Controlling rotation in the molecular frame with an optical centrifuge

Emil J Zak,Jochen Küpper,Andrey Yachmenev

doi:10.1103/physrevresearch.3.023188

Abstract

We computationally demonstrate a new method for coherently controlling the rotation-axis direction in asymmetric top molecules with an optical centrifuge. Appropriately chosen electric-field strengths and the centrifuge's acceleration rate allow to generate a nearly arbitrary rotational wavepacket. For D$_2$S and 2H-imidazole (C$_3$H$_4$N$_2$) we created wavepackets at large values of the rotational quantum number $J$ with the desired projections of the total angular momentum onto two of the molecules' principal axes of inertia. One application of the new method is three-dimensional alignment with a molecular axis aligned along the laser's wave vector, which is important for the three-dimensional imaging of molecules yet not accessible in standard approaches. The simultaneous orientation of the angular momentum in the laboratory frame and in the molecular frame could also be used in robust control of scattering experiments.

Highlights

Preparing well-defined molecular samples, maximally fixed in three-dimensional space, has been a long-term goal in physics, chemistry, and related fields such as quantum technology [1,2,3,4]
We computationally demonstrate a new method for coherently controlling the rotation-axis direction in asymmetric top molecules with an optical centrifuge
We computationally demonstrate a new type of rotational coherent control by exciting the rotation of an asymmetric top molecule about two different axes of inertia with simultaneously fully controlled orientation of the angular momentum in both, the laboratory-fixed and the molecule-fixed, frames

Summary

INTRODUCTION

Preparing well-defined molecular samples, maximally fixed in three-dimensional space, has been a long-term goal in physics, chemistry, and related fields such as quantum technology [1,2,3,4]. A highly efficient technique used to generate and control the molecule’s angular momentum is the optical centrifuge [37,38], which is a strong nonresonant linearly polarized laser pulse that performs accelerated rotation of its polarization about the direction of propagation. It can excite molecules into rotational states with extremely large angular momentum, creating an ensemble of superrotors [39,40]. By adjusting the turn-off time we demonstrate the two types of three-dimensional (3D) alignment of asymmetric top molecules, with either of the two stable rotation axes pointing along the field’s wave vector, so called k alignment [13,14,49]

PRINCIPAL-ROTATION STATES

RESULTS AND DISCUSSION

SUMMARY