Intensity studies in Raman effect

The dependence of the relative intensities of Raman lines, having different polarisation characters, on the mode of excitation has been studied using unpolarised, horizontally and vertically polarised incident light. Standard intensities have been obtained in the cases of CCl₄, CHCl₃, C₆H₆, C₂Cl₄, C₂H₂Cl₂, C₂H₄Cl₂, C₆H₅Cl, C₆H₅CH₃ and C₆H₅CH₂OH with the intensity of the 458 cm^?1 line of CCl₄ as standard and from these, the values ofα′, the derived polarisability, have been obtained in the case of total symmetric lines characteristic of particular bonds and certain conclusions regarding the intensity variations of corresponding lines in the different liquids have been arrived at. Values of derived anisotropy have also been obtained in the case of the depolarised lines relative to that of 313 cm^?1 line in CCl₄.     

Investigations in (0-0) isotopic bands of the C2 Swann system

Employing the various isotopes of carbon, (0-0) bands of the C₂ Swann system have been investigated. Comparisons have been made between the observed rotational line positions and those obtained by computer calculations with the respective constants evaluated from ¹²C₂. There is a good agreement (within ± 0.5 cm^?1 in most of the cases) between the two sets of values. The studies include the effect of change of nuclear mass and spin on different aspects of rotational structure and intensity pattern.     

Magnetocaloric effect and magnetic properties in YMnO3 perovskite

The magnetic properties and magnetocaloric effect in YMnO₃ have been investigated using Monte Carlo simulations. The thermal magnetization, specific heat and magnetic entropy have been obtained for different values of exchange interactions and for a several external magnetic field values. The variation of adiabatic temperature change with the temperatures has been obtained for several values of external magnetic field. It has been found that the sample exhibited a paramagnetic to ferromagnetic phase transition at 30 K. The transition temperature of YMnO₃ has been deduced for different values of size (1/L) and different values of exchange interactions. The relative cooling power with several values of external magnetic field has been established.     

Intensity studies in Raman effect

The intensities of Raman lines due to CH, CH₂ and CH₃ groups in the case of some n-paraffin hydrocarbons have been obtained relative to the peak intensity of the 458 cm^?1 line of CCl₄ and compared. The integrated intensity as well as the standard intensity of the C=O frequency in some unconjugated and conjugated ketones, aldehydes and esters have been obtained and the influence of conjugation has been discussed. The intensity of the C=C frequency has also been obtained in the conjugated compounds and compared with the results obtained for the unconjugated compounds.     

Direct determination of the dissociation probability in highly focused IR multiple photon dissociation

Laser-induced fluorescence (LIF) has been used to directly determine the dissociation probability per pulse in highly focused infrared multiple-photon dissociation (IRMPD). The fluence dependence of CDCl₃ IRMPD has been determined by LIF and FTIR spectrometry. The particular LIF irradiation and detection system’s geometry implemented allowed us to monitor the local CCl₂ radicals concentration in the intersection zone of the observation and the dissociation volumes. The fluence dependence of the LIF intensity was modeled with the cumulative log-normal distribution. The dependence of the global values of the fraction of molecules dissociated per pulse on fluence was obtained from FTIR spectrometry. The dissociation probabilities per pulse were derived from the deconvolution of these values using the cumulative log-normal distribution. A very good agreement between the values of the parameters σ and Φ _sat obtained from the deconvolution technique with those resulting from the fluorescence intensity fit was found, showing the validity of the method proposed.     

Ar- and air-broadening coefficients in the ν3 band of CS2 at room and low temperatures

Using a diode-laser spectrometer, Ar-broadening coefficients for 16 spectral lines in the fundamental ν₃ band of CS₂ have been measured at five temperatures: 298.0, 273.2, 248.2, 223.2 and 198.2 K. These lines with J values ranging from 2 to 64 are located in the spectral range 1519-1547 cm⁻¹. The broadening coefficients are also calculated from a semiclassical impact model performed by using a simple empirical intermolecular potential. From the theoretical and experimental results obtained at the different temperatures, we have determined the n exponent values governing the temperature dependence of the broadening coefficients. The air-broadening coefficients for four spectral lines in the ν₃ band of CS₂ have also been measured experimentally at the same temperatures. They are compared to the values derived from those obtained previously for the perturbers N₂, O₂ and also Ar.     

