18
H. Kaur et al.
Fig. 8 Theoretical curves
for orientation studies using
ATR-IR spectroscopy
showing variation in dichroic
ratio as a function of tilt
angle α of the IR dipole
moment at 1000 cm −1 for
the Ge/water and ZnSe/water
interfaces
and p-polarization of incident IR radiation beam respectively. Figure 8 represents the
theoretical curve showing the variation of DR with tilt angle α for the water layer at
two different crystals with 45° as the angle of incident IR beam. It is evident from
the plot that the orientation curves for the water molecule tilt angles at Ge and ZnSe
interface are significantly different. A zero dichroic ratio corresponds to normally
oriented IR-dipole moment with respect to the surface; whereas DR value of 1.07 and
1.26 corresponds to flat conformation of the water dipole i.e., parallel to the Ge/water
and ZnSe/water surface respectively. One can obtain the orientation information
of an IR dipole from the intersection of the respective theoretical curve with the
experimentally obtained DR value. Thus, the ATR technique of IR spectroscopy
probes the molecular interactions and their impacts in the bulk medium as well as
the orientation of molecules at the boundary between the ATR crystal and the sample
under investigation [17, 18, 33, 34].
4 Recent Trends in the Application of ATR-FTIR
Spectroscopy for Molecular Characterization in Aqueous
Media
The preceding sections briefly introduced the background and some elementary
instrumental and theoretical segments of the ATR-FTIR vibrational spectroscopy.
The understanding of inter- and intra-molecular interactions hold the key to extract
the detailed physical and chemical behavior of various compounds in the aqueous
phase. In the current section, we intend to focus on certain contemporary research
contributions inspecting the fundamentals of molecular vibration by employing the
ATR-FTIR vibrational spectroscopic tool.
H. Kaur et al.
Fig. 8 Theoretical curves
for orientation studies using
ATR-IR spectroscopy
showing variation in dichroic
ratio as a function of tilt
angle α of the IR dipole
moment at 1000 cm −1 for
the Ge/water and ZnSe/water
interfaces
and p-polarization of incident IR radiation beam respectively. Figure 8 represents the
theoretical curve showing the variation of DR with tilt angle α for the water layer at
two different crystals with 45° as the angle of incident IR beam. It is evident from
the plot that the orientation curves for the water molecule tilt angles at Ge and ZnSe
interface are significantly different. A zero dichroic ratio corresponds to normally
oriented IR-dipole moment with respect to the surface; whereas DR value of 1.07 and
1.26 corresponds to flat conformation of the water dipole i.e., parallel to the Ge/water
and ZnSe/water surface respectively. One can obtain the orientation information
of an IR dipole from the intersection of the respective theoretical curve with the
experimentally obtained DR value. Thus, the ATR technique of IR spectroscopy
probes the molecular interactions and their impacts in the bulk medium as well as
the orientation of molecules at the boundary between the ATR crystal and the sample
under investigation [17, 18, 33, 34].
4 Recent Trends in the Application of ATR-FTIR
Spectroscopy for Molecular Characterization in Aqueous
Media
The preceding sections briefly introduced the background and some elementary
instrumental and theoretical segments of the ATR-FTIR vibrational spectroscopy.
The understanding of inter- and intra-molecular interactions hold the key to extract
the detailed physical and chemical behavior of various compounds in the aqueous
phase. In the current section, we intend to focus on certain contemporary research
contributions inspecting the fundamentals of molecular vibration by employing the
ATR-FTIR vibrational spectroscopic tool.