Rotasjonskonstant

Rotasjonskonstant is a term used in physics, particularly in spectroscopy and molecular physics, to describe a fundamental property of a rotating molecule. It is a measure of the energy associated with a molecule's rotation. The rotasjonskonstant is inversely proportional to the moment of inertia of the molecule and is directly related to the molecule's shape and mass distribution. Specifically, for a diatomic molecule, the rotasjonskonstant, often denoted by B, is calculated as B = h / (8π²cI), where h is Planck's constant, c is the speed of light, and I is the moment of inertia of the molecule. The moment of inertia depends on the masses of the atoms and the distance between them (bond length).

The value of the rotasjonskonstant is crucial for understanding and interpreting rotational spectra. When molecules absorb or emit radiation, they can transition between different rotational energy levels. The energy difference between these levels is quantized and directly proportional to the rotasjonskonstant. Therefore, by measuring the frequencies of lines in a rotational spectrum, scientists can determine the rotasjonskonstant for a molecule. This, in turn, allows for the determination of molecular parameters such as bond lengths and molecular geometries. Different isotopes of the same molecule will have different rotasjonskonstanter due to their differing masses, which can be used to identify and quantify isotopic compositions.