Narrow Line Spectra Research Articles

Autotransformation and ageing of acid-treated montmorillonite catalysts: a solid-state 27Al NMR study

Solid-state 27Al magic-angle spinning (MAS) NMR has been used to study ageing processes in acid-treated clay catalysts. Acid-treated montmorillonite has been aged under conditions of high humidity. Elemental analysis has shown that Al migrates from the clay lattice to ion-exchange sites on the clay surface (autotransformation). Simultaneously, the cation-exchange capacity of the clay falls. NMR has shown that migration of Al from octahedral and tetrahedral lattice sites occurs at comparable rates. Despite exhibiting the same chemical shifts, hydrated Al3+(narrow-line spectrum) can be distinguished from octahedral lattice Al (broad line) under appropriate conditions. Hydrated Al3+ ions arising from autotransformation appear to occupy two distinct sites, and possibly other asymmetric sites in which the Al centres are NMR invisible.

Evidence for a massive, dark gravitational lensing object in Q2345 + 007

view Abstract Citations (10) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evidence for a Massive, Dark Gravitational Lensing Object in Q2345+007 Duncan, Robert C. Abstract We analyze the narrow absorption line spectra of the double quasar Q2345 +007. The observed pattern of Lyα forest absorption lines gives evidence that the quasar is gravitationally lensed, with 4-to-1 odds in favor of lensing. If Q2345+007 is lensed by an object at z = 1.49, as suggested by observations of heavy-element absorption lines, then a low-luminosity lensing mass of ~10^13^ M_sun_ contained within a transverse distance ~40h^-1^_0_kpc is implied. The Lyα cloud diameters at Z~2 would then be 20+/-10h^-1^_0_kpc [q_0_=0.5] or 28.0+/-14h^-1^_0_kpc [q_0_=0]. If the quasar is not lensed, then the Lyα clouds are larger by a factor of 6.5. We suggest several observational tests which might verify the presence of a massive, dark, lensing object and elucidate its properties. Publication: The Astrophysical Journal Pub Date: July 1991 DOI: 10.1086/186083 Bibcode: 1991ApJ...375L..41D Keywords: Dark Matter; Gravitational Lenses; Quasars; Absorption Spectra; Astronomical Spectroscopy; Luminosity; Lyman Alpha Radiation; Astrophysics; DARK MATTER; GRAVITATIONAL LENSES; QUASARS full text sources ADS | data products NED (5) SIMBAD (2)

High-Resolution Observations of the M81 Nucleus

The nucleus of the nearby Sb galaxy M81 has been shown to exhibit many of the features prominent in luminous active galactic nuclei: a variable, compact VLBI radio source (Kellermann et al. 1976, Jones, Sramek and Terzian 1981), a central variable X-ray source (Elvis and van Speybroeck 1982, Fabbiano 1988), and broad wings of Balmer emission similar in extent to those typical to Seyfert 1 nuclei (Peimbert and Torres-Peimbert 1981, Shuder and Osterbrock 1981). The nucleus also shows a narrow-line spectrum in many ways typical of LINERs (Heckman 1980), now known to be representative of early-type spiral nuclei in general.

Electron paramagnetic resonance studies of Mn(II)Mn(II) interaction in yeast inorganic pyrophosphatase

