  We investigate whether the force and torque exerted by light pressure on an
irregularly shaped dielectric resonator allow to detect resonant frequencies,
delivering information complemental to the scattering cross section by
mechanical means. The peak-to-valley ratio in the torque signal can be many
times larger than in the scattering cross section, and, furthermore, depends on
the structure of the resonance wave pattern. The far-field emission pattern of
the associated quasi-bound states can be tested by the angular dependence of
the mechanical probes at finite amplification rate. We relate the force and
torque to the scattering matrix and present numerical results for an annularly
shaped dielectric resonator.
