  In this paper we present the first high-resolution laser spectroscopy results
obtained at the GISELE laser laboratory of the GANIL-SPIRAL2 facility, in
preparation for the first experiments with the S$^3$-Low Energy Branch. Studies
of neutron-deficient radioactive isotopes of erbium and tin represent the first
physics cases to be studied at S$^3$. The measured isotope-shift and hyperfine
structure data are presented for stable isotopes of these elements. The erbium
isotopes were studied using the $4f^{12}6s^2$ $^3H_6 \rightarrow 4f^{12}(^3
H)6s6p$ $J = 5$ atomic transition (415 nm) and the tin isotopes were studied by
the $5s^25p^2 (^3P_0) \rightarrow 5s^25p6s (^3P_1)$ atomic transition (286.4
nm), and are used as a benchmark of the laser setup. Additionally, the tin
isotopes were studied by the $5s^25p6s (^3P_1) \rightarrow 5s^25p6p (^3P_2)$
atomic transition (811.6 nm), for which new isotope-shift data was obtained and
the corresponding field-shift $F_{812}$ and mass-shift $M_{812}$ factors are
presented.
