Using the example of the HCN molecule, we study theoretically the possibility of selectively breaking the stronger bond in a triatomic molecule by rotationally accelerating it in an optical centrifuge using a combination of two oppositely chirped and counter-rotating strong laser fields. In our simulation the resultant field forces rotational acceleration of the HCN molecule to a point where the centrifugal force between the two heavy atoms ͑C and N͒ exceeds the strength of their ͑triple͒ bond. The effects of bending, rovibrational coupling, and the Coriolis force, which conspire to prevent the molecule from rotational dissociation into HCϩN, can be efficiently counteracted by simple optimization of the frequency chirp.The dipole moment induced in a molecule by a laser field depends on the orientation of the molecule with respect to the laser polarization vector. In turn, interaction of the induced dipole with the same laser field creates an angledependent potential that tends to align the molecule along the laser polarization direction. 1,2 In the simplest case of a linearly polarized far off-resonant field with intensity I 0 and a linear molecule with parallel and perpendicular polarizability tensor components ␣ ʈ and ␣ Ќ , the effective potential is U 0 cos 2 , where is the angle between the molecular axis and the polarization vector, and the well depth U 0 ϭ(␣ ʈ Ϫ␣ Ќ )I 0 /4. Typically, in diatomic molecules such as Cl 2 , I 2 , N 2 , a well-depth of a few tens of meV can be created and sustained for tens of picoseconds using infrared radiation, 3,4 without ionizing the molecule. This well depth can exceed room temperature (kTϷ25 meV), and give rise to efficient alignment of rotationally hot molecules.For a molecule with three different polarizability tensor components, an elliptically polarized field has been used to align the molecule in three dimensions. 5 Molecular alignment has also been used to control simple unimolecular reactions triggered by either parallel or perpendicular transitions; 6,7 the efficiency of the parallel vs the perpendicular transition is controlled by aligning the molecule.The same basic physics can be used to force molecular rotation 8,10 in the so-called ''optical centrifuge,'' as was demonstrated experimentally in Ref. 11 for the diatomic molecule Cl 2 . In that experiment Cl 2 was rotationally accelerated to reach angular momentum states JϾ400 until the centrifugal force broke the bond. The centrifuge involves using a linearly polarized laser field whose polarization vector is slowly rotated. A molecule aligned with the field follows this rotation, and controlled rotational acceleration is forced by accelerating the rotation of the polarization vector. 8 Such a laser field has the form,where L is the carrier frequency, L (t) defines the direction of polarization, and f (t) is the pulse envelope. The centrifuge is created 8 by combining two circularly polarized, counter-rotating fields with slightly different frequencies Ϯ ϭ L Ϯ⍀. In this case the polarization vector rotates with...