Sub-Doppler and Doppler spectroscopy of DCN isotopomers in the terahertz region: ground and first excited bending states (v1v2v3)=(0 1 0)

The rotational spectra of the deuterium cyanide isotopic species DCN, D¹³CN, DC¹⁵N, and D¹³C¹⁵N were recorded in the vibrational ground and first excited bending state (v₂=1) up to 2 THz. The R-branch transitions from J=3←2 to J=13←12 were measured with sub-Doppler resolution. These very high resolution (∼70 kHz) and precise (±3-10 kHz) saturation dip measurements allowed for resolving the underlying hyperfine structure due to the ¹⁴N nucleus in DCN and D¹³CN for transitions as high as J=10←9. Additional high JR-branch (J=25←24 to J=28←27) transitions around 2 THz and direct l-type (ΔJ=0, J=19 to J=25) transitions from 66 to 118 GHz were recorded in Doppler-limited resolution. For the ground state of D¹³C¹⁵N, the J=1←0 transition was measured for the first time. The transition frequency accuracies for the other deuterated species were significantly improved. These new experimental data, together with the available infrared rovibrational data and previously measured direct l-type transitions, were subjected to a global least squares analysis for each isotopomer. This yielded precise sets of molecular constants for the ground and first excited vibrational states, including the nuclear quadrupole and magnetic spin-rotation coupling constants of the ¹⁴N nucleus for DCN and D¹³CN. The hyperfine structure due to the D, ¹³C, and ¹⁵N nuclei have not been resolved, but led to a broadening of the observed saturation dips.     

“Forbidden” millimeter-wave transitions in arsine

A millimeter-wave spectrometer having a sensitivity of 4 × 10^?10 cm^?1 in the 2-mm region has been used for observation of the “forbidden” transitions J → J, K = ±4 → ±1 and J → J, K = ±5 → ±2 in AsH₃. A comprehensive computer analysis was made of the frequencies measured in this work together with available microwave frequencies of other transitions. This analysis provides accurate values of the rotational constants, nuclear quadrupole couplings, and effective structural parameters of the molecule. The spectral constants B₀ and C₀ (in MHz) are 112 470.597 and 104 884.665, respectively.     

Hydrogen and nitrogen broadening of the lines of C2H2 at 14 μm

Collision broadening of 14 μm acetylene transitions was studied using a diode laser spectrometer. Fifteen P(J) and Q(J) transitions in the v₅ fundamental band, broadened by hydrogen and nitrogen, were used in the study. The reduced Lorentz-widths per unit pressure obtained from the observed Voigt-widths were fitted to a model quadratic in J, i.e. γ⁰_L = a + bJ + cJ². The results for the nitrogen-broadened lines are 0.0853 cm^-1-atm^-1 for the collision broadening coefficient a at J = 0, b = -1.63 x 10^-3, and c = 3.92 x 10^-5 cm^-1-atm^-1. The results for the hydrogen broadened lines in cm^-1-atm^-1 are 0.0812, -1.16 x 10^-3, and 2.93 x 10^-5, respectively.     

Pressure broadening coefficients of transitions in the ν5 band of methyl bromide from fitting to Voigt and Galatry line profiles

Tuneable diode laser absorption spectroscopy has been used to measure the room temperature pressure broadening coefficients (γ) of rotational transitions in the v₅ fundamental band of methyl bromide (¹²CH₃⁷⁹Br and ¹²CH₃⁸¹Br) around 6.9 μm. Nitrogen, oxygen and self-broadening coefficients have been determined for 125 lines in the ^RQ₁, ^PQ₃, ^PQ₅, ^PQ₇ and ^PQ₈ branches and 49 P and R branch transitions. Line profiles within Q branches were recorded at incremental pressures of nitrogen and oxygen up to 15 Torr and fitted to a Voigt profile to yield the broadening coefficients. The nitrogen broadened data for 14 lines, chosen from the five Q branches, were also fitted with Galatry profiles. The line profiles of the P and R branch transitions were recorded for total nitrogen and oxygen pressures of up to 300 Torr and fitted to both Voigt and Galatry profiles. Within individual Q branches, nitrogen broadening coefficients were found to decrease monotonically with increasing J from 0.14 cm⁻¹ atm⁻¹ at low J to 0.09 cm⁻¹ atm⁻¹ at high J. The corresponding values for oxygen were approximately 25% smaller. Self-broadening coefficients were found to vary between 0.48 and 0.16 cm⁻¹ atm⁻¹ with a similar J dependence to the foreign gas broadening for J > 20. However, between J = 2 and J ≈ 20 the broadening coefficient was found to increase with J. The magnitude of the pressure broadening coefficient for P and R branch transitions was found to closely follow the J dependence measured for the Q branch lines.     

