Deformation vibration is a type of molecular vibration characterized primarily by the change of bond-angle within a molecule.
Understanding Deformation Vibration
Unlike stretching vibrations which involve changes in bond length, deformation vibrations focus on how the atoms move relative to each other, causing the angles between chemical bonds to widen or narrow. This change in angle distorts the overall shape of the molecule temporarily during the vibration.
Think of the bonds as springs and the atoms as weights. In a deformation vibration, the "springs" connecting three or more atoms (forming an angle) are bent rather than just stretched or compressed along their length.
Example: Bending Vibration in CO2
A classic example of deformation vibration is the bending vibration in a linear molecule like carbon dioxide (CO2).
- The CO2 molecule consists of a central carbon atom bonded to two oxygen atoms (O=C=O).
- In the bending vibration, the atoms move in a way that changes the angle between the two C=O bonds.
- Specifically, as described by the reference, both oxygen atoms move in a direction perpendicular to the O-C-O bond axis.
- Simultaneously, the carbon atom moves in the opposite direction (and inverse movement occurs in the other phase of the vibration).
- This causes the molecule to bend out of its straight-line configuration.
Characteristics of CO2 Bending Vibration
The bending vibration in CO2 has a particular characteristic:
- It is described as two-fold degenerate. This means that two distinct, independent vibrational modes occur at the same energy level, both corresponding to the bending motion. One mode involves bending in the plane of the screen (say, up and down), and the other involves bending perpendicular to that plane (say, in and out of the screen).
Deformation vibrations, including bending, wagging, rocking, and twisting, are crucial for understanding the vibrational spectra of molecules, particularly in techniques like Infrared (IR) and Raman spectroscopy. They provide valuable information about molecular structure and dynamics.
