ISOMERIZATIONS CONTROLLED BY ULTRASHORT INFRARED-LASER PULSES - MODEL SIMULATIONS FOR THE INVERSION OF LIGANDS(H) IN THE DOUBLE-WELL POTENTIAL OF AN ORGANOMETALLIC COMPOUND, [(C5H5)(CO)2FEPH2]

Model simulations for the inversion of ligands (H) in the double-well potential of [(C5H5)(CO)2FePH2] yield selective isomerizations controlled by a series of intense picosecond infrared (IR) laser pulses. Essentially, these pulses induce a corresponding series of selective molecular transitions, from the vibrational ground state to more excited states of the reactant isomer, via a delocalized state above the potential barrier, to a highly excited state of the product isomer. Simple superposition of the individual laser pulses with analytical, e.g., Gaussian, shapes yield the effective overall pulse which may have a rather complex structure, Optimal laser parameters are tailored to maximum population of the product isomers. Repeated application of these overall pulses produces pure product isomers. This rather general strategy for selective isomerization is compared with inefficient alternative ones. The simulations involve various theoretical techniques, from quantum chemical ab initio calculations of the relevant double-well potential energy surface and electric dipole function, to calculations of vibrational states and dipole matrix elements, to evaluation of the laser-induced molecular dynamics by propagation of the algebraic version of the time-dependent Schrodinger equation.