Facile synthesis and luminescence properties of uniform and monodisperse KY3F10:Ln3+ (Ln=Eu,Ce, Tb) nanospheres

Highly uniform and monodisperse KY₃F₁₀:Ln³⁺ (Ln=Eu, Ce, Tb) nanospheres, with an average diameter of 300 nm, have been successfully prepared through a simple template-free and surfactant-free stirring method under ambient conditions. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra were used to characterize the samples. The SEM images illustrate that these spheres were actually composed of randomly aggregated nanoparticles. The doped rare earth ions show their characteristic emission in the KY₃F₁₀ samples, i.e., Eu^{3+ 5}D₀–⁷F_J (J=1, 2, 3, 4), Tb^{3+ 5}D₄–⁷F_J (J=6, 5, 4, 3, 2) and Ce³⁺ 5d–4f transition emissions, respectively. An energy transfer phenomenon from Ce³⁺ to Tb³⁺ has been observed in KY₃F₁₀ nanospheres, and the energy transfer efficiency depends on the doping concentration of Tb³⁺ if the concentration of Ce³⁺ is fixed.     

Measurement and analysis of the infrared absorption spectrum of the 2ν2 band of 12CH4

Approximately 500 infrared absorption lines with room-temperature strengths between 3 × 10^?5 and 1 × 10^?2 atm^?1 were assigned to the 2ν₂ band of ¹²CH₄ in the region from 2930 to 3250 cm^?1. These determine 207 of the 212 upper-state energy levels through J′ = 12 as well as a number of levels with J′ = 13 and 14. All but 17 of the levels with J′ ≤ 12 are calculated to 0.03 cm^?1 or better on the basis of a Hamiltonion that contains Coriolis and Fermi interaction terms coupling the upper states of the five bands, 2ν₄, ν₂ + ν₄, ν₁, ν₃, and 2ν₂.     

Hyperfine structure measurements in the4 I 9/2 ground state of141Pr

Using the atomic beam magnetic resonance method, the five hyperfine structure separations in the 4f ³ 6s ^{2 4}I_9/2 ground state of ₅₉ ¹⁴¹ Pr have been measured. The results are:F F′ E _FF′ ^* /h (MHz) 7 6 6477.913423(17) 6 5 5556.359848 (6) 5 4 4633.023306 (2) 4 3 3708.201146 (5) 3 2 2782.190601(15) From these quantities, the multipole interaction constantsA _k,k=1, 2, 3, 4 between the nucleus and the electron shell have been calculated.A ₄ especially then served to give the following limit for the intrinsic hexadecapole moment: ¦Q ₄₀¦<0.4eb ². Furthermore, theg _J -factors of the⁴ I multiplet have been measured at magnetic fields of 300 Oe. The results are:g _J(⁴ I _9/2)=0.7310371(15)g _J(⁴ I _11/2)=0.9651476(20)g _J(⁴ I _13/2)=1.1063197(40)g _J(⁴ I _15/2)=1.197963 (30) Small corrections due to perturbations by neighbouring fine structure levels are included.     

Fast and efficient VUV/UV emissions from (Ba,La)F2:Er crystals

We report observation of fast and efficient VUV/UV luminescence from the mixed (Ba,La)F₂:Er crystals. The broad bands, peaking at 162.5, 181.9, 194.2, 202.8, 216.1, 233.5 and 281.5 nm and decaying, at 10 and 293 K, with time constants of 46 and 35 ns respectively, are due to spin-allowed transitions from the low-spin (LS) state of the 4f¹⁰5d configuration.We also observed a weak and slow broad band emission peaking at 170 nm due to the spin-forbidden transition from the high-spin (HS) state of the 4f¹⁰5d configuration.While at room temperature the excitation into any of the three identified LS bands (J=8, 7 and 6) dominating the excitation spectrum yields fast VUV and UV emissions, at 10 K the excitation into higher lying J=7 and 6 bands generates slow and sharp line emissions. The positions of these lines fit energies of transitions originating from the ²G_7/2 multiplet at 66140 cm⁻¹. The emission from the ²G_7/2 multiplet has been never, to the best of our knowledge, observed before.The efficient and fast VUV and UV emissions from the higher (LS, J=8) with almost no contribution from the lower (HS, J=8) level of the 4f¹⁰5d configuration are possible because the modified crystal field in (Ba,La)F₂ shifts the level of the (LS, J=8) state below the ²F_5/2 multiplet which, therefore, does not contribute to nonradiative relaxation between the LS and HS levels.We conclude that the ²G_7/2 and ²F_5/2 levels have major impact on VUV and UV emissions from the Er³⁺ ion in (Ba,La)F₂ contributing to complex emission pattern described in this report Their key role, elucidated by the VUV and UV luminescence spectroscopy, is consistent with predictions from a simple configuration coordinate model based on experimental results and calculations of the 4f¹¹ energy levels.     