Tm3+掺杂的MFT玻璃材料的升频转换发光及光学性质的JO计算

本文报道了Tm³⁺离子在MFT玻璃材料中的光学性质.测量了吸收光谱,利用JO理论计算了不同能级的寿命、跃迁分支比及跃迁几率,计算了一些能级的辐射跃迁振子强度.测量了650nm激发下蓝色升频转换发光,讨论了升频转换发光强度与激发光功率的关系,计算了¹D₂→³H₄和¹G₄→³H₆两个蓝色跃迁的发射截面.     

Measurement of K X-ray intensity ratios in Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn employing carbon and nitrogen projectiles – VTT method

A method is suggested to effect the self absorption correction in a different way to estimate the K X-ray intensity ratios particularly when heavy ions are used as projectiles. Employing this method, the K_β/K_α intensity ratios are measured in some 3d shell elements by using Carbon and Nitrogen ions as exciting agents. The K_β/K_α intensity ratios thus obtained in the present work are compared with the intensity ratios due to some previous authors and also with Scofield theoretical values. Received 14 August 2000 and Received in final form 3 January 2001     

Die Erzeugung von Seriengrenzkontinua mit Hilfe von Gleitfunken zur Absolutmessung im Vakuum-Ultraviolett

A lithium plasma is produced by discharging a 40 kV, 0,3 μF capacitor through a lithium-hydride-capillary (diameter 2 mm, length 20 mm) in vacuum (p～10^?4 Torr). During the first half-cycle (0,6 μs) Bremsstrahlung of Li III is observed in the visible and infrared, and the Lyman series of Li III together with the recombination continuum in the vacuum UV (100 Å). The high members of the Lyman series are broadened by Stark effect giving an electron density of about 6 · 10¹⁸ cm^?3. In the infrared the radiation is emitted from an optically thick plasma at a time when the free-free continuum in the visible is emitted from an optically thin plasma. Temporal development of electron temperatureT _e and electron density N_e has been measured from the absolute intensity in these spectral regions. Typical values ofT _e=230 000° K andN _e 5 · 10¹⁸ cm^?3 e.g. have been obtained. For these values the relaxation time for an ionisation equilibrium is short compared to the observation time. The complete ionisation of Li III has been checked by absorption measurements near 100 A. Thus the absolute intensity of the recombination continuum could be calculated. An experimental arrangement was built to measure simultaneously the time history of the intensity in the vacuum ultraviolet, in the visible, and infrared spectral regions.     

Small angle neutron scattering from oxygen precipitates in silicon

The formation of silicon oxide precipitates from Czochralski grown silicon depends on the time and temperature of the heat treatment as well as on the initial content of interstitially dissolved oxygen. Samples containing between 5×10¹⁷ O_i/cm³ and 13×10¹⁷ O_i/cm³ have been heated at 750° C for 96 h. SiO₂ precipitates of various shape and size have been obtained and investigated by means of small angle neutron scattering (SANS) in the Q-range 0.05 Å^–1<Q<0.2 Å^–1. The obtained SANS patterns reveal a typical anisotropy of their intensity distribution, which splits into a central peak at Q<0.1 Å^–1 due to the shape of the individual particles and a number of weak intensities for large Q-values, originating from a correlation between defects, possibly between the precipitates. While these correlation peaks in the SANS patterns are seen best for rather low values of about (5–7)×10¹⁷ O_i/cm³ oxygen content, the central peak anisotropy is most pronounced for higher values of ca 10×10¹⁷ O_i/cm³. The integrated intensity of the central peak increases with increasing initial oxygen content. For comparison, untreated samples of the same initial oxygen content do not reveal any anisotropic SAN scattering or a broadened central peak beam.     

Annihilation of positrons in aluminium oxide and phase transformations in this compound

Measurements have been made of the angular correlation N(θ) of positron annihilation quanta, the triquanta annihilation intensity I_3γ by the peak-to-peak method, and the average lifetimes of positrons in A1₂O₃. The measured quantities depend on the temperature at which the Al₂O₃ was obtained. It is assumed that there are two conversion centers of ortho -Ps. One is molecular oxygen adsorbed on the oxide surface and the other is the O^? ion which exists in A1₂O₃ obtained at lower temperatures, both on the surface and in the interior of the grains. The temperature ranges have been determined within which the changes in properties of the oxide with respect to the annihilation of positrons, occur slowly as well as those within which the changes occur rapidly. Among these properties are the vanishing of the postulated O^? ions with rise in temperature a probable diffusion of aluminium ions, and the vanishing of vacancies in the lattice structure (I_Ps). From the measurements of the rate characteristics the complete annihilation intensity I_xxx was calculated within the range from 0.34 to 96ns, and also annihilation intensity from para states of positronium I_p.     

