Analysis of light-scattering samples
Integrating sphere
SPECORD S600 accessories Edition 09/2014 87
Vertical installation
The integrating sphere is shown in that position it is inserted into the
SPECORD S600 for reflectance measurements of powdery samples (vertical
arrangement). With this arrangement, the reflectance sample is located
underneath the sphere body. In this vertical position, also liquid samples in cells
are analyzed in front of the beam-exit aperture (1 in Fig. 20-7).
Horizontal installation
The sphere body may also be inserted swiveled by 90° (horizontal
arrangement), if you want to measure solid samples. In this way, the measuring
aperture is easily accessible without the need for removing the sphere body
from the sample compartment.
Fig. 20-2 Integration sphere in vertical and horizontal installation
With the sphere body pushed to the right side up to the stop, the quartz lens (7
in Fig. 20-1) ensures that only the area of the sampling aperture (14 in Fig.
20-7) is imaged onto the entrance slit of the spectrometer and not the
Spectralon surface of the bottom hemisphere (11 in Fig. 20-7).
The holder of the mirror and the mirror itself prevent the transmission or
reflectance samples from being directly exposed to lamp light.
The two hemispheres made of Spectralon and the Spectralon insert ensure the
maximum possible reflectance throughout the entire spectral range.
In reflectance measurements, the measuring geometry is h/8°, i.e. the sample is
diffusely illuminated from the hemisphere and the radiation is measured under
an angle of 8° with reference to its surface normal.
In transmittance measurements, the measuring geometry is h/0°, i.e. the
sample is diffusely illuminated from the hemisphere and the radiation is
measured under an angle of 0° with reference to its surface normal.
Please consider that due to the distribution of the light energy of the lamp onto
the entire inner surface of the sphere the level of the measured signal drops to
a few percent compared to measurements at the same integration time but
without integrating sphere. This means that you must take the measurements
with longer integration times. Then, you can work linearly at a high accuracy up
to an absorbance of about 2.
In measurements with the integrating sphere, the deuterium lamp is ineffective.
When initializing the SPECORD, you can switch off this lamp.
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