Anomalous Line Research Articles

Picosecond vibrational relaxation modulated by critical slowing down in ferroelectric K4Fe(CN)6

Accurate time-resolved stimulated Raman measurement of anomalous line broadening of a vibrational excitation weakly coupled to a lattice mode which shows critical slowing down is presented. Dephasing of the Raman-active internal ${\mathit{A}}_{1\mathit{g}}$ CN stretching mode in ferroelectric ${\mathrm{K}}_{4}$Fe(CN${)}_{6}$\ensuremath{\cdot}${3\mathrm{H}}_{2}$O is found to result from a superposition of energy-exchange dephasing from coupling to the internal ${\mathit{T}}_{1\mathit{g}}$ Fe-C?N bending mode and pure dephasing from coupling to the (tunneling motion of the) crystal water. Anomalous broadening of the ${\mathit{A}}_{1\mathit{g}}$ line at the Curie temperature (248.5 K) results from critical slowing down of the water reorientational tunneling motion.

Temperature dependence of the anomalous emission line intensities in57Co:LiTaO3-initial population and relaxation

Mossbauer spectra of57Co: LiTaO3 single crystals were recorded in an external longitudinal magnetic field of 6 T at different temperatures between 4.2 K and 150 K. The spectra were taken at two different orientations of the crystallographicc-axis relative to the magnetic field. The line intensities of the Fe3+-subspectra show a temperature dependent anomalous population of the three Kramers doublets of the Fe3+ spinS=5/2 ground state. A relaxation broadening is observed at higher temperatures, which cannot successfully be reproduced within a relaxation model taking into account only the six lowest lying electronic states.

Non-equilibrum population of the Fe3+ electronic states after the electron capture in57Co: LiTaO3

Mossbauer emission spectra of57Co: LiTaO3 show as a consequence of the nuclear decay anomalous emission line intensities in the subspectra of Fe2+ and Fe3+. Magnetic field and angle dependence of Fe3+ intensities can be explained by taking into account polarization-and crystal-field effects in the excited states. The experimental results for LiTaO3 are in good agreement with theory and previous measurements on LiNbO3.

Anomalous positrons from heavy ion collisions: Past results and future plans

The current status of the experimental study of anomalous lines observed in the spectra of positrons produced in heavy ion collisions is reviewed. A new experiment to measure positron-electron coincidences is discussed.

Trace lead composition of sulfides from mineralizations in the Proterozoic Råppe supracrustal belt, northern Sweden

Abstract At Rappe (30 km NW of Kiruna), basic to intermediate volcanites, volcanogenic sediments, and schists with intercalated carbonates form a supracrustal belt which encloses minor Cu-Fe and Zn-Pb impregnations. In addition, Zn-Pb mineralizations occur in discordant veins. The trace lead compositions from pyrrhotites and sphalerite from these mineralizations define an anomalous lead line, which is interpreted as a mixing line. The mixing, which is associated with the remobilization of the Zn-Pb mineralizations, probably occurred in connection with the Caledonian orogeny. The added radiogenic lead was leached locally from the surrounding upper crustal rocks and has, therefore, locally varying isotopic composition, as illustrated by the differences in lead composition from mineralizations in the Viscaria, Pahtohavare, and Rappe supracrustal belts. Althought the primary Rappe lead composition is not known, the Rappe lead had a different initial composition than the lead from other small greenstone belts ...

Spectroscopic studies of Wolf-Rayet stars. IV - Optical spectrophotometry of the emission lines in galactic and large Magellanic Cloud stars

