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.

High-resolution FTIR spectroscopy of trisulfane HSSSH: a candidate for detecting parity violation in chiral molecules.

We report the first successful high-resolution analyses of the Fourier transform infrared (FTIR) spectrum of trisulfane. A band centered at 861.0292 cm can be assigned unambiguously to the chiral trans conformer by means of ground state combination differences in comparison with known rotational spectra.

Effects of corn silage and grass silage in ruminant rations on diurnal changes of microbial populations in the rumen of dairy cows.

Here, we examined diurnal changes in the ruminal microbial community and fermentation characteristics of dairy cows fed total mixed rations containing either corn silage (CS) or grass silage (GS) as forage. The rations, which consisted of 52% concentrate and 48% GS or CS, were offered for ad libitum intake over 20 days to three ruminal-fistulated lactating Jersey cows during three consecutive feeding periods. Feed intake, ruminal pH, concentrations of short chain fatty acids and ammonia in rumen liquid, as well as abundance change in the microbial populations in liquid and solid fractions, were monitored in 4-h intervals on days 18 and 20.