Wiktionary
hyperfine
a. Extremely fine, especially of the hyperfine structure in the spectra of atoms and molecules.
WordNet
hyperfine
adj. extremely fine or thin, as in a spectral line split into two or more components; "hyperfine structure"
Wikipedia
Usage examples of "hyperfine".
The hyperfine and superhyperfine splittings could now be measured accurately, but that was only the start.
At top left is a schematic representation of the hyperfine transition between parallel and antiparallel proton and electron spins of the neutral hydrogen atom.
The supernova cloud appears to have an unusual hyperfine structure, but there doesn’.