Perspectives on parity violation in chiral molecules: theory, spectroscopic experiment and biomolecular homochirality.

The reflection (or 'mirror') symmetry of space is among the fundamental symmetries of physics. It is connected to the conservation law for the quantum number parity and a fundamental 'non-observable' property of space (as defined by an absolute 'left-handed' or 'right-handed' coordinate system). The discovery of the violation of this symmetry - the non-conservation of parity or 'parity violation' - in 1956/1957 had an important influence on the further development of physics.

Nuclear Spin Symmetry Conservation Studied for Symmetric Top Molecules (CHD, CHD, CHF, and CHCl) in Supersonic Jet Expansions.

We report results on nuclear spin symmetry conservation studied by high resolution spectroscopy of relative line intensities for the A and E nuclear spin isomers of symmetric top molecules CHD, CHD, CHF, and CHCl in supersonic jet expansions with He and Ar as carrier gases. Infrared absorption spectra were measured around 3000 cm by an infrared (lead salt) diode laser and a continuous wave IR-OPO (infrared optical parametric oscillator) locked to a frequency comb. A detailed analysis of the R(2)-line intensities of the CH-stretching fundamental shows that nuclear spin symmetry is conserved for CHD, CHF, and CHCl during the expansion.

Intramolecular vibrational energy redistribution in HCCCHX (X = Cl, Br, I) measured by femtosecond pump-probe experiments in a hollow waveguide.

From the analysis of high resolution overtone spectra it is well established that intramolecular vibrational energy redistribution (IVR) from an initially excited CH-stretching vibration is strongly influenced by its chemical environment. Due to a pronounced Fermi resonance between the CH-stretching and CH-bending vibrations a vibrational energy redistribution on the subpicosecond time scale (∼100 fs) is found for alkyl (sp3) CH-chromophores, whereas this doorway for energy flow is blocked for the acetylenic (sp) CH-stretching vibration because of the much lower CH-bending frequency. From the analysis of the high resolution spectra lifetimes for the initial CH-vibrational excitation of 10-100 ps or longer have been derived.

Synchrotron-Based Highest Resolution Terahertz Spectroscopy of the ν Band System of 1,2-Dithiine (CHS): A Candidate for Measuring the Parity Violating Energy Difference between Enantiomers of Chiral Molecules.

The chiral C symmetric molecule 1,2-dithiine (1,2-dithia-3,5-hexadiene, CHS) has been identified as a possible candidate for measuring the parity violating energy difference between enantiomers. We report here the observation and analysis of the low-frequency fundamental ν using highest resolution synchrotron-based interferometric Fourier transform infrared (FTIR) spectroscopy in the terahertz range with a band center of ν = 6.95375559 THz (ν̃ = 231.