  We have identified a novel phase stability mechanism from the intracavity
field-induced self-organization of a fast-moving molecular beam into travelling
molecular packets in the bad cavity regime, which is then used to decelerate
the molecular packets by feedback-controlled time-varying laser pumps to the
cavity. We first applied the linear stability analysis to derive an expression
for this self-organization in the adiabatic limit and show that the
self-organization of the beam leads to the formation of travelling molecular
packets, which in turn function as a dynamic Bragg grating, thus modulating
periodically the intracavity field by superradiant scattering of the pump
photons. The modulation encodes the position information of the molecular
packets into the output of the intracavity field instantaneously. We then
applied time-varying laser pumps that are automatically switched by the output
of the intracavity field to slow down the molecular packets via a feedback
mechanism and found that most of the molecules in the molecular packets are
decelerated to zero central velocity after tens of stages. Our cavity-based
deceleration proposal works well in the bad cavity regime, which is very
different from the conventional cavity- based cooling strategies where a good
cavity is preferred. Practical issues in realizing the proposal are also
discussed.
