  Using the effective rotational Hamiltonian method, we have conducted an
analysis of the D218O ground and the first excited vibration state rotational
energy levels. The analysis was based on the effective Hamiltonians represented
in several forms: the Watson Hamiltonian, the Hamiltonian expressed in terms of
Pad\'e-Borel approximants, and the Hamiltonian in terms of generating function
expansions. The rotational and centrifugal constants have been determined from
the fitting, which describe the rotational energy levels with an accuracy close
to that of the experimental data. The predictive performance of the model with
respect to highly excited rotational states has been evaluated against the
global variation calculations. The radii of convergence of the effective
rotation Hamiltonian series have been determined.
