# Guiding neutral polar molecules by electromagnetic vortex field --- a classical approach

## TL;DR

This paper demonstrates, through classical mechanics, that electromagnetic vortex fields can potentially trap and guide neutral molecules with permanent electric dipole moments, though practical implementation faces challenges due to small dipole values and chaotic trajectories.

## Contribution

It introduces a classical approach to guiding neutral molecules with PEDMs using electromagnetic vortex fields, highlighting conditions for stable trajectories and the influence of additional electric fields.

## Key findings

- Electromagnetic vortex fields can trap molecules with PEDMs.
- Stable circular trajectories require precise parameter tuning.
- Chaotic trajectories are common without special adjustments.

## Abstract

It is shown, within classical mechanics, that the field of an electromagnetic vortex is capable of capturing and guiding neutral molecules endowed with a permanent electric dipole moment (PEDM). Similarly as in the case of the magnetic field applied to elementary particles or atoms, this effect turns out to be very delicate because of the small values of PEDM observed in real molecules. They amount to $2\times10^{5}\, e{\mathrm{fm}}$ (electron charge $\times$ fermi) or less, which requires the use of very strong electric fields. It has also been observed that there exists a threshold in field strength above which the particles are ejected from the trap. Trajectories of guided particles are usually quite chaotic, which is a consequence of non-linearity of the equations of motion. With a very special and precise adjustment of parameters, a regular (i.e., circular, in the transverse plane) trajectory can be obtained. The presence of an additional constant electric field pointing along the direction of the wave propagation might help to achieve the necessary tuning and realize such trajectories.