A study of the vibration characteristics of a deoxyguanosine molecule and a deoxyadenosine molecule bonded onto the
surface of silicon is presented. The vibrations of the systems can be classified into five modes: nonlocal vibrational
modes, local vibrational modes, quasi-local modes, backbone vibrational modes and molecular bond vibrational modes.
The general separation of the molecular bond modes (i.e., which occur in the infrared region) and other vibrational
modes (i.e., which occur in the far-infrared (Far-IR) region) is only weakly influenced by mounting the molecules onto
the surface of silicon through linker molecules. The main influence of the binding of the molecule onto to the surface of
a silicon substrate is the shifting of the vibrational modes towards the terahertz regime (i.e., ~ 100 cm-1) and an
associated increase of the number of these low frequency modes. Furthermore, the FAR-IR active vibrational regions
(i.e., defined where there exists the strongest absorption peaks) are in the range of 300 cm-1 to 1903 cm-1 for a
deoxyguanosine molecule and 500 cm-1 to 1841 cm-1 for a deoxyadenosine molecule, respectively. For frequencies
below these Far-IR regions, the absorption intensity is small. However, the vibrations in this region are almost all nonlocal
vibration modes which are important for the study of interaction between bases and for the development of
sequence information of DNA molecules in terms of optical techniques.