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).     

Energy level scheme and the effect of magnetic order on the optical transitions in europium chalcogenides

The optical constants of Eu-chalcogenide single crystals have been determined at room temperature for photon energies from 1 to 6 eV. In the same energy range the transmission of thin evaporated films (except for EuO) has been measured with polarized light above and below the magnetic ordering temperature. The observed polarization-dependent splittings of the two main absorption maxima in the region of magnetic order suggest transitions from the 4f⁷-level into the crystal field split 5dt_2g- and 5de_g-states. An attempt has been made to relate the maxima of the absorption coefficient to interband transitions and transitions from the localized 4f-states. With this assumption we derived a consistent energy level scheme of the four Eu-chalcogenides. From the scheme we gained useful information about the width of the 5d-states, the crystal field splitting and the possible type of conductivity. Finally we tried to explain theoretically the splittings observed in the region of magnetic order. For this purpose a one-particle model has been used to calculate the transition probabilities for the 4f⁷?4f⁶(⁷F _J ) 5dt_2g and the 4f⁷?4f⁶(⁷F _J ) 5de_g transition, taking into account an exchange interaction as well as a spin-orbit coupling. Although this simple model can explain the splittings of the excited 4f⁶(⁷F _J ) 5de_g-state, a complete explanation of the effect of magnetic order on the 4f⁶(⁷F _J ) 5dt_2g-state fails up to now.     

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.     

Infrared electronic transitions of Eu+3 in GdAlO3

Infrared ⁷F_O → ⁷F_J electronic transitions are reported for Eu⁺³ in GdAlO₃. The low symmetry of the crystalline field allows the observation, for the first time, of transitions with J = 3, 4, 5 and 6. The spectra are explained by means of a crystal-field model where a C_s term is added as a perturbation to the cubic field in order to take into account the lattice distortion. This model predicts energy levels which are in good agreement with the experimental data.     

The brute-force polarization of 23Na and the 23Na(n, γ)24Na reaction

A Na target has been polarized by brute force to 22% and the γ-radiation produced by polarized thermal neutron capture has been investigated. The J^π = 2⁺ channel spin contribution has been determined model-independently and unambiguously for 22 primary transitions. The average J^π = 2⁺ channel contribution is 5.8(5)%. The data resulted in one spin assignment and two spin restrictions. The energies and lifetimes of positive-parity levels as well as branching ratios and the magnetic moment of the ground state are in agreement with a shell-model calculation in the complete sd shell.     

Extrinsic lyoluminescence of aluminum induced by lanthanide chelates in alkaline aqueous solution

Reactive Al/OH⁻(aq) interface was studied and used as a source of chemical energy in the generation of chemiluminescence. The observed extrinsic lyoluminescence emission during dissolution of aluminum in an alkaline Tb(III) or Eu(III) chelate solution was clearly based either on ⁵D₄→⁷F_J radiative transitions of Tb(III) or ⁵D₀→⁷F_J transitions of Eu(III). In this process, these chelates were chemically excited via analogous one-electron redox pathways as known from extrinsic lyoluminescence of irradiated, electrolytically- or additively-colored alkali halides, and from hot electron-induced electrochemiluminescence. Calibration curves of Tb(III) chelates, peroxodisulfate and hydroxide ions were linear over several orders of magnitude of concentration. In addition, the method seems to be suitable for relatively rough chemical measurements of the thicknesses of aluminum oxide films free from trapped charges.     

