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Photolysis of Tris(trimethylsilyl)methylsilane in the Presence of 2-Propenol
부봉현,홍승기,강성권,Bu, Bong Hyeon,Hong, Seung Gi,Gang, Seong Gwon Korean Chemical Society 1995 Bulletin of the Korean Chemical Society Vol.16 No.1
UV photolysis of the titled polysilane (Me3Si)3SiMe (I) in the presence of a trapping agent of 2-propenol has been performed to investigate the interaction of short-lived silicon species formed from the photolysis of I with 2-propenol. Product studies show that the Me(Me3Si)Si: (II) and (Me3Si)3Si${\cdot}$(III) are primarily formed as the major reactive species which saturate their valencies via O-H insertion and H-abstraction, respectively. Some products are unstable toward further secondary reaction such as photodissociation and intermolecular reaction. The PM3 semiempirical calculations are performed to deduce the energetics of the photoinduced chemical reactions of I with the substrate.
부봉현,Sukmin Kang,Ari Furuya,Ken Judai,Nobuyuki Nishi 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.11
Infrared multiphoton dissociation (IRMPD) spectra of various protonated 1,2-diaminoethane-water clusters DAE-H+-(H2O)n (n = 1-6) were measured in the wavelength range of 3000-3800 cm−1. The IRMPD spectra of the well separated ionic clusters were simulated by the MP2 method employing various basis sets. Comparison of the IRMPD spectra with the theory indicates that each cluster may exist as several low-lying conformers, and the sum spectra of the various conformers reveal almost one to one correspondence between theory and experiment. Free N-H and O-H stretches are observed in the ranges of 3400-3500 and 3600-3800 cm−1, respectively. The O-HLN and N-HLO stretches are, however, observed in the broad region of 3000-3600 cm−1. The theoretical calculations on DAE-H+-(H2O)n (n = 1-4) show gradual decrease of the average binding energy between DAE-H+ and H2O as the cluster size increases, attaining the lowest value of 55 kJ/mol when n = 4. We found a low energy barrier of 21 kJ/mol to the isomerization converting the lowest energy cluster of DAE-H+-H2O to the second lowest one.
Fluorescence Spectroscopic and Time-Dependent Density-functional Theory Studies of Diphenylsilane
부봉현,이재광 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.3
We investigated fluorescence and fluorescence excitation of diphenylsilane (DPS) in a solution and molecular beams in combination with the aid of the DFT method. When the molecule was photoexcited at 250 nm in a cyclohexane solution, normal and excimer fluorescences were observed in the ranges of 260-320 and 330-450 nm, respectively. The fluorescence excitation spectrum indicates that the channel leading to the intramolecular excimer formation is not efficient in comparison with the normal fluorescence. Vibrationally resolved fluorescence excitation spectra were measured for the DPS molecules cooled in pulsed supersonic expansion of He in the range 262.2-271.7 nm, in which we can see several electronic excitation spectra exhibiting the electronic band origins. We found that the simulated absorption spectrum based on the time-dependent densityfunctional theory calculations accords well with the absorption spectrum.
부봉현,Inosuke Koyano 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1
Ion-pair formation for nitrous oxide was studied by using time-of-flight mass spectrometry coupled to linearly polarized synchrotron radiation in the range from 35 to 130 eV. At critical ion detection angles of 0˚, 55˚, and 90˚ with respect to the beam polarization, the ratios of the intensities for photoion-photoion coincidences (PIPICO) were measured as a function of the incident photon energy. The anisotropic angular distributions of the PIPICO intensities are interpreted as being due to molecular photofragmentation related to the symmetry and dynamics of the dissociation processes.
부봉현,Hanjoung Cho,Jae Kwang Lee,Edward C. Lim 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1
Resonant 2-photon ionization and fluorescence excitation spectroscopies of dodecamethylcyclohexasilane (DDMCHS) were investigated in the range from 262 to 290 nm in a supersonic molecular beam. We observed the parent ion, Si6Me+12, and its various daughter ions, Si6Me+11, Si5Me+9 ,Si4Me+9 , Si3Me+7 , Si3Me+6 , Si2Me+3 , and Si2Me+2 , in the whole photon energy range. The occurrences of consecutive bond scissions and rearrangements with excess energy accumulated by additional photon absorption after the two-photon ionization of the DDMCHS molecule could explain the formation of various ionic products. The experimental vertical excitation energies are favorably compared with the values predicted by using the TD DFT calculation.
부봉현,류수영,강희성,고상곤,박찬조 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.21
We have studied the excited-state properties of carbazole and poly(N-vinylcarbazole) (PNVC) by means of femtosecond time-resolved fluorescence and time-dependent density-functional theory (TD DFT) calculations. When we excite the polymer at 280 nm, the polymer is shown to exhibit normal fluorescence peaks at 351 and 362 nm and an excimer peak above 400 nm. The lifetimes of the normal and excimer S1 states for PNVC were measured to be tF = 5.34 ± 0.03 ns for normal fluorescence and tF = 6.98 ± 0.03 ns for excimer fluorescence. In the DFT calculation, the chromophores in the ground-state PNVC are shown to be parallel. Owing to the intramolecular hindrance, the chromophores in the singlet excited-state PNVC may not be parallel, giving rise to a slightly red-shifted excimer peak. TD DFT calculations indicate that the vertical excitation energies are almost independent of the conformational changes and the degree of polymerization.