Half-width Of Line Research Articles

Pressure responses of portlandite and H–D isotope effects on pressure-induced phase transitions

The pressure responses of portlandite and the isotope effect on the phase transition were investigated at room temperature from single-crystal Raman and IR spectra and from powder X-ray diffraction using diamond anvil cells under quasi-hydrostatic conditions in a helium pressure-transmitting medium. Phase transformation and subsequent peak broadening (partial amorphization) observed from the Raman and IR spectra of Ca(OH)2 occurred at lower pressures than those of Ca(OD)2. In contrast, no isotope effect was found on the volume and axial compressions observed from powder X-ray diffraction patterns. X-ray diffraction lines attributable to the high-pressure phase remained up to 28.5 GPa, suggesting no total amorphization in a helium pressure medium within the examined pressure region. These results suggest that the H–D isotope effect is engendered in the local environment surrounding H(D) atoms. Moreover, the ratio of sample-to-methanol–ethanol pressure medium (i.e., packing density) in the sample chamber had a significant effect on the increase in the half widths of the diffraction lines, even at pressures below the hydrostatic limit of the pressure medium.

Brittle-plastic relaxation of misfit stresses in the Si(001)/Si1 − x Ge x system

It is found that stressed luminescent samples of Si(001)/Si1 − xGex/Si with a germanium concentration of up to 16% contain microcracks. In contrast to ordinary cracks, microcracks are characterized by partial cracks of the substrate that are not perpendicular to the plane of the plate and are detected by specially designed X-ray analysis techniques. In a 60-nm-thick layer of SiGe with a germanium concentration of 5%, individual microcracks arise in samples near the edges of the same type, and the traces of these microcracks coincide with the ripple profiles of the corrugated growth surface. As the germanium concentration increases, first, the number of microcracks near the edges of a sample increases, while the corrugated growth relief nearly completely disappears, and then microcracks appear even in the central region of the sample, thus leading to the vanishing of the curvature of the structure in this region without visible signs of plastic relaxation. At the same time, even a thin (20 nm) layer of SiGe exhibits a layered structure, and diffuse scattering near the peak of the SiGe layer increases, which points to the presence of fragments of the layer that are misoriented by ±0.015°; the intensity of the diffuse scattering may amount to 0.5% of the layer intensity. A spatial analysis of the luminescence of samples with microcracks shows that the emergence of microcracks hardly affects the peak position and the half-width of the emission line of the SiGe layer. At the same time, the intensity of exciton emission from both the SiGe layer and the bulk of silicon is significantly (several times) changed when passing to the regions with microcracks. All the phenomena observed can be accounted for under the assumption that, between the stages of the loss of the plane crystallization front and the development of plastic relaxation of misfit stresses, there exists an earlier unknown stage of growth in which the concentration of nonequilibrium vacancies increases by four to five orders of magnitude and then the vacancies condensate into micropores.

Decay of rabi oscillations induced by magnetic dipole interactions in dilute paramagnetic solids

Decay of Rabi oscillations of equivalent spins diluted in diamagnetic solid matrix and coupled by magnetic dipole interactions is studied. It is shown that these interactions result in random shifts of spin transient nutation frequencies and thus lead to the decay of the transient signal. Averaging over random spatial distribution of spins within the solid and over their spectral positions within magnetic resonance line, we obtain analytical expressions for the decay of Rabi oscillations. The rate of the decay in the case when the half-width of magnetic resonance line exceeds Rabi frequency is found to depend on the intensity of resonant microwave field and on the spin concentration. The results are compared with the literature data for E1' centers in glassy silica and [AlO4] centers in quartz.

