Important collective modes which are generally neglected within curren
t descriptions of nuclear excitations in terms of fluid dynamics, are
studied here. The intrinsic vortical modes are defined in a general wa
y from which a specific mode, both simple and versatile enough, is par
ticularly discussed. In this paper the main emphasis is made on the co
upling of the chosen intrinsic mode to the rotation of the nuclear pri
ncipal axes frame with respect to the laboratory system. A semi-quanta
l description of such excitations is proposed which is a generalizatio
n of the so-called routhian approach of global rotations. The results
of a semiclassical treatment of the corresponding variational problem
are presented. A simple mean field approach where the one-body potenti
al is mocked up by a harmonic oscillator is discussed in a somewhat de
tailed fashion. The broad range of validity of a quadratic approximati
on for the collective energy in terms of the relevant angular velociti
es, is hinted from the previous simple model approach. Some general co
nsequences of the latter are then drawn which have bearing on some pos
sible fingerprints for the existence of such excitations, as the stagg
ering phenomenon observed in gamma transition energies in some superde
formed states and the occurrence of identical rotational bands in neig
hbouring nuclei. (C) 1997 Elsevier Science B.V.