Knowledge Bank

The first singlet-singlet transition of naphthalene in biphenyl reveals spectral line $structure1$ at $2\circ K$. Further spectra, involving $C10D8$ in $C12H8$ in $C12D10$ confirm that the hindered rotational motion is pseudo-localized at the naphthalene guest site. These localized phonons are energetically well within the biphenyl host phonon band.