Spectral shifts produced by scattering of Rectangular Gaussian Schell Model sources from a deterministic medium

Within the accuracy of the first-order Born approximation, we investigate the scattering of Rectangular Gaussian Schell Model (RGSM) sources incident upon a deterministic medium. The analytical expression for the far-zone scattered spectrum is derived. Numerical results show that red shift or blue shift can be produced in the far-zone scattered spectrum, and the spectral shifts are mainly influenced by the scattering direction and the source parameters (i.e., the source width and the source correlation widths along the x and y directions).     

Multispectrum analysis of CH4 in the ν4 spectral region: II. Self-broadened half widths, pressure-induced shifts, temperature dependences and line mixing

Accurate values for line positions, absolute line intensities, self-broadened half width and self-pressure-induced shift coefficients have been measured for over 400 allowed and forbidden transitions in the ν₄ band of methane (¹²CH₄). Temperature dependences of half width and pressure-induced shift coefficients were also determined for many of these transitions. The spectra used in this study were recorded at temperatures between 210 and 314 K using the National Solar Observatory's 1 m Fourier transform spectrometer at the McMath-Pierce solar telescope. The complete data set included 60 high-resolution (0.006-0.01 cm⁻¹) absorption spectra of pure methane and methane mixed with dry air. The analysis was performed using a multispectrum nonlinear least squares curve fitting technique where a number of spectra (20 or more) were fit simultaneously in spectral intervals 5-15 cm⁻¹ wide. In addition to the line broadening and shift parameters, line mixing coefficients (using the off-diagonal relaxation matrix element formalism) were determined for more than 50 A-, E-, and F-species transition pairs in J manifolds of the P- and R-branches. The measured self-broadened half width and self-shift coefficients, their temperature dependences and the line mixing parameters are compared to self-broadening results available in the literature and to air-broadened parameters determined for these transitions from the same set of spectra.     

Etude spectroscopique d'un jet de plasma d'argon hors d'equilibre thermodynamique local

We have studied the properties of an argon plasmajet seeded with a few percent of hydrogen. At atmospheric pressure, significant deviations from local thermodynamic equilibrium (L.T.E.) are shown. The plasma parameters (electrondensity N_e, temperature T) have been determined from the broadening and the absolute intensity of hydrogen lines. The transition probabilities and the broadening parameters (width and shift) of some AI lines between 4000 and 6000 Å have been measured.     

Valence inhomogeneities in intermediate-valent Eu compounds

In each of the intermediate valent compounds EuNi₂P₂, EuPd₂Si₂, and EuPd₆B₄, the line width of the ¹⁵¹Eu-Mössbauer resonance attains a maximum when its isomer shift varies most strongly with temperature. We associate this anomalous line broadening with a distribution of the local Eu valence, which may be described by an inhomogeneous width, Δ, of the interconfigurational excitation energy, E_exc, in addition to the homogeneous fluctuation width, k_BT_f. Applying this model to the analysis of isomer shift, line width, and magnetic susceptibility, the model parameters Δ, E_exc, and k_BT_f are obtained. Δ is found to attain maximal values at temperatures where E_exc varies most steeply with temperature.     

A multispectrum analysis of the ν4 band of CH4: Widths, shifts, and line mixing coefficients

Line positions, Lorentz air-broadened half width and air pressure-induced shift coefficients have been measured for nearly 200 transitions in the ν₄ band of ¹³CH₄ from high-resolution spectra recorded with the McMath-Pierce Fourier transform spectrometer. Three room temperature spectra of ¹³CH₄ used in the previous study of Malathy Devi et al. (Air-broadened Lorentz halfwidths and pressure-induced line shifts in the ν₄ band of ¹³CH₄. Appl. Opt. 1988; 27: 2296-2308) were analyzed together with a large number of additional spectra of self- and air-broadened CH₄ recorded at 210-314 K and one room-temperature spectrum of self-broadened ¹³CH₄. Analyses applying the multispectrum nonlinear least squares fitting technique were performed to retrieve the spectral line parameters. In addition to air-broadened half width and shift coefficients, self-broadened half width and shift coefficients were determined for at least 56 ¹³CH₄ ν₄ transitions. Off-diagonal relaxation matrix element coefficients for air-broadened line mixing were also determined for 28 pairs of P and R transitions in a number of J manifolds, and mixing parameters for self-broadening were also determined for some of these pairs. Temperature-dependences of the pressure-induced shift and mixing parameters for the ¹³CH₄ lines could not be determined from the spectra used in the present analysis, but temperature dependences of the half width coefficients were determined for the strongest transitions. The results of this study are compared with other studies of air- and self-broadened ¹³CH₄ and ¹²CH₄.     

