A Characterisation of the Wavelength Modulated Diode Laser Absorption Spectrometry Technique in Graphite Furnace
Marco Regalia - University of Umeå - [1999-00]
The Wavelength Modulated Diode Laser Absorption Spectrometry technique applied to a Graphite Furnace (WM – DLAS – GF) has been applied to the detection of low concentrations of rubidium atoms in liquid samples. A variety of experiments has been carried out in order to analyse the non-homogeneity of the atomic distribution in the furnace. Experiments were performed by selecting a small part of the laser beam passing through the furnace. Many quantities, such as beam intensity, atoms density, linearity of response and matrix recovery have been measured and detailed data and graphs are reported. Relevant not-homogeneities have been discovered in all such quantities. A comparison of the signal strength and signal-to-noise ratio for the detection at the frequencies of the second (2f) and fourth (4f) harmonics of modulation has been performed and it is shown that 4f is the mode of detection to be preferable at low concentration.
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