218
IFS 125M User Manual Bruker Optik GmbH
Glossary F
Laser The laser is a coherent source of monochromatic radiation. It is
an essential part of the interferometer system. Due to laser
light interference the position of the movable mirror, and the
data sampling positions are determined.
Micrometer (µm)
Micrometer is a length unit of 10
-6
meter, which is equal to a
thousandth of a millimeter.
MIR Mid InfraRed; covers the spectral range from 4,000 to 400cm-1
wavenumbers. In this range fundamental vibrations are typi
-
cally excited.
NIR Near InfraRed covers the spectral range from 12,800 to
4,000cm
-1
. Overtones and combination vibrations are excited.
Optical path The optical path is the distance of the light passing through the
spectrometer. The distance between two points in the light
beam is calculated in longitudinal direction, and multiplied by
the refraction index of the medium.
Reflectance Reflectance describes the ratio of the radiation energy
reflected from a surface to the radiation energy incident on the
surface. It is the percentage or part of the incident light (=
100%), which an object reflects again.
Reflection In case of reflection light incidents on a sample and is con-
verted to radiation energy. This kind of energy is subsequently
reflected by the sample surface at a defined wavelength.
Relative humidity Relative humidity is the amount of water vapor in the air, which
can be between 0 and 100%.
Resolution Resolution in FT-IR is determined by the maximum optical path
difference reached in the measurement of an interferogram.
The spectral resolution corresponds to the minimum possible
spectral distance between 2 adjacent spectral lines which can
be resolved by the spectrometer. It is produced by the instru
-
mental spectral line shape and the line width of the sample’s
absorption.
The instrumental line shape is reciprocally related to the travel
distance of the movable mirror in the interferometer, and also
influenced by the apodization function and divergence in the
interferometer. The higher the spectral resolution (smaller val
-
ues), the higher the noise in the spectrum.
Sample A sample is a special kind of substance which is put into the
spectrometer sample position and measured.
To Next Page
Loading...