The Wolf–Rayet star HD 192163 as a possible evolutionary progenitor of a low-mass X-ray binary

We have used 46 high-resolution echelle spectra of the Wolf-Rayet star HD 192163 taken in 2005–2009 at the Cassegrain focus of the 2-m Zeiss-2000 telescope of the Shamakha Astrophysical Observatory to study profiles of the five strongest emission lines (HeII 4859, HeII 5411, CIV 5808, HeI 5875, (HeII + Hα) 6560). We also obtained four echelle spectrograms of the Wolf-Rayet star HD 191765 for a comparative study of the NaI 5890 (D2) and NaI 5896 (D1) interstellar absorption lines. The echelle spectrograms were reduced using the DECH20 code. We determined the equivalent widths, radial velocities, central intensities, and half-widths of the emission lines. We detected variations in the violetwing of the (HeII + Hα) 6560 emission band (between λ ∼ 6496 A and λ ∼ 6532 A). Our statistical analysis of the radial velocities available for the (HeII + Hα) 6560 emission band reveals a peak at the ∼1% level at the frequency ν = 0.195 d−1, corresponding to the period P = 5.128d. We also studied the NaI 5890 (D2) and NaI 5896 (D1) interstellar absorption lines, which are important for understanding the nature of the nebula NGC 6888, whose origin is related to HD 192163. Asymmetric profiles were found for the NaI 5890 and NaI 5896 interstellar absorption lines, interpreted as reflecting a contribution from NGC 6888 to these lines. We suggest that the detected profile variations of the (HeII + Hα) 6560 emission band and the periodic variations of its Doppler shifts (P = 5.128d) are due to the existence of a low-mass K-M star companion to the Wolf-Rayet star. HD 192163 is a possible evolutionary progenitor of a low-mass X-ray binary.

Effect of deposition temperature on the properties of CeO 2 films grown by atomic layer deposition

Cerium oxide dielectric thin films have been grown on n-type silicon by atomic layer deposition using a monomeric homoleptic Ce IV alkoxide precursor with water vapour. Herein we report the dielectric properties of CeO 2 films deposited from tetrakis(1-methoxy-2-methyl-2-propanolate)cerium. The resulting films exhibit permittivities in the range 25–42 at 1 MHz with a strong dependency on the deposition temperature. The microstructural origin of this behaviour has been investigated. The as-deposited films were found to be crystalline and they exhibited the cubic fluorite structure for deposition temperatures in the range 150 °C to 350 °C. Variations in the crystallite sizes are governed by the deposition temperature and have been estimated using a Debye–Scherrer analysis of the X-ray diffraction patterns. The changing crystallite size correlates with changes seen in the triply-degenerate F 2g first-order Raman line half-width at 465 cm − 1 . It is concluded that the frequency dependency of the film dielectric properties is strongly influenced by the crystallite size which in turn is governed by the growth temperature.

Visualization of nanodomains in lithium niobate single crystals by scanning laser confocal Raman microscopy

We demonstrated the possibility of application of scanning laser confocal Raman microscopy for visualization of the ferroelectric nanodomains in lithium niobate single crystals. The changes of the inte-grated intensity, half-width and frequency of several Raman lines in the vicinity of nanodomain boundaries were demonstrated. These nanodomains were formed after crystal heating by pulse laser. Recording of the spectral line parameters during two-dimensional scanning was used for the reconstruction of the nanodomain structure image.

Investigation on the fabrication and luminescence characteristics of Yb3+ and Al3+ Co-doped silicate glasses

We demonstrate a new method for fabrication of rare-doped silica-based glass, which is liquid doped with non-chemical vapor deposition (non-CVD) melting process. The Ytterbium doped silica-based glass with the ratio of 98SiO2-0.5Yb2O3-1.5Al2O3wt% is achieved by using this method. The refractive index (nD) and the density(ρ) of the glass are 1.519 and 2.62g/cm3 respectively. In measurement experiment, it shows that it has strong absorption in the wavelength range from 850nm to 1050nm, and the main absorption peak is at 978nm and the secondary absorption peak is at 919nm. Using the laser with wavelength of 978nm as pumping source, the emission peak is at 1018nm in the fluorescence spectrum with a 71.8nm fluorescence half-line width. Meanwhile, the integrated absorption cross section, stimulated emission cross section, fluorescence time, saturated pump intensity, minimum pump intensity and other parameters are calculated. Test results indicate that the doped silica-based glass has good thermal stability and large power threshold, which is an ideal gain medium for large power photonic crystal fiber lasers.

