2.6 The Terahertz Spectrum of Water
85
Table 2.6 Best-fit parameters of the oscillatory 5 THz mode of liquid H 2 O, D 2 O, and H 2 O 18 at
room temperature (data from [80]) and ice at 266 K
s
ν s (THz)
γ s (THz)
∞
H 2 O
1.25
1.11
1.22
0.85
D 2 O
5.30 (0.05)
5.36 (0.03)
4.95 (0.04)
5.44 (0.03)
H 2 O 18
5.40 (0.20)
5.06 (0.08)
4.25 (0.09)
2.93 (0.25)
Ice
2.34 (0.02)
2.29 (0.01)
2.28 (0.01)
2.2 (0.1)
Fig. 2.20 a A comparison
of the Raman [81] and
infrared spectra of water. The
dashed line is obtained by
subtracting the
high-frequency modes. The
shaded areas are the
components of the spectrum
according to (2.25) and
(2.26). b The temperature
dependence of the Raman
mode central frequencies.
Calculated using data from
[82]
close to those in the IR spectrum. The ν
R
D3 corresponds to the third relaxation mode
of the IR spectrum (see Fig. 2.4) and the ν
R
s coincides with the ν s mode of the IR
spectrum, discussed above. Note that the IR-ν s mode is perfectly matched with that
in the Raman spectrum when the high-frequency contributions are taken out (see the
red dashed line Fig. 2.20a).
Two main features of the Raman spectrum, ν
R
D3 and ν
R
s , have been assigned, by
analogy with the IR spectral features, to O–O–O bending [83], and O–O stretching along the O–H· · · O line [84], respectively. Walrafen showed [85] that the 60
and 175 cm
−1 Raman peaks have a more complex nature, and correspond to transverse spherical acoustic shear and longitudinal spherical acoustic dilatational waves,
respectively, and both involve the displacement of the center of mass of H 2 O, which
85
Table 2.6 Best-fit parameters of the oscillatory 5 THz mode of liquid H 2 O, D 2 O, and H 2 O 18 at
room temperature (data from [80]) and ice at 266 K
s
ν s (THz)
γ s (THz)
∞
H 2 O
1.25
1.11
1.22
0.85
D 2 O
5.30 (0.05)
5.36 (0.03)
4.95 (0.04)
5.44 (0.03)
H 2 O 18
5.40 (0.20)
5.06 (0.08)
4.25 (0.09)
2.93 (0.25)
Ice
2.34 (0.02)
2.29 (0.01)
2.28 (0.01)
2.2 (0.1)
Fig. 2.20 a A comparison
of the Raman [81] and
infrared spectra of water. The
dashed line is obtained by
subtracting the
high-frequency modes. The
shaded areas are the
components of the spectrum
according to (2.25) and
(2.26). b The temperature
dependence of the Raman
mode central frequencies.
Calculated using data from
[82]
close to those in the IR spectrum. The ν
R
D3 corresponds to the third relaxation mode
of the IR spectrum (see Fig. 2.4) and the ν
R
s coincides with the ν s mode of the IR
spectrum, discussed above. Note that the IR-ν s mode is perfectly matched with that
in the Raman spectrum when the high-frequency contributions are taken out (see the
red dashed line Fig. 2.20a).
Two main features of the Raman spectrum, ν
R
D3 and ν
R
s , have been assigned, by
analogy with the IR spectral features, to O–O–O bending [83], and O–O stretching along the O–H· · · O line [84], respectively. Walrafen showed [85] that the 60
and 175 cm
−1 Raman peaks have a more complex nature, and correspond to transverse spherical acoustic shear and longitudinal spherical acoustic dilatational waves,
respectively, and both involve the displacement of the center of mass of H 2 O, which