5<Emphasis Type="Italic">p</Emphasis>-4<Emphasis Type="Italic">d</Emphasis> Emission spectrum with a cascade decay of the 3<Emphasis Type="Italic">d</Emphasis> vacancy in the Xe atom

The 5p-4d emission spectrum, obtained during cascade de-excitation of the initial deep 3d vacancy in the Xe atom, was calculated by directly constructing a decay tree in a stepwise manner. The cascade decay tree was constructed with allowance for all radiative and nonradiative channels of decay for the initial and all intermediate ionic configurations of the cascade. The probabilities of branching and transition energies were calculated in a one-electron approximation with averaging over configurations. The 5p-4d cascade emission spectrum has a complex structure with many components, which reflects the transitions from the wide variety of the many-hole intermediate configurations generated by the cascade. The calculated data agree well with the experiment.     

Tunable luminescence and energy transfer process between Tb3+ and Eu3+ in GYAG:Bi3+, Tb3+, Eu3+ phosphors

A series of Eu³⁺ ions co-doped (Gd_0.9Y_0.1)₃Al₅O₁₂:Bi³⁺, Tb³⁺ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of the GYAG:Bi³⁺, Tb³⁺, Eu³⁺ phosphors consists of broad bands in the shorter wavelength region due to 4f⁸ → 4f⁷5d¹ transition of Tb³⁺ ions overlapped with 6s² → 6s¹6p¹ (¹S₀ → ³P₁) transition of Bi³⁺ ions and the charge transfer band of Eu³⁺–O^2?. The present phosphors exhibit green and red colors due to ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions and ⁵D₀ → ⁷F₁ transition of Eu³⁺ ions, respectively. The emission was shifted from green to red color by co-doping with Eu³⁺ ions, which indicate that the energy transfer probability from Tb³⁺ to Eu³⁺ ions are dependent strongly on the concentration of Eu³⁺ ions.     

Lifetime measurements of some TmI odd parity levels

Eleven new lifetimes of odd parity excited energy levels in four configurations: 4f ¹² 5d 6s6p, 4f ¹² 6s² 6p, 4f ¹³ 5d6s and 4f ¹³ 6s7s of atomic thulium have been mesured with atomic-beam laser spectrocopy. Two pulsed dye lasers are used for stepwise excitation and the time-resolved fluorescence decay was used to determine lifetime values. The accuracy of the measurements is about 10%.     

Preparation and luminescence properties of green-light-emitting afterglow phosphor Ca8Mg(SiO4)4Cl2:Eu2+

Green-light-emitting long-lasting phosphorescence phosphor, Eu²⁺ activated calcium magnesium chlorosilicate Ca₈Mg(SiO₄)₄Cl₂, has been prepared by a modified solid-state reaction method using Ca₂SiO₄:Eu²⁺ as a precursor. Its properties have been discussed and analyzed utilizing XRD, photoluminescence, excited-state decay curve and long-lasting phosphorescence decay curve. Upon UV light excitation, the emission spectrum of Ca₈Mg(SiO₄)₄Cl₂:Eu²⁺ phosphor is composed of two separate bands centered at 425 nm and 505 nm, respectively. Furthermore, after irradiation by a 320-nm UV light for 3 min, the 2% Eu²⁺-doped Ca₈Mg(SiO₄)₄Cl₂ phosphor emits intense green-light-emitting afterglow from the 4f⁶5d¹→4f⁷ transition of Eu²⁺, and its afterglow can be seen with the naked eye in the dark clearly for more than 3 h after removal of the excitation source. The disappearance of the high-energy 425 nm band in the afterglow emission spectrum is explained by its different crystallographic sites. The afterglow decay curve of the Eu²⁺-doped Ca₈Mg(SiO₄)₄Cl₂ phosphor contains a fast decay component and another slow decay one. The possible mechanism of this long-lasting phosphorescence phosphor is also discussed based on the experimental results.     

Stereoselective synthesis of 2-methylenepyrrolizidines by tandem cyclization of N-propargylaminyl radicals

Tandem cyclization of N-propargylaminyl radicals, generated by N-chlorination of (E)-alk-4-enylamines 2a-d and 2f followed by treatment with tributyltin radical, afforded 2-methylenepyrrolizidines 3a-d and 3f in a highly stereoselective manner. A similar radical cyclization of (Z)-N-propargyl-1-methyl-5-phenylpent-4-enylamine (2e) gave pyrrolizidine 3b having the same stereochemistry as that obtained from the E isomer 2b.     