D3→FJ emission of Tb doped sol–gel silica

Amorphous silica samples doped with 0.1 and 1 mol% of terbium (Tb) were synthesized by the sol–gel method. In addition to the green light associated with ⁵D₄→⁷F_J transitions of Tb³⁺, the sample containing 0.1 mol% also emitted blue light as a result of ⁵D₃→⁷F_J transitions during photoluminescence (PL) measurements. As a result of concentration quenching this blue emission was not observed for the samples doped with the higher concentration (1 mol%). However the blue ⁵D₃ →⁷F_J emission was observed in the 1 mol% doped samples during cathodoluminescence (CL) measurements. Since a rough calculation indicated that the excitation rate in the CL system where the blue emission is observed may be similar to a laser PL system under conditions where the blue emission is not observed, the difference is attributed to the nature of the excitation sources. It is suggested that during the CL excitation incident electrons can reduce non-luminescent Tb⁴⁺ ions in the silica, substituting for Si⁴⁺ ions, to the excited (Tb³⁺)? state and that these are responsible for the blue emission, which does not occur during PL excitation.     

Diode laser spectroscopy of the ν6 band of 12CH3I

The vibration-rotation spectrum of the ν₆ fundamental of methyl iodide has been recorded in the 824 to 862 cm^?1 region by using a tunable semiconductor diode laser spectrometer. The rotational analysis performed for six Q branches ^pQ(J,3), ^pQ(J,4), ^pQ(J,5), ^pQ(J,6), ^pQ(J,7), and ^qQ(J,8) led to accurate values for several molecular constants. The nuclear quadrupole splitting arising from the spin of iodine has been observed very clearly in the low J transitions and for various K values.     

Far infrared spectrum and spectroscopic constants of AsH3 in the ground state

The far ir spectrum of arsine, AsH₃, was recorded in the range 25–100 cm^?1 with a resolution of approximately 0.004 cm^?1. ΔJ = +1, ΔK = 0 rotational transitions were measured and assigned up to J″ = 12. These transitions, together with the presently available microwave and submillimeter-wave data and ground state combination differences, were analyzed on the basis of a rotational Hamiltonian which includes Δk = ±3 and Δk = ±6 interaction terms. The derived ground state molecular parameters reproduced the transition frequencies of both allowed and “perturbation allowed” transitions within the accuracy of the measurements. The equilibrium structure was determined for the AsH₃ molecule.     

New measurements of the emission spectra of Sm2+ in KMgF3 and NaMgF3 crystals

The fluorescence of divalent samarium in KMgF₃ and NaMgF₃ crystals is investigated. The emission is observed to originate from transitions between the ⁵D_J, and ⁷F_J multiplets of the 4?⁶ configuration. More precisely, the lowest ⁵D_J level, ⁵D₀, appears to be the most efficient emitting level in the temperature range 4–300K. Contrary to what has been reported elsewhere, the Sm²⁺ fluorescence in both crystals does not exhibit any broad band emission even at room temperature. The great number of lines in the ⁵D₀→⁷F_J patterns gives evidence of the multiple-center origin of the fluorescence.     

Der Zerfall des Xe123,T 1/2=2,08h

Xe¹²³ (T _1/2=2.08 h) was produced by bombarding Te¹²² with 48 MeV α-particles. The radioactive Xe¹²³ gas was collected during irradiation in liquid air cooled glass ampoules. The gamma rays associated with the decay of Xe¹²³ have been investigated using Ge(Li)- and NaJ(Tl)-counters and a Ge(Li)-NaJ(Tl)-coincidence circuit. 57 gamma transitions in the energy range from 148.7 keV to 2559.1 keV have been found. By depositing the radioactive Xe-ions on Ti-foils sources were obtained thin enough to study the conversion electrons using a Si(Li)-counter. The conversion coefficients for the intensive J¹²³ transitions with low energy were determined. A level scheme for Xe¹²³→J¹²³ which accounts for almost all observed γ-transitions having 16 levels is proposed. Furthermore some new data for the J¹²¹ and J¹²³ decay are presented.     

