Search results for "absorption."
showing 10 items of 2682 documents
Integrated InGaAlAs/InP laser-modulator using an identical multiple quantum well active layer
2005
We present experimental results on 40 Gb/s large-signal modulation performance of 1.31 μm monolithic integrated laser-modulator in the InGaAlAs/InP material system, exploiting the gain and absorption properties of an identical multiple quantum well (MQW) active layer. In continuous wave operation, at 15◦ C, the devices achieved threshold currents < 28 mA, fiber coupled optical power levels up to +0.4 dBm. The measured small signal modulation bandwidth was about 32 GHz. An air-cavity based Fabry-Perot interferometer has been realized to characterize the spectral chirp of the integrated structures in the time domain up to 40 Gb/s.
The elastic scattering of 25MeV α-particles and neutron shell effects in the A = 50 TO A = 93 mass region
1982
Abstract Experimental elastic scattering angular distributions of 25 MeV α-particles scattered from 28 nuclei ranging from 50Cr to 93Nb have been measured and then analysed in terms of a regular optical model with standard Woods-Saxon geometries for both the real and imaginary potentials. The experimental distributions are well fitted over the whole angular range from 5° to 175° c.m. by the predictions, provided that a smaller than normal diffuseness is used for the imaginary potentials. The usual families of potentials with volume integrals differing by approximately 100 MeV · fm3 are found. The family with volume integral ranging from 540 to 420 MeV· fm3 over the nuclei studied has been c…
On the soft excess in the x-ray spectrum of circinus X-1: Revisitation of the distance to circinus X-1
2005
We report on a 300 ks BeppoSAX (0.12-200 keV) observation of Circinus X-1 (Cir X-1) at phases between 0.62 and 0.84 and on a 90 ks BeppoSAX observation of Cir X-1 at phases 0.11-0.16. Using the canonical model adopted until now to fit the energy spectrum of this source, large residuals appear below 1 keV. These are well fitted using an equivalent hydrogen column of 0.66¿1022 cm-2, adding absorption edges of O VII, O VIII, and Ne IX in the spectra extracted from the observation at phases 0.62-0.84 and adding absorption edges of O VII, O VIII, Mg XI, and Mg XII and absorption lines of O VIII and Mg XII in the spectra extracted from the observation at phases 0.11-0.16. During the observation a…
A Hard Tail in the Broad Band Spectrum of the Dipper XB 1254-690
2001
We report on the results of spectral analysis of the dipping source XB 1254-690 observed by the BeppoSAX satellite. We find that the X-ray dips are not present during the BeppoSAX observation, in line with recent RXTE results. The broad band (0.1-100 keV) energy spectrum is well fitted by a three-component model consisting of a multicolor disk blackbody with an inner disk temperature of ~0.85 keV, a comptonized spectrum with an electron temperature of ~2 keV, and a bremsstrahlung at a temperature of ~20 keV. Adopting a distance of 10 kpc and taking into account a spectral hardening factor of ~1.7 (because of electron scattering which modifies the blackbody spectrum emitted by the disk) we e…
Phototransition of Na(3p3/2) into high Rydberg states and the ionization continuum
2005
A model potential method is used to investigate photoabsorption from the Na(3p3/2) state. Absorption cross sections into higher Rydberg states and photoionization cross sections are presented as an analytical function of photo electron energy. Einstein coefficients for spontaneous emissions 3p3/2 ← ns1/2, nd5/2, nd3/2 are tabulated for n up to 50. The Einstein coefficients and low-energy ionization cross sections are believed to be accurate to better than 2–3%, above 1 eV the error may increase to 4–6%.
MultiChannel Multiple Scattering Theory for XAFS. Application to L2,3 Edges of Ca
2005
We present a multichannel extension of the multiple scattering method for x-ray absorption fine structure (XAFS) spectroscopy that allows to take account of atomic multiplet-like electron correlation effects in condensed systems, on the basis of ab initio electron structure calculations. The formalism is outlined and an application to near-edge XAFS at the L2,3 edges of Ca metal is presented. In this system, the experimentally observed branching ratio deviates strongly from that obtained from the standard (one-electron) approach to XAFS. This is due to that fact that one-electron theory neglects the multiplet coupling between the photo-electron and the 2p core-hole. Within the multi-channel…
Interpretation of unexpected behavior of infrared absorption spectra ofScF3beyond the quasiharmonic approximation
2016
Scandium fluoride (${\mathrm{ScF}}_{3}$), having cubic ${\mathrm{ReO}}_{3}$-type structure, has attracted much scientific attention due to its rather strong negative thermal expansion (NTE) in the broad temperature range from 10 to 1100 K. Here we use the results of diffraction and extended x-ray absorption fine-structure (EXAFS) spectroscopy to interpret the influence of NTE on the temperature dependence of infrared absorption spectra of ${\mathrm{ScF}}_{3}$. Original infrared absorption and EXAFS experiments in a large temperature range are presented and interpreted using ab initio lattice dynamics simulations within and beyond quasiharmonic approximations. We demonstrate that ab initio e…
Resonant scattering in macromolecular structure research. Applications in molecular biology and material science
1983
Abstract This report concerns the X-ray resonance scattering work carried out using the instrument X15 which receives synchrotron radiation from the storage ring DORIS. X15 covers a wavelength range from 0.6 to 3.3 A. It therefore accesses resonance scattering at the K-absorption edges of the elements with Z = 20 (Ca) to Z = 42 (Mo) and at the L 3 -absorption edges from Z = 50 (Sn) to all heavier atoms. The instrument consists of a double monochromator with a vertical offset of the beam by 1.22 m and a camera of 10 m length. A multiwire proportional chamber (from A. Gabriel) at the end of the evacuated beam line detects the scattered X-ray photons on its area 200 mm × 200 mm. The distances …
Intensity Invariance of Strong-Field Two-Photon Absorption
2010
We demonstrate experimentally and theoretically the intensity-invariant scaling formula of coherent control of two-photon absorption as a function of pulse-shape parameters of ultrafast laser field in the strong-interaction regime.
Total absorption spectroscopy study of the β decay of Br86 and Rb91
2017
The beta decays of 86Br and 91Rb have been studied using the total absorption spectroscopy technique. The radioactive nuclei were produced at the IGISOL facility in Jyvaskyla and further purified using the JYFLTRAP. 86Br and 91Rb are considered high priority contributors to the decay heat in reactors. In addition 91Rb was used as a normalization point in direct measurements of mean gamma energies released in the beta decay of fission products by Rudstam et al. assuming that this decay was well known from high-resolution measurements. Our results shows that both decays were suffering from the Pandemonium effect and that the results of Rudstam et al. should be renormalized.