Microwave-optical double resonance of a supersonic beam: ICI B3Π(O+) v = 0

Several microwave transitions have been observed between hyperfine levels in I³⁵Cl B³Π(0⁺) v=0 using the technique of microwave-optical double resonance. The ICI was cooled to 3 K in a seeded supersonic expansion, allowing examination of low J lines. Values for the rotational constant, B₀ = 0.085873(6) cm^?1, and quadrupole coupling constant cQqI = ?664(9) MHz, were determined.     

Experimental ground stateg J-factor of Ba+ in a Penning ion trap

We observed the Zeeman-splitting of the 6S _1/2 – 6P _1/2 resonance transition of Ba⁺-ions (493.4 nm) in a 6T magnetic field. The ions were stored in a Penning quadrupole trap. We polarized the ground state by optical pumping and in a microwave-optical double resonance experiment we measured the ground state Zeeman-splitting. From the resonance frequency and the cyclotron frequency of electrons stored in the same trap we derived theg-factor of the 6S _1/2 state. The result isg _J(6S _1/2)=2.002 490 6(11), in reasonable agreement with recent calculations.     

Microwave-optical double resonance of the triplet state of cyclopentanone

Fine structure and hyperfine structure information on the chemically reactive ³nπ* state of cyclopentanone is obtained by the low field microwave-optical double resonance (MODOR) technique. The hyperfine structure is interpreted tentatively to indicate that the magnetic z axis lies perpendicular to the carbonyl bond and nearly parallel to the C₅C₁C₂ plane. The principal values of the fine structure spin hamiltonian are D/hc = ±0.1404±0.0001 cm⁻¹, E/hc = ^+- 0.0271 ± 0.0001 cm⁻¹.     

Microwave-Optical Double Resonance and Intermodulated Fluorescence Studies of Thioformaldehyde

Studies of the 4¹₀ band of the à ¹A₂ X?¹A₁ transition of thioformaldehyde by means of intermodulated fluorescence and microwave-optical double resonance have revealed numerous small perturbations in the excited state levels caused by high rovibronic levels of the ground state. Singlet-triplet perturbations have been studied by the same techniques and also by anticrossings produced in the presence of a magnetic field. The use of microwave-optical double resonance for studying collisional processes is discussed.     

Optical energy storage properties of Sr<Subscript>2</Subscript>MgSi<Subscript>2</Subscript>O<Subscript>7</Subscript>:Eu<Superscript>2+</Superscript>,R<Superscript>3+</Superscript> persistent luminescence materials

The details of the mechanism of persistent luminescence were probed by investigating the trap level structure of Sr₂MgSi₂O₇:Eu²⁺,R³⁺ materials (R: Y, La-Lu, excluding Pm and Eu) with thermoluminescence (TL) measurements and Density Functional Theory (DFT) calculations. The TL results indicated that the shallowest traps for each Sr₂MgSi₂O₇:Eu²⁺,R³⁺ material above room temperature were always ca. 0.7 eV corresponding to a strong TL maximum at ca. 90 °C. This main trap energy was only slightly modified by the different co-dopants, which, in contrast, had a significant effect on the depths of the deeper traps. The combined results of the trap level energies obtained from the experimental data and DFT calculations suggest that the main trap responsible for the persistent luminescence of the Sr₂MgSi₂O₇:Eu²⁺,R³⁺ materials is created by charge compensation lattice defects, identified tentatively as oxygen vacancies, induced by the R³⁺ co-dopants.     

Separation of cerium and europium by extraction with tributyl phosphate and di(2-ethylhexyl)phosphoric acid in n-alkane from nitrate solutions

The following extraction systems have been studied: (Ce³⁺+Eu³⁺) (NO₃)-(EDTA, DCTA, DTPA)/TBP in n-alkane and (Ce³⁺+Eu³⁺)(NO₃)/DEHPA in n-alkane at concentration ratios as follows: [Ce³⁺]=trace –1 mol·dm^–3, [Eu³⁺]=trace –0.1 mol·dm^–3. [TBP]=(0.183–1.83) mol·dm^–3, [DEHPA]=(5·10^–3–0.1) mol·dm^–3, [(H, Na)NO₃]=(0.1–6) mol·dm^–3, [Eu³⁺]: [EDTA, DCTA, DTPA]=11–110. The initial concentration of Eu³⁺ in aqueous phase in the extraction system containing a mixture of Ce³⁺ and Eu³⁺ was trace, 1% and 10% compared with the Ce³⁺ concentration. The distribution of the elements between the phases was observed radiometrically using¹⁴¹Ce,¹⁵²Eu and¹⁵⁴Eu. The results are documented by the distribution ratios D_Ce, D_Eu and separation factor =D_Eu/D_Ce as functions of variable parameters of the systems.     