view Abstract Citations (178) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopic Studies of Wolf-Rayet Stars. IV. Optical Spectrophotometry of the Emission Lines in Galactic and Large Magellanic Cloud Stars Conti, Peter S. ; Massey, Philip Abstract We present spectrophotometry of the leading emission-line features for nearly all the Wolf-Rayet stars in the Galaxy and in the Large Magellanic Cloud (LMC). These form the empirical basis of the normal relationships among the various lines. Emission lines have a wide range of strengths, but all lines in a given star are strong or weak together, aside from the well-understood ionization effects. We present the first extensive data of the N IV λ3480 feature in WN stars. This line persists to earlier types than does the singlet N IV λ4057 line, probably due to decreasing optical depth in the latter transition. Among those very few WN stars with anomalous lines, there are eight objects, mostly single stars, with inordinately strong C IV; we label them "WN/WC" and suggest that they have a "transition" composition between the WN and WC subclasses. We give quantitative descriptions of "early" (WNE; WCE) and "late" (WNL; WCL) types for the WN and WC classes, respectively. Among WC stars, the persistence of the C III λ4650 feature to the earliest subtypes (where C III λ5696 has already disappeared) suggests the importance of the contribution of C IV λ4658 to the blend, or an anomalous triplet-singlet behavior in the C III ions similar to that observed in N IV in the WN sequence. We compare the emission-line fluxes of He II λ4686 with the M_v_ for the WN stars of the LMC. Aside from the ionization effects, there is a nice correlation of these parameters since brighter stars have more continuum flux present at 4686 A. Although WCL stars have not been found in the LMC, the line strengths of the other W-R stars are very similar in that system and in our own Galaxy. Publication: The Astrophysical Journal Pub Date: February 1989 DOI: 10.1086/167101 Bibcode: 1989ApJ...337..251C Keywords: Emission Spectra; Magellanic Clouds; Optical Emission Spectroscopy; Stellar Spectrophotometry; Wolf-Rayet Stars; Abundance; Helium; Line Spectra; Statistics; Tables (Data); Astrophysics; GALAXIES: MAGELLANIC CLOUDS; SPECTROPHOTOMETRY; STARS: STELLAR STATISTICS; STARS: WOLF-RAYET full text sources ADS | data products SIMBAD (148) Related Materials (5) Part 1: 1983ApJ...268..228C Part 2: 1984ApJ...280..181T Part 3: 1986ApJ...300..379T Part 5: 1989ApJ...341..113C Part 6: 1990ApJ...354..359C

Spin dynamics in undoped trans-(CH) x

Dynamics of neutral soliton (domain wall) of undoped trans-polyacetylene t-(CH) x has been studied by analyzing ESR line width as a function of frequency from 3 to 500 MHz at temperatures from 10 to 300 K. Comparing the result analyzed at f>6 MHz with that of t-(CD) x, it was concluded that the spin dynamics both in t-(CH) x and t-(CD) x are almost the same as each other; the diffusion rate along the chain D // is 5 × 10 13 rad/sec, which is consistent with that of NMR T 1, and varies approximately as T 2 between 10 and 300 K. An anomalous line broadening of ESR at frequencies lower than 6 MHz was found at all the temperatures studied. This can be attributed to a non-secular broadening of the width by soliton trapping. This gives the soliton spin density ϱ ≈ 0.1 at the center of neutral soliton.

Sample-dependent resolution in scanning tunneling microscopy.

In any microscopy or spectroscopy, quantitative analysis of data requires some knowledge of the instrumental resolution function. Analysis in fact often involves image deconvolution, at least implicitly. However, for scanning tunneling microscopy (STM), the very definition of resolution becomes problematic and has until now been addressed only for metals, the simplest case. Here a natural general expression for the resolution of STM is developed. This definition gives a resolution function which may be strongly sample dependent in the case of semiconductors or semimetals, and which has an anomalous line shape and linewidth in certain cases. Thus image deconvolution is not generally possible, even in principle, without an understanding of the sample electronic structure.

Random electron paramagnetic resonance sampling of the modulated structure in incommensurate phases of betaine calcium chloride dihydrate

The successive phase transitions in betaine calcium chloride dihydrate crystals were investigated in the range between 300 and 100 K with VO2+ and Mn2+ electron paramagnetic resonance (EPR) probes substituted for Ca2+ ions in the lattice. Preceded by B2u soft phonons in the normal phase, these transitions are continuous, and found to consist of stepwise changes of a collective librational fluctuation of the Ca–betaine complexes. Below the normal-to-incommensurate transition at 164 K, the fluctuation became slower than the EPR frequencies so that the spectra exhibited anomalous line shapes resulting from random sampling of the modulated structure. In addition, such anomalies as observed at 9.2 and 36 GHz indicated clear evidence for time-dependent lattice modulation in these phases. Sampling results by VO2+ and Mn2+ probes yielded complementary information about the modulated structure, which were interpreted by the plane-wave approximation of the anharmonic librational mode.