Pressure effect on optical properties and structure stability of LaPO 4:Eu 3+ hollow spheres

Uniform monoclinic monazite structure LaPO 4:Eu 3+ hollow spheres were synthesized via an attractive hydrothermal method owing to the higher yield and simplicity. Photoluminescence and Raman spectra of the sample were investigated under high pressure up to 26 GPa using diamond anvil cells. At ambient pressure, the sample exhibited same luminescent properties with that of bulk monazite LaPO 4:Eu 3+. With the increase of pressure, the emission intensity of Eu 3+ decreased and the half-widths of transition lines increased, while emission peaks showed a red shift toward longer wavelengths due to increase in crystal-field strength. No phase transformation appeared before amorphization for monoclinic LaPO 4:Eu 3+ hollow spheres, which was confirmed based on the analysis of high pressure Raman spectra. The large surface energy of hollow spheres was proposed to prevent the occurrence of phase transformation.

Pressure Effect on Optical Properties and Structure Stability of LaPO<SUB>4</SUB>:Eu<SUP>3+</SUP> Microspheres

Uniform monoclinic core-shell and hexagonal urchin-like LaPO4:Eu(3+) spheres are synthesized via an attractive hydrothermal method owing to the higher yield and simplicity. Photoluminescence and Raman spectra of two samples have been investigated under high pressure up to 28 GPa using diamond anvil cells. At ambient pressure, both samples exhibit same luminescent properties with that of bulk monazite LaPO4:Eu(3+). With the increase of pressure, the emission intensity of Eu(3+) decreases and the half-widths of transition lines increase for both samples, while emission peaks show a red shift toward longer wavelengths due to increase in both the crystal-field strength and the covalency. Monoclinic core-shell LaPO4:Eu(3+) becomes amorphous finally while hexagonal urchin-like one transforms to monoclinic structure at lower pressure of 3.2 GPa and turns into amorphous structure at higher pressures, which are presented based on the analysis of high pressure Raman spectra.

Uncertainties associated with theoretically calculated N2-broadened half-widths of H2O lines

With different choices of the cut-offs used in theoretical calculations, we have carried out extensive numerical calculations of the N2-broadend Lorentzian half-widths of the H2O lines using the modified Robert–Bonamy formalism. Based on these results, we are able to thoroughly check for convergence. We find that, with the low-order cut-offs commonly used in the literature, one is able to obtain converged values only for lines with large half-widths. Conversely, for lines with small half-widths, much higher cut-offs are necessary to guarantee convergence. We also analyse the uncertainties associated with calculated half-widths, and these are correlated as above. In general, the smaller the half-widths, the poorer the convergence and the larger the uncertainty associated with them. For convenience, one can divide all H2O lines into three categories, large, intermediate, and small, according to their half-width values. One can use this division to judge whether the calculated half-widths are converged or not, based on the cut-offs used, and also to estimate how large their uncertainties are. We conclude that with the current Robert–Bonamy formalism, for lines in category 1 one can achieve the accuracy requirement set by HITRAN, whereas for lines in category 3, it is impossible to meet this goal.

Development of New Positive-Tone Molecular Resists Based on Fullerene Derivatives for Extreme Ultraviolet Lithography

We have developed and evaluated new chemically amplified molecular resists based on fullerene derivatives with an excellent solubility in a standard alkali developer for extreme ultraviolet (EUV) lithography. We controlled the electron acceptability of fullerene derivatives and applied photo-acid generators (PAGs) with a high electron acceptability through ionization by EUV irradiation. As a result, sensitivities of positive-tone molecular resists based on fullerene derivatives were markedly improved, and we succeeded in obtaining good resolution, by applying an organic underlayer substrate without pattern collapse. Delineations of 45 nm half pitch (hp) and line width roughness (LWR) of 5.7 nm were achieved at an exposure dose of 12.5 mJ/cm2 on the organic underlayer.