Test of advanced hyperfine structure theory by precision radio-frequency and laser spectroscopy in molybdenum

The hyperfine structure splittings of 32 even parity states and of 26 odd partity states of molybdenum have been measured by atomic beam magnetic resonance and by laser induced fluorescence. The analysis of the hyperfine structure data of the even parity configurations (4d+5s)⁶ yields experimental evidence for second order hyperfine interactions. In addition, theg _J factors of 19 fine structure levels have been determined in order to test the quality of intermediate coupling wave functions for the (4d+5s)⁶ configurations.     

Doppler free “dark resonances” for hyperfine measurements and isotope shifts in Ca+ isotopes in a Paul trap

We have observed dark resonances in theA-type level structure, formed by the 4S_1/2 ground state, the 4P_1/2 excited state and the low lying metastable 3D_3/2 state in the Calcium ion, confined in a Paul radio-frequency trap. These Doppler-free and potentially very narrow resonances were used to determine the magnetic dipole hyperfine interaction constant A for the 4P_1/2 and 3D_3/2 state of⁴³Ca⁺, giving –142(8) MHz and –48.3(1.6) MHz, respectively. From measurements of the P-D (E1) and S-D (E2) transition wavelength in a mixture of⁴³Ca⁺ and⁴⁰Ca⁺ we determined the isotope shifts of these lines.     

Energy transfer between the Eu2+ sites in KY3F10 single crystals

UV lines of KY₃F₁₀ : Eu²⁺ single crystals are assigned to various sites of Eu²⁺on theK⁺ sublattice. The splitting of the ⁶P_{$\text{7}\text{2}$} level is very weak (<0.6 cm^?1). The activation appears to be non-selective, Eu²⁺ is located both on K⁺ and Y ³⁺ sites. Eu²⁺(K⁺) → Eu²⁺(Y³⁺) energy transfer is pointed out, due to dipole-dipole interaction between Eu²⁺ ions.     

Hyperfine structure and core polarization in Nd I 4f 4f 4 5d6s

The high resolution laser-atomic-beam technique was used to investigate the hyperfine structure in Nd I 4f ⁴ 5d6s ⁷ L, ⁷ K, ⁷ I, ⁷ H, ⁷ G, ⁵ L, ⁵ K, and ⁵ I for both of the stable odd isotopes. The metastable states were populated by an arc discharge burning in the atomic beam, and 31 transitions to higher odd levels have been studied. Knowledge of the hyperfine constants of 34 levels of 4f ⁴ 5d6s allowed a comprehensive parametric analysis to be performed, using the effective tensor operator formalism. Compared to earlier analyses, a significant reduction of errors has been achieved for all the parameters. The contact parameter a _4f ¹⁰ has been fitted freely, thus providing an experimental value for the core-polarization effects. They are about six times larger than the relativistic effects.     

Luminescence and energy transfer in a highly symmetrical system: Eu2Ti2O7

Luminescence and energy transfer properties of Gd₂Ti₂O₇: Eu and Eu₂Ti₂O₇ are reported. Transfer between unperturbed (intrinsic) Eu³⁺ ions and perturbed (extrinsic) Eu³⁺ ions has been observed. At low temperatures the emission spectra of Eu₂Ti₂O₇ are dominated by trap emission, due to direct energy transfer from the intrinsic Eu³⁺ ions to the extrinsic Eu³⁺ ions. Above 10 K energy migration among the Eu³⁺ ions to quenching centers occurs. The interaction between the Eu³⁺ ions is probably exchange in character. The nature of the extrinsic Eu³⁺ ions has been elucidated.     

