Rabi cycling of a vibrational wavepacket between two harmonic potentials.
Consider a system with Hamiltonian
![H0](ch15/img/formul153.png)
having only two eigenstates,
![The Actual Formula](ch15/img/formul154.png)
and
![The Actual Formula](ch15/img/formul155.png)
with energies
![The Actual Formula](ch15/img/formul156.png)
Define
![The Actual Formula](ch15/img/formul157.png)
The most general wavefunction for this system may be written as
The coefficients
a(t) and
b(t) are subject to the constraint that
![The Actual Formula](ch15/img/formul159.png)
If we couple this system to a light field, represented as
![The Actual Formula](ch15/img/formul160.png)
then we may write the Time Dependent Schrödinger Equation in matrix form as:
Invoking the Rotating Wave Approximation (neglecting the effort of
![The Actual Formula](ch15/img/formul166.png)
and choosing intial conditions
![The Actual Formula](ch15/img/formul162.png)
the populations as functions of time are given by:
where
![The Actual Formula](ch15/img/formul164.png)
and the Rabi frequency,
![The Actual Formula](ch15/img/formul167.png)
is defined as
![The Actual Formula](ch15/img/formul168.png)
The movie shows the evolution of a wavepacket between two harmonic surfaces under strong field excitation. For
![X0](ch15/img/formul165.png)
the system reduces to a 2-level system and the Rabi solution is recovered (with the addition of the counterrotating terms).