It is theoretically shown that an attractive effective potential is
generated via optical phonon exchange between two quasi-free, different
particles in deuterated Pd which, in turn, enhances the probability of
their nuclear fusion reaction. Mechanisms, that
may be responsible for extra heat production and nuclear isomer formation,
are also discussed. Creation of 4He pairs due
to the significantly increased probability of the p + 7Li $\rightarrow$
24He + 17.35 MeV and d + 6Li $\rightarrow$
24He + 22.37 MeV
nuclear reactions is predicted. Some of the basic questions of fusion reactions in
solids seem to be successfully explained.