钙钛矿结构荧光材料MZrO3:Eu3+,A (M=Ca2+, Ba2+; A=Li+, Na+, K+)的制备及其发光性质

Calcium and barium zirconate powders based upon CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) were prepared by combustion synthesis method and heating to ~1000℃ to improve crystallinity.The structure and morphology of materials were examined by X-ray diffraction (XRD) and scanningelectron microscopy (SEM). XRD results showed that CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) perovskites possessed orthorhombic and cubic structures, respectively. The morphologies of all powderswere very similar consisting of small, coagulated, cubical particles with narrow size distributions andsmooth and regular surfaces. The characteristic luminescences of Eu³⁺ ions in CaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) lattices were present with strong emissions at 614 and 625 nm for ⁵D₀→⁷F₂ transitions with other weakeremissions observed at 575, 592, 655, and 701 nm corresponding to ⁵D₀→⁷F_n transitions (where n=0, 1, 3, 4 respectively). In BaZrO₃:Eu³⁺ both the ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at 595 and 613 nm were strong.Photoluminescence intensities of CaZrO₃:Eu³⁺ samples were higher than those of BaZrO₃:Eu³⁺ lattices. Thisremarkable increase of photoluminescence intensity (corresponding to ⁵D₀→⁷F_n transitions) was observedin CaZrO₃:Eu³⁺ and BaZrO₃:Eu³⁺ if co-doped with Li⁺ ions. An additional broad band composed of manypeaks between 440 to 575 nm was observed in BaZrO₃:Eu³⁺,,A samples. The intensity of this band wasgreatest in Li⁺ co-doped samples and lowest for K⁺ doped samples.     

Laser and radiofrequency spectroscopy of the 5d 4 6s 6 D multiplet in Ta I

The hyperfine structure (hfs) of¹⁸¹Ta has been investigated using laser radio-frequency double resonance and high resolution laser spectroscopy on collimated atomic beams. The magnetic dipole and electric quadrupole hyperfine structure coupling constants of the 5d ^{4 6} s 6D _{3/2, 5/2, 7/2, 9/2} metastable states have been determined using radio-frequency spectroscopy. In the 5d ⁴ 6s ⁶ D _1/2 metastable state and the excited 5d ³ 6s 6p ⁴ D _3/2,⁶ D _{5/2, 9/2} as well as the unidentified 28 182.6 cm^–1 and 30 021.2 cm^–1 states, hfs constants have been obtained from high resolution laser spectroscopy. A radio-frequency converter has been developed in order to reach the frequency region 2.7–10 GHz.     

Enhanced photoluminescence of Ba2GdNbO6: Eu/Dy phosphors by Li doping

The Ba₂GdNbO₆: Eu³⁺/Dy³⁺ and Li⁺-doped Ba₂GdNbO₆: Eu³⁺/Dy³⁺ phosphors were prepared by solid-state reaction process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and photoluminescence (PL) as well as lifetimes, was utilized to characterize the resulting phosphors. Under the excitation of ultraviolet light, the Ba₂GdNbO₆: Eu³⁺/Dy³⁺ and Li⁺-doped Ba₂GdNbO₆: Eu³⁺/Dy³⁺ show the characteristic emissions of Eu³⁺ (⁵D₀-⁷F_1,2,3 transitions dominated by ⁵D₀-⁷F₁ at 593 nm) and Dy³⁺ (⁴F_9/2-⁶H_15/2,_13/2 transitions dominated by ⁴F_9/2-⁶H_15/2 at 494 nm), respectively. The incorporation of Li⁺ ions into the Ba₂GdNbO₆: Eu³⁺/Dy³⁺ phosphors has enhanced the PL intensities depending on the doping concentration of Li⁺, and the highest emission was obtained in Ba₂Gd_0.9NbO₆: 0.10Eu³⁺, 0.01Li⁺ and Ba₂Gd_0.95NbO₆: 0.05Dy³⁺, 0.07Li⁺, respectively. An energy level diagram was proposed to explain the luminescence process in the phosphors.     

Synthesis and optical properties of novel red phosphors YNbTiO6:Eu3+ with highly enhanced brightness by Li+ doping

Highly luminescent euxenite phased YNbTiO₆:Eu³⁺ and Li⁺-doped YNbTiO₆:Eu³⁺ red phosphors have been prepared through a facile sol–gel combustion process and investigated for the first time. The introduction of Li⁺ ions into YNbTiO₆:Eu³⁺ is able to result in significant changes of the crystallinity and particle size, and bring a clear red-shift of absorption edge. A dominant red emission peak at 611 nm due to the ⁵D₀ → ⁷F₂ transition of Eu³⁺ was observed from photoluminescence spectra of the YNbTiO₆:Eu³⁺ and Li⁺-doped YNbTiO₆:Eu³⁺ phosphors. In particular, the emission intensity of the optimal Li⁺-doped YNbTiO₆:Eu³⁺ was examined to be close to 400% of commercial Y₂O₃:Eu³⁺ phosphor. The mechanism of the enhanced emission by Li⁺ doping was discussed.     

