  Proton-scattering experiments followed by the coincident spectroscopy of
$\gamma$ rays have been performed at the Institute for Nuclear Physics of the
University of Cologne to excite low-spin states in $^{112}$Sn and $^{114}$Sn,
to determine their lifetimes and extract reduced transitions strengths $B(\Pi
L)$. The combined spectroscopy setup SONIC@HORUS has been used to detect the
scattered protons and the emitted $\gamma$ rays of excited states in
coincidence. The novel $(p,p'\gamma)$ DSA coincidence technique was employed to
measure sub-ps nuclear level lifetimes.
  74 level lifetimes $\tau$ of states with $J = 0 - 6$ were determined. In
addition, branching ratios were deduced which allowed the investigation of the
intruder configuration in both nuclei. Here, $sd$ IBM-2 mixing calculations
were added which support the coexistence of the two configurations.
Furthermore, members of the expected QOC quintuplet are proposed in $^{114}$Sn
for the first time. The $1^-$ candidate in $^{114}$Sn fits perfectly into the
systematics observed for the other stable Sn isotopes.
  The $E2$ transition strengths observed for the low-spin members of the
so-called intruder band support the existence of shape coexistence in
$^{112,114}$Sn. The collectivity in this configuration is comparable to the one
observed in the Pd nuclei, i.e. the 0p-4h nuclei. Strong mixing between the
$0^+$ states of the normal and intruder configuration might be observed in
$^{114}$Sn. The general existence of QOC states in $^{112,114}$Sn is supported
by the observation of QOC candidates with $J \neq 1$.
