  A practical computation method to find the eigenvalues and eigenspinors of
quantum mechanical Hamiltonian is presented. The method is based on reduction
of the eigenvalue equation to well known geometric algebra rotor equation and,
therefore, allows to replace the usual det(H-E)=0 quantization condition by
much simple vector norm preserving requirement. In order to show how it works
in practice a number of examples are worked out in Cl_{3,0} (monolayer graphene
and spin in the quantum well) and in Cl_{3,1} (two coupled two-level atoms and
bilayer graphene) algebras.
