Simulated optical forces to cool and trap CH radicals
Abstract
Ultracold molecules provide access to quantum-state controlled chemistry and reaction dynamics through careful studies of reactants, transient intermediates, and products. Today’s experiments are restricted to either species indirectly assembled from laser-cooled atoms or the few species that have been directly laser cooled and trapped using the radiative force. When laser cooling molecules, the multi-level nature of optical cycling schemes naturally decreases the maximum radiative force attainable compared to atoms. While these weaker forces are sufficient to capture and cool molecules in magneto-optical traps (MOTs), they also lead to inefficient slowing of molecular beams prior to loading a MOT. The proposed program aims to tackle this inefficiency by applying a strong rectified dipole force, specifically the bichromatic force (BCF), to the chemically relevant molecule methylidyne (CH) to efficiently slow a molecular beam. The BCF scales linearly with the Rabi frequency O of the driven transition and so, for sufficient laser intensity, can be substantially larger than the radiative force. This point is particularly advantageous for molecules since larger forces can slow molecular beams in shorter times with less spontaneous emission and hence less rovibrational branching into unaddressed dark states. The CH radical appears particularly well-suited to the BCF given its reasonable electronic transition dipole moments (supporting large O at accessible laser intensities) coupled with its large recoil velocity (approximately 7 cm-s). The relatively long-lived excited A2. and B2S- states (greater than300 ns) are also favorable and limit spontaneous emission, the required rovibrational closure and number of repump lasers needed as the beam is slowed. This proposal requests funds for a continuous wave frequency doubled Ti-Sapphire laser to apply the BCF to CH radicals and realize the proposed research goals. Initial experiments plan to characterize the BCF via transverse deflection of the molecular beam before incorporating the required repump lasers and finally slowing the CH beam. We project that the BCF will slow approximately 10^3 times more molecules to the capture velocity of a CH MOT than the equivalent radiative force, which would also require several more repump lasers. This could establish a route towards magneto-optically trapping molecules with less favorable properties for applications such as tests of ultracold organic chemistry and improved precision measurements.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 29, 2024
- Source ID
- FA95502310074
Entities
People
- Daniel Mccarron
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Connecticut