• Bulletin of the Korean Chemical Society
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• 제10권5호
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• pp.434-437
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• 1989

The pH dependence of the absorption and fluorescence of 4-hydroxy-2-methyl-1,2-benzothiazinenecarboxylat es, piroxicam and HMBDC have been measured and compared with the solvent dependence of the spectra reported previously. Four different prototropic species are observed in both ground and excited states of piroxicam ; the cation, the neutral, the anion and the dianion, while three different species such as the cation, the neutral and the anion are observed in HMBDC. The $pK_a$ and $pK_a^{\ast}$ have been determined by absorptiometric titration and Forster cycle method, respectively. The probable structure of each species has been proposed on the basis of the intramolecular phototautomerism.

• Journal of Photoscience
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• 제6권4호
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• pp.165-170
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• 1999

Asymmetric recognition of chiral alcohol by fluorenone derivatives with chiral substituents through intermolecular hydrogen bonding interaction in the singlet excited state was attempted. 1-((1S, 2R, 5S)-(+)-Menthyloxycarbonyl)aminofluoren-9-one (1-MAF) and 1-((1S, 2R, 5S)-(+)-menthyloxycarbonyl)oxyfluoren-9-one (1-MOF) were synthesized and their photophysical behaviors were characterized by the measurement of absorption and fluorescence spectra, as well as the quantum yield and the lifetime of fluorescence. The excited singlet states of 1-MAF and 1-MOF were revealed to have characteristics similar to those of fluorenone, though the intramolecular CT nature was fairly suppressed as compared with 3- and 4-substituted aminofluorenones. Fluorescences of 1-MAF and 1-MOF in acetonitrile were quenched by the addition of alcohols. Differences in fluorescence quenching efficiency were hardly observe for rather small chiral alcohols such as (R)-(-)- or (S)-(+)-2-butanol, while bulky alcohols such as menthol and isopinocampheol showed chiral recognition effects in their fluorescence quenching of 1-MAF in either acetonitrile or butyronitrile.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.245-252
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• 2002

The computationally simple quantum mechanical method (VSCF-DWB-IOS) has been applied to studying the Ar-$CO_2$ vibrational predissociation phenomenon. The new methodology utilizes the vibrational self-consistent field method to determine the vibrational structure of the van der Waals complex, the distorted-wave Born approximation for dissociating process, and the infinite-order sudden approximation for the continuum dissociating product of $CO_2$. The dissociation due to the coupling of the symmetric stretching vibrational motion of $CO_2$ with the motion of the Ar van der Waals mode has been extensively investigated. The lifetimes of transient excited vibrational states, linewidths of absorption peak, and the rotational state distributions of the product, $CO_2$ have been computed. It has been found that the lifetime of the Ar-$CO_2$ in excited vibrational state is very long compared with that of triatomic van der Waals complexes and the product $CO_2$ carries a major portion of dissociation energy as a rotational energy.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.189-194
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• 2002

Two-photon resonant third photon ionization of atomic bromine $(4p^5\;^2P_{3/2}\;and\;^2P_{1/2})$ has been studied using a photoelectron imaging spectroscopy in the wavelength region 250 - 278 nm. The technique has yielded simultaneously both relative branching ratios to the three levels of $Br^+(^3P_2,\;^3P_{0.1}\;and^1D_2)$ with $4p^4$ configuration and the angular distributions of outgoing photoelectrons. The product branching ratios reveal a strong propensity to populate particular levels in many cases. Several pathways have been documented for selective formation of $Br^+(^3P_2)$ and $Br^+(^3P_{0.1})$ ions. In general, the final ion level distributions are dominated by the preservation of the ion core configuration of a resonant excited state. Some deviations from this simple picture are discussed in terms of the configuration interaction of resonant states and the autoionization in the continuum. The photoelectron angular distributions are qualitatively similar for all transitions, with a positive $A_2$ anisotropy coefficient of 1.0-2.0 and negligible $A_4$ in most cases, which suggests that the angular distribution is mainly determined by the single-photon ionization process of a resonant excited state induced from the third photon absorption.

• Journal of Photoscience
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• 제3권3호
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• pp.153-158
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• 1996

The effects of $\alpha$- and $\beta$-cyclodextrins (CD) on the twisted intramolecular charge transfer (TICT) behavior of p-N,N'-dimethylaminobenzoic acid (DMABA) in buffered aqueous solution have been investigated by examining formation and decay behaviors of the TICT-typical dual fluorescence. The ratio of the TICT emission to the normal emission (I$_a$/I$_b$) increases linearly $\alpha$-CD concentration increases, while in the presence of $\beta$-CD it shows nonlinear dependences on the CD concentration. The analysis of the CD-dependent changes of the I$_a$/I$_b$ and absorption spectra demonstrates formation of 1:1 inclusion complexes between DMABA and CDs. The decay time of the normal emission (ca. 700 ps) is little affected by the formation of $\alpha$-CD inclusion complex, whereas it increases upto ca. 1.6 ns upon formation of $\beta$-CD inclusion complex. The TICT emission for the $\beta$-CD inclusion complex exhibits two decay components while it shows a single component for the $\alpha$-CD inclusion complex, indicating formation of one or two types of inclusion complex in the presence of $\alpha$-CD or $\beta$-CD, respectively. These results are attributed to the CD cavity size dependence on patterns of complexation between CDs and DMABA. The CD size dependences of the TICT fluorescence properties with the orientation of the guest molecule demonstrate that the specific hydrogen bonding between the carboxylic acid group and water plays an important role in the excited-state TICT.