Site Occupancy of Hydrogen in a Distorted bcc Lattice in Niobium Alloyed with Mo Atoms

In order to study the atomistic state of hydrogen in a bcc lattice, the site occupancies of hydrogen dissolved in Nb–Mo alloys containing 39, 48, and 60 at. % Mo atoms have been investigated at room temperature by the channelling method utilizing a nuclear reaction of 1 H( 11 B,α)αα with a 11 B + beam of about 2 MeV. In addition, the lattice parameters and half-widths of the X-ray reflection lines of the non-hydrogen-doped specimens have been measured at room temperature. Nb–Mo alloys form a solid solution over the entire Mo concentration range, maintaining a bcc crystal structure. From systematic studies including previous experiments on such alloys with lower Mo concentrations, it has been observed that the site occupancy of hydrogen changes very sensitively with Mo concentration. At low Mo concentrations, hydrogen is trapped by Mo atoms and occupies the trapped site ( T tr ), which is displaced by about 0.6 Å from a tetrahedral ( T ) site attached to a Mo atom towards that Mo atom. At approximately 20 at. % Mo, most of the H atoms occupy T sites and some portion of the H atoms occupy octahedral ( O ) sites. With increasing Mo concentration, the O -site occupancy diminishes, and at Mo concentrations higher than about 39 at. % the occupancy of the displaced- T (d- T ) site newly appears, which is displaced by about 0.25 Å from a T site towards its nearest-neighbour O site. It is recognized that there exists a close correlation between such a site change and a change in the half-width of the X-ray reflection line with Mo concentration. On the basis of this correlation, it is concluded that the change in the site occupancy of hydrogen is due to a change in the lattice distortion induced by alloying with undersized Mo atoms, and that the d- T site is a stable site for hydrogen in slightly distorted bcc lattices.

Luminescence spectra fine structure for uranyl sulfate and oxalate crystals

Quasi-line low-temperature (T = 77 and 4.2 K) luminescence spectra of uranyl sulfates and oxalates have been recorded and analyzed. It has been shown that the spectral structure is determined by the manifestation of the internal and external vibrations of both the uranyl ion and molecular groups (SO 4 ) 2- and (C 2 O 4 ) 2- bonded to the uranyl ion. The spectral line half-width is of the order of ≈5-7 cm -1 ; the line shape, close to Lorentzian. The fluorescence spectra may be complicated by structural defects in the crystals.

EVIDENCE FOR A STELLAR DISRUPTION BY AN INTERMEDIATE-MASS BLACK HOLE IN AN EXTRAGALACTIC GLOBULAR CLUSTER

We report [O III] 5007 Angstrom and [N II] 6583 Angstrom emission from a globular cluster harboring the ultraluminous X-ray source (ULX) CXOJ033831.8-352604 in the Fornax elliptical galaxy NGC1399. No accompanying Balmer emission lines are present in the spectrum. One possibility is that the forbidden lines emanate from X-ray illuminated debris of a star that has been tidally-disrupted by an intermediate-mass black hole (IMBH), with this debris also feeding the black hole leading to the observed X-ray emission. The line strengths indicate that the minimum size of the emitting region is ~10^15 cm, and if the 70 km/s half-widths of the emission lines represent rotation around the black hole, a minimum black hole mass of 1000 solar mass is implied. The non-detection of H-alpha and H-beta emission lines suggests a white dwarf star was disrupted, although the presence of strong nitrogen emission is somewhat of a mystery.

Wide-Line 1H NMR and DSC study of phase states of mesomorphic states of 4′-n-alkoxy-4-biphenylcarbonitrile mesogens (n = 3 and 7)

4′-(Propyloxy)-4-cyanobiphenyl (3OCB) and 4′-(heptyloxy)-4-cyanobiphenyl (7OCB) have been studied in the temperature range 20–80°C by wide-line 1H NMR and DSC. The 1H NMR line shapes, half-widths, and second moments, as well as the relaxation characteristics of separate lines, are discussed. The DSC data are compared with the specific features of mesogenic transformations of these homologues and 1H NMR data. At certain temperatures depending on the composition of alkyl moieties, a dynamically disordered fraction of molecules appear in solid crystals. These molecules are involved in the thermotropic transitions of 3OCB to isotropic liquid and of 7OCB to nematic liquid crystal. The temperature ranges, stabilities, and other characteristics of the transitions of 3OCB to isotropic liquid and of 7OCB to nematic liquid crystal were determined.

