Characterising and optimising impulsive molecular alignment in mixed gas samples

Accessing the molecular frame through strong-field alignment of distributions of gas phase molecules

A rationale for creating highly aligned distributions of molecules is that it enables vector properties referenced to molecule-fixed axes (the molecular frame) to be determined. In the present work, the degree of alignment that is necessary for this to be achieved in practice is explored. Alignment is commonly parametrized in experiments by a single parameter, [Formula: see text], which is insufficient to enable predictive calculations to be performed. Here, it is shown that, if the full distribution of molecular axes takes a Gaussian form, this single parameter can be used to determine the complete set of alignment moments needed to characterize the distribution. In order to demonstrate the degree of alignment that is required to approach the molecular frame, the alignment moments corresponding to a few chosen values of [Formula: see text] are used to project a model molecular frame photoelectron angular distribution into the laboratory frame. These calculations show that [Formula: see text] needs to approach 0.9 in order to avoid significant blurring to be caused by averaging.This article is part of the theme issue 'Modern theoretical chemistry'.

Role of rotational wave packets in strong field experiments

Complex revival features of rotational wave packets are obtained from the interplay of a molecular rotational distribution and a measured physical observable. The analysis of the measured temporal behavior can be used to retrieve either one or both quantities. We show here the first observation of high order fractional revival (up to 1/12 in CO2) using time-of-flight measurements of ion yields leading to the information required for full reconstruction of the rotational wave packet. We further show via an analysis of higher order fractional revivals in high harmonic generation that new information on the participating ionic channels can be clearly identified, showing the general implication of our results.