into the 4S3/2 multiplet. The studies of the upconversion phenomena in YAG: Er3+ crystal have also been focused on the 4F9/2 multiplet, in which one-colour and two-colour laser excitation processes were employed. Radiative properties of RE-ion-doped crystal have also been investigated at liquid helium temperature using spectral hole burning and coherent transient spectroscopy. The hyperfine level splittings of the 1D2 and 3H4 states and the homogeneous linewidth of the lowest crystal-field states of the zero-phonon 3H4 - 1D2 transition in Pr3+:KY(WO4)2 were obtained. The radiative lifetime of the 1D2 state was measured with the time-resolved fluorescence and three-pulse photon echo techniques. In addition, the spectroscopy of Ho3+:LuYO4 and Ho3+:YVO4 was studied in this thesis as well. Experiments related to laser stabilization using hole burning in combination with a radio frequency (rf) field were partially performed in Pr3+:Y2SiO5.
34.	Xu, Huailiang, et al. (författare) Theoretical and experimental lifetime and oscillator strength determination in singly ionized neodymium (Nd II) 2003 Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 346:2, s. 433-440 Tidskriftsartikel (refereegranskat)abstract Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 24 levels of Nd II in the energy range 20 500- 32 500 cm(-1). For 17 levels, no previous experimental data exist. These results have allowed the testing of new theoretical calculations with the relativistic Hartree-Fock method taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for this complex ion. A new set of calculated oscillator strengths, accurate within a few per cent for the strongest transitions, is presented for 107 lines of astrophysical interest appearing in the wavelength range 358.0-1100.0 nm. These results will be useful to evaluate abundance values of neodymium in chemically peculiar stars in relation with cosmochronology.
35.	Xu, Huailiang, et al. (författare) Time-resolved laser-induced fluorescence lifetime measurements and relativistic Hartree-Fock calculations of transition probabilities in SmII 2003 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36:24, s. 4773-4787 Tidskriftsartikel (refereegranskat)abstract Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 47 levels of the astrophysically important ion Sm1+ over the energy range 21000-36 000 cm(-1). The new results have been compared with previous measurements but also with theoretical calculations taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for many levels of this complex ion. New calculated transition probabilities are deduced from the experimental lifetimes and from the theoretical branching fractions for 162 transitions of astrophysical interest. These results will help astrophysicists in the quantitative investigation of the chemical composition of CP stars.
36.	Xu, Huailiang, et al. (författare) Upconversion dynamics in Er3+-doped YAG 2005 Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 111:3, s. 191-198 Tidskriftsartikel (refereegranskat)abstract Green, blue, violet and ultraviolet upconversion luminescence is reported at room temperature in a YAG: 10.5% Er3+ crystal pumped by one-colour (647 nm) and two-colour (647 + 618 nm) laser excitation. The upconversion mechanism was studied by means of time-resolved luminescence spectroscopy and the energy flow pathways are described. Based on the results it appears that energy transfer upconversion is the dominant contribution to the upconverted luminescence upon 647 nm excitation, and excited state absorption is the dominating mechanism upon 647 + 618 nm excitation.
37.	Yu, Xiance, et al. (författare) Radiative lifetimes, branching fractions and oscillator strengths of some odd-parity levels in Ru I 2011 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 44:21 Tidskriftsartikel (refereegranskat)abstract Radiative lifetime measurements have been performed for six odd-parity levels of Ru I using a time-resolved laser-induced fluorescence technique. Branching fractions of seven odd-parity levels were also measured using a grating spectrometer with a hollow-cathode lamp. The results of lifetimes and branching fractions obtained here are combined to determine the absolute oscillator strengths of 25 lines for Ru I. The obtained results are compared with previous results when available.

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