• Proceedings of the Optical Society of Korea Conference
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• 1990.07a
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• pp.94-100
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• 1990

The rapid quenching dynamics of the F-center excitation by CN- defects in CsCl crystals were investigated by monitoring the ground state bleach recovery kinetics of F-centers, using a picosecond streak camera absorption spectrometer. The F-centers in CN- doped quenched samples show two bleach recovery components. Optical aggregation converts the slow component to the fast component. The slow one is due to the normal relaxation of the F*-centers as found in CN_ free crystals. The fast one is due to the energy transfer of the F-center electronic excitation to the vibrational energy levels of CN_ molecualr defects. The energy transfer occurs only in the F-center-CN_ defect pairs, FH(CN_)-centers.

• Bulletin of the Korean Chemical Society
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• v.8 no.6
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• pp.449-453
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• 1987

The temperature dependence of the vibrational relaxation of NO(= 2) by NO(v = 0) has been investigated over the temperature range 100-3000 K. We have assumed that the deexcitation of NO(2) by NO(0) undergoes vibration-to-vibration (VV) energy exchange with the transfer of the energy mismatch ${\Delta}$E through rotation (R) and translation(T). The relaxation rate constants are calculated by solving the time-dependent Schrodinger equation. The sum of V-V, T, and V-V, R contributions shows very weak temperature dependence and is in reasonable agreement with observed data over the temperature range 300-3000 K.

• Journal of the Korean Chemical Society
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• v.29 no.6
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• pp.592-598
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• 1985

The total vibrational deexcitation rate constants $k_{v,v-1}$ of HF(v = 5-7) by HF(${\mu}$ = 0) and DF(${\mu}$ = 9-12) by DF(${\mu}$= 0) including both the vibration to vibration (V ${\to}$ V) and vibration to rotation and translation (V ${\to}$ R, T) energy transfer channels have been calculated semiclas-sically using a simplified collision model. The calculated results are in reasonably good agreement with those obtained by experimental and other theoretical studies. The rate constants increase with increasing temperature and also with increasing v. They also show that the relaxation of the highly excited HF and DF occurs predominantly via the V ${\to}$ R, T path at low temperature. The effectiveness of the V ${\to}$ V path, however, increases as the temperature is raised.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1706-1712
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• 2014

The OH($X^2{\Pi}$, ${\upsilon}^{\prime\prime}=0,1$) internal state distribution following the reaction of electronically excited oxygen atom ($O(^1D_2)$) with cyclo-$C_3H_6$ has been measured using laser-induced fluorescence, and compared with that following the reaction of $O(^1D_2)$ with $C_3H_8$. The overall characteristics of the OH internal energy distributions for both reactions were qualitatively similar. The population propensity of the ${\Pi}(A^{\prime})$ ${\Lambda}$-doublet sub-level suggested that both reactions proceeded via an insertion/elimination mechanism. Bimodal rotational population distributions supported the existence of two parallel mechanisms for OH production, i.e., statistical insertion and nonstatistical insertion. However, detailed analysis revealed that, despite the higher exoergicity of the reaction, the rotational distribution of the OH following the reaction of $O(^1D_2)$ with $C_3H_8$ was significantly cooler than that with cyclo-$C_3H_6$, especially in the vibrational ground state. This observation was interpreted as the effect of the flexibility of the insertion complex and faster intramolecular vibrational relaxation (IVR).

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1649-1656
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• 2010

Internal reorganization energy due to the structural relaxation in hole or electron hopping mechanism is one of the measurements of key indices in designing an organic thin film transistor (OTFT) for flexible display devices. In this study, the reorganization energies of dicyanoanthracenes for the hole and electron transfer were estimated by adiabatic potential energy surface and normal mode analysis method in order to examine the effect on the energies for the positional variation of the cyano substituents in the anthracene as a protocol of acenes to design an organic field effect transistor. The reorganization energy for the hole transfer was reduced considerably upon cyanation of anthracene, especially at the 9,10-positions of anthracene, and the origin of the reduction was interpreted in terms of understanding the coupling of vibrational modes to the hole transfer.