Synthesis and characterization of fast-decaying bluish green phosphors of Tb3+-doped CaSi2O2N2 for 2D/3D plasma display panels

Oxynitride phosphor powders comprising of CaSi₂O₂N₂ doped with Tb³⁺ were successfully synthesized using a high-temperature solid-state reaction method. The experimentally determined photoluminescence (PL) properties of the produced phosphors meet the requirements of 2D/3D plasma display panels (PDPs). In particular, under the excitation of vacuum ultraviolet (VUV) synchrotron radiation and ultraviolet (UV) irradiation, emission peaks corresponding to the ⁵D₃→⁷F_J (J=6, 5, 4, 3) and ⁵D₄→⁷F_J (J=6, 5, 4, 3) transitions of Tb³⁺ ions were recorded. Monitoring the ⁵D₄→⁷F₅ emission of Tb³⁺ at 545 nm, the excitation bands were assigned to the host-related absorption as well as the 4f–5d (fd) and the 4f–4f (ff) transitions of Tb³⁺. The produced phosphors can be efficiently excited at 147 nm, and have an adequately short decay time (τ_1/10=1.14 ms).     

High-resolution vibration-rotation spectroscopy of fluoroform-d

The vibration-rotation spectrum of the ν₂ and ν₅ fundamentals of CDF₃ have been recorded using a Nicolet 7199 Fourier transform infrared spectrometer; in addition the Q branch and several subbands of each of these transitions have been investigated using a tunable semiconductor diode laser spectrometer. The Q branch and the K structure in several P(J) and R(J) subbands of ν₂, and in several Q branches of ν₅, are resolved and assigned for the first time. Constants derived for these bands are (in cm^?1) ν₂ = 1111.1823₆, B₂ = 0.32928₂, A₂ = 0.18872₂, α₂^B = 16.44₅ × 10^?4, α₂^B ? α₂^A = 12.43₅ × 10^?4, D₀^j = 3.7₃ × 10^?7, D₂^J = 4.8₃ × 10^?7; ν₅ = 975.39₁, B₅ = 0.33062, A₅ = 0.18887, α₅^B = 2.83₁ × 10^?4, α₅^A = 2.4₃ × 10^?4, ζ₅ = 0.736, D₅^J ? D₀^J = 1.2₂ × 10^?8. Some of these constants are nearly 100 times more precise than those reported in previous work.     

Laser-Stark spectrum of NH3 with the CO laser: Determination of the ground state dipole moment

Results from analysis of sub-Doppler laser-Stark spectra of ¹⁴NH₃ obtained using a CO laser and an intracavity Stark cell are given. Over 1500 Lamb dips have been identified, associated with about 200 NH₃ lines. The data are analyzed to determine relative frequencies between the laser lines and the NH₃ lines. In favorable cases this can be done with an accuracy of 5–10 MHz. Analyses of a portion of the data yield the expression for the ground state dipole moment in Debye, μ^H(J, K) = 1.47182(30) + 1.654(190) × 10^?4J(J + 1) ? 3.095(300) × 10^?4K².     

Quantum Monte Carlo Investigation of the magnetic properties of weakly interacting antiferromagnetic chains with an alternating exchange interaction with spin S = 1/2

An approximation dependence of the spontaneous magnetic moment at a site, σ/σ(0) ? 1 = and the antiferromagnet-singlet state phase boundary, J ₂/J ₁ = 0.52(3)δ, are determined by the quantum Monte Carlo method in the self-consistent sublattice molecular field approximation for weakly inter-acting (J ₂) antiferromagnetic chains with spin S = 1/2 and alternating exchange interaction (J ₁ ± δ). The Néél temperature and a number of critical temperatures which could be related with the filling energy of two singlets (ΔS ^z = 0) and one triplet (ΔS ^z = 1) spin bands, each of which is split by the sublattice field (h ^{x, y} ≠ h ^z into two subbands, are determined on the basis of the computed correlation radii of the two-and four-spin correlation function, the squared total spin 〈 (S ^z)²〉 with respect to the longitudinal components, the dimerization parameter, and the correlation functions between the nearest neighbors with respect to longitudinal and transverse spin components. On the basis of the Monte Carlo calculations, the critical temperatures and possible energy gaps at the band center are determined for the antiferromagnets CuWO₄ and Bi₂CuO₄ and for the singlet compounds (VO)₂P₂O₇ and CuGeO₃, agreeing satisfactorily with existing results, and new effects are also predicted.     

