Thermo Scientific MIRAN 205B Series, Инструкция по эксплуатации

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13-1
Chapter 13
Infrared Spectroscopy Tutorial
OVERVIEW
The MIRAN SapphIRe Infrared Analyzer quickly measures concentrations of a wide
range of chemical substances present in the air. In identifying and measuring various
gases in the air, it uses fundamental principles of how molecules composing these
substances absorb infrared energy.
Infrared energy is but one type of energy composing the electromagnetic spectrum. Other
familiar types of electromagnetic energy are radio frequencies, microwaves, and visible
light.
ELECTROMAGNETIC ENERGY
Figure 13-1 is a chart of the entire electromagnetic spectrum from electric power
radiation to x-rays.
Electromagnetic waves can exist at virtually any frequency. Electromagnetic energy at
the top of the spectrum (television and radio waves) have much longer wavelengths and
correspondingly lower frequencies and energy than wavelengths towards the top of the
chart (x-rays, gamma rays, and cosmic rays). The wavelengths of radio can be measured
in dozens of feet whereas the wavelengths of x-rays can be measured in billionths of an
inch.
Infrared energy is located toward the middle of the electromagnetic spectrum. It is in the
same area as the only visible portion of the spectrum - light. The visible portion of the
spectrum includes wavelengths from 0.4 to 0.7
μ m (microns) or a slightly broader region
under appropriate conditions. Thus the naked eye can only perceive a very small part of
the electromagnetic spectrum.
At either end of the visible spectrum are invisible wavelengths. At longer wavelengths,
just beyond the red end of the visible spectrum, is the infrared region (infra meaning
frequencies below those of red light). Radiation in this region was demonstrated in 1800
by William Herschel, the English astronomer (Figure 13-2). Herschel placed a blackened
thermometer just outside the red end of the spectrum of sunlight formed by a prism. He
found that the temperature rose even though no visible light was hitting the thermometer.
As this suggests, infrared radiation, like light, is a portion of the electromagnetic
spectrum. But just as the pitch of sound can get too high or too low to hear, the
wavelengths of light can get too long or too short to see. Although people cannot see
infrared energy, they can feel it as heat. Radiated heat is infrared energy.