Synthesis and luminescent properties of Eu2+ doped nitrogen-rich Ca-α-SiAlON phosphor for white light-emitting diodes

Yellow/orange-emitting nitrogen-rich Ca_0.9Si₉Al₃(O,N)₁₆: Eu²⁺ phosphors were successfully prepared by solid-state reaction synthesis. The fluorescence excitation spectra of all of the nitrogen-rich Ca_0.9Si₉Al₃(O,N)₁₆: Eu²⁺ phosphor powders displayed two broad bands centered at about 300 nm and 400–475 nm. The first peak was assigned to the absorption of the host lattice and the second to the 4f⁷ → 4f⁶5d¹ absorption of the Eu²⁺ ions, its means enhanced 4f⁷ → 4f⁶5d excitation of Eu²⁺ ion. The absorption peak intensity increased upon increasing the Eu²⁺ doping amount, but only up to a Eu²⁺ concentration ratio of 0.15. The emission spectra of the prepared Ca_0.9Si₉Al₃(O,N)₁₆: Eu²⁺ phosphors all exhibited a single broad band in the 500–700 nm region, maximum emission peak observed at 591 nm. The room temperature decay times were observed τ₁ = 1.27 μs and τ₂ = 9.90 μs.     

NMR study of (C6H5)3-nPXn (X = Cl,Br, I; n = 0-3) and (C6H6)3-n PXnCr(CO)5 compounds

The ³¹P chemical shift of the (C₆H₅)_3-nPX_n ligands (X = Cl, Br, I; n = 0–3) is dominated by the electronegativity of the substituents. π bonding is only important for derivatives with three strongly electronegative substituents. The ³¹P chemical shift of the corresponding complexes (C₆H₅)_3-nPX_nCr(CO)₅ is governed by the simultaneous effects of the electronegativity, steric hindrance and π bonding. The resonance parameter, δ', indicates an increasing (p_ring → d_p)π and (d_cr→ d_p)π electron delocalization with halogen substitution.     

Laser photoionization of metastable Xe* (J=0) atoms in the range 462–430 nm

Absolute cross sections for photoionization of metastable Xe* (5p ⁵ 6s′³ P ₀) atoms are presented over the wavelength range 462–430 nm (photoelectron energy ε=0–200 meV), including the 7p′[3/2]₁ and 7p′[1/2]₁ autoionization resonances. In addition the angular distribution of the photoelectrons is reported across the 7p′ resonances (ε=90–180 meV). The experimental data are compared with Hartree-Fock calculations of the photoionization process.     

Large atomic natural orbital basis sets for the first transition row atoms

Large atomic natural orbital (ANO) basis sets are tabulated for the Sc to Cu atoms. The primitive sets are taken from the large sets optimized by Partridge, namely (21s13p8d) for Sc and Ti and (20s12p9d) for V to Cu. These primitive sets are supplemented with threep, oned, sixf, and fourg functions. The ANO sets are derived from configuration interaction density matrices constructed as the average of the lowest states derived from the 3d ⁿ 4s ² and 3d ⁿ⁺¹4s ¹ occupations. For Ni, the¹ S(3d ¹⁰) state is included in the averaging. The choice of basis sets for molecular calculations is discussed.     

A new langbeinite‐type phosphate K2GdHf(PO4)3: synthesis,crystal structure,band structure and luminescence properties

Langbeinite‐type compounds are a large family that include phosphates, sulfates and arsenates, and which are accompanied by interesting physical properties. This work reports a new disordered langbeinite‐type compound, K₂GdHf(PO₄)₃ [dipotassium gadolinium hafnium tris(phosphate)], and its structure as determined by single‐crystal X‐ray diffraction. Theoretical studies reveal that K₂GdHf(PO₄)₃ is an insulator with a direct band gap of 4.600 eV and that the optical transition originates from the O‐2p→Hf‐5d transition. A Ce³⁺‐doped phosphor, K₂Gd_0.99Ce_0.01Hf(PO₄)₃, was prepared and its luminescence properties studied. With 324 nm light excitation, a blue emission band was observed due to the 5d¹→4f¹ transition of Ce³⁺. The average luminescence lifetime was calculated to be 5.437 µs and the CIE chromaticity coordinates were (0.162, 0.035). One may expect that K₂Gd_0.99Ce_0.01Hf(PO₄)₃ can be used as a good blue phosphor for three‐colour white‐light‐emitting diodes (WLEDs).     

