Time-dependent photoelectron angular distributions from multiphoton ionization of molecules with broad rotational wave packets

Rotational dynamics of impulsively aligned N$_{\mathrm{2}}$ and CO$_{\mathrm{2}}$ molecules are used to study the photoelectron angular distributions from multiphoton ionization by 266 nm pulses. Electron momentum distributions are recorded using a velocity map imaging spectrometer, Abel-inverted using the pBasex algorithm, and then fitted to delay-dependent moments of the molecular axis distributions. The analysis provides access to high-order asymmetry ($\beta )$ parameters of the photoelectron angular distributions.