  The existence of stable bound states of three solitons in a Bose-Einstein
condensate with nonlocal interactions is demonstrated by means of variational
approach (VA) and numerical simulations. The potential of interaction between
solitons derived from VA is shown to be of molecular type, i.e. attractive at
long distances and repulsive at short distances. Normal modes of a
three-soliton molecule are investigated by computing small amplitude
oscillations of individual solitons near their equilibrium positions. Symmetric
and asymmetric stretched states of the molecule are prepared and used as
initial conditions in numerical simulations of the nonlocal Gross-Pitaevskii
equation. As opposed to usual triatomic molecules, we find that the frequency
of the asymmetric mode of a three-soliton molecule is smaller than the one of
the symmetric mode. Possible experimental settings for the observation of these
results are briefly discussed.
