  The dilute A_3 model is a solvable IRF (interaction-round-a-face) model with
three local states and adjacency conditions encoded by the Dynkin diagram of
the Lie algebra A_3. It can be regarded as a solvable version of a critical
Ising model in a magnetic field. One therefore expects the scaling limit to be
governed by Zamolodchikov's integrable perturbation of the c=1/2 conformal
field theory. We perform a detailed numerical investigation of the solutions of
the Bethe ansatz equation for the off-critical model. Our results agree
perfectly with the predicted values for the lowest masses of the stable
particles and support the assumptions on the nature of the Bethe ansatz
solutions which enter crucially in a recent thermodynamic Bethe ansatz
calculation of the factorized scattering matrix.
