Strong infrared fields can be used for controlled spinning of molecules to very high angular momentum states. The angular momentum acquired can be sufficient to break molecular bonds. The approach is suitable for all anisotropic molecules, and we illustrate it by dissociating a homonuclear diatomic Cl2, with optical centrifuge efficiently separating Cl 35 and Cl 37 isotopes and thus demonstrating high sensitivity to the moment of inertia. [S0031-9007(99)09026-2] PACS numbers: 33.80.Rv, 82.50.Fv Optical manipulation of atoms (trapping, cooling, acceleration) has grown into a well-developed and established field. Its successful use of resonant processes is difficult to mimic for manipulation of molecules, due to the complexity of molecular energy spectra. However, intense nonresonant fields can provide forces similar to or even stronger than the resonant weak fields used in atom optics. Nonresonant forces have been long utilized in the manipulation of microscopic particles [1,2] but were only recently demonstrated for molecules, in optical deflection [3] and trapping [4] experiments. Molecular optics has a rich potential due to additional degrees of freedom offered by molecules. A range of molecular optics devices has been proposed [5] to control the external degrees of freedom using strong fields, while the field of coherent (or, more generally, active) control has been exploring ways to control the internal degrees of freedom [6]. We propose to use a nonresonant strong field to exert large optical torques on anisotropic molecules, leading to controlled molecular rotations induced with a simple pulse. This follows the work on strong field alignment [7] and complements the application of feedback control methods [8] to optimally excite specific angular momentum states. Molecular dissociation via rotations is used to demonstrate our method. The scheme distinguishes between molecules based on their moment of inertia, and thus acts as an optical centrifuge. An anisotropic molecule placed in a linearly polarized infrared laser field experiences a time-averaged (over the laser cycle) potential 2U0 cos 2 u due to the induced dipole moment interacting with the electric field. Here u is the angle between laser polarization and molecular axis, and U0 › s1y4 ds a k 2a ’ d E 2 , with E the field amplitude and ak and a’ the polarizability components parallel and perpendicular to the molecular axis [7]. Oblong molecules have ak .a ’ and align with the electric field. For most diatomics, U0 , 30 100 meV can be achieved before ionization becomes important on the nanosecond time scale [3]. Imagine now slowly rotating the polarization of the infrared field about a fixed axis —the molecule will follow and rotate with the same angular frequency. Accelerating the rotation of the polarization will increase the molecule’s angular momentum in a controlled manner. This rotation results in large centrifugal forces which can distort or even break the molecular bonds, including those in homonuclear diatomics which do not readily absorb in the infrared. The slowly rotating potential is produced by the field $ E › E0 cosvt f ˆ x cosfLstd 1 ˆ