• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3389-3394
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• 2011

Isomeric trimethylbenzyl radicals were generated and vibronically excited from precursor 1,2,3,5-tetramethylbenzene, isodurene, with a large amount inert carrier gas helium in a corona excited supersonic expansion (CESE) using a pinhole-type glass nozzle. A long-path monochromator was used to record the visible vibronic emission spectra of the jet-cooled benzyl-type radicals in the $D_1{\rightarrow}D_0$ electronic transition. From the analysis of the spectra, we identified the evidence of the presence of three isomeric trimethylbenzyl radicals in the corona discharge, and obtained the electronic energy and a few vibrational mode frequencies in the ground electronic state for each isomer.

• Rapid Communication in Photoscience
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• 제4권2호
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• pp.34-36
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• 2015

New spectroscopic characteristics of amorphous ferric hydroxide ($Fe(OH)_3$), interestingly in the near infrared (NIR) region, are presented in this study. The absorption spectrum of ferric hydroxide covers wide spectral regions from ultraviolet to NIR (200~900 nm). Unique emission bands were newly observed in the NIR regions (800~1400 nm). Several bands of this NIR emission are quiet well overlapped with the combinational vibrational absorption bands of water. From photothermal conversion study, very interestingly, temperature of aqueous mixture solution including the amorphous ferric hydroxide was significantly increased from ambient temperature to $38^{\circ}C$ for 30 minutes under irradiation of a standard helium lamp.

• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.439-443
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• 2011

Using the projection operator technique, a reduced density matrix theory for linear absorption spectrum of energy transfer systems is developed for the theoretical absorption line shape of the systems with non-Condon transitions. As an application, we considered a model system of OH vibrations of water. In the present model calculation, the OH vibration modes are coupled to each other via intra-molecular coupling mechanism while their intermolecular couplings are turned off. The time-correlation functions appearing in the formulation are calculated from a mixed quantum/classical mechanics method. The present theory is successful in reproducing the exact absorption line shape. Also the present theory was improved from an existing approximate theory, time-averaged approximation approach.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.151-156
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• 2005

The conformational dynamics of heme pocket, a small vacant site near the binding site of heme proteins -myoglobin (Mb) and hemoglobin (Hb), was investigated after photolysis of carbon monoxide from MbCO and HbCO in D$_2$O solution at 283 K by probing time-resolved vibrational spectra of photolyzed CO. Two absorption bands, arising from CO in the heme pocket, evolve nonexponentially in time. The band at higher energy side blue shifts and broadens with time and the one at lower energy side narrows significantly with a negligible shift. These spectral evolutions are induced by protein conformational changes following photolysis that modify structure and electric field of heme pocket, and ligand dynamics in it. The conformational changes affecting the spectrum of photolyzed CO in heme pocket likely modulates ligand-binding activity.

• Journal of Photoscience
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• 제4권3호
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• pp.121-125
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• 1997

The 77 K emission and excitation, and room-temperature visible spectra of cis[Cr(cyclam)Br$_2$]Br (cyclam=1,4,8,11-tetraazacyclotetradecane) are reported. The mid- and far-infrared spectra at room-temperature are also measured. The vibrational intervals of the electronic ground state are extracted from the far-infrared and emission spectra. The ten electronic bands due to spin-allowed and spin-forbidden transitions are assigned. It is found that nitrogen atoms of the cyclam ligand have strong $\sigma$-donor characters, but bromide ligand has weak $\sigma$- and $\pi$-donor properties toward chromium(III) ion. The zerophonon line in the excitation spectrum splits into two components by 172 cm$^{2-}$, and the large $^2E_g$ splitting can be reproduced by the ligand field theory.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1111-1115
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• 2002