Isotope shifts and hyperfine structures investigation of doubly excited levels in SrI

We measured isotope shifts and hyperfine structure of visible transitions of stable strontium isotopes by means of Doppler-free saturated absorption spectroscopy. In particular, we investigated transitions between excited states where the upper level involves two excited electrons. We report hyperfine coupling constants for the levels 5p4d¹D₂, 5p4d³F₂, 5s4d³D₁, 5s6s³S₁, 5s5p³P₁ and, for some of the studied transitions, we separate the specific mass and volume contribution to the isotope shifts.     

Collisional relaxation measurements on Pb+ hyperfine levels

The time constants for population relaxation of optically pumped Pb⁺ ions in a Paul ion trap have been determined in a He buffer gas atmosphere with additional components of other gases. For the 6P _1/2 ground state of Pb⁺ and an ion temperatur of 10⁴ K we find cross sections of 0.72(0.33)·10^?17 cm²; 0.59(0.38)·10^?15 cm²; and 2.56(0.74)·10^?14 cm² for He, N₂ and O₂, respectively. The error includes an estimated 20% uncertaincy in the pressure calibration of a residual gas analyser.     

Multiple magnetic phase transitions,dilute Fe hyperfine fields and europium valence instabilities in RMn2Si2-xGex,R=rare earth

Mössbauer studies of dilute⁵⁷Fe and¹⁵¹Eu in RMn₂Si_2-xGe_x (R=La, Sm, Eu and Gd) at temperatures 4.2 K to 480 K have been performed. The diamagnetic iron and europium reveal the magnetic order of the Mn and rare earth sublattices through transferred hyperfine interactions. The⁵⁷Fe studies show that in LaMn₂Si₂, LaMn₂Ge₂, and SmMn₂Ge₂ the Mn is magnetically ordered above the known Curie temperatures, and the compounds are antiferromagnets up to T_N=470 K, 415 K and 385 K respectively. Studies of¹⁵¹Eu in R_1-xEu_xMn₂Si₂, (R=La, Gd) display Eu subspectra corresponding to Eu²⁺, Eu³⁺ and intermediate valant Eu. All display large magnetic hyperfine fields.     

Analytical atomic spectroscopy using ion trap devices

Investigations using ion trap devices for analytical atomic spectroscopy purposes have focused on the use of an inductively coupled plasma (ICP) ion source with ion trap mass spectrometric (ITMS) detection. Initial studies were conducted with an instrument assembled by simply appending an ion trap as the detector to a fairly conventional ICP/MS instrument, i.e. leaving an intermediate linear quadrupole between the plasma source and the ion trap. The principal advantages found with this system include the destruction of nearly all problematic and typical ICP/MS polyatomic ions (e.g., ArH⁺, ArO⁺, ArCl⁺, Ar₂⁺, etc) and a dramatic reduction of the primary plasma source ion, Ar⁺. These results prompted the development of a second-generation plasma source ion trap instrument in which direct coupling of the ICP and ion trap has been effected (i.e. no intermediate linear quadrupole); the same performance benefits have been largely preserved. Initial operation of this instrument is described, characterized, and compared to the originally described ICP/ITMS and conventional ICP/MS systems. In addition, experiments aimed at improving ICP/ITMS sensitivity and selectivity using broadband resonance excitation techniques are described. Finally, the potential for laser optical detection of trapped ions for analytical purposes is speculated upon.     

Collisional Line Assignments and Hyperfine Structure Interpretation in Cs2 23△1g State

Accurately known energy level structure of the Cs₂ A¹∑⁺_u -b³Πu complex of states from a recent global de-perturbation of these states has enabled additional assignments of 140 per-turbation facilitated infrared-infrared double resonance (PFIIDR) transitions to the 2³△_1g state from collisionally populated intermediate A¹∑⁺_u levels. Together with the 221 previ-ously observed 2³△_1g←A¹∑⁺_u← X¹∑⁺_g double resonance lines [J. Chem. Phys. 128, 204313 (2008)], molecular constants and the Rydberg-Klein-Rees potential energy curve of the 2³△_1g state have been recalculated (excluding 54 perturbed levels). The centrifugal distortion con-stant has been determined and agrees well with the value calculated based on standard empirical formulas. The hyperfine structure of the 2³△_1g state, which has not resolved in our sub-Doppler excitation spectra of the 2³△_1g state, has been interpreted with a preliminary simulation.