Skobeltsyn Institute of Nuclear Physics
Lomonosov Moscow State University

Different factors having effect on the structure of ground and low energy (E_g < 1-2 MeV)
states of Sn isotopes were investigated. The succession of nuclear shells filling for ^100-135Sn
isotopes was constructed. The effect of pairing forces on the low energy spectrum of Sn isotopes
was considered. Comparison between single particle neutron shells energy obtained from the
analysis of the experimental data and results of calculations according to different theoretical
models was carried out.