Abstract
Recent theoretical investigations have indicated that rapid optical cycling should be feasible in complex polyatomic molecules with diverse constituents, geometries and symmetries. However, as a composite molecular mass grows, so does the required number of photon scattering events necessary to decelerate and confine molecular beams using laser light. Utilizing coherent momentum exchange between light fields and molecules can suppress spontaneous emission and significantly reduce experimental complexity for slowing and trapping. Working with BaH as a test species, we have identified a robust, experimentally viable configuration to achieve large molasses-like cooling forces for molecules using polychromatic optical fields addressing both $X-A$ and $X-B$ electronic transitions, simultaneously. Using numerical solutions of the time-dependent density matrix as well as Monte Carlo simulations, we demonstrate that creation of Suppressed Emission Rate (SupER) molasses with large capture velocities ($\sim 40$ m/s) is generically feasible for polyatomic molecules of increasing complexity that have an optical cycling center. Proposed SupER molasses are anticipated to not only extend quantum control to novel molecular species with abundant vibrational decay channels, but also significantly increase trapped densities for previously laser-cooled diatomic and triatomic species.
Highlights
We have presented an experimentally viable method for achieving large optical molasses-like cooling forces for molecules using polychromatic optical fields driving coherent dynamics in a four-level system
Using direct numerical solutions of the time-dependent density matrix as well as Monte Carlo simulations of the cooling dynamics, we provide evidence that achieving rapid damping of a wide velocity capture range toward zero velocity should be possible for diatomic and polyatomic molecules with various constituents and geometries. proposed suppressed emission rate (SupER) molasses method relies on spontaneous emission coupling between two coherently driven two-level systems and should be realizable with many complex nonlinear molecules for which scattering ∼100–1, 000 photons has been previously proposed [14,64] or already experimentally demonstrated [16,31]
We anticipate that large velocity damping coefficients together with a broad velocity capture range will enable extension of laser-based cooling and coherent quantum control to novel molecular species with complex internal structures, weak optical transitions, and abundant vibrational decay channels, providing a fruitful experimental platform for realizing many exciting applications in fundamental physics and applied quantum technologies
Summary
Optical control over atomic spatial degrees of freedom is one of the cornerstones of modern atomic physics [1,2] and quantum technologies [3,4]. For certain diatomic species with small off-diagonal FCFs (i.e., v = v ), one or two additional lasers can be used to repump molecules from excited vibrational levels v > 0 back to the ground vibrational state v = 0, enabling scattering of 104 photons [25,26,27] needed to slow molecular beams to below the capture velocity of a 3D molecular magneto-optical trap with vcap ≈ 5–10 m/s [28,29]. (F00 = 0.954), eight additional repumping lasers are needed to scatter ∼104 photons [15,30,31], presenting a significant technical challenge for extending Doppler slowing and trapping methods to heavier (e.g., YbOH) or more complex (e.g., CaOCH3) molecules Toward this end, various alternative techniques have been developed for efficient momentum transfer from the laser light to atoms or molecules, while minimizing spontaneous emissions [32]. The proposed suppressed emission rate (SupER) molasses could be either combined with coherent slowing techniques or used with previously magneto-optically trapped species to capture and cool molecules with v > vcap,MOT
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