The rotational invariance under the usual physical angular momentum of the
SUq(2) Hamiltonian for the description of rotational molecular spectra is
explicitly proved and a connection of this Hamiltonian to the formalism of
Amal'sky is provided. In addition, a new Hamiltonian for rotational spectra is
introduced, based on the construction of irreducible tensor operators (ITOs)
under SUq(2) and use of q-deformed tensor products and q-deformed
Clebsch-Gordan coefficients. The rotational invariance of this SUq(2) ITO
Hamiltonian under the usual physical angular momentum is explicitly proved and
a simple closed expression for its energy spectrum (the ``hyperbolic tangent
formula'') is introduced. Numerical tests against an experimental rotational
band of HF are provided.Comment: 27 pages, LaTe