Coherent Enantiomer‐Selective Population Enrichment Using Tailored Microwave Fields

We report the experimental demonstration of coherent enantiomer‐selective enrichment of chiral molecules by employing a novel microwave five‐pulse scheme. Our results show that enantiomers can be selectively transferred to a rotational level of choice by applying sequences of resonant microwave pulses in a phase‐ and polarization‐controlled manner. This is achieved by simultaneously exciting all three kinds of electric dipole‐allowed rotational transitions and monitoring the effect on a fourth rotational transition of choice. Using molecular beams, we apply our method to two chiral terpenes and obtain a 6 % enantiomeric enrichment, which is one order of magnitude larger than that recently reported in a buffer‐gas cell experiment. This approach establishes a robust scheme for controlled manipulation of enantiomers using tailored microwave fields and opens up new avenues for chiral purification and enrichment that can be used in a broad scope of analytical or spectroscopic applications.     

Inside Cover: Switching the Chirality of Single Adsorbate Complexes (Angew. Chem. Int. Ed. 22/2009)

Wrong handedness? No problem! K.‐H. Ernst et al. describe in their Communication on page 4065 ff. how the chirality of single adsorbates can be switched into the opposite enantiomeric state. By using inelastically tunneling electrons from the tip of a scanning tunneling microscope in an ultra‐high vacuum, certain molecular vibrations are excited that, in turn, cause different actions such as hopping, rotation, and chirality conversion at the surface.