  We provide integral formulae for the Laplace transform of the entrance law of
the reflected excursions for symmetric L\'evy processes in terms of their
characteristic exponent. For subordinate Brownian motions and stable processes
we express the density of the entrance law in terms of the generalized
eigenfunctions for the semigroup of the process killed when exiting the
positive half-line. We use the formulae to study in-depth properties of the
density of the entrance law such as asymptotic behavior of its derivatives in
time variable.
