Strong Differential Photoion Circular Dichroism in Strong-Field Ionization of Chiral Molecules.

We investigate the differential ionization probability of chiral molecules in the strong-field regime as a function of the helicity of the incident light. To this end, we analyze the fourfold ionization of bromochlorofluoromethane (CHBrClF) with subsequent fragmentation into four charged fragments and different dissociation channels of the singly ionized methyloxirane. By resolving for the molecular orientation, we show that the photoion circular dichroism signal strength is increased by 2 orders of magnitude.

Absolute ion detection efficiencies of microchannel plates and funnel microchannel plates for multi-coincidence detection.

Modern momentum imaging techniques allow for the investigation of complex molecules in the gas phase by detection of several fragment ions in coincidence. For these studies, it is of great importance that the single-particle detection efficiency ε is as high as possible, as the overall efficiency scales with εn, i.e., the power of the number of detected particles. Here we present measured absolute detection efficiencies for protons of several micro-channel plates (MCPs), including efficiency enhanced "funnel MCPs." Furthermore, the relative detection efficiency for two-, three-, four-, and five-body fragmentation of CHBrClF has been examined. The "funnel" MCPs exhibit an efficiency of approximately 90%, gaining a factor of 24 (as compared to "normal" MCPs) in the case of a five-fold ion coincidence detection.

Influence of parity violating weak nuclear potentials on vibrational and rotational frequencies in chiral molecules

We study the effect of parity violation on the vibrational and rotational frequencies of CHBrClF. We report the parity violating potentials as a function of reduced normal coordinates for all nine internal vibrational modes omega(1) to omega(9), using our new, accurate multiconfigurational-linear response (RPA and complete-active-space self-consistent field) approach. All modes omega(i) show a strongly mode dependent relative shift Delta(pv)omega(i)/omega(i) (between 0.08x10(-16) and 13.3x10(-16), much smaller than all previous experimental tests could detect, including the most recent ones). The results are discussed in relation to other tests of parity violation.

Molecular chirality and the fundamental symmetries of physics: influence of parity violation on rovibrational frequencies and thermodynamic properties.

We introduce the topic of fundamental symmetries of physics in relation to molecular chirality by a brief review of the development and current status of the theory of parity violation in chiral molecules. We then discuss in some detail CHBrClF (bromochlorofluoromethane) as a test case, to which the work of André Collet has contributed importantly. For this molecule and its isotopomers, we report here the first detailed theoretical calculations of the influence of parity violation on statistical thermodynamic properties. High-quality ab initio calculations (RPA, random phase approximation, and CASSCF, complete-active-space self-consistent-field) were performed to determine the small energy difference between R- and S-enantiomers of H and D isotopomers of bromochlorofluoromethane (CHBrClF, CDBrClF), and fluorooxirane ((1)H(3)C(2)OF) introduced by the parity-violating weak interaction. Together with vibrational and rotational frequency shifts caused by parity violation, these were used to determine the statistical thermodynamic quantities from the corresponding partition functions within the separable harmonic and in part also anharmonic adiabatic approximation. Temperature-dependent equilibrium constants for the stereomutation were calculated and are discussed in relation to biochemical homochirality.