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Discriminatory optical force for chiral molecules

Robert P Cameron, Stephen M Barnett, Alison M Yao
2014 New Journal of Physics  
We suggest that the force F exerted upon a chiral molecule by light assumes the form F = a∇w + b∇h under appropriate circumstances, where a and b pertain to the molecule whilst w and h are the local densities of electric energy and helicity in the optical field; the gradients ∇ of these quantities thus governing the molecule's centre-of-mass motion. Whereas a is identical for the mirrorimage forms or enantiomers of the molecule, b has opposite signs; the associated contribution to F therefore
more » ... on to F therefore pointing in opposite directions. A simple optical field is presented for which ∇w vanishes but ∇h does not, so that F is absolutely discriminatory. We then present two potential applications: a Stern-Gerlach-type deflector capable of spatially separating the enantiomers of a chiral molecule and a diffraction grating to which chiral molecules alone are sensitive; the resulting diffraction patterns thus encoding information about their chiral geometry.
doi:10.1088/1367-2630/16/1/013020 fatcat:q63gxaj3ufdlposeh3jcqvspca