Anomalous line shapes in delayed optical–optical double resonance studies of N2

Anomalous dips are observed in time-delayed, ionization-detected optical–optical double resonance (OODR) experiments on molecular nitrogen. These dips arise from the competition between radiative decay and photoionization of the upper level of the probe transition, and are therefore of considerable potential importance in the application of ionization-detected OODR to molecules.

High Resolution Neutron Powder Diffraction Studies of the Ferroelastic Phase Transition in LaNbO4

ABSTRACTAnalysis of high resolution neutron powder diffraction data of ferroelastic LaNbO4 indicates a monoclinic to tetragonal structural phase transition that is accompanied by anomalous line broadening. The origins of this line broadening have been investigated using a novel modification of the Rietveld technique. The results show that strain broadening is associated with the ferroelastic phase transition both above and below the transition temperature. This anomalous ‘microstrain’ is well-described by a second rank strain tensor, the principal axes of which are collinear with the spontaneous lattice strain. This phenomenon may be a general feature of proper ferroelastic phase transitions.

Intensity anomaly in the A2?+?X2? resonant-(2+2) multiphoton ionization spectra of NO

The two-photon resonant four-photon ionization spectra of NO via A2∑+←X2∏ (v=0,1) states have been measured. Some intensity-anomalous lines have been found. Based on the signal-power dependence measurement for the normal and anomalous lines, a double resonance and collision ionization model is suggested to elucidate the intensity anomaly.

Continuous-wave NMR in spin-polarized atomic hydrogen.

Simultaneous continuous-wave NMR and total-pressure measurements on spin-polarized atomic hydrogen gas in a 5-T magnetic field are reported. During sample loading we observe positive nuclear polarization. The rf susceptibility of the decaying sample is nonlinearly related to the density. This and the anomalous NMR line shape are discussed in light of the identical spin-rotation effect and the hydrodynamic spin-wave model. The analysis of the time evolution of the NMR signal area and of the pressure gives the two-body exchange recombination-rate coefficients ${K}_{\mathrm{aa}}$=1.8\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}19}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ and ${K}_{\mathrm{ab}}$=1.6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}19}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, and the one-body relaxation rate ${G}_{1}$=1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ in the absence of rf field, at T=370 mK.

Anomalous X‐ray Line Broadening Observed in γ‐Fe2O3 Derived from γ‐FeOOH

Defect structure of fine‐grained γ‐Fe2O3 powder obtained by dehydroxylation of y‐FeOOH powder has been studied by X‐ray diffraction and high‐resolution electron micrographs. An anomalous X‐ray line broadening was observed in the γ‐Fe2O3 powder. It is found that the X‐ray line breadth is dependent on the crystal structure factors of each reflection line: the reflections from net planes consisting of only metal ions on tetrahedral sites and octahedral sites of spinel structure are much broader than those from net planes including oxygen ions. The anomalous X‐ray line broadening is explained on the basis of stacking faults in the spinel structure.

Magnon sideband in the one-dimensional antiferromagnet CsCoCl 3 · 2H 2O under magnetic field — I.

The anomalous line shape with a double peak was observed for the magnon sideband in CsCoCl 3 · 2 H 2 O under a magnetic field parallel to the a-axis. This anomalous line shape can be qualitatively explained by a calculation considering an increase of the intrachain exciton transfer.

