A special, seemingly infinite sequence of saddle-node bifurcations of the driven double-well Duffing oscillator is investigated. It occurs in resonances with even torsion number and shows period-adding behavior. The sequence of saddle-node bifurcations gives rise to a regular window structure of higher and higher period. An empirical law is given of the organization of periods and torsion numbers when proceeding along the sequence to the limit.

• Received 3 January 1991

DOI:https://doi.org/10.1103/PhysRevA.44.916