• 제목/요약/키워드: chemical states

Search Result 857, Processing Time 0.029 seconds

Radiochemical cis-trans Isomerization of ${\beta}$-Styrylnaphthalene (${\beta}$-스티릴나프탈렌의 방사화학적 시스-트란스 이성질화 반응)

  • Sang Chul Shim;George S. Hammond
    • Journal of the Korean Chemical Society
    • /
    • v.20 no.4
    • /
    • pp.290-294
    • /
    • 1976
  • Radiation-induced cis-trans isomerization of ${\beta}$-styrylnaphthalene is studied by determination of G values and the radiostationary states. The results are compared with data obtained in direct and sensitized photoisomerization of the compound. Both the excited singlet and triplet states are involved in the isomerization of ${\beta}$-styrylnaphthalene in the radiolysis of benzene solution.

  • PDF

Femtosecond Photoelectron Imaging of N2 at 410 nm

  • Guo, Wei;Wei, Shanshan;Lu, Xingqiang;Wang, Li
    • Bulletin of the Korean Chemical Society
    • /
    • v.31 no.12
    • /
    • pp.3693-3696
    • /
    • 2010
  • We experimentally measure the kinetic energy and angular distributions of photoelectrons of $N_2$ as a function of 410 nm femtosecond laser intensity by using velocity map imaging technique. The strong-field multiphoton ionization of molecules shares many of the characteristics with those of atoms. Electron kinetic energies are nearly independent of laser intensities. The independence suggests that the electron peaks in the photoelectron spectrum actually result from a two-step process, indicative of the occurrence of real population in the intermediate states. The relative amplitudes of electron peaks indicate that in the two-step process, nonresonant population transfer dominates for low intensities, while resonant population transfer dominates for higher intensities.

Theoretical Studies on the Photochemical Reactions of 5,7-Dimethoxycoumarin with Adenosine. The Electronic States of 5,7-Dimethoxycoumarin and their Photoadducts

  • Kim, Ja-Hong;Han, Goang-Lae;Song, Young-Chil;Sohn, Sung-Ho
    • Bulletin of the Korean Chemical Society
    • /
    • v.10 no.3
    • /
    • pp.223-226
    • /
    • 1989
  • The chemical reactivity of 5,7-dimethoxycoumarine with adenosine has been calculated by the frontier electron and PPP-Cl MO methods. Results suggest that the major reactivity of the 5,7-dimethoxycoumarin is highest at the carbon-4 (position 4), whereas the electrophilic reactivity is generally spread all over the 5,7-dimethoxycoumarin molecule. These results are consistent with the experimental photoaddition reaction products. The small change of bond orders on excitation does not give enough reactivity to triplet states or the efficient intersystem crossing from $T_1\;to\;S_0$ inhibits photoaddition of 5,7-dimethoxycoumarine to adenosine. Although the relative intensity of the singlet band appears to be considerably higher than the triplet band intensity, its integrated intensity, i.e. oscillator strength, is comparable to that of the 5,7-dimethoxycoumarin and adenosine bands.

$^1H$ NMR Estimation of Multi-Redox potentials of Cytochrome $c_3$ from Desulfovibrio vulgaris Hildenborough

  • 박장수;강신원;최성낙
    • Bulletin of the Korean Chemical Society
    • /
    • v.16 no.4
    • /
    • pp.331-336
    • /
    • 1995
  • The macroscopic and microscopic redox potentials of tetrahemoprotein, cytochrome c3 from Desulfovibrio vulgaris(Hildenborough) (DvH) were estimated from 1H NMR and differential pulse polarography(DPP). Five sets of NMR resonances were confirmed by a redox titration. They represent cytochrome c3 molecules in five macroscopic redox states. The electron transfer in cytochrome c3 involves four consecutive one-electron steps. The saturation transfer method was used to determine the chemical shifts of eight heme methyl resonances in five different oxidation states. Thirty two microscopic redox potentials were estimated. The results showed the presence of a strong positive interaction between a pair of particular hemes. Comparing the results with those of Desulfovibrio vulgaris Miyazaki F (DvMF), it was observed that the two proteins resemble each other in overall redox pattern, but there is small difference in the relative redox potentials of four hemes.