Yeast inorganic pyrophosphatase, EC3.6.1.1. (PPase), has two high affinity Mn(II) sites per PPase subunit in the absence of phosphoryl ligands and three high affinity sites in the presence of a phosphoryl ligand such as hydroxymethane bisphosphonate (PCHOHP) [1]. We here present strong evidence from Mn(II) EPR studies that in the presence of PCHOHP 1) the Mn(II) ions in one pair of the divalent metal ion sites are close enough to one another to show significant magnetic (dipolar or exchange) interaction and 2) the Mn(II) ions in another pair of the sites show weaker magnetic interaction. Further, the Mn(II) ions in these latter sites have EPR spectra that are indistinguishable from one another. EPR Spectra of PPase, Mn(II) and PCHOHP Q-band (35 GHz) spectra for solutions of PPase and different amounts of Mn(II) in the absence of phosphoryl ligand are shown in Fig. 1(a) and 1(b). Spectrum 1(b) is quite similar to that for Mn(H 2O) 6 +2 with respect to both g value (1.999 vs. 2.001, respectively) and peak to peak line width (1.75 gauss vs. 15 gauss, respectively) and is indicative of isotropic and relatively isolated Mn(II) sites. it should be noted, however, that raising the Mn(II) stoichiometry from one to two per subunit actually results in a modest decrease in spectral intensity, probably indicative of a weak Mn(II): Mn(II) magnetic interaction. The concentration of free Mn(II) is negligible in these solutions, since the dissociation constant of Mn(II) from each of two sites on a PPase subunit is equal to 10 −5 M [1]. In Fig. 2, Mn(II) spectra are shown, at increasing Mn(II) to PPase molar ratio, in the presence of the strong competitive inhibitor of PPase, PCHOHP [2]. It is quite clear that addition of PCHOHP leads to much more complex spectra compared to those seen in Fig. 1. The multiplicity of lines clearly distinguishable in Fig. 2a and 2b is similar to that reported by Markham in studies of Mn 2+ bound to S-adenosyl-methionine synthetase [3], and is suggestive of Mn(II)Mn(II) coupling, although it must be noted that EPR spectra of the same solutions at X-band (9 GHz) did not show the same multiple line EPR spectral patterns, perhaps due to broadening effects, that Markham was able to demonstrate (data not shown). Alternatively, the spectra seen in Fig. 2a and 2b could be accounted for either as a superposition of two spectra with slightly different zero field splittings or by anisotropy in the − 1 2 to + 1 2 transition. In any event, the broadness of all of the peaks in Fig. ▪ ▪ 2a, b compared to those seen in Fig. 1 (even the relatively narrow peak at 12,275 gauss has a peak to peak line width of 27 gauss) and the marked decrease in intensity in the low field line at 12,275 gauss as more than one equivalent of Mn(II) is added, provide strong evidence for significantly enhanced Mn(II)Mn(II) magnetic interaction in the presence of PCHOHP [4]. EPR Spectra of PPase, Mn(II), PCHOHP and Ca 2+ Based on our previous binding studies [1] it is evident that in the presence of 1.5–2.0 equivalents of limit of 7–8 Å can be set for the separation between the Mn(II) ions in these two sites; beyond this limit, the two ions would have only a small (< 10%) broadening effect on one another [4]. This result is consistent with preliminary work Dunaway-Mariano and Villafranca as quoted in Knight et al. [7]. The addition of Ca 2+ displaces Mn(II) from the partially filled site C and the displaced Mn(II) is redistributed amongst the partially filled sites A and B. Since site C is filled with diamagnetic Ca 2+, the Mn(II)Mn(II) magnetic interaction between sites B and C is suppressed and a narrow line spectrum, corresponding to Mn(II) population of sites A and B, is observed. The increased intensity of this spectrum as a function of added Ca 2+ is reasonable since the population of Mn(II) at these sites is increased by displaced Mn(II) from site C. Finally, from the observed lack of zero field splitting, the results presented in Figs. 1(b) and 3(d) show that the Mn(II) ions in sites A and B have ligand environments with near octahedral symmetry which are indistinguishable from one another, at least as judged by their EPR spectra.

Optically resolved zero field splittings in the phosphorescence spectra of aromatic thioketones

The phosphorescence spectra of xanthione (XS), thioxanthione (TXS), and thiofluorenone (TF) have been investigated at different temperatures below 4.2 K. Narrow-line spectra are observed in n-alkine matrices, the full width at half maximum intensity being ≈4.5 cm −1 for XS in n-hexane. The emissions of XS and TXS consist of two optically resolved subspectra which are assigned to the (T x , T y ), and T z triplet sublevel manifolds. The intensity of the latter subspectrum vanishes when T is reduced to 1.1 K. The T dependence of the relative intensifies of the subspectra is consistent with the populations of the sublevels existing in thermal equilibrium over the entire temperature range over which T z emission is observable. The lack of T z emission at 1.1 K, the lowest temperature obtained in these measurements, provides strong evidence that intersystem crossing leads to the selective population of T x and T y . We find that D = −5 ± 1 cm −1 for both XS and TXS from measurement of the splitting of the 0,0-bands. Resolved are not observed in the TF phosphorescence, but T-dependent line positions allow an estimate of D = −8 cm −1. The smaller zero field splitting between T x and T y is obtained for each molecule by ODMR. The large value of | D| is attributed to spin-orbit coupling induced by the presence of the S atom as well as the presence of a low-lying 3A 1 state. The latter is predicted to lie within ≈ 10 3 cm −1 of T ⊥ in XS.

Discovery of a narrow line quasar

A stellar object is reported which, while having X-ray and optical luminosities typical of quasars, has narrow permitted and forbidden emission lines over the observed spectral range. The narrow-line spectrum is high-excitation, the Balmer lines seem to be recombinational, and a redder optical spectrum than that of most quasars is exhibited, despite detection as a weak radio source. The object does not conform to the relationships between H-beta parameters and X-ray flux previously claimed for a large sample of the active galactic nuclei. Because reddish quasars with narrow lines, such as the object identified, may not be found by the standard techniques for the discovery of quasars, the object may be a prototype of a new class of quasars analogous to high-luminosity Seyfert type 2 galaxies. It is suggested that these objects cannot comprise more than 10% of all quasars.