Measurement of the strong interaction parameters in antiprotonic deuterium

Antiprotonic deuterium K_α X-rays were seen for the first time. Their analysis resulted in spin-averaged 1s strong interaction parameters, namely −1050±250 eV (repulsive) for the 1s shift and 1100±750 eV for the 1s width. The large errors are mainly due to low statistics. In addition, values for the K_α/L_α and L_total/L_α yields at low pressure (20 mbar) were obtained: 0.005±0.003 and 1.34±0.05. Furthermore, a 2p mean absorption width of 80 ≤Γ_2p≤ 350 meV was deduced. The results for the 1s ground state are somewhat surprising, especially the narrow 1s width which is similar to the spin-averaged antiprotonic hydrogen 1s width. However, our 1s width is in agreement with low-energy scattering data [A. Zenoni et al., Phys. Lett. B 461 (1999) 413] (see preceding paper).     

Investigations of the pion-nucleus optical potential from pionic atoms

The explicit dependence of the zero-energy π^?-nucleus optical potential on its various parameters, as well as its implicit dependence on neutron radii, is investigated for a selected set of particularly accurate level shift and width data. Among the various effects studied are some possible variations in the form of the Lorentz-Lorenz term, terms induced by the so-called “angle-transformation”, and the smearing of the π 2N terms which allows for a finite range in the absorption process. The pionic atom data are equally well fitted by any of the several forms used for the optical potential, with the persistent failure to fit the recently reported widths of 3d levels in ¹⁸¹Ta, Re and ²⁰⁹Bi and the width of the 1s level in ²³Na.     

Magnetic phase transitions in Fe80-xNixCr20 (14 ⩽ x ⩽ 30) alloy studied by using 57Fe Mössbauer spectroscopy

This paper reports ⁵⁷Fe Mössbauer spectroscopic studies of the polycrystalline samples of the substitutionally disordered, isostructural (fcc), ternary alloy system Fe_80-xNi_xCr₂₀ for x = 30, 26, 19 and 14 in the temperature range of 10–295 K. The data have been analyzed in terms of the magnetic phase transitions occurring in these alloys by examining the temperature dependence of the various Mössbauer parameters like line‐width, center shift, resonance area, distribution of hyperfine field, P(H), and the average hyperfine field 〈H〉. An estimate of the magnetic transition temperature T _C is made for the alloys with x = 30 and 26 and these results are compared with those previously obtained by magnetic measurements and neutron diffraction experiments. The data for the second order Doppler shift have been analyzed to estimate the Debye temperature ΘD for alloys with x = 30 and 26.     

狭缝微等离子体的光谱线形研究

在狭缝微等离子体中,研究了Ar Ⅰ(2P2→1S5)光谱线的展宽和频移随放电参数的变化.为了测量谱线频移,采用低气压(10 Pa左右)氩气放电发射的Ar Ⅰ光谱线作为参考线.实验在氩气含量为99.92%的氩气/空气放电中,测量了气压从1×104Pa增大到6×104 Pa时Ar Ⅰ谱线的频移和展宽.结果表明随着气压的升高...     

Investigation of the sensitivity of H-shaped nano-grating surface plasmon resonance biosensors using rigorous coupled wave analysis

The sensitivity of an angle-resolved surface plasmon resonance biosensor is not only determined by the shift of the resonance angle, but also the width of the SPR curves and reflective amplitude. The three factors should be considered simultaneously in designing a SPR biosensor. In this study, a H-shaped nano-grating-based SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA). Electric field distribution around the nano-grating are also given out to directly explain the performance difference for various structural parameters. Larger resonance angle shift, reflectance amplitude and sharper SPR curves’ width are obtained simultaneously under optimized structural parameters. Our study is usefully for understanding of the enhancement mechanism of the nano-grating SPR biosensor and also provides instructions for fabricating highly sensitive SPR biosensors. PACS 42.79.Dj; 42.81.Gs; 73.20.Mf; 07.07.Df     

Partially coherent Airy beam and its propagation in turbulent media

The properties of partially coherent Airy beam propagating in turbulent media are investigated. Firstly the variations in the intensity profile and the location of the Airy beam peak with respect to dislocation and width parameters are examined. On the source plane, it is shown that there is a threshold value of the dislocation parameter which determines whether the beam peak will lie on the negative or positive side of the axis. The changes in source beam power and source beam size with respect to dislocation and width parameters are also examined. Then analysis is made for partially coherent Airy beam propagating in turbulence against variations in propagation distance, dislocation and width parameters, structure constant and partial coherence. It is found that the peak of the Airy beam will always shift to the right for increasing propagation distance. But this shift will become less as the dislocation and width parameters are increased. Finally it is shown that higher levels of turbulence and partial coherence will lead to more spreading and shift the beam peak more toward the on-axis position.     

Broadening and shift of neutral chromium absorption lines by various perturbing gases

The broadening and shift of the absorption lines (a⁷S-z⁷P°, a⁷S-y⁷P° and a⁵S-z⁵P°) of the neutral chromium atom were observed at various temperatures (1500–1800 K) and densities (0.24-3.2x 10¹⁹/cm³) of foreign perturbers (He, Ar, N₂, H₂). The dependence of width and shift on temperature and density was studied. The collisional broadening and shift rates were determined from the profile measurements. The results are interpreted in terms of the Lindholm-Foley interaction potential between radiating atom and perturbers. Semi-quantitative agreement of theory and experiment was found in some cases for the temperature dependence of width and shift and for the differences of attractive constants ΔC₆ between upper and lower states of chromium lines.     

