Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (03): 473-478.doi: 10.3866/PKU.WHXB201212273


Experimental Test of“Parity-Time Asymmetry”in Electron Spin-Flip Raman Scattering of the N+H…O Hydrogen Bond in Chiral Alanine Crystals

WANG Wen-Qing1, GONG Yan1,2, SHEN Xin-Chun1, ZHANG Yu-Feng1,2   

  1. 1 Beijing National Laboratory for Molecular Sciences, Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China;
    2 School of Materials Science & Engineering, Beijing Institute of Fashion Technology, Beijing 100029, P. R. China
  • Received:2012-11-13 Revised:2012-12-24 Published:2013-02-25
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21002006, 20452002) and Special Program for Key Basic Research of the Ministry of Science and Technology, China (2004-973-36).


Spontaneous symmetry breaking of the N+H…O bond in chiral alanine crystals around 270 K was detected in situ by Raman vibrational scattering with b(cc)b geometry. An electron spin-flip transition of the N+H…O mode in D-/L-alanine was observed by the scattering of light with left/right orientation and its spin projection antiparallel to the direction of propagation. It is an internal magnetic field originated from the spin-orbit interaction. An obvious Raman wavenumber shift with opposite in sign and roughly one third of the asymmetry (A) of the scattered photon between D- and L-alanine crystals was observed. This shift was not seen in polycrystalline powder measurements because spin is an axial vector. An electron spin-flip transition of the methyne (Cα-H) mode around 260 K was shown to be approximative coincidence by examining the temperature-dependent relative intensity of asymmetric Raman scattering with c(aa)c geometry. This article provides evidence for the true chirality and parity-time (PT) asymmetry in molecular clusters of D- and L-alanine crystals.

Key words: Parity-time asymmetry, Spontaneous symmetry breaking, Asymmetric Raman scattering, Polar N+H…O bond, Methyne, Electron spin-flip transition, True chirality, D- and L-alanine crystals