  Temperature and angular momentum dependence of the quadrupole deformation is
studied in the middle of the sd-shell for 28Si and 27Si isotopes using the
spherical shell model approach. The shell model calculations have been
performed using the standard USD interaction and the canonical partition
function constructed from the calculated eigen-solutions. It is shown that the
extracted average quadrupole moments show a transitional behavior as a function
of temperature and the inferred transitional temperature is shown to vary with
angular-momentum. The quadrupole deformation of the individual eigen-states is
also analyzed.