• Korean Journal of Optics and Photonics
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• v.9 no.4
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• pp.221-226
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• 1998

Ternary heavy metal oxide glasses in the $PbO-Bi_2O_3-Ga_2O_3$ system doped with $Er_2O_3$ were prepared and their spectroscopic properties, such as radiative transition probability, calculated and measured radiative lifetimes and cross-sections of 1.5 $\mu\textrm{m}$ and 2.7 $\mu\textrm{m}$ emissions were analyzed. Enhanced quantum efficiencies of some electronic transitions were evident mainly because of the low vibrational phonon energy ($~500cm^{-1}$) inherent in the host glasses. This seems to be the main reason for obtaining the 2.7 $\mu\textrm{m}$ luminescence which is normally quenched in the conventional oxide glasses. In addition, green and red fluorescence emissions were observed through the frequency upconversion processes of the 798 nm excitation. Non-radiative transition due to the multiphonon relaxation is a dominant lifetime-shortening mechanism in the 4f-4f transitions in $Er^{3+}$ ion except for the $^4S_{3/2}{\rightarrow}^4I_{15/2}$ transition where a non-radiative transfer to band-gap excitation of the host glasses is dominant. Melting of glasses under an inert gas atmosphere and (or) addition of the typical glass-network former into glasses is necessary in order to enhance the quantum efficiency of the transition.

• Journal of Photoscience
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• v.9 no.2
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• pp.106-109
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• 2002

Archaeal rhodopsins possess retinal molecule as their chromophores, and their light-energy and light-signal conversions are triggered by all-trans to 13-cis isomerization of the retinal chromophore. Relaxation through structural changes of protein then leads to functional processes, proton pump in bacteriorhodopsin (bR) and transducer activation in phoborhodopsin (pR). It is known that sensory rhodopsins can pump protons in the absence of their transducers. Thus, there should be common and specific features in their protein structural changes for function. In this paper, our r ecent studies on pR from Natronobacterium pharaonis (ppR) by means of low-temperature Fourier-transform infrared (FTIR) spectroscopy are compared with those of bR. In particular, protein structural changes upon retinal photoisomerization are studied. Comparative investigation of ppR and bR revealed the similar structures of the polyene chain of the chromophore and water-containing hydrogen-bonding network, whereas the structural changes upon photoisomerization were more extended in ppR than in bR. Extended protein structural changes were clearly shown by the assignment of the C=O stretch of Asnl05. FTIR studies of a ppR mutant with the same retinal binding site as in bR revealed that the Schiff base region is important to determine their colors.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.135-135
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• 2003

The fast evolution in the fold of optical communication systems demands powerful optical information treatment. These functions can be performed by integrated optical systems. A key component of such systems is erbium doped waveguide amplifier(EDWA). The intra 4f radiative transition of Er at 1.5 $\mu\textrm{m}$ is particularly interesting because this wavelength is standard in optical telecommunications. The fabrication of waveguide amplifier for integrated optics using sol-gel process has received an increasing attention. Potential advantage of lower cost by less capital equipment and easy processing makes this process an attractive alternatives to conventional technologies like flame hydrolysis deposition, ion exchange and chemical vapor deposition, etc. In addition, sol-gel process has been found to be extremely suitable for the control of composition and refractive index related directly with optical properties. The main drawback of such an amplifier with respect to the EDWA is the need for a much higher Er3+ concentration to compensate for the smaller interaction length. However, the high doping of Er might be resulted in the non-radiative relaxation by clustering of Er ions End co-operative upconversion. In order to solve this problem, we investigate the possibility of avoiding short Er-Er distances by encapsulation of Er3+ ions in hosts such as organic-inorganic hybrid materials. For inorganic-organic hybrid sols, methacryloxypropyltrimethoxysilane (MPTS), zirconyl chloride octahydrate and erbium(III) chloride hexahydrate were used as starting materials, followed by conventional sol-gel process. It was observed by TEM that nano sols having core/shell toplology were formed, depending on the mole ratio of Zr/Er. The surface roughness for the coatings on Si substrate was investigated by AFM as a function of Zr/Er ratio. The local environment and vibrational Properties of Er3+ ions were studied using Near-IR, FT-IR, and UV/Vis spectroscopy. Nano hybrid coatings derived from polymer and Er doped encapsulation Eave the good luminescence at 1.55$\mu\textrm{m}$.