Biomedical Engineering Reference
In-Depth Information
This energy is supplied by one quantum of radiation and is absorbed by
atoms or molecules. If energy supplied by one quantum radiation is smaller
than excitation energy, no excitation state occurs. Two or more photons with
lower energy than that required for excitation cannot combine their energies
to produce the excitation energy ΔE [4].
Regions of the Spectrum
The electromagnetic spectrum (Figure 1.3) includes a wide range of electro-
magnetic radiations from the radiofrequency region to the γ-ray region. The
approximate wavelength, frequency, energy, and their nature of interaction
with atoms and molecules are given in Table 1.1 [5].
Vibrational spectroscopy is a powerful light-scattering/absorption tech-
nique used to investigate the internal structure of molecules and crystals.
As the technique is specific to the chemical bonds and molecular structures,
it is commonly used in chemistry and has been considerably covered by
scientists and research groups from different disciplines [6,7]. However,
the technique is rapidly emerging not only as a potential tool for biological
studies, but also as a technique of choice for studying the chemical struc-
tural properties of biological molecules. This is due to the fact that the spec-
tra are highly detailed, allowing subtle differences in biochemistry to be
identified. Theoretically, any physiological change or pathological process
Visible light
Low energy
High energy
Frequency (s
-1
)
3 × 10
10
3 × 10
12
3 × 10
14
3 × 10
16
3 × 10
18
Radio
waves
Gamma
rays
Microwaves
Infrared
Ultraviolet
-rays
10
-1
10
-2
10
-3
10
-4
10
-5
10
-6
10
-7
10
-8
10
-9
10
-10
10
-11
Wavelength (m)
Figure 1.3
(See colour insert.)
Electromagnetic spectrum.
Search WWH ::
Custom Search