Abstract:

We show that the quantum dynamics of a system comprised of a subspace Q coupled to a much larger subspace P can be recast as a reduced set of ordinary differential equations with constant coefficients.  These equations can be solved by a single diagonalization of a general complex matrix.  The efficiency of the method is demonstrated via computations on large molecular systems, as the radiationless transitions in pyrazine.  We also present a solution to the "Multi-Channel Quantum Control" problem, where selective and complete  population transfer from an initial bound state to M energetically degenerate continuum channels is achieved.  The control is affected by coherently controlled Adiabatic Passage proceeding via N bound intermediate states.  We illustrate the viability of the method by computationally controlling the multi-channel photodissociation of methyl iodide.