The photoluminescence of calixarene crystals has been studied as functions of temperature, time, and concentration. The vibronic bands shift to longer wavelength and become significantly sharper as temperature decreases. The experimental results r eveal that the structural transformation occur during the annealing process. Time-resolved spectra of calixarene at 12 K are monitored. Spectral features, which demonstrate characteristic of energy transfer processes, are not observed. The depopulation of excited state density is mainly controlled by unimolecular decay process dominating other decay processes. The lifetime was found to be 2.6 $\pm$ 0.1 ns. For the case of calixarene mixed with naphthalene, the fluorescence spectrum shows that the band centered at 340 nm lies 2840 $cm^{-1}$ below the relatively broad 310 nm band found for calixarene crystals. The spectra also exhibit that the emission intensity increases with increasing calixarene concentration. The results are evident that the calixarene emission is quenched by the naphthalene. Phosphorescence of calixarene mixed with naphthalene crystals is observed to determine whether the emission is due to naphthalene. The phosphorescence peaks were compared with the ground-state vibrational frequencies of naphthalene and found to be in good agreement. The results indicate that inter-molecular energy transfer occurs between calixarene and naphthalene.

• Bulletin of the Korean Chemical Society
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• 제31권4호
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• pp.941-948
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• 2010

Ab initio and density functional theory methods have been employed to study all theoretically possible conformers of fluoroacetic acid. Molecular geometries and energetic of cis and trans monomers and cis dimers in gaseous phase have been obtained using HF, B3LYP and MP2 levels of theory, implementing 6-311++G(d,p) basis set. It was found that cis rotamers are more stable. In addition, it was found that in comparison with acetic acid the strength of hydrogen bonding in fluoroacetic acid decreased. The infrared spectrum frequencies and the vibrational frequency shifts are reported. Natural population and atom in molecule analysis performed to predict electrostatic interactions in the cyclic H-bonded complexes and charges. The proton transfer reaction is studied and activation energy is compared with acetic acid proton transfer reaction.

• 소음진동
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• 제9권2호
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• pp.409-417
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• 1999

A new method is proposed for the isolation of resonances from scattered waves for the isolaton of resonances from scattered waves for acoustic wave resonance scattering problems. The resonance scattering function consisting purely of resonance information is defined. Acoustic wave scattering from a variety of submerged bodies is numerically analyzed. The classical resonance scattering theory (RST) and the new method compute identical magnitudes of the resonances from each partial wave, however, the phases are significantly different. The exact $\pi$-radians phase shifts through the resonance and anti-resonance frequencies show that the proposed method properly extracts the vibrational resonance information of the scatterer. Due to the differences in phases of the resonances from each partial wave, the new method and RST generate different total resonance spectra.

• Bulletin of the Korean Chemical Society
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• 제20권1호
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• pp.81-84
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• 1999

The emission and excitation spectra of [Cr(NH3)5(imH)](ClO4)3·H2O (imH=imidazole) taken at 77 K are reported. The 298 K visible and far-infrared spectra are also measured. The vibrational intervals of the electronic ground state are extracted from the far-infrared and emission spectra. The ten electronic bands due to spin-allowed and spin-forbidden transitions are assigned. Using the observed transitions, a ligand field analysis has been performed to determine the bonding properties of coordinated imidazole in the title chromium(Ⅲ) complex. It is confirmed that nitrogen atom of the imidazole ligand has a medium it-acceptor property toward chromium(Ⅲ) ion. The zero-phonon line in the excitation spectrum splits into two components by 181 cm-1, and the large 2Eg splitting can be reproduced by the ligand field theory.

• Bulletin of the Korean Chemical Society
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• 제10권2호
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• pp.142-147
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• 1989

Fluorescence enhancements of ethidium bromide (EB) by solution species of low molecular weights such as DNA base molecules and nucleosides in water are reported. The degree of enhancements was determined by intensity as well as lifetime measurements for EB fluorescence. Experiments including solvent effects on absorbance and fluorescence spectra of EB, effects of protonation on the EB absorbance spectrum, and determination of equilibrium constants for EB-DNA bases have been performed to help explain the fluorescence enhancement. The results suggest that the excited state stabilization in the hydrophobic environment, the loss of torsional/vibrational energy of amino groups, and the change in the electronic transition characteristics are all responsible for the fluorescence enhancement.