Photoinduced molecular rotational and fragmentation dynamics are dramatically affected by very strong radiative interactions. The hybrid molecule-plus-field system, described in terms of pendular states, offer the possibility of producing aligned molecules. The HCN molecule, within a linear rigid rotor description, is taken as an illustration. The results show, in particular, the difference in the alignment properties when the molecule is excited by sudden versus adiabatic laser pulses. Dissociation enhancement and stabilisation processes are controlled by a few elementary high field mechanisms. In the IR (low frequency) regime, the dissociation cross-section may be enhanced by barrier suppression mechanism. But, there still exits a possibility of stabilisation, when a proper synchronisation between nuclear vibrational motion and the field oscillation is reached (dynamical quenching). In the Vis-UV (high frequency) regime, the chemical bond is modified (softened or hardened) by barrier lowering or vibrational trapping mechanisms. These mechanisms are the basis of a comprehensive interpretation of angular results kinetic energy distributions of the multiphoton above-threshold dissociation spectra. The H₂⁺ molecule, photodissociating by interaction with an Nd:YAG laser at 532 nm and for intensities of 10-50 TW/cm², is taken as an illustrative exmaple, for which some experimental data are available.

"Atoms, Molecules and Quantum Dots in Laser Fields: Fundamental Processes", N. Bloembergen, N. Rahman & A. Rizzo, eds., Italian Physical Society Conference Proceedings 71, 29 (2000).

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