円偏光アンジュレーターと外部磁場によるアミノ酸の光不斉化反応の研究

研究期間:平成13-14年度 ; 研究種別:基盤研究C2 ; 課題番号: 13640593発表論文などあり

Molecular deformation in the O 1s[-1] 2πu excited states of CO2 probed by the triple-differential measurement of fragment ions

Measurement of mass-, energy-, and angle-resolved fragment ions reveals that the β value for C+ with kinetic energy ≥~3 eV is ∼0.9 in the region of the O 1s→2πu excitation and that the β value for O+ with kinetic energy ≥~4 eV varies from -0.23 to -0.57 across the O 1s→2πu resonance. These findings postulate that the CO2 molecule excited to the lower branch of the vibronically split O 1s[-1]2πu excited states deforms into a bent geometry while the molecule excited to the higher branch remains in a linear geometry

Optimization of asymmetric figure-8 undulator as circularly polarized light source

In the soft x-ray region, the demand for helicity switching of circularly polarized undulator radiation is increasing to study circular dichroism. The asymmetric figure-8 undulator is an insertion device to provide circularly polarized radiation (CPR) and a simple method of helicity switching which has been proposed and built at SPring-8. Because of its complicated magnetic structure, it is important to optimize the magnetic parameters for more effective utilization of CPR. Using an analytical method, the relation between the magnetic parameters to maximize the degree of circular polarization is obtained. The impact of the finite emittance of electron beams on the polarization performance is also investigated numerically

Mass Spectroscopic Approach to Amino Acids Formation Processes by UV Irradiation to Simple Organic Molecules in Aqueous Solution

We have studied amino acid formation by UV (193 nm) irradiation to organic molecules (amines, alcohols and amides) in aqueous solution. Among several types of detected amino acids, small aliphatic amino acids (Gly and α-, β-Ala and α-, β-, γ-ABA) were quantitatively identified. Among these small aliphatic amino acids, certain amino acids were formed in its free form, even before hydrolysis, contrary to the results of UV irradiation to a gas mixture of CO, NH3, and H2O, where amino acids were hardly detected before hydrolysis. The species distribution of identified amino acids showed a dependence on the starting organic molecules, and also on the presence of ammonia. The formation processes of the identified small aliphatic amino acids were investigated with the aid of electrospray ionization (ESI) MS and MS/MS measurements of photoproducts. Possible formation processes of these amino acid precursors from each starting molecules are proposed. By identifying the amino acid precursor, which has a chiral carbon atom, a new possibility is suggested for asymmetric photosynthesis of amino acid from achiral organic molecules

Ionic fragmentation processes of core-excited α-alanine in gas phase

Ionic fragmentation of core-excited α-alanine in gas phase was observed. The most dominant ionic species is COOH+ for all core-ionizations at C 1s, N 1s, and O 1s. An increase in COO+ and a decrease in COOH+, which were observed as core-hole atom selectivity for the O 1s ionization, are explained by the enhancement of O-H bond scission. Further state-selective O-H bond scission, observed at the O 1s second peak, is attributed to the OOH 1s → 3s/σ* transition

Formation of H3O+ by the soft X-ray ionization of ethanol clusters

Time-of-flight mass spectra have been measured for inner-shell ionization of ethanol molecules, its clusters, and methanol clusters at the oxygen K-edge regions. Only in the case of the ethanol clusters, a fairly intense signal corresponding to H3O+ has been observed. The measurements for ethanol-d1 (C2H5OD) suggest that at least one H atom in the H3O+ ion originates from the C2H5 group of neighbouring ethanol. It is proposed that in addition to the O-H--OH type hydrogen bonding in the ethanol clusters, the H in the C2H5 group and OH interact with each other