Fr.: structure fine
Closely spaced components seen at high resolution in a → spectral line. The phenomenon is explained by the fact that instead of a single → energy level corresponding to a given value of the → quantum number n, there are actually a number of energy levels lying close to one another. → fine-structure constant, → fine-structure line.
sâxtâr-e abar-nâzok (#)
Fr.: structure hyperfine
In spectroscopy, the → splitting of a spectral line into a number of very thin components. It results from a small perturbation in the energy levels of atoms or molecules due to the magnetic dipole-dipole interaction arising from the interaction of the nuclear → magnetic moment with the → spin of the electron. It can be observed only at high spectral dispersion. → fine structure.