Amino wagging and inversion in hydrazine: K′ = 1 levels in the first excited state of the antisymmetric wagging vibration

The infrared absorption spectrum of NH₂NH₂ vapor has been observed in the region 899–1077 cm^?1, where the antisymmetric wagging band (v_a = 1 ← 0) appears, by the use of a Fourier transform spectrometer with a practical resolution of 0.003 cm^?1. In the region 925.0–925.6 cm^?1, the spectrum was also observed with a tunable diode laser, and a component, β, of the ^pQ₂ cluster has been further resolved. Most of the absorption lines assignable to β-^pP₂(J″), γ-^pP₂(J″), β-^pQ₂(J″), γ-^rQ₀(J″), β-^rR₀(J″), and γ-^rR₀(J″), where J″ = 2 ～ 15, have been identified. From these observed transition frequencies, in combination with the ground state energy levels given by microwave spectroscopy, the energy level structure of the K′ = 1 rotational states was determined. From this, the following molecular parameters for the v_a = 1 state were determined: molecular asymmetry, B′-C″ = 0.00017 cm^?1; a parameter q₅ describing an umbrella motion Coriolis interaction (q₅K) about the a axis, q₅ = ?0.0030 cm^?1; its J(J + 1) variation, q_5j = 0.00014 cm^?1; and a parameter describing an umbrella-motion K-type doubling g₅J(J + 1), g₅ = 0.000021 cm^?1.     

Triple differential cross section for angle,atomic number and energy (or angular momentum transfer) calculated for the 280MeV40Ar+58Ni (or 365MeV63Cu+197Au) system in a simple model

Highly excited levels of³³S populated by α-particle capture in²⁹Si have been investigated forE _α=1.962 MeV to 4.287 MeV. Excitation curves measured with Ge(Li) and BF₃ detectors are reported. More than fifty resonances can be identified with levels in³³S. (α, γ) angular distributions measured on five strong resonances have yieldedJ ^π values 1/2+, 3/2 +, 5/2?, 5/2?, 5/2? and 3/2+ respectively, for theE _x =10.054, 10.466, 10.523, 10.721, 10.758 and 10.776 MeV levels in³³S. Elastic scattering experiments have been performed and theJ ^π assignments are found to be consistent with thel-values inferred from the elastic scattering data. Decay schemes from the above³³S levels have been proposed. A new level at 9.245 MeV is also suggested and theJ ^π values for the 4.425 and 2.87 MeV states are shown to be consistent with 7/2+ and 3/2+ assignment, respectively. Nuclear Reactions²⁹Si(α, γ) and²⁹Si(α, α),E _α=1.962-4.287 MeV. Measured relative σ(E). DeducedJ ^π andE _γ of³³S levels. New³³S level atE _x =9.245 MeV. Enriched targets.     

Analysis of the 2ν3 band of 12CD3F at 5.06 μm recorded under high resolution

The 2ν₃(A₁) band of ¹²CD₃F near 5.06 μm has been recorded with a resolution of 20–24 × 10^?3 cm^?1. The value of the parameter (α^B ? α^A) for this band was found to be very small and, therefore, the K structure of the R(J) and P(J) manifolds was unresolved for J < 15 and only partially resolved for larger J values. The band was analyzed using standard techniques and values for the following constants determined: ν₀ = 1977.178(3) cm^?1, B″ = 0.68216(9) cm^?1, D″_J = 1.10(30) × 10^?6 cm^?1, α^B = (B″ ? B′) = 3.086(7) × 10^?3 cm^?1, and β^J = (D″_J ? D′_J) = ?3.24(11) × 10^?7 cm^?1. A value of α^A = (A″ ? A′) = 2.90(5) × 10^?3 cm^?1 has been obtained through band contour simulations of the R(J) and P(J) multiplets.     

