Atomic and molecular spectra of vapors evolved in a graphite furnace. Part 5: gallium, indium and thallium nitrates and chlorides

The vaporization behavior and vapor spectra of Ga. In and Tl nitrates and chlorides in the tube furnace was investigated using an UV spectrometer with CCD detector. Fifty spectra in the wavelength range of 200-475 nm were collected in each experiment during the vaporization step, with temperature increase from 473 to 2673 K. The vaporization patterns were compared for the pyrocoated, non-pyrocoated graphite tubes, and Ta-lined tubes. Nitrate and chloride aqueous solutions and chloride slurries in chloroform were used to distinguish the impact of hydrolysis on the vaporization behavior of these chlorides. The spectra of oxygen and chlorine containing molecules, presumably of suboxides, chlorides and dichlorides were identified upon variation of the experimental conditions. The release of suboxide vapors due to the reduction of oxides by carbon was promoted after the decomposition of nitrates. The presence of other elements on the vaporization surface, or the isolation of the sample from the graphite surface by Ta-lining, impeded the vapor release and reduced the intensity of molecular bands. Adsorption of chlorine onto graphite caused a decrease of chloride and dichloride bands. The suboxide bands were observed in the spectra of Ga and In chlorides introduced in the tube as aqueous solutions, due to partial hydrolysis. (C) 2002 Elsevier Science B.V All rights reserved.