I created a laser induced alignment simulator during my PhD in physical chemistry at Femtolab in Aarhus. The program solves the time-dependent Schrödinger equation for the rotation of a molecule subject to one or more intense and ultra-short laser pulses (fs-ps-ns).  It works for linear molecules and symmetric tops. The program has proven very useful for understanding alignment experiments, and quickly reproduces experimental results accurately and reliably.

To my knowledge, this is the first program ever to simulate 〈cos²θ_2D〉, the 2D degree of alignment, which is the typical observable used in alignment experiments employing Coulomb explosion with the widely used velocity-map imaging spectrometer technique. Here, the alignment is projected down to the 2D detector surface. Other simulators only calculate 〈cos²θ〉 the 3D degree of alignment, which is difficult or expensive to measure.

In this way, theory can be compared directly to experiment. Read chapters 2 and/or 3 of my PhD thesis for much more information and comparisons with real experiments.

You can download the alignment calculator with git

git clone https://andersaspegren.dk/git/alignment_calculator.git

or directly as a tar.bz2 or zip file. If you use the calculator or code from it in your research, please cite A. A. Søndergaard, B. Shepperson and H. Stapelfeldt, The Journal of Chemical Physics 147, 1, 013905 (2017), doi: 10.1063/1.4975817.

Example screenshots