  It is commonly believed that electromagnetic spectra of atoms and molecules
can be fully described by interactions of electric and magnetic multipoles.
However, it has recently become clear that interactions between light and
matter also involve toroidal multipoles - toroidal absorption lines have been
observed in electromagnetic metamaterials. Here we show that a new type of
spectroscopy of the hitherto largely neglected toroidal dipolar interaction
becomes feasible if, apart from the classical r{\times}r{\times}p toroidal
dipole density term responsible for the toroidal transitions in metamaterials,
the spin-dependent r{\times}{\sigma} term (that only occurs in relativistic
quantum mechanics) is taken into account. We show that toroidal transitions are
odd under parity and time-reversal symmetries; they can therefore be observed
and distinguished from electric multipole and magnetic dipole transitions.
