Cw. Leblanc et Mw. Blades, SPATIALLY-RESOLVED TEMPERATURE-MEASUREMENTS IN A FURNACE ATOMIZATION PLASMA EXCITATION SPECTROMETRY SOURCE, Spectrochimica acta, Part B: Atomic spectroscopy, 50(11), 1995, pp. 1395-1408
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.