Venytysvärähtelyjen

Venytysvärähtelyt, also known as stretching vibrations or simply stretching, refer to a type of molecular vibration where the distance between two atoms in a molecule changes periodically. This change in bond length can be an increase or decrease in the internuclear distance. In a diatomic molecule, there is only one stretching vibration mode, which is the symmetric stretching of the bond. For molecules with more than two atoms, stretching vibrations can occur in various ways.

In polyatomic molecules, stretching vibrations can be classified as symmetric or asymmetric. A symmetric stretching vibration occurs when two or more bonds of the same type stretch or compress simultaneously and in phase. For example, in a molecule like water (H2O), the two O-H bonds can stretch together. An asymmetric stretching vibration, on the other hand, involves bonds stretching or compressing out of phase with each other. In water, this would mean one O-H bond stretches while the other compresses.

The frequency of a stretching vibration is primarily determined by the strength of the chemical bond and the masses of the atoms involved. Stronger bonds, like double or triple bonds, vibrate at higher frequencies than weaker single bonds. Lighter atoms also vibrate at higher frequencies compared to heavier atoms, according to the principles of classical mechanics. These vibrational frequencies are characteristic of specific functional groups within a molecule and are therefore widely used in spectroscopy, particularly infrared (IR) spectroscopy and Raman spectroscopy, for molecular identification and structural analysis. Each bond type and atom combination will absorb or scatter light at a specific frequency range corresponding to its stretching vibration.