chemical physics of discharges - Argonne National Laboratory

emission in a few cases may be by decomposition of the phosphor,
es vas shom in the case of the silver-activated zinc sulfides.
The manganese-activated zinc phosphate (Sylvania No. 151) phosphor
appeared to give the most intense luminescence emission in methane-air
flames of my tested, and, accordingly, its light emission was investi-
-
aated further. \Then the phosphor was coated on a fritted disk and the
Eisk used as e porous-plate burner, a steady emission was obtained with
a hyerocen dif'fusion f'lame. However, no emission could be obtained in
this manner vhm the fritted-disk burner was fed with Qure methane or
vith a --thane-air mixture. Only when the phosphor was brought into a
i3dnsnn flair.? -;:as the light emission observed. We do not know the cause
sf this effsct. A greater concentration of hydrogen atoms in the hydro-
play a. role. The high diffusivity and other properties
hz't zause its flame to burn closer to the solid surface
rL or greate? importance.
Sssctre recor2ed with the Beclanan DK-2 spectrophoto.meter were used
to' zonpare the light emission of this phosphor in the hydrogen flame
vith its emission in the methane-air flame. The phosphor was coated
on 2 silicon carbide rod for this experiment. No significant differ- ,
ence other than that of the emission from the flame itself was observed
('izurc, 3 ) . I
T!ie effect of temperature on the light emission of the phosphor was
i nvasti.?at?5 by electrically heating the silicon carbide rod. With a
nethanerair flame impinging .on the phosphor-coated rod, and with the
spectrophotometer focused on the rod near one of its water-cooled ends,
the Li&t emission increased to a maximum with an increase in electrical .
hGatin5, then decreased to near extinction with further heating. This
agrees with the observation of Neunhoeffer (9) that the hydrogen flame.
candoluminescence of calcium oxide impregnated with various activators '
eshibit s temperature maxima.
When'the phosphor was heated to a still higher temperature, thermal
emission appeared. When the emission of the phosphor was corrected
'i
for the emission of the flame, no essential difference in emission at
high temperatures with and without the flame was evident. These experi- .'
ments indicated that the low-temperature light emission experienced
with this. phosphor is candoluminescence, but that candoluminescence is
not involved in the high-temperature emission.
I
This phosphor was'the only one of several tested that luminesced in
E carbon monoxide flame. The question of excitation in this flame by
high-energ;; species other than hydrogen atoms was not pursued.
Spectra of the luminesccnces from several phosphors excited by
hydrogen burning on the surface of a sintered glass disk were obtained, '
a& the effect of the addition of small amounts of carbon monoxide and
methan? to the fuel was observed. The.phosphors were calcium silicate '
aztivatec with lead and manganese (Sylvania No. 290), calcium oxide ,
activated vith ytterbium, calcium oxide activated with praseodymium,
and salcim oxide activated with samarium. The spectra obtained from
the f5rst three of these phosphors when they are excited with pure
hj-d?Ggen burning on a fritted disk are shown in Figure 4. The Sylvania 1,
KG. 24.9 phosphor emits with a broad peak in the green. Praseodymiumecti:retc.c
cal2im oxide shows two peaks - one at 595 millimicrons /
(p110:.1) and a weaker one at 490 millimicrons (blue-green). Ytterbium- 1
i