The pure rotational atmospheric lines of hydroxyl

Pure rotational line positions of the hydroxyl radical (OH) have been calculated for all vibrational levels expected in the earth's atmosphere (v = 0–9) and for lower rotational quantum numbers J″=0.5–12.5. These positions have been tabulated and compared with those derived from energy levels obtained from precise near-i.r. vibration-rotation bands and show good agreement for low J″ values. A tentative identification has been made of three v = 0 lambda-type doublets in a high-resolution far-i.r. (30–120 cm^-1) emission spectrum of the atmosphere obtained at 30 km from a balloon-borne platform. Line strength (S_J′J″) and integrated intensity (S_q cm^-2atm^-1) values have been derived for these pure rotational transitions as an aid to further work and instrument design.     

Optical characterization, 1.5 μm emission and IR-to-visible energy upconversion in Er-doped fluorotellurite glasses

The optical properties of Er³⁺ ions in a novel glass based on TeO₂-PbF₂-AlF₃ oxyfluoride tellurites have been investigated using steady-state and time-resolved spectroscopies as a function of the rare-earth doping concentration. Basic optical characterizations have been performed measuring and calculating the absorption and emission spectra and the cross-sections, the Judd-Ofelt intensity parameters, the radiative probabilities and the fluorescence decays and lifetimes. Special attention has been devoted to the broad ⁴I_13/2→⁴I_15/2 emission transition at around 1.53 μm since, with a wide broadening of around 70 nm and a relative long lifetime of around 3 ms compared to others glass hosts, it shows potential applications in the design of erbium-doped fiber amplifiers. The absorption, the stimulated emission and the gain cross-sections of this transition have been obtained and compared with that obtained in different hosts. Finally, infrared-to-visible upconversion processes exciting at around 800 nm have been analyzed and different mechanisms involved in the energy conversion have been proposed.     

A study of the influence of chemical environment on the Li (i = 1–3) subshell X-ray intensity ratios and the L3 absorption-edge energy for some compounds of 66Dy using synchrotron radiation

In the present work, the X-ray intensity ratios, I_Lk/I_Lα (k = l, β, γ_1,5, γ₂,₃, γ₄), have been measured for different compounds of ₆₆Dy, namely, Dy₂O₃, Dy₂(CO₃)₃, Dy₂(SO₄)₃.8H₂O, DyI₂, and the ₆₆Dy metallic foil by tuning the incident photon energies across its L_i (i = 1–3) absorption-edge energies covering the region 7.8–10 keV in order to investigate the influence of chemical effects on these intensity ratios in the presence of the many-body effects, which become significant at photon energies in proximity to the L_i absorption-edge energies. The present measured intensity ratios I_Lk/I_Lα have been compared with two sets of values calculated using the nonrelativistic Hartree–Fock–Slater model-based L_i (i = 1–3) subshell photoionization cross sections, the Dirac–Fock model-based X-ray emission rates, and two sets of the fluorescence and Coster–Kronig yields. The L₃ absorption-edge energy of ₆₆Dy in its different compounds and metallic foil has been deduced from the XANES spectra recorded in the present work. The L₃ absorption-edge energy shifts obtained from these absorption-edge energies are found to increase linearly with the partial charge on the metal atom (₆₆Dy).     

Energy Levels and Spectroscopic Parameters of Neodymium Trifluorides

A great deal of spectroscopic work has been done in the last decade to study rare earths in different environments. Recently, crystals of NdF₃ and NdF₃ doped with hydrogen and deuterium have been studied¹ spectroscopically and, from the extra electronic lines appearing on the longer wave lenght side of the usual rare earth electronic transititions, the isotope shift have been calculated. Since no informations, regarding interelectronic repulsion, spin-orbit interaction, nephelauxetic effect, bonding, electronic energy states and nature of transitions involved, have yet been obtained, it was thought worthwile to carry out the present calculations.

The present communication reports the values of Slater-Condon (F_k), Racah (E^k), and Lande (4f) parameters for HdF₃, Hyd. NdF₃ and Deu. HdF₃ crystals.     

