Measured Intensity Ratios Research Articles

Quantitative X-ray Diffraction Analysis of Smectites: I – Mass Attenuation Calculations for Smectite Analyses

In smectite analyses, the investigation of the attenuation contribution to quantitative x-ray diffraction (XRD) analysis is a most important topic, including Fe content and distribution. This is the first part of a comprehensive study on smectite analysis addressing the nature and location of Fe atoms within the octahedral sites, interlayer regions, and intergranular interfaces. This first paper treats the mass attenuation measurements and calculations (Davis and Johnson, 1987). Additional reports will be made in the future on Fe studies involving measured and calculated reference intensity ratio measurements and structural studies based on SEM and TEM analysis.

Polycyclic Aromatic Hydrocarbon Solute Probes. Part X: Evaluation of Select Hydrogenated Pyrene, Benzo[ghi]perylene, and Naphthacene Derivatives as Possible Solvent Polarity Probes

Fluorescence emission spectra are reported for 3,4,5-trihydrobenzo[cd]pyrene, 3,4-dihydrobenzo[ghi]perylene, 5,6,7,8,9,10-hexahydrobenzo[ghi]perylene, trans-10b,10c-dihydro-10b,10c-dimethylpyrene, trans-12b,12c-dihydro-12b,12c-dimethylbenzo[a]pyrene, and trans-14b,14c-dihydro-14b,14c-dimethylnaphtho[2,1,8-qra]naphthacene dissolved in organic nonelectrolyte solvents of varying polarity. Dihydrobenzo|ghi]perylene was found to exhibit probe character, as evidenced by a systematic variation in emission intensity ratio with solvent polarity. It has a dynamic range of 0.98 and a high fluorescence quantum yield and is thought to be noncarcinogenic. Also reported are mathematical expressions which correlate measured intensity ratios and solvent polarity probe behavior of dihydrobenzo[ghi]perylene, pyrene, benzo[ghi]perylene, coronene, and ovalene in 48 solvents of varying polarity.

Angular momentum reorientation in CO(A 1Π)–He rotational energy transfer studied by optical–optical double resonance multiphoton ionization spectroscopy

An optical–optical double resonance multiphoton ionization (OODR-MPI) technique has been developed for measuring the angular momentum reorientation in CO(A 1Π)–He inelastic thermal collisions. In this scheme, two-photon pumping of CO(A 1Π) by using a circularly polarized laser creates a highly anisotropic oriented angular momentum distribution in CO(A 1Π). A second counterpropagating circularly polarized laser probes the oriented CO(A 1Π) via 1+1 photon resonance ionization. A depolarization factor (D), which can be calculated from the measured intensity ratios between R and P branches in the OODR-MPI spectrum, is introduced to characterize the amount of collisional reorientation in the J→J′ rotational energy transfer (RET). This method has the advantage of both high sensitivity and simplicity in data processing. The experimental results show the propensities that the depolarization factor D increases with ΔJ but decreases with increasing initial J. The D’s are asymmetric with respect to ±ΔJ. For comparison, theoretical D’s have been computed by an irreducible tensor formalism under the infinite-order-sudden approximation by Alexander and Davis [J. Chem. Phys. 78, 6754 (1983)] which is further simplified by using an exponential energy gap term to represent the dynamic effects. The computed curves of D vs ΔJ/J reproduce the experimental propensities. The best fit between theory and experiment is obtained with an average impact parameter b=2.9 Å, corresponding to a cross section of 26.4 Å2, which is close to the experimental total cross section of CO(A 1Π)–He rotational energy transfer (∼28 Å2).

Magnetic resonance signal intensity ratio of gray/white matter in children: Quantitative assessment in developing brain

Magnetic resonance imaging (MRI) findings in 87 children with various clinical entities were used to determine the signal intensity ratio of gray/white matter in T 1- and T 2-weighted images using a 1.5 T MR Scanner. Signal intensity ratio changes in both T 1- and T 2-weighted images correlated well with advancing age ( y=0.9349−0.001575, r=−0.584, P<0.0001 in T 1-weighted images; y=0.9798+0.002854, r=0.723, P<0.0001 in T 2-weighted images), but the correlation was more linear when we included only normally developed (34) children ( y=0.9689−0.001967, r=−0.654, P<0.0001 in T 1-weighted images; y=0.9882+0.002965, r=0.747, P<0.0001 in T 2-weighted images). Abnormal ratios were observed in patients with congenital hydrocephalus, inherited metabolic diseases and cerebral palsy. Although the gray/white matter differentiation would not delineate the myelination itself, measurement of the signal intensity ratio of gray/white matter is a practical way to evaluate delayed myelination in a busy MR center.