Seyfert galaxies with weak broad H alpha emission lines

Spectrophotometric measurements show five galaxies with strong narrow emission lines combined with weak, broad H-alpha and H-beta components to have line and continuum spectral properties intermediate between those of Seyfert 1 and Seyfert 2 galaxies. Because they are closer to the latter, they are called Seyfert 1.8 and Seyfert 1.9, depending on the presence of broad H-beta emissions in the scans. The observed intensity ratios of the broad H-alpha/H-beta emission lines are large compared with those of typical Seyfert 1 galaxies, suggesting the importance of dust in the broad-line regions. Narrow-line spectra of the Seyfert 1.8 and 1.9 are found to have low ionization, implying that their narrow-line region is reached by few high-energy photons. Emphasis is placed on the correlation between a strong, featureless continuum and broad H I emission lines in Seyfert and radio galaxies.

ESR experiments on atomic hydrogen

ESR experiments at 9 GHz have been performed on atomic hydrogen gas in a cavity coated at 0.6∘K with a helium film and at 4.2∘K with solid molecular H 2. At 0.6∘K three-body recombination is observed from the decay of the gas density. At 4.2∘K, in addition to the narrow line spectrum of H atoms in the gas a broad line spectrum is observed, which is ascribed to atoms trapped at fixed sites on the surface of solid H 2.

Analyses of Vibrational Progressions in Luminescence Spectra of Platinum‐Group d6Complexes

AbstractLow temperature (10 K) luminescence spectra of powder samples and single crystals of various Rh(III), Ir(III), and Pt(IV) complexes have been recorded. Some of these show vibrational fine structure which is explained by several progressions arising from different promoting modes. Band analyses carried out by decomposing the emission profile into a series of lorentzian or gaussian distributions lead to accepting mode frequencies which match frequencies in vibrational spectra. By comparing intensity distributions in the progressions with theoretical line shape functions from recent vibronic theories, some optical and geometrical parameters pertaining to the excited electronic states (potential minima shifts, changes in oscillator frequencies with respect to the ground state) have been calculated. For this analysis the quality of the vibrational resolution is of importance. Broad band vibronic spectra which cannot be resolved at low temperature can also be used to a certain degree for determining excited state properties. The results obtained from simple models seem to agree well with the data obtained from the narrow line spectra.

Paramagnetic impurities in Cr(CO) 6 crystals : The EPR spectrum of Mn(CO) 5Cl −

The use of Cr(CO) 6 as a host matrix for single-crystal EPR studies of metal carbonyls is discussed. A narrow-line spectrum observed in γ-irradiated crystals of Cr(CO) 6 doped with Mn(CO) 5Cl is assigned to Mn(CO) 5Cl − (or possibly Mn(CO) 4Cl −).

An alternative to enhanced quantum diffusion in solid H 2 below 0.3K

In samples of bulk solid H 2 having orthohydrogen concentration (x o) below 3.1% that are cooled quickly at higher temperatures, it is found that the nmr lineshape and intensity are not time dependent at fixed temperature below 0.3K. Also, it is found that it is unnecessary to assume enhanced quantum diffusion rates to explain the temperature dependent lineshape changes observed, as they can be accounted for by changes in the transition rate between the rotational sublevels of unpaired oH 2 molecules. Measurements of the relative signal amplitudes of various parts of the NMR spectrum as a function of x o are consistent with the assumption that the narrow line spectrum near the Larmor frequency is due to HD impurities.

Preparation of Cathodes for Use in Demountable Hollow Cathode Lamps

The hollow cathode lamp produces intense, stable, and narrow line spectra. Because of these properties, and the fact that it is inexpensive and easy to operate, it is the source of resonance radiation most commonly used in atomic absorption spectroscopy. Most often the lamps used are the sealed type commercially available from various sources. Demountable lamps have been shown, however, to have some advantages when compared to the sealed variety, and are now available commercially. Often water cooling is incorporated into the lamp allowing the lamp to be run at higher currents, thus producing nonreversed lines of greater intensity than can be obtained in sealed lamps. The sealed lamps are only useful for a finite period before they need replacement. In addition, an individual lamp is needed for each element to be analyzed, whereas only the cathode needs replacement in a demountable lamp to change from element to element. The interchangeable cathodes are easily prepared if the material to be excited can be obtained in a machinable form. This is true of many metals, but often cathodes of nonmachinable elements are needed or a machinable piece of the desired material is not readily available. The latter situations are the subject of this correspondence.

