Alignment of asymmetric-top molecules using multiple-pulse trains

TL;DR

This paper theoretically investigates how multiple-pulse laser sequences can effectively align asymmetric-top molecules like SO_2, highlighting the impact of pulse timing and polarization on alignment strength and dynamics.

Contribution

It introduces and compares two pulse sequence strategies for aligning asymmetric-top molecules, revealing the advantages of fast pulse trains and explaining differences from symmetric-top behavior.

Findings

Fast pulse sequences produce stronger one-dimensional alignment.

Equally spaced pulses matching revival times optimize alignment.

Elliptically polarized pulses do not improve alignment.

Abstract

We theoretically analyze the effectiveness of multiple-pulse laser alignment methods for asymmetric-top molecules. As an example, we choose SO_2 and investigate the alignment dynamics induced by two different sequences, each consisting of four identical laser pulses. Each sequence differs only in the time delay between the pulses. Equally spaced pulses matching the alignment revival of the symmetrized SO_2 rotor model are exploited in the first sequence. The pulse separations in the second sequence are short compared to the rotation dynamics of the molecule and monotonically increase the degree of alignment until the maximum alignment is reached. We point out the significant differences between the alignment dynamics of SO_2 treated as an asymmetric-top and a symmetric-top rotor, respectively. We also explain why the fast sequence of laser pulses creates considerably stronger one-dimensional molecular alignment for asymmetric-top molecules. In addition, we show that multiple-pulse trains with elliptically polarized pulses do not enhance one-dimensional alignment or create three-dimensional alignment.