Stark-ladder transitions and their oscillator strengths in GaAs/AlAs superlattices.

We have studied Stark-ladder transitions and their oscillator strengths in GaAs/AlAs superlattices with different miniband widths 2\ensuremath{\Delta} by low-temperature photocurrent spectroscopy. The measured intensity ratio as a function of an electric field F of the nth-order Stark-ladder transition normalized by the zeroth-order transition shows a clear ${\mathit{F}}^{\mathrm{\ensuremath{-}}2\mathit{n}}$ dependence in the limit of high field. A ${\mathrm{\ensuremath{\Delta}}}^{2}$ dependence of the measured intensity ratio on the miniband width is also obtained. These results support the tight-binding theory of Bleuse, Bastard, and Voisin [Phys. Rev. Lett. 60, 220 (1988)].

Hyperfine structure of HCN J = 1-0 and implied physical information concerning NGC 7538 IRS1

The so-called intensity anomalies of hyperfine components of HCN(v = 0, J = 1-0) in the NGC 7538 molecular cloud are studied with a high resolution spectrometer. The measured intensity ratio R02 = T(a)*(F = 0-1)/T(a)*(F = 2-1) is clearly larger than the value 0.2, which is expected under the optically thin local thermodynamic equilibrium (LTE) condition, and the ratio R12= T(a)*(F = 1-1)/T(a)*(F = 2-1) smaller than the LTE value 0.6 at most of the observed positions. Radiative transfer calculations were performed using the large velocity gradient (LVG) model with a spherically symmetric velocity field. The line overlaps have also been taken into account. The analysis of the observational data shows that the three hyperfine components of the J = 1-0 transition are optically thick. While the optical depths of F = 2-1 and F = 1-1 are much larger than that of F = 0-1 hyperfine component, the scattering effect must be taken into account. The stronger two hyperfine components, F = 2-1, and F = 1-1, are formed in the envelope with the average hydrogen density 1.6 X 10(4) cm-3, but the thinner F = 0-1 hyperfine component in the core and in the envelope. The excitation temperatures of the three hyperfine components are different and the LTE assumption for the HCN hyperfine intensity ratio is unrealistic.

Sn and Sb segregation and their possible use as surfactant for short-period Si/Ge superlattices

The incorporation behaviour of antimony and tin in Ge was studied by means of Auger electron spectroscopy. By comparing the measured intensity ratios with a simple incorporation model, we find that Sn is stronger segregating than antimony. The activation energies are 0.34 and 0.27 eV, respectively. Using both materials in order to improve the interface sharpness of short-period Si/Ge superlattices, we can show that antimony improves the superlattice structure up to growth temperatures of 600°C, while with tin the superlattice growth is destroyed.

Determination of branching ratio and collisional mixing rate of potassium (52PJ) doublets following 193-nm photodissociation of potassium iodide in the presence of argon, helium, methane, and carbon dioxide

Using a three-level kinetic model, we have accurately determined the branching ratio of the nascent photofragment K in the 5 2 P J fine-structure states following photodissociation of KI by a 193-nm excimer laser. The branching ratio of the K(5 2 P 3/2 ) component in the presence of Ar, He, CH 4 , and CO 2 is determined respectively to be 0.800, 0.798, 0.797, and 0.785 with ±1% accuracy. The model has liken into account the rapid energy transfer between the 5 2 P J doublets, thereby leading to a more accurate result than the measurement of direct fluorescence intensity ratios under the low-pressure condition

The near-infrared Fe II forbidden lines of MWC 922

Spectrophotometry from 0.8-1,6 μm of the peculiar emission-line object and strong [Fe II] source MWC 922 is presented. Detections or useful upper limits are given for nine [Fe II] features between 1.25 and 1.54 μm which are used to test the accuracy of theoretically derived transition probabilities. The measured intensity ratios of all the lines were found to agree with the values predicted from the transition probabilities of Nussbaumer and Storey to within 30%. The derived electron density and temperature for the gas producing the [Fe II] emission are 10 5 cm -3 and 5000 K

