Bichromatic magneto-optical trapping for $ J\rightarrow J,J-1 $ configurations

TL;DR

This paper introduces a bichromatic magneto-optical trapping scheme for $J ightarrow J,J-1$ transitions, demonstrating effective cooling and trapping forces even without Zeeman splitting, through theoretical models and simulations.

Contribution

It presents a novel bichromatic MOT configuration for $J ightarrow J,J-1$ transitions, enabling trapping without Zeeman effect in the excited state.

Findings

Effective cooling and trapping forces are achieved with bichromatic fields.

The scheme works even when Zeeman splitting is absent in the excited state.

Simulations confirm the theoretical predictions for molecular ions like C$_2^-$.

Abstract

A magneto-optical trap (MOT) of atoms or molecules is studied when two lasers of different detunings and polarization are used. Especially for $J\rightarrow J,J-1$ transitions, a scheme using more than one frequency per transition and different polarization is required to create a significant force. Calculations have been performed with the simplest forms of the $J\rightarrow J-1$ case (i.e. $J''=1 \rightarrow J'=0$) and $J\rightarrow J$ case (i.e. $J''=1/2 \rightarrow J'=1/2$). A one dimensional (1D) model is presented and a complete 3D simulation using rate equations confirm the results. Even in the absence of Zeeman effect in the excited state, where no force is expected in the single laser field configuration, we show that efficient cooling and trapping forces are restored in our configuration. We study this mechanism for the C$_2^-$ molecular anion as a typical example of the interplay between the two simple transitions $J \rightarrow J,J-1$.