  The glueball-to-vacuum matrix elements of local gluonic operators in scalar,
tensor, and pseudoscalar channels are investigated numerically on several
anisotropic lattices with the spatial lattice spacing in the range 0.1fm --
0.2fm. These matrix elements are needed to predict the glueball branching
ratios in $J/\psi$ radiative decays which will help to identify the glueball
states in experiments. Two types of improved local gluonic operators are
constructed for a self-consistent check, and the finite volume effects are also
studied. The lattice spacing dependence of our results is very small and the
continuum limits are reliably extrapolated.
