Rabi cycling of a vibrational wavepacket between two harmonic potentials.
Consider a system with Hamiltonian

having only two eigenstates,

and

with energies

Define

The most general wavefunction for this system may be written as
The coefficients
a(t) and
b(t) are subject to the constraint that

If we couple this system to a light field, represented as

then we may write the Time Dependent Schrödinger Equation in matrix form as:
Invoking the Rotating Wave Approximation (neglecting the effort of

and choosing intial conditions

the populations as functions of time are given by:
where

and the Rabi frequency,

is defined as

The movie shows the evolution of a wavepacket between two harmonic surfaces under strong field excitation. For

the system reduces to a 2-level system and the Rabi solution is recovered (with the addition of the counterrotating terms).