Resonant interactions of diatomic molecules with intense laser fields: time-independent multi-channel Green function theory and application to experiment

The resonant interactions of diatomic molecules with UV and VUV intense las er radiation are investigated within an original non-perturbative approach of multi-channel nuclear wave functions and Green's functions. The interact ions are considered in a quantum-electrodynamic picture where the laser fie ld and molecule are treated as quantum objects. The presented theoretical a pproach is formulated as a multiquantum technique to calculate analytically the resonant laser-molecule interactions and molecular photoprocesses. The method permits to include the non-linear impact of a resonant laser upon i ntra-molecular motion beyond an adiabatic approximation and may be applied for laser intensities until 10(15) W cm(-2). The theory of wave functions a nd Green's functions of multi-channel Schrodinger equation is elaborated wi thout perturbative restrictions on inter-channel couplings. The multi-chann el quasi-classical approximation is developed to integrate the coupled equa tions for nuclear motion in simple matrix form. The theoretical approach pr oposed is used to study the intense-field photodissociation and photoabsorp tion, multi-photon resonant ionization and dissociation, dynamic polarizabi lity and resonance Raman scattering from rotating diatomic molecules. The w ell-known laser-induced hardening and softening of intra-molecular bonds ar e reformulated. The new resonances in the molecular absorption, ionization and dissociation, arisen in resonant laser fields, are examined too. The ph enomena of resonant laser field selective orientation and alignment of non- dipole diatomic molecules, laser-induced molecular dipole moment, temperatu re-dependent polarization of molecular gases, non-perturbative amplificatio n of scattered laser radiation in resonant medium are analysed in detail. T he known experimental observations of laser-induced non-linear effects and circumstances for new strong-field experiments are discussed. (C) 2000 Else vier Science B.V. All rights reserved.