Crossed-second-order-effects of the isotope shift and hyperfine-structure parameters in the Eu I configuration 4f 7 6s6d

In the Eu I configuration 4f ⁷ 6s6d the isotope shift (IS) and hyperfine-structure (hfs) of the termse ⁶ D ande ¹⁰ D were determined from fourteen transitions (4f ⁷ 6s6d-4f ⁷ 6s6p) with computer supported interference spectroscopy. From the IS of altogether nine levels of 4f ⁷ 6s6d the crossed-second-order-parameterg ₃(4f,6s)=?0.90(6)mK was evaluated. The ratiog ₃/G ₃=?4.4(3)·10^?6 (G ₃: Slater Integral of the fine structure) is of the same size as that from five other independent investigations and one theoretical value. The single electron hfs splitting constantsa _4f ¹⁰ =?1.9(3)mK,a _6s ¹⁰ =391(3)mK, anda _6d ¹² =0.9(3)mK were also evaluated and are compared with those of other Eu 4f ⁷ 6snl configurations.     

Synthesis of the complex fluoride LiBaF3 and optical spectroscopy properties of LiBaF3:M(M=Eu,Ce) through a solvothermal process

The complex fluoride LiBaF₃ and LiBaF₃:M(M=Eu, Ce) is solvothermally synthesized at 180°C and characterized by means of X-ray powder diffraction, scanning electron microscopy, thermogravimetric analysis and infrared spectroscopy. In the solvothermal process, the solvents, molar ratios of initial mixtures and reaction temperature play important roles in the formation of products. The excitation and emission spectra of the LiBaF₃:M(M=Eu,Ce) have been measured by fluorescence spectrophotometer. In the LiBaF₃:Eu emission spectra, there is one sharp line emission located at 360 nm arising from f→f transition of Eu²⁺ in the host lattice, and typical doublet 5d-4f emission of Ce³⁺ in LiBaF₃ powder is shown.     

Final-state effects in the 3d and 4d X-Ray photoelectron spectra of CeO2

The complex 3d and 4d X-ray photoelectron spectra of CeO₂ arc re-interpreted with the aid of multiple scattering Xα and intermediate coupling calculations. Features in the 3d spectrum are identified with Ce 3d⁹4f⁰, 3d⁹4f¹VB^?1, and 3d⁹5p⁵np final-state configurations. Multiplet coupling in the 3d⁹4f¹ system is found to be significant.     

Photoluminescence of Ce, Pr and Tb activated Sr3Ln(PO4)3 under VUV-UV excitation

The spectroscopic properties in VUV-Vis range for the eulytite structural phosphors Sr₃Gd(PO₄)₃:Ln³⁺ (Ln³⁺=Ce³⁺, Pr³⁺, Tb³⁺), Sr₃Ce(PO₄)₃, Sr₃Gd(PO₄)₃ and Sr₃Tb(PO₄)₃ were investigated. The bands near 170 nm in VUV excitation spectra are assumed to connect with the host lattices related absorption. The f-d transitions of Ce³⁺, Pr³⁺ and Tb³⁺ in the host lattices are assigned and corroborated. A convenient experiment formulation on the relationship between the lowest f-d transition energies and n value for trivalent 4fⁿ-series rare earth ions in these host lattices is applied.     

Synthesis of 3,6‐Branched β‐d‐Glucose Oligosaccharides

A glucohexasaccharide, β‐d‐Glcp‐(1 → 3)‐[β‐d‐Glcp‐(1 → 3)‐β‐d‐Glcp‐(1 → 6)]‐β‐d‐Glcp‐(1 → 3)‐β‐d‐Glcp‐(1 → 3)‐β‐d‐Glcp was synthesized as its 4‐methoxyphenyl glycoside via 2 + 2 + 2 strategy with benzylidenated glucose mono‐ and disaccharides as the key intermediates.     

The luminescence of Pr3+ in BaY4Si5O17

The cell constants of four new monoclinic compounds BaR₄X₅O₁₇ (R = Y, Gd; X = Si, Ge) are given. The luminescence of various RE activators in the silicates is reported. Pr³⁺-activated BaY₄Si₅O₁₇ shows efficient ultraviolet 5d → 4f emission and weak 4f → 4f emission (mainly red luminescence from the ¹D₂ level). The 5d → 4f emission is ascribed to Pr³⁺ on Y sites, the 4f → 4f emission to Pr³⁺ on Ba sites. Energy transfer from Pr³⁺ to Gd³⁺ has been observed. Gd³⁺ plays an intermediate role in the energy transfer from Pr³⁺ to Sm³⁺ and to Dy³⁺ in BaGd₄Si₅O₁₇. Upon activation with Tb³⁺ the silicates show characteristic green Tb³⁺ luminescence with a quantum efficiency of 75% for ultraviolet excitation.     

