Prof. Dr. Peter Schwerdtfeger, Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University (Albany Campus), Auckland, New Zealand
Lundi 10 octobre 2010, 11^h00
Emil Fischer's studies of peptides and sugars led to chiral molecules (D-sugars and L-amino acids) and to the confirmation of Pasteur's conjecture that the universe is disymmetric. Friedrich Hund regarded the existence of stable chiral molecules as paradoxial (the Hund Dilemma). A fundamental discovery of this century is that our Universe is left handed (Weinberg-Salam-Glashow theory), the electro-weak interaction (parity-odd) gives rise to primarily left-spinning electrons during beta decay. In 1957 Lee and Yang discovered parity violation (PV) in the K+ decay, which was confirmed shortly after by Wu et al. for the β- decay. In the last decade PV effects in atomic transitions have been measured and calculated very accurately confirming the so-called standard model in particle physics. It is now well accepted that PV can lead to a small energy difference between enantiomers of chiral molecules (Vn -Ae coupling for the Z-exchange), although there is no experimental verification yet of this symmetry breaking effect. Current high resolution optical spectroscopy carried out in the CO2 laser frequency range (878-1108 cm-1) currently achieves resolutions of about Δν= 1 Hz. Recent calculations show that PV effects in vibrational transitions of chiral methane derivates CFXYZ (X,Y,Z= H, Cl, Br, I) are in the mHz range and below the detection limit. Our research group is currently searching for molecules including heavy elements (Z5-scaling) to achieve PV effects in the Hz range. Two new compounds are promising candidates, Cl-Hg- CHFCl and OSeClI. A short discussion on the Yamagata hypothesis is provided, which states that one chiral form is stabilized by PV giving rise to biomolecular homochirality in nature.