# Coherent Bichromatic Force Deflection of Molecules

February 12, 2018

Fig. 1* [Reprinted with permission]

In a recent article in Physics Review Letters, members of Doyle group, with colelagues from University of Connecticut, Storrs, demonstrate the effect of the coherent optical bichromatic force on a molecule, the polar free radical strontium monohydroxide (SrOH). A dual-frequency retroreflected laser beam addressing the ${\stackrel{˜}{X}}^{2}{\mathrm{\Sigma }}^{+}↔{\stackrel{˜}{A}}^{2}{\mathrm{\Pi }}_{1/2}$ electronic transition coherently imparts momentum onto a cryogenic beam of SrOH. This directional photon exchange creates a bichromatic force that transversely deflects the molecules. By adjusting the relative phase between the forward and counterpropagating laser beams, the researchers reverse the direction of the applied force, achieving a momentum transfer of $70\hslash k$ with minimal loss of molecules to dark states. Modeling of the bichromatic force is performed via direct numerical solution of the time-dependent density matrix and is compared with experimental observations. The authors believe these results open the door to further coherent manipulation of molecular motion, including the efficient optical deceleration of diatomic and polyatomic molecules with complex level structures.

* See Ivan Kozyryev, Louis Baum, Leland Aldridge, Phelan Yu, Edward E. Eyler, and John M. Doyle, "Coherent Bichromatic Force Deflection of Molecules," Phys. Rev. Lett. 120 (8 Feb 2018) DOI: https://doi.org/10.1103/PhysRevLett.120.063205.