  We study the influence of proton-neutron (p-n) correlations on alpha-decay
width. It is shown from the analysis of alpha Q values that the p-n
correlations increase the penetration of the alpha particle through the Coulomb
barrier in the treatment following Gamow's formalism, and enlarges the total
alpha-decay width significantly.
  In particular, the isoscalar p-n interactions play an essential role in
enlarging the alpha-decay width.
  The so-called "alpha-condensate" in Z > 84 isotopes are related to the strong
p-n correlations.
