Molecular influence on nuclear-quadrupole-coupling effects in laser induced alignment

TL;DR

This paper investigates how nuclear-quadrupole interactions influence the laser-induced alignment of asymmetric-top molecules, highlighting the roles of hyperfine structures, nuclear spins, and rotational states in the dynamics.

Contribution

It provides a detailed analysis of nuclear-quadrupole effects on molecular alignment, emphasizing the dependence on nuclear spins and rotational excitation levels, which was not thoroughly explored before.

Findings

Hyperfine splittings significantly affect spin-rotational dynamics.

Quadrupole coupling impact diminishes at high rotational excitations.

Nuclear spin and molecular symmetry influence alignment behavior.

Abstract

We studied the effect of nuclear-quadrupole interactions on the field-free impulsive alignment of different asymmetric-top molecules. Our analysis is focused on the influence of the hyperfine- and rotational-energy-level structures. These depend on the number of nuclear spins, the rotational constants, and the symmetry of the tensors involved in the nuclear spin and external field interactions. Comparing the prototypical large-nuclear-spin molecules iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, and 2,5-diiodobenzonitrile, we demonstrate that the magnitude of the hyperfine splittings compared to the rotational-energy splittings plays a crucial role in the spin-rotational dynamics after the laser pulse. Moreover, we point out that the impact of the quadrupole coupling on the rotational dynamics decreases when highly excited rotational states dominate the dynamics.