SPATIALLY-RESOLVED TEMPERATURE-MEASUREMENTS IN A FURNACE ATOMIZATION PLASMA EXCITATION SPECTROMETRY SOURCE

Spatially resolved atomic emission intensities from helium, and molecu lar emission intensities from OH and N-2(+) have been measured in a fu rnace atomization plasma excitation spectrometry (FAPES) source. He I emission at 388.86 nm was used to monitor the spatial structure of the plasma in the source while increasing the radio frequency (r.f.) powe r applied to its center electrode. At higher r.f. power the He I emiss ion intensity increased significantly while its spatial structure rema ined relatively unchanged. The He I emission was found to be most inte nse adjacent to the center electrode. Some less intense emission was o bserved adjacent to the graphite cuvette wall and some very weak emiss ion was seen throughout the volume of the source. These observations s uggest that the FAPES source operates as an r.f. glow discharge. Emiss ion intensities from the OH (0-0) rotational A (2) Sigma(+) --> X (2) Pi(i) and N-2(+) (0-0) rotational B (2) Sigma(u)(+) --> X (2) Sigma(g) (+) bands were used to monitor the effects of increasing the r.f. powe r applied to the center,electrode of the source. From these measuremen ts, rotational temperatures for these molecules were calculated. The i ntensity measurements showed that there is a significant thermal gradi ent in the source with OH rotational temperatures ranging between 680 and 1050 K and N-2(+) rotational temperatures ranging between 580 and 1920 K with 60 W r.f. power applied to the center electrode. At higher r.f. powers there is an increase in rotational temperatures and an in crease in the dissociation of molecular species in the FAPES source. L ead excitation temperatures were calculated using the line ratio metho d by measuring the emission of the Pb I 280.119 and 283.306 nm lines a t different r.f. powers. The temperature was found to increase monoton ically with r.f. power over the range of 35 to 75 W.