Right handed or left handed? Forbidden x-ray diffraction reveals chirality.
Enantiomers, or stereoisomers, have crystal structures that are mirror images of each other and are thus handed, like our right and left hands. The physical properties of enantiomers are identical except for optical activity, which rotates linearly polarized light by equal amounts but in opposite directions. While conventional x-ray Bragg diffraction can determine crystal structures, it does not distinguish between right- and left-handed crystals. We show resonant Bragg diffraction using circularly polarized x rays reveals the handedness of crystals by coupling x-ray helicity to a crystal screw axis. The intensity of resonantly allowed reflection of alpha-quartz is well described by an admixture of a parity-even and a parity-odd process. Our results are of general importance and demonstrate a new method to directly study chiral motifs in structures that include biomaterials, liquid crystals, magnets, multiferroics, etc.
RIKEN SPring-8 Center, Sayo, Hyogo 679-5148, Japan.
Yoshikazu
Y
Tanaka
Tomoyuki
T
Takeuchi
Stephen W
SW
Lovesey
Kevin S
KS
Knight
Ashish
A
Chainani
Yasutaka
Y
Takata
Masaki
M
Oura
Yasunori
Y
Senba
Haruhiko
H
Ohashi
Shik
S
Shin
D001672:Biocompatible Materials / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D011791:Quartz / Q000737:chemistry*; D013237:Stereoisomerism; D014961:X-Ray Diffraction
D001672:Biocompatible Materials; D011791:Quartz