Analysis of Biocompatible TiO2 Oxide Multilayer by the XPS Depth Profiling

  • Jang, Jae-Myung;Choe, Han-Cheol
    • Proceedings of the Korean Institute of Surface Engineering Conference
    • /
    • 2017.05a
    • /
    • pp.156-156
    • /
    • 2017
  • In this work, analysis of biocompatible TiO2 oxide multilayer by the XPS depth profiling was researched. the manufacture of the TiO2 barrier-type multilayer was accurately performed in a mixed electrolyte containing HAp, Pd, and Ag nanoparticles. The temperature of the solution was kept at approximatively $32^{\circ}C$ and was regularly rotated by a magnetic stirring rod in order to increase the ionic diffusion rate. The manufactured specimens were carefully analyzed by XPS depth profile to investigate the result of chemical bonding behaviors. From the analysis of chemical states of the TiO2 oxide multilayer using XPS, the peaks are showed with the typical signal of Ti oxide at 459.1 eV and 464.8 eV, due to Ti 2p(3/2) and Ti 2p(1/2), respectively. The Pd-3d peak was split into Pd-3d(5/2) and Pd-3d(3/2)peaks, and shows two bands at 334.7 and 339.9 eV for Pd-3d3 and Pd-3d5, respectively. Also, the peaks of Ag-3d have been investigated. The chemical states consisted of the O-1s, P-2p, and Ti-2p were identified in the forms of PO42- and PO43-. Based on the results of the chemical states, the chemical elements into the TiO2 oxide multilayer were also inferred to be penetrated from the electrolyte during anodic process.The structure characterization of the modified surface were performed by using FE-SEM, and from the result of biological evaluation in simulated body fluid(SBF), the biocompatibility of TiO2 oxide multilayer was effective for bioactive property.

  • PDF

Theoretical Approach for the Equilibrium Structures and Relative Energies of C7H7+ Isomers and the Transition States between o-, m-, and p-Tolyl Cations

  • Shin, Chang-Ho;Park, Kyung-Chun;Kim, Seung-Joon;Kim, Byung-Joo
    • Bulletin of the Korean Chemical Society
    • /
    • v.23 no.2
    • /
    • pp.337-345
    • /
    • 2002
  • The equilibrium structures for the ground and transition states of $C_7H_7^+$ isomers have been investigated using sophisticated ab initio quantum mechanical techniques with various basis sets. The structures of tropyrium and benzyl cations have been fully optimized at the DZP CCSD(T) levels of theory. And the structures of o-, m-and p-tolyl cations are optimized fully up to the DZ CCSD(T) levels of theory. The geometries for the transition states between three isomers of tolyl cations have been optimized up to DZP CISD level of theory. The SCF harmonic vibrational frequencies for tropylium, benzyl, and three isomers of tolyl cations are all real numbers, which confirm the potential minima and each unique imaginary vibrational frequencies for TS1 and TS2 confirm the true transition states. The relative energy of the benzyl cation with respect to the tropyrium cation is predicted to be 28.5 kJ/mol and is in good agreement with the previous theoretical predictions. The 0 K heats of formation, ${\Delta}H^{\circ}_{f0}$, have been predicted to be 890, 1095, 1101, and 1110 kJ/mol for tropylium, ortho-, meta-, and para-tolyl cations by taking the experimental value of 919 kJ/mol for the benzyl cation as the base level. The relative stability between tolyl cations is in the order of ortho

Effect of Transition Metal Dopant on Electronic State and Chemical Bonding of MnO2 (MnO2의 전자상태 및 화학결합에 미치는 천이금속 첨가의 효과)

  • 이동윤;김봉서;송재성;김양수
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.17 no.7
    • /
    • pp.691-696
    • /
    • 2004
  • The electronic state and chemical bonding of $\beta$-MnO$_2$ with transition metal dopants were theoretically investigated by DV-X$_{\alpha}$ (the discrete variational X$_{\alpha}$) method, which is a sort of the first principles molecular orbital method using the Hartree-Fock-Slater approximation. The calculations were performed with a $_Mn_{14}$ MO$_{56}$ )$^{-52}$ (M = transition metals) cluster model. The electron energy level, the density of states (DOS), the overlap population, the charge density distribution, and the net charges, were calculated. The energy level diagram of MnO$_2$ shows the different band structure and electron occupancy between the up spin states and down spin states. The dopant levels decrease between the conduction band and the valence band with the increase of the atomic number of dopants. The covalency of chemical bonding was shown to increase and ionicity decreased in increasing the atomic number of dopants. Calculated results were discussed on the basis of the interaction between transition metal 3d and oxygen 2p orbital. In conclusion it is expected that when the transition metals are added to MnO$_2$ the band gap decreases and the electronic conductivity increases with the increase of the atomic number of dopants. the atomic number of dopants.