Reference.Variables.expect
Variable "expect" in MATLAB version of WavePacket
This global, structured(!) variable holds expectation values of observables. Inside WavePacket, they are only used for plotting and logfile output. However, they may also be used for post-processing outside WavePacket since they contain the main physical results from wavefunction or trajectory calculations. After running a WavePacket simulation, this information is made available in the Matlab console by simply issueing the "global expect" command.
- For time-independent calculations using qm_bound, the index i denotes the i-th calculated eigenstate.
- For time-dependent calculations using qm_propa, the index i denotes the i-th main time step.
For the observables listed in the following table, expectation values are routinely calculated in every WavePacket simulation
| observable | description | cell index |
|---|---|---|
| pop | populations of channels | n.a. |
| pos {•} | positions | spatial components |
| mom {•} | momenta | spatial components |
| pot | potential energy | n.a. |
| kin | kinetic energy | n.a. |
| amo {•} | additional multiplicative operators; if defined in hamilt.amo | individual AMO's |
For each of the above observables of interest, WavePacket creates an object of the (generic) class +exp/generic, containing information for each channel, as well as averaged over all channels. In particular, this class contains the following properties
| property | description |
|---|---|
| cha {•} | mean/average values for each channel |
| unc {•} | uncertainties for each channel |
| tot | total, i.e. averaged over all channels |
For example, you'll find the expectation value of the third component of the position vector for the second channel for the 42nd time step here:
expect.pos{3}.cha{2}(42)
In addition to the above objects, the structure "expect" also holds a field "total", simply containing a time series of the total energy, i.e. averaged over all channels, obtained from the full Hamiltonian, including the contributions of coupling to external fields (which is not (yet?) included in any of the values listed above). For example, you'll find the total energy for the 42nd time step here:
expect.total(42)
