title: Multiphoton population transfer in systems violating the classical twist condition: a comparative study of separatrix crossing in phase space.
abstract: Population transfer in Hamiltonian systems, such as between Rydberg states of atoms and vibrational modes in diatomic molecules, has been both experimentally and theoretically demonstrated. All these systems have the property that the classical frequency of the motion changes monotonically with energy. Referred to as the twist condition, this property makes it possible to transfer population both by chirping a driving field within a ladder climbing scheme and by adiabatically chirping through a multiphoton resonance connecting two bound states. In this paper, we demonstrate that the latter method for population transfer can still be made to work in a system which violates the classical twist condition. We use classical rigid rotor as an example system where the frequency changes monotonically with energy and compare the responsible separatrix crossing mechanism in phase space to that in a system which exhibits an extremum in the frequency-energy profile. We perform both one-dimensional classical and quantum simulations and find that the quantum phase-space distribution mirrors its corresponding classical counterpart.
authors: Department of Physics, Auburn University, Alabama 36849-5311, USA.
authors: Turker
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authors: Topcu
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