New infrared integrated band intensities for HC3N and extensive line list for the ν5 and ν6 bending modes

The infrared spectrum of cyanoacetylene (also called propynenitrile) has been investigated from 400 to 4000 cm⁻¹ at a resolution of 0.5 cm⁻¹. Integrated intensities of the main bands and a number of weaker bands have been obtained with an uncertainty better than 5%. Inaccurate values in previous studies have been identified in particular concerning the intensity of the strong ν₅ stretching band at 663.2 cm⁻¹. Former results on the temperature dependence of integrated intensities have also been revisited.Synthetic spectra calculation has been performed for the ν₅ and ν₆ bands on the basis of the best available high resolution data. It has been shown that the GEISA line parameters for HC₃N are not sufficient to reproduce the band intensities and some hot band features observed in our experimental spectra at room temperature. As a first step, the model spectra has been improved by including a number of missing hot subbands and by calculating accurately the hot band relative intensities. Finally, a perfect agreement between calculated and observed spectra was achieved on the basis of a global analysis of HC₃N levels up to 2000 cm⁻¹ combined with the new integrated intensity measurements. A new extensive line list for the ν₅ and ν₆ bending modes of HC₃N has been compiled.     

Study of molecular surface coating on the stability of maghemite nanoparticles

In this study γ-Fe₂O₃ nanoparticle, surface-coated with increasing amount of oleic acid, have been prepared while the stability against particle degradation under laser excitation intensity was investigated. Maghemite nanoparticle was obtained via oxidation of magnetite nanoparticle, the latter synthesized by co-precipitation of Fe (II) and Fe (III) ions in alkaline medium. By varying the experimental conditions of surface-coating maghemite nanoparticles with oleic acid, samples with different grafting coefficient were obtained and investigated using X-ray diffraction and different spectroscopic techniques, namely Raman, Mössbauer, and infrared. The amount of oleic acid adsorbed on the maghemite surface was estimated via the carbon content obtained from elemental analysis.     

Combustion synthesis and photoluminescence of Eu, Dy-doped La2Zr2O7 nanocrystals

A facile and energy saving sol-gel combustion method has been used to prepare La₂Zr₂O₇ nanocrystallines. The pyrochlore La₂Zr₂O₇ nanocrystals have been obtained at a relatively low temperature with the grain size ranging from 45 to 70 nm. Eu³⁺ and Dy³⁺ have been introduced into the La₂Zr₂O₇ crystal structure, respectively, and the intense photoluminescence was observed. The relative intensity of electric dipole transition and magnetic dipole transition is considered for luminescence emission both of Eu³⁺ and Dy³⁺. The dependence of luminescence intensity on dopant concentration and the effect of Dy³⁺ co-doping on Eu³⁺ luminescence are also discussed.     

Overview and calculation of X-ray K-shell transition yields for comprehensive data libraries

The simulation of atomic relaxation relies on data libraries with tabulated partial fluorescence yield values of radiative transitions, commonly derived from the Evaluated Atomic Data Library (EADL). However, recent studies support that the data library EADL could be improved by adopting Scofield's Hartree-Fock calculations instead of current Scofield's Hartree-Slater calculations. This work presents a bibliography overview of relevant atomic parameter values in order to verify the partial fluorescence yields presented in EADL. The references include libraries and articles, in which the atomic parameter values were theoretically calculated, experimentally measured, or obtained with semi-empirical and empirical fitting formulas. We present a comparison of total K-shell fluorescence yields and partial K-L₂, K-L₃, K-M₂, K-M₃ fluorescence yields that are either obtained directly from its references, or are derived from atomic parameters presented in these references. Additionally, we obtain comprehensive partial fluorescence yield values from the combination of semi-empirical and empirical fitting functions from different references. The comparisons performed in this work confirm that total K-shell, partial K-L₂, and partial K-L₃ fluorescence yield values, obtained from Scofield's Dirac-Slater calculations have better agreement with the most recent empirical values. Partial K-M₂, and partial K-M₃ fluorescence yield values obtained from Scofield's Dirac-Fock calculation have better agreement with the most recent empirical values. Therefore, further studies should be performed before changing the EADL data library.     

Study of L2,3M4,5M4,5 Auger spectra of Zn and Cu in molecular ZnCl2 and (CuCl)3 vapours

L_2,3M_4,5M_4,5 Auger electron spectra of Zn and Cu have been measured in molecular ZnCl₂ and (CuCl) ₃ vapours. The spectra have been analyzed and compared with the corresponding free-atom spectra. It is found that the main features of the spectra are atomic-like. The energies are shifted by 0.55 eV in ZnCl₂ and by 3.2 eV in (CuCl)₃ towards higher kinetic energy compared with the corresponding free-atom spectra. For the intensity ratios between the L₃ and L₂ groups, the values 2.8 and 3.7 are obtained for Zn and Cu, respectively. These intensity ratio, together with energy considerations based on free-atom Dirac—Fock calculations and observed Auger shifts, indicate that the L₂L₃M_4,5 Coster—Kronig process is energetically possible in (CuCl)₃ molecular clusters but not in ZnCl₂. The satellite structure in the spectra studied also supports this conclusion.