  The one dimensional S=1/2 XXZ model with dimerization (1-j) and
quadrumerization \delta is studied by the numerical exact diagonalization of
finite size systems. Using the conformal field theory and the level
spectroscopy method, we calculate the ground state phase diagram with XY-like
anisotropy \Delta (0<\Delta<1). The ground states of this model contain the
Haldane state, S=1 dimer state, S=1 large-D state and S=1/2 dimer state as
limiting cases. The \Delta and \delta-dependence of the critical exponent \nu
of the energy gap is determined from the conformal dimensions of excited
states.