• Bulletin of the Korean Chemical Society
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• 제9권3호
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• pp.171-175
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• 1988

The spectral properties of piroxicam in different solvents are similar to those of its skeletal precursor, HMBDC. The maximum absorption and emission wavelengths strongly depend on the hydrogen bonding ability of the solvent, and it is shown that intramolecular hydrogen bonding between the -OH and the ortho carbonyl group of the parent benzothiazine ring plays an important role in the solvent-dependence of their spectroscopic properties. The fluorescence spectra in aprotic nonpolar solvent exhibit abnormally large Stokes-shifted (${\sim}9,000cm^{-1}$) emission bands in contrast to the spectra in water. In ethanol, dual emission bands with two different fractional components of lifetimes have been observed. These results suggest that the abnormally red-shifted emission is attributed to the proton transferred form of an intramolecularly hydrogen-bonded closed conformer.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3211-3217
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• 2013

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been employed to investigate the molecular structures and absorption spectra of three D-${\pi}$-A-type organic dyes (C1-1, D5 and TH208) containing identical ${\pi}$-spacers and electron acceptors, but different aromatic amine electron-donating groups (tetrahydroquinoline, triphenylamine and phenothiazine). The coplanar geometries indicate that the strong conjugation is formed in the dyes. The electronic structures suggest that the intramolecular charge transfer from the donor to the acceptor occurs, and the electron-donating ability of tetrahydroquinoline is stronger than those of triphenylamine and phenothiazine. The computed orbital energy levels of these dyes confirm that the electrons could be injected from the excited dyes to the semiconductor conduction band and the oxidized dyes could be reduced effectively by electrolyte. The TD-DFT results show that the CAM-B3LYP/6-31+G(d, p) is suitable for calculating the absorption spectra. The first absorption band for these dyes is assigned to the HOMO${\rightarrow}$LUMO and HOMO-1${\rightarrow}$LUMO transitions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
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• pp.220-222
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• 2005

We can classify two cases in a way to observe an atom of gas state or a molecule using the laser. First case is way to use dispersion phenomenon like Rayleigh scattering, Thomson scattering, Mie scattering, Raman Scattering. And Second case is a way to use change phenomenon like a LAS (Laser Absorption Spectroscopy), LIF (Laser Induced Fluorescent). In this paper, we have measured the meta-stable density and the distribution by using a LAS method in Xe discharge lamp. The laser absorption spectroscopy (LAS) is useful to investigate the behavior of such species. The xenon atoms in the $1S_4$ and $1S_5$ generate excited $Xe^*$(147nm) and $Xe_{2}^*$(173nm) dimers in Xe plasma. It is found that the intensity of VUV 147nm emission is proportional to that of the IR 828nm emission, and the VUV 173nm emission is roughly proportional to that of the IR 823nm emission. The laser is used CW laser that consist of AlGaAs semiconductor and energy level is used 823.16nm wavelength. We measured signal of monochrometer from the lamp center while will change a discharge electric current by 6mA in 3mA and calculated meta-stable state density of a xenon atom through a measured value.

• 대한화학회지
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• 제34권3호
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• pp.255-259
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• 1990

Benoxaprofen (BXP)의 들뜬상태를 직접 검출하기 위하여, 질소 레이저 플래쉬 광분해 분광기를 제작하였다. 이 분광기의 성능을 확인하기 위하여 표준시료로써 안트라센을 사용하여 실험하였다. 에탄올에 녹은 BXP의 레이저 광들뜸을 질소기체 존재하에서 수행하였으며 파장범위 400-600 nm에 걸쳐 순간흡수 스펙트럼을 측정하고 이에 대한 산소 및 베타 카로틴의 효과를 조사하였다. 그 결과 415nm에서의 최대순간흡수띠는 BXP의 삼중항 상태에 기인하며 삼중항 에너지는 22 Kcal/mole 이상임을 확인하였다. 또한, BXP의 라디칼로 추정되는 중간체에 기인하는 최대순간 흡수띠가 520nm에 관측되었다. 이들 결과에 의해 BXP의 광증감 메카니즘을 논의하였다.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1452-1458
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• 2009

The change in the electronic absorption and emission energy of 7-aminocoumarin derivatives in binary solvent mixtures has been studied. The electronic transition energy along with the Stokes' shift is correlated with the orientation polarizability of the solvent as well as the empirical solvent polarity parameters $E_T$ (30). It is observed that the emission peak shift traces the change of $E_T$ (30) value very closely in binary solvent mixtures. The emission transition more strongly depends on the solvent polarity than the absorption, which indicates the dipole moment gets larger on excitation. From the dependence of the Stokes’ shift of 7-aminocoumarins with the solvent polarity parameters and the ground state dipole moment obtained by the semi-empirical calculations, the excited state dipole moment was estimated. The fluorescence lifetime change of 7-aminocoumarins in binary solvent mixtures was measured and the results are explained in terms of molecular conformation and solvent polarity. The study indicates the empirical solvent polarity $E_T$ (30) is a good measure of microscopic solvent polarity and it probes in general the non-specific solvent interactions.