Suitable Excitation Wavelength Research Articles

Detection of titanium in electrothermal atomizers by laser-induced fluorescence. Part 1. Determination of optimum excitation and detection wavelengths

A detailed investigation has been performed of suitable excitation and detection wavelengths of Ti for the technique of laser-induced fluorescence in electrothermal atomizers. Fluorescence spectra (most often in the 250–350 nm region) from the 39 excitation wavelengths conjectured to be the most important (in the 220–270 nm region) have been investigated in more detail by the use of an intensified CCD detector. The fluorescence spectra were found to have a rich occurrence of peaks (about 50 each), of which many cannot be found in existing atomic wavelength data in the literature. All of the peaks found (with one exception) could be identified thanks to a home-made program that calculates atomic wavelengths from existing energy level data. Most of the spectra are dominated by “indirect” transitions (i.e. fluorescence from an upper level that is different from the one accessed by the laser) despite the prediction of existing “direct” transitions. This indicates that the collisional redistribution processes the excited levels, in general, are faster than typical fluorescence rates for Ti in graphite furnaces. Suitable excitation and detection wavelength combinations are given. One such suitable choice is excitation at 264.662 nm since the fluorescence following this excitation consisted of peaks of almost equal magnitude in three different wavelength regions (around 295, 319 and 338 nm).

Detection of titanium in electrothermal atomizers by laser-induced fluorescence. Part 1. Determination of optimum excitation and detection wavelengths

A detailed investigation has been performed of suitable excitation and detection wavelengths of Ti for the technique of laser-induced fluorescence in electrothermal atomizers. Fluorescence spectra (most often in the 250–350 nm region) from the 39 excitation wavelengths conjectured to be the most important (in the 220–270 nm region) have been investigated in more detail by the use of an intensified CCD detector. The fluorescence spectra were found to have a rich occurrence of peaks (about 50 each), of which many cannot be found in existing atomic wavelength data in the literature. All of the peaks found (with one exception) could be identified thanks to a home-made program that calculates atomic wavelengths from existing energy level data. Most of the spectra are dominated by “indirect” transitions (i.e. fluorescence from an upper level that is different from the one accessed by the laser) despite the prediction of existing “direct” transitions. This indicates that the collisional redistribution processes the excited levels, in general, are faster than typical fluorescence rates for Ti in graphite furnaces. Suitable excitation and detection wavelength combinations are given. One such suitable choice is excitation at 264.662 nm since the fluorescence following this excitation consisted of peaks of almost equal magnitude in three different wavelength regions (around 295, 319 and 338 nm).

The influence of substituents on the luminescence properties of the Eu(III) and Tb(III) chelates of 4-(phenylethynyl)pyridine derivatives

42 differently substituted 2,2′,2″,2‴-“[4-(phenylethynyl)pyridine-2,6-diyl]bis(methylenenitrilo)”tetrakis(acetic acids) ( 1–42) were synthesized with the purpose of studying the influence of substituents on the luminescence properties of the Eu(III) and Tb(III) chelates. With the Eu(III) ion, all derivatives (amides, ketones, esters, acids, ethers, halides and nitriles), with the exception of amines, gave a strong emission with suitable excitation wavelengths while, with the Tb(III) ion, only metasubstituted carbonyl derivatives had moderate luminescence properties.

High-speed characterization of p-i-n photodetectors by nonlinear photocurrent spectroscopy

By analyzing the photocurrent nonlinearity, observed under excitation with two successive picosecond optical pulses, we investigate the carrier transport and electric field recovery in high-speed p-i-n photodetectors containing In0.2Ga0.8As/GaAs quantum wells in the intrinsic region. The nonlinearity originates from the distortion of the electric field by the free carriers generated by the leading pulse, which changes the absorption of the subsequent pulse. The nonlinear signal is resonantly enhanced by orders of magnitude at suitable excitation wavelengths due to excitonic resonances. For the recovery time of the electric field we find values less than 15 ps.