Environmental Engineering Reference
In-Depth Information
4
1
2
3
1. Laser beam
2. Mechanical
block
3. Monochromator
transmitting signal
4. Camera for
transmitting signals
5. Optical camera
6. Monochromator
receiving signal
7. Detector
5
7
6
ermal infrared camera
FIGURE 6.10
Thermal.infrared.camera.
During. the. molecular. excitation. process,. the. sample. can. receive. light. of.
a. narrow. band. of. wavelength. for. quantitative. analysis,. or. the. sample. can.
receive.light.of.progressively.changing.wavelengths.(scanning).for.qualita-
tive.identiication.of.investigative.compounds.
The. luminescence. that. is. excited. in. the. sample. by. the. excitation. mono-
chromator. is. viewed. by. the. emission. monochromator's. entrance. slit.. The.
emission. monochromator. spectrally. resolves. the. molecular. emission. char-
acteristics. of. the. sample. and. the. emitted. light. intensity. at. each. dispersed.
wavelength.is.registered.on.a.photo.detector.at.the.exit.slit.of.the.emission.
monochromator..A.photo.multiplier.detector.is.usually.employed.as.a.detec-
tor,. and. the. monochromator's. dispersing. element. is. rotated. by. a. scanning.
motor..The.scanning.operation.of.the.emission.monochromator.is.generated.
as.an.emission.spectrum.
In.a.similar.fashion,.the.scanning.operation.of.the.excitation.monochroma-
tor.generates.an.excitation.spectrum..The.excitation.spectrum.has.the.most.
characteristics,.since.it.generally.has.more.distinctive.features.and.it.relates.
to.a.compound.in.normal.UV.and.absorption.spectrum..The.energy.of.UV.
light.can.be.determined.by.the.classic.formula:
E = h
C
.
λ
.
(6.42)
Here:
E.is.the.energy.in.ergs.(the.erg.is.a.unit.of.energy.in.the.metric.system);
The.h.is.a.proportional.constant.known.as.“Planck's.Constant,”.which.has.
the.value.of.6.62*10
-27
.erg.sec./photon;
C.is.the.speed.of.light.in.a.vacuum.of.C,.which.equals.3.00*10
10
.cm/sec.;
λ.is.the.wavelength.in.cm..For.UV.light,.the.spread.of.250.to.475.cm.is.
the.wavelength;
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