Determination of fluid and gel domain sizes in two-component, two-phase lipid bilayers. An electron spin resonance spin label study

The average sizes of fluid and gel domains in the two-component, two-phase system formed from mixtures of dimyristoyl phosphatidylcholine and distearoyl phosphatidylcholine were determined from an analysis of the electron spin resonance spectral lineshapes of a dimyristoyl phosphatidylcholine-nitroxide spin label as a function of spin label concentration. The ratio, R, of the intensities measured at two magnetic field strengths was found to be diagnostic of a statistical distribution of spin labels in disconnected domains. R is defined as V'/2Vpp, where Vpp is the maximum intensity and V' is the intensity at a position in the wings of a first derivative electron spin resonance line that is a constant multiple of the peak-to-peak linewidth. The intensity ratio for Gaussian or Voigt lineshapes is less than or equal to the value for a Lorentzian lineshape. The intensity ratio was found to be greater than the value for a Lorentzian line when spectra from disconnected domains containing a statistical distribution of spin labels undergoing spin-spin interactions were summed. The intensity ratio, R, calculated by spectral simulations as a function of the average number of labels per domain, N, was found to increase to a maximum with increasing N and then to decrease. The dependence on spin label concentration of the experimentally measured intensity ratios paralleled this predicted behavior. A method is presented to calculate the average number of lipids per fluid or gel domain based on a knowledge of R, and of the distribution of the spin label between the fluid and gel phases determined from the phase diagram. The results demonstrate that the number of lipids per domain increases linearly from a fixed number of nucleation sites, as the fraction of the phase that is disconnected increases. At any given mole fraction of the particular phase, the gel domains are bigger than the fluid domains because they have a lower nucleation density. The results also suggest that the disconnected domains are, in most cases, nonrandomly distributed in the plane of the bilayer.

In-depth profiling with the electron-probe microanalyzer

In a recent publication we have given a brief outline of the procedure we followed in extending our “PROZA” φ(ρ·z) bulk matrix correction program into a thin film analysis program. With such a program it is possible to determine film thicknesses and compositions of a number of films simultaneously using measured intensity ratios of all elements involved as input. As long as each particular element in the layered system is confined only to one specific layer or the substrate only one measurement for each element at one suitable accelerating voltage will be sufficient to find thicknesses and compositions in a double iterative procedure. If one or more elements occur in more than one film or also in the substrate then more measurements over a suitable range in accelerating voltages are necessary.The ultimate challenge in multi-layer analysis is, beyond any doubt, the determination of the concentration-distribution as a function of depth for all the elements in a particular matrix.

Thermal ionisation mass spectrometry of Li 2BO +2 ions: determination of the isotopic abundance ratio of lithium

Thermal ionisation mass spectrometric investigations of Li 2BO + 2 ions have been carried out. The central idea is to study the feasibility of making an accurate isotopic analysis of lithium employing an experimentally measured intensity ratio(s) of Li 2BO + 2 ions of different specific charges ( m/ z). This paper presents the results along with a discussion on the merits and demerits of the method. The studies show that the intensity ratios of Li 2BO + 2 ions are definitely changing with time owing to a certain amount of fractionation of lithium isotopes, the extent of which could, however, be controlled, leading to the determination of the 6Li/ 7Li abundance ratio with a reasonable accuracy without applying any correction factor. Factors affecting the accuracy of this molecular ion beam method of isotopic analysis are discussed. It is shown that the accuracy is governed by error propagation rather than by the achievable precision and accuracy of mass spectrometric measurements. This particular point is illustrated with examples of varying isotopic abundance patterns of lithium and boron. As a logical consequence, it is pointed out that a mere selection of the most abundant Li 2BO 2 molecules as monitors for mass spectrometric measurements may not always ensure accurate isotopic analysis of a constituent element.

Localized 1H NMR spectra of glutamate in the human brain.

Localized 1H NMR spectra at TE = 12 ms were obtained from cerebral cortex of human subjects using ISIS with surface suppression. The 2.29-ppm resonance was assigned to C4 glutamate with contributions from C4 glutamine and GABA using in vivo spectral editing and comparison of chemical shift with pure compounds. The measured intensity ratio between the 2.29 resonance and the creatine resonance at 3.03 ppm was in good agreement with the ratio predicted from previously reported measurements of glutamate, glutamine, and GABA concentrations in biopsied human brain tissue.

