Search results for "Voigt profile"
showing 8 items of 8 documents
Microstructural analysis (Voigt function method) of mullite in whiteware triaxial porcelains
2020
Triaxial porcelains were produced of two whiteware blends containing kaolin B (of “high-crystallinity” kaolinite) or halloysitic kaolin M (also with “low-crystallinity” kaolinite) in two different industrial firing cycles (fast or slow) with final temperatures 1270 °C, 1300 °C, 1320 °C and 1340 °C. The crystalline microstructure of mullite in all porcelain samples was studied by X-ray diffraction through analysing 110 and 001 reflections using the Voigt function method and by optical and electron microscopy. Mean crystallite sizes were determined independently for both 110 and 001 diffraction directions as principal semi-quantitative characteristics for all sixteen specimens. They illustrat…
Crystallite size of kaolinites as indicator of different geochemical types of bauxite
2009
A simple microstructural X-ray diffraction analysis using the Voigt function method reveals differences between bauxite deposits in the Iberian Range Catalanides area (NE, Spain). The highest values of apparent crystallite sizes, measured by volume weighted Dv values from 001 kaolinite reflection, have been found in bauxites of type 1.
Protein dynamics: conformational disorder, vibrational coupling and anharmonicity in deoxy-hemoglobin and myoglobin.
1993
In this work we study the temperature dependence of the Soret band lineshape of deoxymyoglobin and deoxyhemoglobin, in the range 300-20 K. To fit the measured spectra we use an approach originally proposed by Champion and coworkers (Srajer et al. 1986; Srajer and Champion 1991). The band profile is modelled as a Voigt function that accounts for the coupling with low frequency vibrational modes, whereas the coupling with high frequency modes is responsible for the vibronic structure of the spectra. Moreover, owing to the position of the iron atom out of the mean heme plane, inhomogeneous broadening brings about a non-Gaussian distribution of 0-0 electronic transition frequencies. The reporte…
Dynamic properties of some β-chain mutant hemoglobins
1995
The thermal behavior of the Soret band relative to the carbonmonoxy derivatives of some beta-chain mutant hemoglobins is studied in the temperature range 300-10 K and compared to that of wild-type carbonmonoxy hemoglobin. The band profile at various temperatures is modeled as a Voigt function that accounts for homogeneous broadening and for the coupling with high- and low-frequency vibrational modes, while inhomogeneous broadening is taken into account with a gaussian distribution of purely electronic transition frequencies. The various contributions to the over-all bandwidth are singled out with this analysis and their temperature dependence, in turn, gives information on structural and dy…
Structure-dynamics-function relationships in Asian elephant (Elephas maximus) myoglobin. An optical spectroscopy and flash photolysis study on functi…
1993
In this work we report the thermal behavior (10–300 K) of the Soret band lineshape of deoxy and carbonmonoxy derivatives of Asian elephant (Elephas maximus) and horse myoglobins together with their carbon monoxide recombination kinetics after flash photolysis; the results are compared to analogous data relative to sperm whale myoglobin. The Soret band profile is modeled as a Voigt function that accounts for the coupling with high and low frequency vibrational modes, while inhomogeneous broadening is taken into account with suitable distributions of purely electronic transition frequencies. This analysis makes it possible to isolate the various contributions to the overall lineshape that; in…
Analytical model of transit time broadening for two-photon excitation in a three-level ladder and its experimental validation
2012
We revisit transit time broadening for one of the typical experiment designs in molecular spectroscopy, that of a collimated supersonic beam of particles crossing a focused Gaussian laser beam. In particular, we consider a Doppler-free arrangement of a collimated supersonic beam of Na${}_{2}$ molecules crossing two counterpropagating laser beams that excite a two-photon transition in a three-level ladder scheme. We propose an analytical two-level model with a virtual intermediate level to show that the excitation line shape is described by a Voigt profile and provide the validity range of this model with respect to significant experimental parameters. The model also shows that line broadeni…
Tests of atomic charge-exchange cells for collinear laser spectroscopy
2012
Abstract The performance characteristics of two charge-exchange cells (CECs) with horizontal and vertical cell configurations were determined by neutralizing a 10-keV rubidium ion beam in a potassium vapor. The neutralization efficiency and the fluorescence line shape of the 5s 2 S 1 / 2 ↔ 5 p 2P3/2 (D2) transition in neutral 85Rb were investigated as a function of the reservoir temperature used to control the potassium vapor density. The CECs exhibited similar neutralization performance and at neutralization efficiencies greater than 25–50% an asymmetric line shape of the rubidium D2 fluorescent signal was observed. The asymmetry was attributed to inelastic channels in the charge-exchange …
A new FESEM procedure for assessment of XRD microstructural data of kaolinites
2007
Abstract A sample preparation method for FESEM microstructural analysis of sheet silicates using oriented aggregates on metallic strips parallel to the electronic beam is described. The method allows the easy measurement of thickness of kaolinite crystallites. The results have been compared to the apparent crystallite size measured by XRD The performed measurements for a set of selected kaolinites are in the range 15–60 nm and show a good correlation with XRD crystallite thickness (in the range 11–48 nm) obtained by the Voigt function method.