The production method of QCC described in detail by Sakata et al.
([1984]) is summarized here. The QCC condensate is prepared by
the technique of hydrocarbon plasma deposition. The source gas of
methane is ionized by microwave discharge, and is spouted out into a
vacuum chamber through a small nozzle. The plasma gas adiabatically
expands and is immediately quenched to solid material. The condensate
is deposited onto NaCl or CaF2 substrates placed in the vacuum
chamber. The NaCl/CaF2 substrates are used because of high
transmittance and no spectral features in the 3 m region.
Then the QCC films are moved into an evacuated quartz tube, and set
in an electronic furnace. The temperature of the furnace is raised at
a rate of 5 K per minute to a predetermined temperature. The sample is
heated in the furnace at the temperature for 20 minutes. A portion of
deposited QCC film evaporates by heating, and re-sticks to the cooler
part of the quartz tube. The amount of evaporation grows with the
annealing temperature, for instance, more than 90% in mass is lost
from the fresh deposition after the annealing at 800 K. We adjust the
duration of deposition process five to ten times longer than the
sample for no annealing in order to prepare the thicker deposition for
annealing at higher temperature. As a result we obtain eight samples
at the temperatures of 600, 700, 723, 740, 760, 823, 873 K as well as
as-deposited film whose absorptions are fairly constant (15%).
In order to obtain the thermal emission spectra of QCC we use a
near-infrared spectrograph originally developed for astronomical
observations Imanishi et al. ([1996]). The spectrograph is
equipped with an InSb detector array and covers
m in a
single exposure with a wavelength resolution of about 1300. The
annealed and as-deposited samples are fixed in a holder in front of
the spectrograph window, and heated by a ceramic resistance that
contacts to the substrate. So as to reduce the background emission
from the environment, a liquid nitrogen surface is viewed through a
mirror put behind the sample holder. We measure the temperature of the
emitting material with Pt resistance attached to the substrate.
A net spectrogram of QCC sample is obtained by subtracting a spectrum of a blank substrate. The sensitivity of the spectrograph is calibrated by measuring thermal emission spectrum of the room temperature assuming a blackbody emission. The baseline of the spectrum is fitted with spline function and subtracted to compare the extracted spectral features with the observational data.
The absorbance of QCC films is taken by a Shimazu FTIR - 8600 PC spectrophotometer at room temperature with a wavelength resolution of about 1500. The baseline of the absorption spectra attributable to the the net continuum absorption of QCC and substrates are fitted with spline function and subtracted.
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