Hyperfine structure and isotope shift of some even parity levels in the YbI spectrum

Using laser induced fluorescence spectroscopy the hyperfine structure of the even parity levels 4f ¹⁴6s6d ³ D ₁, 4f ¹⁴ 6s8s ³ S ₁ and 4f ¹³ 5d6s6p (7/2, 5/2)J=1,2,3 as well as of the odd parity level 4f ¹⁴ 6s6p ³ P ₂ in neutral ytterbium has been investigated. The isotope shift of the transitions 4f ¹⁴6s6p ³ P ₀ → 4f ¹⁴ 6s6p ³ D ₁ and 4f ¹⁴ 6s6p ³ P ₂ → 4f ¹⁴ 6s8s ³ S ₁, 4f ¹³ 5d6s6p (7/2, 5/2)J=1,2,3 could be measured with high accuracy. The results for the 4f ¹⁴ 6s6p ³ D ₁ level show a considerable influence of second order effects of the hyperfine interaction. The isotope shifts of the 4f ¹⁴ 6s8s ³ S ₁ and 4f ¹³ 5d6s6p (7/2, 5/2)J=1 levels indicate a possible configuration mixing for these levels.     

Preparation via the polymer route and photoluminescence properties of CeSi3N5

CeSi₃N₅ has been prepared via the polymer route, a one-pot and liquid-phase synthesis, based on a reaction between SiCl₄ and liquid NH₃ in which Ce[N(Si(CH₃)₃)₂]₃ was suspended. The sample was characterized by powder X-ray diffraction analysis, diffuse reflection and photoluminescence spectroscopies. CeSi₃N₅ exhibits a strong absorption peaking at 365 nm. Furthermore, it has a broad emission band at 468 nm due to 4f⁰5d¹ → 4f¹ transition of Ce³⁺. Obviously, CeSi₃N₅ appears to be a good candidate for use as a blue phosphor, which can be pumped by near-UV-LEDs.     

Application of a laser produced plasma: Experimental Stark widths of single ionized lead lines

The optical emission spectroscopy from laser produced plasma generated by a 10,640 Å radiation, with an irradiance of 1.4 × 10¹⁰ W cm^− 2 on several lead targets, in vacuum and in an atmosphere of argon, was recorded and analyzed between 1900 and 7000 Å. The Local Thermodynamic Equilibrium conditions and plasma homogeneity have been checked. Stark widths for 31 lines of Pb II have been measured. These lines measured in this work correspond to the transitions 7s → 6p, n(n = 8, 9, 10)s → 7p, n(n = 7, 8)p → 7s, n(n = 7, 8)p → 6p², n(n = 7, 8)d → 7p, n(n = 5, 6)f → 6d, n(n = 5, 6)f → 6p². The population level distribution and the corresponding temperatures were obtained using Boltzmann plots. The plasma electron densities were determined using well-known Stark broadening parameters of spectral lines. Special attention was dedicated to the possible self-absorption of the different transitions. Temporal evolution of the plasma parameters was studied between 0.1 and 9 μs. Stark broadening parameters of the spectral lines were measured at 2.5 μs where the electron temperature was close to 11,300 K and the electron density to 0.8 × 10¹⁶ cm^− 3. The experimental results obtained have been compared with the experimental and theoretical values given by other authors. A systematic trend of this parameter versus temperature of 4244.9 Å Pb II line has been presented.     

Resonant and Off-resonance ionization of laser-excited sodium vapor

Electrons produced in a sodium effusive beam irradiated by pulsed laser light have been energy-analyzed. For resonant excitation of the atoms to the 3p state, we have studied associative ionization of excited Na(3p) (AI), Penning ionization (PI) and photoionization of highly-excited Na(n l),n l=3d, 4p, 5s, 4d/4f, by measurements of electron energy spectra. Our interpretation of the spectra is supported by a numerical analysis of the data which leads to estimates of the cross sections compatible with values previously measured in other experiments. Off-resonance ionization is considered at a particular wavelength. It is presumed to involve laser-excited dimers Na ₂ ^** . Spectra show that highly-excited atoms are produced by photodissociation of Na ₂ ^** or from Na ₂ ^** -Na collisional energy transfer, and that these atoms support the dominant off-resonance ionization channel in our laser excitation conditions.