Microwave spectrum of methyl chloride in the excited vibrational states: Coriolis interaction between the ν2 and ν5 states

The rotational spectra of CD₃³⁵Cl, CD₃³⁷Cl, CH₃³⁶Cl, and CH₃³⁷Cl in the ν₂, ν₃, ν₅, and ν₆ states were observed and analyzed. A few lines of the J = 3 → 2 transition were also detected for ¹²CD₃³⁵Cl in the 2ν₃ state and for ¹³CD₃³⁵Cl in the ν₃ state. For CH₃³⁵Cl in the ν₆ state the present data on the J = 1 ← 0 and J = 2 ← 1 transitions were combined with the millimeterwave spectra reported by Sullivan and Frenkel to determine the molecular constants. Special attention was given to the ν₂ and ν₅ spectra which showed the effect of Coriolis resonance. By transferring some of the constants involved from the laser-Stark spectra we determined B₅^*, B₂^*, and q₅^* for CD₃Cl. The large effective q₅ constant permitted observation of the direct l-doubling transitions of high J. The analysis of the CH₃Cl spectra was much less complete than that on CD₃Cl because of limited data. The B rotational constants obtained were compared with the previous microwave and infrared results when available.By using the infrared data on ν₁ and ν₄ we evaluated the equilibrium B_e constants (α₄^B of CD₃³⁷Cl was estimated), and refined the equilibrium structure of methyl chloride reported by Duncan.     

The ν4 state inversion spectra of 15NH3 and 14NH3

The frequencies and assignments of 45 inversion transitions of ¹⁵NH₃ and 15 additional inversion transitions of ¹⁴NH₃ in the ν₄ state are reported. The J = 0 inversion frequency and K-type doubling constant for K,l = 2, ?1 are 31 602.72 MHz and 2.000 MHz for ¹⁵NH₃. The expression containing the effective l-type doubling constant, q₀ - 5q_J - Δη…, is calculated from the (J,K,l) = (1,1,1), (1,1,?1), (2,1,1), and (2,1,?1) transitions as 10 166.022 MHz. The contribution to this expression from the Coriolis coupling with 2ν₂ is estimated for ¹⁴NH₃.     

Charge transfer effects on the luminescent properties of Eu3+ in oxysulfides

Energy shifts of 4f⁶ states of Eu³⁺ in matrices, and phonon sidebands, linewidths and luminescence decay of Eu³⁺ in Ln₂O₂S (Ln=Lu, Y, Gd and La) have been studied. The charge transfer state (CTS) of Eu³⁺ is described by a model in which a hole is transferred from Eu³⁺ to ligands. Septet states obtained from the 4f⁷(⁸S) + hole configuration of CTS interact with the ⁷F term of the 4f⁶ configuration. This effect causes downward shifts of ⁷F_J states in matrices. Diffuse charge distributions for ⁷F_J states due to the mixing with CTS make the curvatuve of their adiabatic potential curves be smaller than that for ⁵D_J'. Such a difference in the potential curves between ⁷F_J and ⁵D_J' causes broadening of the absorption lines compared with the corresponding emission linewidths in Y₂O₂S. A dynamic Jahn-Teller model is proposed for the concentration-enhanced phonon sidebands accompanying 4f-4f transitions. The vibronics appear only in the excitation spectra and not in the emission spectra. Spectral distributions of the effective density of phonon states are obtained from the observed phonon sidebands for Ln₂O₂S: 5%Eu. The phonon spectra indicate delocalization of the 4f orbitals of Eu³⁺ with increasing the host-cation radius. The observed lifetimes of ⁵D₀ show a decrease in the same order due to decrease in the 4f-CTS mixing.     

Analysis of the ν6(A″2) band of cyclopropane-d6 recorded under high resolution

The parallel band ν₆(A″₂) of C₃D₆ near 2336 cm^?1 has been studied with high resolution (Δν = 0.020 – 0.024 cm^?1) in the infrared. The band has been analyzed using standard techniques and the following parameters have been determined: B″ = 0.461388(20) cm^?1, D″_J = 3.83(17) × 10^?7 cm^?1, ν₀ = 2336.764(2) cm^?1, α^B = (B″ ? B′) = 8.823(12) × 10^?4 cm^?1, β^J = (D″_J ? D′_J) = 0, and α^C = (C″ ? C′) = 4.5(5) × 10^?4 cm^?1.     

Angular correlation study of levels in 16C

Angular correlation measurements using the ¹⁴C(t, pγ)¹⁶C reaction result in the following spin assignments to levels in ¹⁶C: E_x = 1.766 MeV, J = 2; E_x = 3.980 MeV, J = 2; E_x = 4.083 MeV, J = 3; E_x = 4.138 MeV, J = 4.     