EXCITON AND MAGNON SIDEBAND IN THE ONE-DIMENSIONAL ANTIFERROMAGNET CsCoCl3⋅2H2O UNDER HIGH MAGNETIC FIELD

The absorption spectra corresponding to the transition 4T1 (4F)→2T1(2P) of Co2+ in CSCoCl32H2O were investigated under high magnetic fields up to 230kOe with a hybrid magnet. The anomalous line shapes of the magnon sideband with a double peak were observed under the magnetic fields parallel to the a- and c-axes. The behavior of the magnon sideband under the external magnetic fields is related to the exciton transfer. The intrachain exciton transfer becomes large under the magnetic field that induces the ferromagnetic components of the spins. This change of the exciton dispersion is reflected in the line shape of the magnon sideband. The anomalous behavior of the magnon sideband under the external fields was elucidated by the calculation of the line shape taking into account the field dependence of the exciton transfer.

Human helper-T-cell function does not require T4 antigen expression

The relationship between immunoregulatory T-cell function and the expression of T-cell subset-specific differentiation antigens was examined using a phenotypically anomalous human T-cell line (TCL), termed H-1. H-1 cells were found to express T11, extremely high levels of T3, but no T4 nor T8 antigen. Despite their lack of T4 antigen expression, H-1 cells could be activated by coculture with pokeweed mitogen (PWM), anti-T3 antibody, or autologous B cells to provide potent help for B-cell differentiation into plaque-forming cells (PFC). In contrast, H-1 cells did not suppress the PFC response triggered by PWM-activated T4+ cells. These results demonstrate that the expression of the T-cell subclass-specific differentiation antigen, T4, is not required for a T cell to become activated and to implement the program for helper function. In addition, enhanced expression of T3 on the T4-, T8-, H-1 cell surface may reflect a compensatory upregulation of the T3/Ti receptor complex on T cells which are deficient in these nonpolymorphic associative recognition structures.

Order-disorder dynamics of the ferroelectric phase transition in tris-sarcosine calcium chloride crystals.

Critical anomalies in the ${\mathrm{Mn}}^{2+}$ impurity spectra near the ferroelectric phase transition in tris-sarcosine calcium chloride (TSCC) crystals have been interpreted in terms of a collective fluctuation in the polar pseudospin system representing Ca(sarcosine${)}_{6}$ complexes in the lattice. The anomalous line broadening in the paraelectric phase was found to be closely related to the splitting of the line below the transition temperature ${T}_{c}$. At temperatures close to ${T}_{c}$ in the ferroelectric phase the line shape was asymmetrical, indicating that sinusoidally distributed pseudospins were randomly sampled by ${\mathrm{Mn}}^{2+}$ impurities. The time scale of EPR measurements modified the line shape, where the presence of a slow fluctuation between the pair of lines was evident. Contrary to recent spectroscopic and dielectric results on TSCC crystals, the critical anomalies in the ${\mathrm{Mn}}^{2+}$ spectra were well resolved to give grounds for the order-disorder dynamics of the transition.

Coherence effects in laser-rf double resonance.

An ``amplitude model'' of the laser-rf double-resonance process has been quantitatively verified, providing a complete explanation of the anomalous line shapes observed in studies of ${\mathrm{Na}}_{2}$ hyperfine structure. We find excellent agreement with new laser-rf double-resonance measurements in low-J'' rotational levels of the ${X}^{1}$${\ensuremath{\Sigma}}_{g}^{+}$(v''=0) ground state of ${\mathrm{Na}}_{2}$ as well as with earlier data for J''=28. These results confirm the idea that absorption and stimulated-emission Rabi cycles in the presence of the laser field create coherence between the ground-state hyperfine levels when these levels are optically unresolved. A novel ground-state ``quantum beat'' experiment is proposed.

Mössbauer emission studies of 57Co‐doped ZnO, Cu2O, and TiCoO3

Abstract57Co‐doped Mössbauer oxide sources are prepared at different temperatures and oxidation pressures. The appearance of the 57Fe3+ anomalous charge state is related with the p‐character of semiconductor oxide. Increasing the acceptor concentration increases the anomalous ferric line intensity in the Mössbauer spectra. The two location sites of 57Co in the ZnO matrix correspond to substitutional and grain boundary sites, respectively. The n‐character of ZnO oxide makes possible the appearance of the ferrous state in the corresponding Mössbauer spectra.