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Journal Articles

EPR studies of 5-bromouracil crystal after irradiation with X rays in the bromine K-edge region

Yokoya, Akinari; Takakura, Kaoru*; Watanabe, Ritsuko; Akamatsu, Ken*; Ito, Takashi*

Radiation Research, 162(4), p.469 - 473, 2004/10

Times Cited Count：3 Percentile：10.08(Biology)

X-ray absorption spectra from single crystals of 5-Bromouracil were measured with the transmission mode in the energy range from 13.41 to 13.50 keV using the linearly polarized synchrotron radiation (SR). A characteristic resonance structure, consisting of four peaks, was recognized in the spectra in the Br K-edge region. The intensities of these peaks were strongly dependent on the crystal rotation about the normal of the crystal b-c plane, which was set perpendicular to the X-ray beam direction. (SR X-rays are polarized in the horizontal plane.) Molecular orbital calculations indicate that these resonance peaks are associated with the transitions from the 1s electron of Br to the Br-C molecular antibonding orbitals and to a shape resonance. The observed anisotropy of each photoabsorption peak might originate from the angular dependences of these molecular orbitals.

Journal Articles

Global potential energy surfaces for the lowest three doublet states (1 $^{2}$ A', 2 $^{2}$ A', and 1 $^{2}$ A") of the BrH $_{2}$ system

Kurosaki, Yuzuru; Takayanagi, Toshiyuki

Journal of Chemical Physics, 119(15), p.7838 - 7856, 2003/10

https://doi.org/10.1063/1.1609398

Times Cited Count：26 Percentile：63.68(Chemistry, Physical)

Adiabatic potential energy surfaces of the lowest three doublet states (1 $^{2}$ A', 2 $^{2}$ A', and 1 $^{2}$ A") for the BrH $_{2}$ system have been calculated globally using the MRCI+Q method with the aug-cc-pVTZ basis set. Spin-orbit effects were considered on the basis of Breit-Pauli Hamiltonian. The calculated adiabatic energies were fitted to the analytical functional form of many-body expansion. The barrier heights of the abstraction and exchange reactions on the ground-state PES were calculated to be 1.28 and 11.71 kcal mol $^{-1}$ , respectively, at the MRCI+Q/aug-cc-pVTZ level of theory. The fits for the three PESs were successful within the accuracy of 0.1 kcal mol $^{-1}$ . Thermal rate constants for the abstraction and exchange reactions and their isotopic variants were calculated with the fitted 1 $^{2}$ A' PES using the ICVT/LAG method. The calculated rate constants for the abstarction reactions agree fairly well with experiment but those for the exchange reactions were much smaller than experiment, which suggests that the reliable experimental data are still insufficient.

Journal Articles

Potential energy surface for the C $_{2}$ H $_{4}$ + Cl $_{2}$ C $_{2}$ H $_{4}$ Cl + Cl reaction; Ab initio molecular orbital study

Kurosaki, Yuzuru

Journal of Molecular Structure; THEOCHEM, 545(1-3), p.225 - 232, 2001/07

The CASSCF and MRCI calculations with the cc-pVTZ basis set have been carried out for the C $_{2}$ H $_{4}$ + Cl $_{2}$ C $_{2}$ H $_{4}$ Cl + Cl reaction. It has been revealed that the reaction has a small barrier from the C $_{2}$ H $_{4}$ Cl + Cl side at the CASSCF level of theory, but it has no barrier at the MRCI level. Namely, the C $_{2}$ H $_{4}$ Cl + Cl C $_{2}$ H $_{4}$ + Cl $_{2}$ reaction was predicted to be a spontaneous reaction. The result of the MRCI calculation strongly supports the prediction of our previous PMP4(SDTQ) calculation [J. Mol. Struct. (Theochem) 503 (2000) 231].