  The electric quadrupole response is investigated theoretically by HFB and QPM
calculations along the Sn isotopic chain with special emphasis on excitations
above the first collective state and below the particle threshold. Depending on
the asymmetry, additional strength clustering as a group of states similar to
the known PDR mode is found. The spectral distributions and electric response
functions are discussed. The transition densities of these Pygmy Quadrupole
Resonances (PQR) states are closely related to the neutron excess and showing
special features being compatible with an oscillation of the neutron skin
against the nuclear core. These features may indicate a new nuclear quadrupole
mode connected to the skin configuration.
