  Amplitude modulation of quantum ion-acoustic waves (QIAWs) in a quantum
electron-pair-ion plasma is studied. It is shown that the quantum coupling
parameter $H$ (being the ratio of the plasmonic energy density to the Fermi
energy) is ultimate responsible for the modulational stability of QIAW packets,
without which the wave becomes modulational unstable. New regimes for the
modulational stability (MS) and instability (MI) are obtained in terms of $H$
and the positive to negative ion density ratio $\beta$. The growth rate of MI
is obtained, the maximum value of which increases with $\beta$ and decreases
with $H$. The results could be important for understanding the origin of
modulated QIAW packets in the environments of dense astrophysical objects,
laboratory negative ion plasmas as well as for the next generation laser solid
density plasma experiments.
