• Rapid Communication in Photoscience
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• v.2 no.3
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• pp.76-78
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• 2013

Photoaddition reactions of aromatic carbonyl compounds with silyl thioketene acetals have been explored. The results of this study show that the acetonphenone react with dimethyl substituted silyl thioketene acetal competitively via either single electron transfer (SET)-desilylation or [2+2]-cycloaddition pathways to produce b-hydroxyester and oxetanes. In contrast, photochemical reactions of the benzaldehyde with dimethyl substituted silyl thioketene acetal mainly lead to the formation of oxetanes arising by [2+2] cycloaddition. A comparison of the results with those of silyl ketene acetal revealed that replacement of sulfur atom in ${\alpha}$-silyl donor substrate bring about dramatic changes in chemoselectivities as well as excited state reaction mechanism.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1276-1278
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• 2009

A novel blue emitting $Ca_{1-x}Mg_2Si_3O_9:Eu_x$ phosphor was synthesized by the solid state reaction and its photoluminescence properties were optimized by controlling concentration of the activator contents and substituting concentration of Ca ion by Sr ion. The photoluminescence (PL) showed that this phosphor is efficiently excited by ultraviolet (UV)-visible light in the wavelength range from 200 to 410 nm. Also this phosphor emits intensely blue light with a broad peak at around 450 nm.

• Journal of the Korean Chemical Society
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• v.20 no.2
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• pp.136-140
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• 1976

The photocyclodehydrogenation reaction of o-terphenyl type compounds has been interpreted with perturbational molecular orbital theory. Results show that the mobile bond order for the first excited state is a good reactivity index and this approach is also consistent with the orbital symmetry conservation rule of Woodward and Hoffmann.

• Bulletin of the Korean Chemical Society
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• v.3 no.1
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• pp.30-33
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• 1982

Photochemical and thermal solvolysis of 2,3,4-picolyl chlorides (2,3,4-PC) were studied in amine solvents and the results were correlated with the electronic structures calculated by PPP-SCF-MO CI method. Activation parameters show that the thermal solvolysis of PC is $S_N2$ type rcaction. The rates of thermal reaction in pyridine or t-butylamine solvent decrease in the order of 2-PC > 3-PC > 4-PC. These results are consistent with the predictions based on the electron densities of picolyl chlorides. In photosolvolysis, the same products as those of thermal reactions were obtained. The results indicate that photochemical solvolysis undergoes through heterolytic cleavage. Relative quantum yields of photosolvolysis of 2,3,4-picolyl chlorides in t-butylamine solvent were determined to be 0.73, 1, and 0.50 respectively. These results are in good agreement with the electron densities of the excited triplet state of picolyl chlorides.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.35-39
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• 2005

Phosphor powders of zinc gal late added with Mg and rare-earth elements were prepared by sol id state reaction to improve luminescent properties. Green emitting $ZnMnGa_{2}O_{4}$ reached maximum intensity at Mn=0,005 mole$\%$ and further improvement was achieved by addition of $Mg^{2+}$. Tm, Mg-added zinc gallate phosphor exhibited a strong blue band emission, peaking at about 420 nm with the maximum intensity at the concentration of 0.003 mole$\%$ Mg and 0.015 mole$\%$ Tm. Deepening of the potential wells of the ground and excited states was suggested to be the cause for the enhancement in emission intensity at optimal doping of Mg and Tm.

• Bulletin of the Korean Chemical Society
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• v.19 no.3
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• pp.308-313
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• 1998

A thermally irreversible photochromic system, 2,3-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride (MTMA), has been studied by semi-empirical molecular orbital methods. There are one pair of stable conformations for the closed-ring form and three pairs for the open-ring form, each pair consisting of two mirror-image conformations. Interconversion between the parallel and anti-parallel conformations of the open-ring form is restricted due to high energy barriers. Only the anti-parallel conformation appears to be responsible for photochromic cyclization. Thermostability of the compound is attributed to an avoided crossing at high energy in the ground states of the isomers, whereas the photoreactivity can be explained by the mutually connected excited singlet (S1) states of the isomers, forming a double well potential with a low energy barrier. The large solvent effects can be partly explained with the low dipole moment of the anti-parallel conformation of MTMA in the S1 state. The large variation of quantum efficiency suggests that excess vibronic energy can be utilized to provide the activation energy for the photochromic reaction.