Electron-spin-resonance investigation of ferroelectric lead titanate

Electron-spin-resonance measurements have been made on axially symmetric spectra of ${\mathrm{Fe}}^{3+}$ in ${\mathrm{PbTiO}}_{3}$. Two spectral systems corresponding to two different environments of the ${\mathrm{Fe}}^{3+}$ ion replacing a ${\mathrm{Ti}}^{4+}$ ion have been found. The spin-Hamiltonian constants $D=1.187\ifmmode\pm\else\textpm\fi{}0.002$ ${\mathrm{cm}}^{\ensuremath{-}1}$, $a=0.020\ifmmode\pm\else\textpm\fi{}0.007$ ${\mathrm{cm}}^{\ensuremath{-}1}$, $F=\ensuremath{-}0.017\ifmmode\pm\else\textpm\fi{}0.01$ ${\mathrm{cm}}^{\ensuremath{-}1}$ for the system with narrow linewidth (\ensuremath{\sim} 100 G) and $D=1.150\ifmmode\pm\else\textpm\fi{}0.003$ ${\mathrm{cm}}^{\ensuremath{-}1}$, $a=0.022\ifmmode\pm\else\textpm\fi{}0.01$ ${\mathrm{cm}}^{\ensuremath{-}1}$, $F=\ensuremath{-}0.02\ifmmode\pm\else\textpm\fi{}0.01$ ${\mathrm{cm}}^{\ensuremath{-}1}$ for the system with wide linewidth (\ensuremath{\sim} 300 G) have been found at -188\ifmmode^\circ\else\textdegree\fi{}C. The temperature dependence of the spin-Hamiltonian constants $D$ have been measured between liquid-nitrogen and room temperatures. The wide-line spectrum has been identified to be due to ferroelectric distortion whereas the narrow-line spectrum arises from a missing oxygen ion due to charge compensation. These results have been compared with an equivalent study in barium titanate; the major intent being to relate the magnitude of polarization to spin-Hamiltonian constants.

Carbon-13 nuclear magnetic resonance and circular dichroism study of the collagen-gelatin transformation in enzyme solubilized collagen

Natural abundance Fourier transform 13C nuclear magnetic resonance (13C NMR) were obtained for enzyme solubilized collagen at 1 degrees intervals through the transition region. The transition of collagen molecules from the rigid triple helical state to single-stranded, random-coil state is accompanied by a change from broadened carbon resonances unobservable under high-resolution conditions to narrow line spectra. Thus distinction can be made between helical and random-coil states of individual residues. The transition is monophasic, as determined by examination of 14 different carbon resonances, and the entire structure is found to melt cooperatively over a temperature interval of 5 +/- 1 degrees. All the residues seem to be involved in the unfolding process concurrently. The transition was also studied by examining the changes in the circular dichroism spectrum brought about by heating. The experiments corroborated the observation that the transition proceeded cooperatively over a temperature interval of 4 degrees. Enzyme soluble collagen is seen to melt less cooperatively than native collagen. The enthalpy change was determined by assuming an equilibrium between three random coil gelatin chains and tropocollogen molecules. From the enthalpy, the average length of the tripeptide sequences (70-85) involved in the transition can be estimated. The shortening of the cooperative unit could arise as a result of some alteration of the native conformation through proctase treatment.

Probing broad lines in molecular spectra by optical site selection spectroscopy

WE report evidence that suggests that narrow-line spectra can be obtained for many organic compounds without the difficulties commonly found with traditional mixed-crystal line-narrowing techniques. Furthermore, our findings suggest a new method by which low temperature line-broadening mechanisms may be studied.

Mössbauer parameters of adducts of tin(IV) halides with amines, nitriles, phosphines, and arsines

Mossbauer parameters are reported for the adducts SnX4,L (L = NMe3, X = Cl or Br; L = PPh3 or Ph2PCH2PPh2, X = Cl) and SnX4,2L (L = NMe3, X = Cl, Br, or I; L = NEt3; X = F; L = Py, PBun3, AsPh3, or AsEt3, X = Cl or Br; L = MeCN, PhCN, PPh3, PPh2Me, PPhEt2, or PEt3, X = Cl). Variations in chemical shifts for the adducts are discussed in terms of s character of the bonds to tin. Of the nitrogen donors, only the nitriles give rise to resolved quadrupole splitting. Triphenyl-phosphine and -arsine adducts give single-line spectra but quadrupole splitting is induced by replacing phenyl groups by alkyl groups. The five-co-ordinate adducts SnCl4,NMe3 and SnBr4,NMe3 give narrow-line spectra which exhibit no quadrupole splitting. I.r. and Raman data in the range 400–100 cm.–1 are reported for the 1 : 2 phosphine and arsine adducts. Attempts to prepare adducts of tin(IV) chloride and bromide with triphenylstibine resulted in reduction of the metal to tin(II).