Tunable far-infrared Raman generation

Tunable resonance enhanced far-infrared stimulated Raman scattering was observed in 60–160 μm range for the Q(J) transitions in hydrogen chloride. The tuning range was about 2.3 cm^-1 around each studied transition (J = 2 to 7) and the photon efficiency was measured to be of the order of 12% giving peak power around 80 kW.     

Spectra, energy levels, and symmetry assignments for Stark components of Eu(4f) in gadolinium gallium garnet (Gd3Ga5O12)

Absorption and fluorescence spectra observed between 450 and 750 nm at 85 K and room temperature (300 K) are reported for Eu³⁺(4f⁶) in single-crystal Czochralski-grown garnet, Gd₃Ga₅O₁₂ (GGG). The spectra represent transitions between the ^2S+1L_J multiplets of the 4f⁶ electronic configuration of Eu³⁺ split by the crystal field of the garnet. In absorption, Eu³⁺ transitions are observed from the ground state, ⁷F₀, and the first excited multiplet, ⁷F₁, to multiplet manifolds ⁵D₀, ⁵D₁, and ⁵D₂. The Stark splitting of the ⁷F_J multiplets (J=0-6) was determined by analyzing the fluorescence transitions from ⁵D₀, ⁵D₁, and ⁵D₂ to ⁷F_J. The Eu³⁺ ions replace Gd³⁺ ions in sites of D₂ symmetry in the lattice during crystal growth. Associated with each multiplet manifold are 2J+1 non-degenerate Stark levels characterized by one of four possible irreducible representations (irreps) assigned by an algorithm based on the selection rules for electric-dipole (ED) and magnetic-dipole (MD) transitions between Stark levels in D₂ symmetry. The quasi-doublet in ⁵D₁ was characterized by an analysis of the magneto-optical spectra obtained from the transitions observed between ⁵D₁ and ⁷F₁. A parameterized Hamiltonian defined to operate within the entire 4f⁶ electronic configuration of Eu³⁺ was used to model the experimental Stark levels and their irreps. The crystal-field parameters were determined through use of a Monte-Carlo method in which nine independent crystal-field parameters, were given random starting values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviation between 57 calculated-to-experimental Stark levels is 5.9 cm⁻¹. The choice of coordinate system, in which the nine are real and the crystal-field z-axis is parallel to the [0 0 1] crystal axis and perpendicular to the xy plane, is identical to the choice we used previously in analyzing the spectra of Er³⁺ and Ho³⁺ garnets.     

Concentration influence on temperature-dependent luminescence properties of samarium substituted strontium tetraborate

The series of divalent samarium substituted strontium tetraborate (Sr_1?xSm_xB₄O₇) polycrystalline samples were prepared by the conventional solid-state reaction. The phase formation of the samples was investigated by X-ray powder diffraction measurements. The luminescence spectra and decay curves of the Sm²⁺ ions were measured. Temperature dependent Sm²⁺ luminescence properties were investigated. The f–d and ⁵D₁–⁷F_J transitions appeared at 350 K and increased with increase in the temperature while the intensity of ⁵D₀–⁷F_J transitions decreased. The emission spectra pointed out that Sm²⁺ occupies of C_2v or lower symmetry site. The photoluminescence decay times of strontium tetraborate doped with different concentrations of Sm²⁺ was investigated as a function of temperature in the range of 100–500 K. However, no obvious concentration quenching was observed.     

Inelastic collision cross section of excited molecules

The (v′=6,J′=43) level in theB ¹Π _u electronic state of Na₂ has been selectively populated by excitation with the 4 880 Å line of the argon laser. Through collisions with He atoms energy is transferred to neighbouring rotational states in Na₂ and the density of these states is determined by observing fluorescence to electronic ground state. From previous measurement of the lifetime of theB ¹Π _u state and new measurements of the intensities of collision induced spectral lines as a function of He pressure, absolute collision cross sections for all rotational transitions up to ΔJ=±5 have been obtained. The total cross section for all rotational transitions observed is σ _rot ^total =65±15 Ų. Preliminary results about collision induced vibrational transitions are also presented.     

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.