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.1
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• pp.27-33
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• 2014

There are several ways to analyse stress resulting from anxiety and fear within dental treatment for children. Surveying questionnaires and monitoring biologic reaction are the most common ways for evaluating stress. Pulse oximeter is a popular device for detecting heart rate but not appropriate for moving children. In this study, we compared a recently introduced wrist- watch type heart rate monitor(Alpha, MIO, USA) with a pulse oximeter(MP110, MECKIS, Republic of Korea) for 10 attendants with two conditions including resting state and excited state after exercise. Data were analyzed using Wilcoxon Signed Rank test and there is no statistical difference between two devices(p < 0.05).

• Journal of the Korean Chemical Society
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• v.38 no.6
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• pp.405-410
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• 1994

Molecular orbital calculations suggest that an interaction between the psoralen derivatives of excite state and the thymine of ground state is dicussed in terms of their differing abilities to molecular complex. PM3-CI-UHF indicates that photocycloadducts across the C3-C4 and C4'-C5' double bonds of the methylpsoralen and hydroxypsoralen with thymine C5-C6 double bonds were deduced to be formed by their preferable frontier orbital interactions. The electronic properties of psoralen derivatives in the ground and excited states correlate with this difference in structure-activity relationship.

• Journal of Photoscience
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• v.6 no.3
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• pp.91-96
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• 1999

Zeolites and microporouos materials continue to attract attention as novel hosts for photochemical reactions. Zeolities are attractive because of their ability to selectivity exchange and incorporate species within the void spaces and interconnecting channels, providing a spatial arrangement of molecules. Our research has primarily focused on intrazeolitic electron transfer from excited Ru(bpy)32+ in supercages of zeolite Y to a series of bipyridinium ions. In the Ru(bpy)32+ viologen-zeolite Y samples, the slowing of the back electron transfer from the bipyridinium radical cation to Ru(bpy)32+ allows for charge propagation via self exchange between diquat molecules. This provides an opportunity for permanent charge separation. When the migrating charge on the diquat radical within the zeolite reaches the surface, it can be transferred to a neutral viologen (PVS) in solution, resulting in permanent charge separation. The advantage of long-lived charge separation can be exploited for useful chemistry if suitable catablysts can be assembled on the zeolities. We have studied Ru(bpy)2 as water oxdiation catalysts. We have demonstrated that synthesis of RuO2 fibers on a zeolite via thermal decomposition of Ru3(CO)12 leads to the most active water decomposition catalyst reported to date. Because of the extensive interest of photochemical water reduction to H2, much is known about catalytic systems usin gone electron catalyst, and even more importantly, that no reaction of viologen occurred with H2 over this catalyst. The present challenge is to incorporate all these elements of the system into an architecture and we are examining zeolite membranes for this purpose.

• Nuclear Engineering and Technology
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• v.24 no.1
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• pp.63-74
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• 1992

The resonant formation rates of muonic molecular ion dtr in the muon-catalyzed fusion are calculated in various fuel temperatures and densities. The elastic scattering cross sections between t$\mu$ and deuterons are obtained by making use of the partial wave method. The transition property of the excited compound molecule [(dt$\mu$)dee]＊ derived by the impulse approximation in the form of a bound-state form factor. The radiative, Auger, and collisional deexcitations are considered as the deexcitation mechanisms of the excited dt$\mu$, and each deexcitation width is calculated as well as back decay width. The resultant reaction widths are used to calculate the formation cross sections of resonant dt$\mu$. The resonant formation rates for dt$\mu$-d and dt$\mu$-t collisions are computed as functions of fuel temperature and density. The calculations show that the resonant formation rates increase with fuel densities and have the maximum values at the particular temperatures where the relative collision energies are equal to the resonant ones.