Far-infrared rotational spectra of some freons; chlorotrifluoromethane,dichlorodifluoromethane, and trichlorofluoromethane

The far-infrared rotational spectra of chlorotrifluoromethane, dichlorodifluoromethane, and trichlorofluoromethane have been observed with an interferometric (Fourier transform) spectrometer in the region 10–40 cm^?1 at a resolution of 0.07 cm^?1. CCl₂F₂ exhibits a continuum spectrum at this resolution, but symmetric top rotational fine structure is observed for CClF₃ and CCl₃F. Isotope splitting is also observed in CClF₃, and analysis yields the rotational constants for C³⁵ClF₃ of B₀ = 0.11112 cm^?1, D_J = 1.6 × 10^?8cm^?1; and for C³⁷ClF₃, B₀ = 0.10835 cm^?1, D_J = 1.5 · 10^?8cm^?1. Isotopic shifts can be allowed for in CCl₃F to yield constants for C³⁵Cl₃F of B₀ = 0.0821 cm^?1, D_J = 1 × 10^?8cm^?1. These values are all in agreement with those deduced from microwave studies of the low J transitions apart from B₀ for C³⁵ClF₃, where the difference is outside the expected experimental error.     

Laser spectroscopy of Nd and Dy ions in lead borate glasses

The spectroscopic and laser properties of Nd³⁺ and Dy³⁺ ions in lead borate glass were studied. Luminescence spectra recorded in the near-infrared and visible ranges correspond to ⁴F_3/2-⁴I_J/2 (J=9, 11, 13) transitions of Nd³⁺ and ⁴F_9/2-⁶H_J/2 (J=11, 13, 15) transitions of Dy³⁺, respectively. Luminescence decay curves were analyzed as a function of activator concentration. Luminescence quenching is observed, which is due to Ln-Ln interaction increasing. Several spectroscopic parameters relevant to laser potential of Ln³⁺ ions (Ln=Nd, Dy) in lead borate glass were determined. The relatively large values of the quantum efficiency and the room-temperature emission cross-section for the ⁴F_3/2-⁴I_11/2 transition of Nd³⁺ at 1061 nm and the ⁴F_9/2-⁶H_13/2 transition of Dy³⁺ at 573 nm imply that Ln-doped lead borate glasses can be considered as promising solid-state materials for laser applications.     

Contribution of hexadecapole alignment to the polarization of quadrupole emission under laser excitation conditions

The linear polarization of quadrupole emission by the J=2-J ₀=0 transition under conditions of laser excitation in a gas medium is studied. Cases of excitation through dipole and quadrupole absorption of monochromatic laser radiation are considered. Taking into account the anisotropy of collisional relaxation, the contributions of polarization moments of the second and fourth ranks, i.e., those with usual and hexadecapole alignments, to the signal of linear polarization of quadrupole emission are calculated. The dependence of this signal on the laser frequency, the density of the gas medium, and the angles determining the orientation of the system of axes of observation of light polarization relative to a laser ray is studied. The numerical calculations of contributions of usual and hexadecapole alignment to the signal of linear polarization are made for the magnetic quadrupole transition J=2-J ₀=0 between the states 2p ⁵(² P ₁ ^2/0 )3p′[3/2]₂ and 2p ⁵(² P ₁ ^2/0 )3s 3s′[1/2]⁰ of neon atoms in the xenon atmosphere.     

Photoluminescence of Eu-doped ZnAl-LDH depending on phase transitions caused by annealing temperatures

An Eu-doped ZnAl-layered double hydroxide (ZnAl-LDH) was synthesized by the coprecipitation method at room temperature. A set of as-prepared samples were subjected to annealing at various temperatures from 100, 200, 300, 500, 600, 700, to 800 °C for 1 h, respectively. The annealed samples were characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscope (SEM), and photoluminescence (PL). New phases occurred with annealing temperatures above 300 °C. Meanwhile, the emissions of Eu³⁺ ions described by ⁵D₀-⁷F_J transition (J=1, 2, 3, 4), especially for the ⁵D₀-⁷F_J transition (J=1, 2), varied with phase transitions of its local host materials from ZnAl-LDH, ZnO, to mixed phases of ZnO and ZnAl₂O₄. The emissions of Eu³⁺ ions depending on its host materials were discussed.