Search results for "Molar absorptivity"
showing 10 items of 33 documents
Determination of an empirical law of aluminium and magnesium alloys absorption coefficient during Nd :YAG laser interaction
2007
International audience; Welding laser modelling requires knowledge about relative changes of many thermo-physical parameters involved in the interaction. The absorptivity of the material is one of the most important. In this study, experimental measurements of absorptivity with an integrating sphere on two alloys (aluminium and magnesium) were made. These results were compared with an analytical calculation that takes into account the trapping of the beam by multiple reflections inside the keyhole. Based on a statistical method, an empirical law is proposed connecting absorptivity with the peak power of the laser and the duration of interaction. During the interaction, two distinct phenomen…
Refractive index controlled by film morphology and free carrier density in undoped ZnO through sol-pH variation
2018
Abstract Zinc oxide thin films, prepared by the sol-gel process, were deposited on glass substrate using spin coating technique. The sol-pH effect on the optical parameters was studied for alkaline sol. The surface roughness was investigated by atomic force microscopy (AFM) and varied from 20 to 40 nm. The optical transmission measurements were carried out to evaluate the behavior of the extinction coefficient and the refractive index. An exponential decay of the refractive index ‘n’ as a function of wavelength was observed. The refractive index increases slightly when the pH increases to pH = 9.5 where it reaches its maximum. Beyond this value, it decreases sharply. This behavior has been …
Identification and characterization of aging products in the glyoxal/ammonium sulfate system – implications for light-absorbing material in atmospher…
2012
Abstract. In this study we report the identification of bicyclic imidazoles in aqueous aerosol mimics using HPLC-ESI-MS/MS. 2,2´-Biimidazole was identified to be a major contributor to the 280 nm absorbance band observed in mixtures of glyoxal and ammonium sulfate, despite the fact that its production rate is two orders of magnitude lower than the previously reported production rates of imidazole or imidazole-2-carboxaldehyde. The molar absorptivity of 2,2´-biimidazole was determined to be (36 690±998) M−1 cm−1. This demonstrates the necessity of molecular product identification at trace levels to enable a better understanding of relevant absorbing species. Additionally the forma…
Systematic Study of Several Causes and Effects Due to Absorbent Blanks in Determinations of One Analyte
1999
A systematic study is performed about several factors involved in the measurements when a absorbent blank is used, as molar absorption coefficient of the formed complex, absorbance of the blank at the measured wavelength, and kind of spectrophotometer used (conventional double-beam or diode-array). It is proved that the usual methodology, measuring against reagent blank, produces less accurate measurements than those obtained against solvent blank. On the other hand, use of the H-Point standard additions method provides always equal or better results than the best ones obtained at single wavelengths by using measurements against solvent bank, at the maximum of the formed complex. To test th…
Polypyrrole films functionalized with pendant titanocene dichloride complexes: Ellipsometric study of the electropolymerization process
2007
Electrochemical and ellipsometric methods have been used to study the electropolymerization process of a functionalized monomer, Tc3Py (in which pyrrole is covalently bonded with titanocene dichloride complex) on platinum electrode from a dilute monomer solution in acetonitrile. The deposition has been performed in the potentiodynamic regime. A new method for the acquisition and treatment of ellipsometric data has been proposed which allowed us to analyze the evolution of the film properties at each potential. The model of a single uniform layer was unable to describe the ellipsometric experimental observations with the necessary precision. A proper fitting of the data has been achieved con…
Synthesis and photovoltaic performance of dihydrodibenzoazepine-based sensitizers with additional lateral anchor
2013
Three novel metal-free organic dyes with dihydro-5H-dibenzo[b,f]azepine as a donor and cyanoacrylic acid as an anchoring unit were designed as an innovative linear skeleton of D-D-pi-A type of organic dyes. The conversion efficiency of the derived dye-sensitized solar cells is moderate. Among them, the dye with a hydroxy group as an additional anchoring moiety exhibited the highest UV-Vis absorption with a maximum molar extinction coefficient of 24,136 M-1 cm(-1) at lambda(max) = 458 nm and the best photovoltaic performance with an overall power conversion efficiency of 4.88%, while the dye with a carboxy group as an additional anchoring moiety exhibited the lowest conversion efficiency (4.…
Comparison of aerosol size distributions measured at ground level and calculated from inversion of solar radiances
2005
Ground-based sunphotometry measurements can be used to investigate atmospheric aerosol optical properties, such as the volume size distribution, an important parameter in the study of the effect of aerosol on atmospheric processes. Most inversion algorithms assume constant aerosol optical characteristics over the whole air column. In this work we present observational evidence of the limitations of this simplifying assumption in cases where the aerosol vertical structure is highly inhomogeneous. During the field campaign VELETA 2002, carried out in Granada (Spain), a quite complete characterization of the atmospheric aerosol was obtained by simultaneously measuring the columnar aerosol char…
Vis/NIR spectroelectrochemical analysis of poly-(Azure A) on ITO electrode
2006
Electrochromic behavior of poly-(Azure A) on indium–tin oxide electrode is analyzed in an aqueous potassium nitrate solution. The dependence of the absorbance on the applied potential during cyclic voltammograms proves very interesting at two selected characteristic wavelengths: at 925 nm, attributed to an intermediate species and another at 735 nm, attributed to the oxidized form of the polymer. Molar absorptivity coefficients for both species have been calculated from the relationship between current and the derivative of absorbance with respect to time. Voltammograms of formation of the intermediate are simulated from spectroelectrochemical results. Keywords: Poly-(Azure A), Spectroelect…
The use of utraviolet-visible spectrophotometry in the determination of average properties of nonylphenol ethylene oxide condensates
1983
Ultraviolet spectrophotometry is usd in the determination of average molecular weight (M), average degree of polymerization (X), the hydrophilic-lipophilic balance (HLB) and ethylene oxide percentage of nonylphenol ethylene oxide condensates. The method is based on determination of the absorptivity a, expressed in g lt-1 cm−1, from the absorbances measured at 275 nm for a series of dilutions of an aqeuous ethanolic solution (60:40, v/v/) of a given product, followed by numerical interpolation of this value in the expression a = f(HLB), log a = f(log M), and log a = f(log X). These expressions are obtained from reference samples or samples previously analyzed. The proposed method gives relat…
Measurement report: Balloon-borne in situ profiling of Saharan dust over Cyprus with the UCASS optical particle counter
2021
This paper presents measurements of mineral dust concentration in the diameter range from 0.4 to 14.0 µm with a novel balloon-borne optical particle counter, the Universal Cloud and Aerosol Sounding System (UCASS). The balloon launches were coordinated with ground-based active and passive remote-sensing observations and airborne in situ measurements with a research aircraft during a Saharan dust outbreak over Cyprus from 20 to 23 April 2017. The aerosol optical depth at 500 nm reached values up to 0.5 during that event over Cyprus, and particle number concentrations were as high as 50 cm−3 for the diameter range between 0.8 and 13.9 µm. Comparisons of the total particle number concentration…