  The influence of the electron environment on the alpha decay is elucidated.
Within the frame of a simple model based on the generalized Thomas-Fermi theory
of the atom, it is shown that the increase of the electron density around the
parent nucleus drives a mechanism which shortens the lifetime. Numerical
results are provided for 144Nd, 154Yb and 210Po. Depending on the nuclide,
fractional lifetime reduction relative to the bare nucleus is of the order of
0.1-1% in free ions, neutral atoms and ordinary matter, but may reach up to 10%
at matter densities as high as 10^4 g/cm3, in a high-Z matrix. The effect
induced by means of state-of-the-art compression techniques, although much
smaller than previously found, would however be measurable. The extent of the
effect in ultra-high-density stellar environments might become significant and
would deserve further investigation.