Reactions in Crystalline Lattices: Chemistry of Lower Valence States of Lanthanides

Reduction of rare-earth (RE) ions to lower valence states in ionic crystals is described in terms of the equilibrium distribution theory for the (alkali halide):RE2+ and (alkaline-earth halide):RE3+ systems. Thermoluminescence glow curves of radiation-reduced CaF2:RE3+ systems reveal that the reoxidation of the divalent ions apparently occurs through thermal excitation of an f electron to the d bands. The additive reduction of RE2+ to the monovalent state in alkali halides yields striking results: While Sm1+ ions in KCl obtained by gamma radiation give rise to broad-band optical spectra which were attributed to 4f66s1 → 4f56s2 transitions, those obtained through high-temperature additive treatment with liquid K give rise to narrow-line spectra that are not easily interpreted. These results illustrate well the major differences between the radiation reduction and additive reduction processes.

Electron spin resonance study of tert-butyl halides and carbon tetrachloride, neopentane and carbon tetrachloride binary mixtures irradiated at 77 °K

Tert-butyl halides and carbon tetrachloride, neopentane and carbon tetrachloride binary mixtures were irradiated at 77 °K and electron spin resonance spectra were recorded at increasing temperatures until the radicals disappeared.Even at high concentrations of tert-butyl halides, the radicals obtained from CCl4 predominate, indicating that CCl4 has a high efficiency for electron capture. Maximum radical yields and the appearance of a narrow line spectrum with rising temperature were observed in (CH3)3C—X – CCl4 mixtures (X = Cl, Br, I) in concentration ranges where only a single phase exists. This spectrum consists of 17 lines which appear to belong to one odd-numbered spectrum (7 lines due to (CH3)2Ċ—X radical) and two even-numbered spectra (4 and 10 lines, the last being due to (CH3)3Ċ radical). The disappearance of the CCl4 broad band and the appearance of these radicals with increasing temperature can be interpreted as due to charge transfer from carbon tetrachloride cation to tert-butyl halide, facilitated by greater freedom of movement in the solid solutions. In contrast, neopentane and carbon tetrachloride mixtures do not display these features.

Spin-Spin and Crystal-Field Interactions in the Rare-Earth Ethyl Sulfates. I. The Spectrum of Gadolinium

The interactions between magnetic rare-earth ions in a set of isomorphic salts have been investigated under the experimental condition $g\ensuremath{\beta}H&gt;\mathrm{kT}$ such that the spins are highly aligned by the external magnetic field. Paramagnetic resonance under these conditions is found to show behavior qualitatively similar to ferromagnetic resonance. The high degree of spin alignment results in a nearly uniform internal field for samples having a regular shape, so that it is possible to observe narrow line spectra in concentrated paramagnetic salts. The spin-spin interactions may be directly determined from the line shifts at low temperatures, and from the observation of resolved structure that results from the resonance absorption of ions having a near neighbor ion whose spin is antiparallel to the magnetic field. In dysprosium ethyl sulfate containing gadolinium as an impurity, the interaction of a Gd ion with its first-, second-, and third-nearest-neighbor Dy ions, as well as the total interaction with all Dy neighbors, has been measured. The interaction may be explained in terms of a dipolar coupling between the spins. The influence of the spin-spin interactions on the angular variation of the Gd spectrum is also examined. The spin-lattice relaxation time of a Gd ion is found to depend on its nuclear spin.

Spectral Characteristics of Exploding Wires for Optical Maser Excitation

As pulsed light sources, exploding wires can be used to provide intense narrow spectral lines as well as the characteristic continuum of very high temperature blackbodies. The surface brightness depends on the wire material and conditions under which the wire is exploded. Optimum conditions for 100–500-μsec long light pulses from wires exploded in air have been found for tungsten, tantalum, and molybdenum wires 0.005 to 0.010 in. in diameter for energy inputs of 3000 J or more. Wires exploded in small diameter vacuum tubes (1–20 μ of Hg) radiate as blackbodies, but narrow line spectra are produced in enclosures of larger dimensions. In the visible and ultraviolet regions of the spectrum the spectral radiance of air-exploded wires is one to three orders of magnitude greater than that of conventional flash lamps. Vacuum-exploded wires have spectral radiance another factor of eight greater. Excitation of various optical masers with exploding wires is discussed.