Analytical representation of half-width for molecular ro-vibrational lines in the case of dipole–dipole and dipole–quadrupole interactions

The analytical formula for half-width of molecular ro-vibrational lines is obtained for the case of dipole–dipole and dipole–quadrupole interactions. This formula depends on the variable parameters, which have to be determined by fitting to experimental half-widths or to half-widths calculated by semi-classical methods. The application of the analytical formula to the H2O–H2O, NH3–NH3, DCl–HCl and CO–H2O systems is discussed.

Wide-line 1H NMR study of mesomorphic states of 4′-(octyloxy)-4-biphenylcarbonitrile

A sample of 4′-(octyloxy)-4-cyanobiphenyl (8OCB) was studied in the temperature range −60–80°C by wide-line 1H NMR. The line shapes, half-widths, and second moments were determined. For the smectic phase of 8OCB, the relaxation times T1 and T2, the correlation time τc, and the degree of order were estimated. The 1H NMR spectral patterns and characteristics were found to be quite different for the crystalline, smectic, and nematic phases of 8OCB, which makes it possible to reliably identify the corresponding transitions and assess the molecular dynamics and molecular order of a structure. The temperature ranges, stability conditions, and other characteristics of the liquid crystalline phases that form on heating 8OCB were determined.

Electron spin resonance of light holes in porous silicon

Abstract A new ESR spectrum labeled Si-AA20 is revealed in porous silicon after annealing at 1000 °C. The AA20 line has a Dyson type that allows to attribute the AA20 to free carrier absorption. The AA20 spectrum is isotropic with g=2.0710. The high value of the g-factor indicates that the absorption can be hole-like. Intensity of the AA20 spectrum considerably changed upon rotation of the magnetic field H in the ( 0 1 ¯ 1 ) plane, at the same time the shape and half-width of the spectrum line did not change. The intensity was maximal with H along 〈1 1 1〉 directions and decreased in 2–3 times with H along 〈0 1 1〉 and 〈0 0 1〉 directions when the intensity reached minimum. The AA20 spectrum can be explained by formation of layers in porous silicon with high concentration of free holes for compensation of negative charged traps.

Properties of permalloy films produced in low-temperature plasma flows with a controlled composition

A simple version of a flow-forming plasma sputtering system is proposed. The causes that determine the properties of the deposited films are revealed when the composition, energy, and particle density of the flow are controlled. The electron component of the plasma flow and an increase in its ion component are found to degrade the magnetic properties of the films. The ferromagnetic resonance (FMR) line half-width of 10- to 150-nm-thick films is shown to mainly depend on the energy of the neutral flow component, which is specified by the sputtering conditions at an anode voltage of 400–700 V. In this rather narrow energy range, the FMR line half-width is 25 Oe for cold substrates.

Optical investigation of 6A 1g( 6S)→ 4T 2g ( 4D) absorption band in magnetic MnF 2 and RbMnF 3 compounds

Spectroscopic measurements of the spectral lines in MnF 2 and RbMnF 3 have been carried out in the temperature range 10–300 K. Observations of exciton–magnon sidebands in the fine structures of the 6A 1g → 4T 2g ( 4D) state of Mn 2+ ions are reported at low temperatures. The temperature dependence of peak positions, oscillator strength and half line widths have been investigated for selected bands. The analysis of the temperature dependence of these parameters confirms that the fine structure of the D band is mainly attributed to spin–orbit interaction combined with spin multiplicity in the ordered state. The ratios for the separation energies between these lines are fitted with the ratios expected from Landé interval rule.