PHYSICAL PROPERTIES OF EXTENDED EMISSION-LINE REGIONS IN ACTIVE AND COOLING-FLOW GALAXIES

ABSTRACT This dissertation utilizes primarily optical observations of extended emission-line regions in active and cooling-flow galaxies to clarify the nature of this nebulosity and its underlying sources of energy. In particular, I employ case studies of Seyfert galaxies in order to elucidate nuclear properties as seen in light that is apparently scattered into our line of sight, and to provide direct measurements of emission-line intensity ratios resulting from a radially diluted, photoionizing continuum for comparison with theory. The apparent Seyfert 2 galaxy NGC 4388 displays a weak, spatially extended, broad-line emission that is most readily understood as scattered light from a hidden Seyfert 1 nucleus. IC 5135 exhibits both Seyfert 2 and starburst activity in its nucleus, and the influence of both can be traced in nuclear emission-line profiles as well as line-intensity ratios of spatially resolved nebulosity. I also report results bearing on star formation and the rate of mass accretion in the cluster cooloing-flow galaxy NGC 1275, as revealed from spectroscopy of the nebular filaments in this system. While preferential low-mass star formation has been invoked to reconcile high X-ray inferred accretion rates in cooling flows with a paucity of apparent cooled matter, data reported here reveal a site of high-mass star formation in material believed to arise from the flow. Detailed scrutiny of this region suggests, moreover, that the initial mass function of star formation in this locale is unlikely to be biased unusually toward low-mass star formation. These results provide additional evidence that the true rate of mass deposition may be less than implied by a simple interpretation of the X-ray data. The same data set is used to derive improved upper temperatures. The ability of these measurements to constrain the accretion rate is limited by exclusion of the galaxy center, which is host to a Seyfert nucleus. Finally, I present results of a narrow-band imaging survey of X-ray selected, early-type galaxies that are examined for evidence linking nebulosity in these sources to cooling-flow or weak Seyfert phenomena. These results suggest that optical nebulosity in these systems probably bears a multiparameter relationship to cooling flows, active nuclei, and accretion from external sources.

X-ray structural study of oriented vinylidene fluoride/trifluoroethylene copolymers

Abstract The orientation of the crystalline regions in the vinylidene fluoride/trifluoroethylene VDF/TrFE)-copolymer with molecular ratio 70:30 has been studied by wide-angle X-ray diffraction. This copolymer crystallizes in the β-phase or form I upon compression moulding. Dumb-bells 90 mm wide by 50 mm long were drawn at 0.25 mm min−1 and 80–85°C to the natural draw ratio of 7; the oriented sheets were void-free, and the crystal phase remained form I. Some samples were then poled at 200 MV m−1. Strips 0.5 mm wide of both unpoled and poled samples were examined in a two-circle X-ray diffractometer, and all equatorial ω scans corrected for absorption of the X-ray beam. Both ( 200 110 ) and ( 310 020 ) composite reflections then showed six distinct intensity maxima round the draw direction, separated by 60° from each other, indicating a high degree of uniplanar-axial orientation within the drawn sheets. Calculation of the structure factors from two crystal models and comparison with the measured intensity ratios round the draw direction by curve-fitting methods showed that most of the polar b axes of the unpoled material are in the sheet plane (bc sheets), and that poling increases the number of these axes taking on positions 60° from this plane, in line with similar results in the poly (vinylidene fluoride) homopolymer.

193 nm photodissociation of KI: Branching ratio and collisional mixing rate of K(5 2P J) doublets

Through a three-level kinetic model, the branching ratio of the nascent photofragment K in the 5 2PJ fine-structure states following photodissociation of KI by a 193 nm excimer laser has been experimentally determined to be K(5 2P3/2)=0.791 and K(5 2P1/2)=0.209 with ±1% accuracy. The model has taken into account the rapid energy transfer between the 5 2PJ doublets and the result appears to be more accurate than those fluorescence intensity ratio measurements under low pressure condition. The cross section of fine-structure mixing induced by H2 collisions has also been measured to be 134±6 Å2 for the transition 5 2P3/2←5 2P1/2 and 72±5 Å2 for its reverse process. The ratio 1.86 is consistent with the value 1.89 predicted by principle of detailed balance. Using the Stern–Volmer equation, we have also obtained the radiative lifetime 137±4 ns for the K(5 2PJ) state and its quenching cross section 10.4±1.8 Å2 by collision with H2 molecule. The latter appears much smaller than those of fine-structure energy transfer processes by an order of magnitude.

