58
2 The Interaction of Electromagnetic Waves with Water
Fig. 2.2 The
ultra-broadband dielectric
spectra of water: real, , and
imaginary, , parts of the
dielectric function (upper
panel) and dynamic
conductivity, σ = 0 ω
(lower panel) in the
temperature interval from
273 to 373 K (0−100 ◦ C).
Colored areas correspond to:
dielectric (Debye) relaxation
(orange), atomic (protonic)
contribution (blue), and
electronic contribution
(yellow). Bold curves are for
20 ◦ C
the electric field, by a factor of 80, which is the static dielectric constant, (0) (see the
next section). Here, the dielectric losses
(0) are negligibly small and correspond
to the static DC conductivity (see the bottom panel in Fig. 2.1). However, when the
electric field is changing relatively fast, the dielectric constant
(ω) reduces (see
red curve in the upper panel), as the molecular system becomes unable to follow the
changes of the electric field. A delay in polarization P in the response of water to
the changing electric field E appears. The time lag between E and P implies the
absorption of electromagnetic radiation caused by an irreversible degradation of free
energy and leads to the attenuation of electromagnetic waves passing through the
medium, showing, in this way, the relaxation band shown in Fig. 2.3 (see blue curve
in the upper panel). This band was named after Peter Debye, who made the first
detailed description of this phenomena [5].
Debye found that the microwave dielectric spectrum of water, which includes
the dielectric relaxation band (orange area in Fig. 2.2), is described by the following
formula:
ε(ω) = ε
(ω) + iε
(ω) = ε ∞ +
1 + iωτ D
,
(2.22)
2 The Interaction of Electromagnetic Waves with Water
Fig. 2.2 The
ultra-broadband dielectric
spectra of water: real, , and
imaginary, , parts of the
dielectric function (upper
panel) and dynamic
conductivity, σ = 0 ω
(lower panel) in the
temperature interval from
273 to 373 K (0−100 ◦ C).
Colored areas correspond to:
dielectric (Debye) relaxation
(orange), atomic (protonic)
contribution (blue), and
electronic contribution
(yellow). Bold curves are for
20 ◦ C
the electric field, by a factor of 80, which is the static dielectric constant, (0) (see the
next section). Here, the dielectric losses
(0) are negligibly small and correspond
to the static DC conductivity (see the bottom panel in Fig. 2.1). However, when the
electric field is changing relatively fast, the dielectric constant
(ω) reduces (see
red curve in the upper panel), as the molecular system becomes unable to follow the
changes of the electric field. A delay in polarization P in the response of water to
the changing electric field E appears. The time lag between E and P implies the
absorption of electromagnetic radiation caused by an irreversible degradation of free
energy and leads to the attenuation of electromagnetic waves passing through the
medium, showing, in this way, the relaxation band shown in Fig. 2.3 (see blue curve
in the upper panel). This band was named after Peter Debye, who made the first
detailed description of this phenomena [5].
Debye found that the microwave dielectric spectrum of water, which includes
the dielectric relaxation band (orange area in Fig. 2.2), is described by the following
formula:
ε(ω) = ε
(ω) + iε
(ω) = ε ∞ +
1 + iωτ D
,
(2.22)