  We show that the shape resonances induced by a one dimensional well of delta
functions disappear as soon as a small constant electric field is applied. In
particular, in any compact subset below the positive real axis there are no
resonances if the non-zero field is small enough. In contrast to the lack of
convergence of the lifetimes computed from the widths of the resonances we show
that the "experimental lifetimes" are continuous at zero field. The shape
resonances are replaced by an infinite set of other resonances whose location
and number we analyze.