Are Einstein’s transition probabilities for spontaneous emission constant in plasmas?

The quenching of spontaneous emission coefficients, presumably by electron collisions, which was recently inferred at Princeton from measured intensity ratios of visible and extreme-ultraviolet lines from a common upper level in laser blow-off plasmas, was investigated using a ruby laser. The line intensity ratios of the Civ 3s-3p and 2s-3p transitions, for similar laser targets, show a similar dependence on separation from the target as the previous experiments. Both of these results can, however, be interpreted in terms of density gradients and Stark broadening without invalidating Einstein A values. This interpretation also applies to Ciii and Nv line intensity ratios, which are further compromised by blends with other lines. The quenching of Arii lines by photon collisions, which had been reported by the same Princeton group, can finally be shown to have been mimicked by other effects, in this case by the Rabi oscillations and associated power broadening in the argon ion laser cavity.

Multiplex CARS for simultaneous measurement of temperature and CO_2 and H_2 concentrations in a combustion environment

Simultaneous temperature and CO(2) concentration measurements with multiplex coherent anti-Stokes Raman scattering (CARS) spectra of CO(2) were performed. CARS spectra of pure CO(2) and various mixtures of CO(2) and N(2) in a furnace were recorded at various temperatures to test the computer code that simulates CO(2) CARS spectra using recent spectroscopic constants. The temperatures obtained from the CO(2) CARS spectra were in good agreement with thermocouple temperature measurements. However, the CO(2) concentrations cannot be accurately extracted from these spectra. It is believed by the authors that the cross-coherent effect, which has not been included in the present model, and the difficulty of accurately accounting for the background are two important factors affecting the CO(2) concentration measurements. H(2) pure rotational lines S(4) and S(5) were found in the CO(2) CARS spectra of a hydrocarbon flame. These assignments were confirmed from intensity ratio measurements of S(4) and S(5) lines at different temperatures. A theoretical study shows that the H(2) concentration measurement from the S(5) line should be more sensitive than that of the S(4) and S(9) lines at the flame temperature. CARS spectra of preanalyzed mixtures of N(2), CO(2), and H(2) in a furnace were recorded to investigate the feasibility of inferring the H(2) concentration from these spectra. Simultaneous CO(2) and H(2) multiplex CARS spectra were also recorded in a CH(4)/O(2) diffusion flame and in the MSU/DIAL test stand to observe the high temperature spectra. The results of these measurements are presented.

Measurement and interpretation of spontaneous line emission from a common upper level in laser-produced carbon plasmas.

The quenching of spontaneous-emission coefficients recently inferred at Princeton from measured intensity ratios of visible and extreme-ultraviolet lines from a common upper level in laser blowoff plasmas is further investigated using a ruby laser. The line intensity ratios of the Civ 3s-3p and 2s-3p transitions, for similar laser targets, show a similar dependence on separation from the target as the previous experiments. Both of these results can, however, be interpreted in terms of density gradients and Stark broadening wihtout invoking changes in Einstein A values.

Characterization of catalysts derived from oxidation of ruthenium-thorium intermetallics

Ru methanation catalysts derived from oxidation of Ru{sub x}Th{sub y} intermetallics were characterized by X-ray photoelectron spectroscopy (ESCA), ion scattering spectroscopy (ISS), X-ray diffraction (XRD), BET surface area measurements, chemisorption, and gravimetric analysis. XRD measurements and gravimetric analysis indicated that all intermetallics were extensively decomposed by oxidation in air at 350{degree}C. ESCA and ISS Ru/Th intensity ratio measurements showed that surface segregation of ThO{sub 2} occurred for all catalysts. The structure of the intermetallic-derived (IM) catalysts can best be described as Ru particles embedded in a ThO{sub 2}-rich overlayer. Comparison of hydrogen and CO uptake with N{sub 2} BET surface area suggests that CO more accurately titrates surface Ru than does hydrogen. Extensive spillover of hydrogen from Ru to ThO{sub 2} was also observed for all IM catalysts. On the basis of CO chemisorption, the CO hydrogenation turnover frequency was comparable for all the IM catalysts.