Goos–Hänchen shifts of a light beam reflected from the interface of colloidal ferrofluids

Controllable Goos–Hänchen shift of a light beam reflected from the colloidal ferrofluids is investigated by using the stationary-phase method. It is found that the Goos–Hänchen shift can be easily controlled by the local H_e factor and the volume factor. Using this scheme, the peak value, the peak position and the width of the Goos–Hänchen shift can all be controlled by adjusting the external magnetic field for a fixed configuration, which also provides a possibility for obtaining larger negative Goos–Hänchen shift by changing the external controlling field. Our results have potential applications in optical devices.     

Temperature and magnetic field dependence of the absorption edge and the conduction band width of ferromagnetic semiconductors

We investigate the shift of the absorption edge and the behaviour of the conduction band width of ferromagnetic semiconductors as functions of temperature T and an external field B, respectively. Numerical results are given for EuO and EuS. As a consequence of electron-magnon scattering processes the band width of EuO is enhanced by more than 14% in the temperature region: 40 K…T…80 K. The external field tries to surpress this effect.     

Accurate evaluation of the 1s wave functions of kaonic hydrogen

Kaonic hydrogen is studied with realistic potentials in an accurate numerical approach based on Sturmian functions. It is found that the ground-state wave function of the exotic atom with realistic strong interactions is considerably different from the hydrogen-like ones at small distances. The K ^???p scattering length extracted from the 1s energy shift of the kaonic hydrogen by applying the Deser-Trueman formula is severely inconsistent with the one derived directly by solving the Schödinger equation. We pay special attention to the recent measurement of the energy shift and decay width of the 1s kaonic hydrogen state by the DEAR Collaboration. Our work strongly supports the argument that the DEAR data of the K ^???p scattering length extracted with the Deser-Trueman formula from the measured 1s energy shift and decay width are not accurate, if not to say, unreliable.     

The impact of chirally odd condensates on the rho meson

Based on QCD sum rules we explore the consequences of a scenario for the ρ meson, where the chiral symmetry breaking condensates are set to zero whereas the chirally symmetric condensates remain at their vacuum values. This clean-cut scenario causes a lowering of the ρ spectral moment by about 120 MeV. The complementarity of mass shift and broadening is discussed. A simple parametrization of the ρ spectral function leads to a width of about 280 MeV if no shift of the peak position is assumed.     

Bottlenecking of indirect g shifts of local moments in metals

The indirect g shift in the electron spin resonance of local moments in metals is examined using the Bloch-Hasegawa equations. The g shift is found to have three components. First the usual Hasegawa term that decreases as the bottleneck increases, and second, a temperature dependent indirect shift that is unaffected by the bottleneck. The third term becomes unobservable in the unbottlenecked limit; it is proportional to the ratio of the non S-state local moment susceptibility to the S-state local moment susceptibility. The width of the resonance is found to be proportional to T — θ, where θ is the ordering temperature, and not to temperature T, thereby providing an explanation for the “negative” residual linewidth frequently observed in magnetically concentrated systems.     

Extracting the complex energy of broad resonances by the <Emphasis Type="Italic">S</Emphasis>-matrix pole method

A new method is proposed for finding the resonance parameters of a nuclear system, obtained from the phase shift analysis of elastic scattering data, by means of a pole representation of an S-matrix in complex momentum space is proposed. This method is based on the expansion of the potential phase shift into a Taylor series within the area of real momentum near the resonance pole. The coefficients of the expansion and resonance parameters are determined by fitting the analytical expression for the experimental phase shift. The proposed method provides reliable values of the energy and width of broad resonances.     

New precision measurements of the strong interaction in kaonic hydrogen

The DEAR experiment performed at the DAΦNE electron-positron collider (Frascati, Italy) studied the strong interaction shift and width of the 1s state in kaonic hydrogen using X-ray spectroscopy. The repulsive character of the kaon-proton interaction at threshold was confirmed and the most precise values of the shift and width were obtained. However, high precision data at the percent level are highly requested to further develop the theories and thus our understanding of the low-energy antikaon-nucleon interaction. Therefore, a new series of precision experiments on kaonic hydrogen and kaonic deuterium are planned at LNF.     

Meson pair production in γγ scattering and implications for scalar mesons

We describe a simple analytic unitary model which provides with a parametrization of low energy (from threshold up to 1.4GeV) two photon production of ππ andK \(\bar K\) pairs in term of a few parameters related to the γγ width of the scalar and tensor resonances. It can be useful for analysing data because of the large continuum found in γγπ⁺π^? production besides thef ₀ (1,270) peak in recent experiments. We show that the present data already provides a strong evidence for the existence of a broad low mass scalar state, the old σ or ε (600) with a γγ width of 5 to 9KeV, and that it will be difficult to get more information on the controversialS ^* parameters from ππ pair production only. In thef ₀ range we explain the downwards shift of the π⁺π^? peak but we expect the π⁰π⁰ peak around 1.27–1.29 GeV which could raise the question either of systematic errors in mass calibration of crystal Ball experiment or of the precise value of thef ₀ mass.