• Bulletin of the Korean Chemical Society
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• 제23권7호
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• pp.971-984
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• 2002

The multichannel quantum defect theory (MQDT) is reformulated into the form of the configuration mixing (CM) method using the geometrical construction of the S matrix developed for the system involving two open and one closed channels. The reformulation is done by the phase renormalization method of Giusti-Suzor and Fano. The rather unconventional short-range reactance matrix K whose diagonal elements are not zero is obtained though the Lu-Fano plot becomes symmetrical. The reformulation of MQDT yields the partial cross section formulas analogous to Fano's resonance formula, which has not easily been available in other's work.

• Bulletin of the Korean Chemical Society
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• 제16권9호
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• pp.850-858
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• 1995

Golden-rule like formulas have been used without theoretical basis to calculate the resonance lifetimes and final state distributions in the predissociation of van der Waals molecules. Here we present their theoretical basis by extending Fano's configuration interaction theory. Such extensions were independently done by Farnonux [Phys. Rev. 1985, 25, 287] but his work, unfortunately, was not well known outside some small group of people in the field of Auger spectroscopy. Since my extension is easier to understand than his, it is presented here. Theoretical basis of Golden rule like formulas used in the predissociation of van der Waals molecules was obtained by using such extensions. Factors responsible for several aspects of predissociation dynamics, such as variations of dynamics as functions of resonance lifetimes, or variations in shapes of final quantum state distributions of photofragments around resonances, were identified. Parameters, or dynamical information that could be obtained from the measurement of partial cross section spectra were accordingly determined. The theory was applied to the vibrational predissociation of triatomic van der Waals molecules and its result was compared with those calculated by close-coupling method. An example where Golden-rule like expression fails and branching ratios vary greatly around a resonance was considered.

• Bulletin of the Korean Chemical Society
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• 제20권11호
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• pp.1281-1287
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• 1999

The low-lying electronic states of diazirine and 3,3'-dimethyldiazirine have been studied by high level ab initio quantum chemical methods. The equilibrium geometries of the ground state and the first excited singlet and triplet states have been optimized using the Hartree-Fock (HF) and complete active space SCF (CASSCF) methods, as well as using the Møller-Plesset second order perturbation (MP2) theory and the single configuration interaction (CIS) theory. It was found that the first excited singlet state is of 1 B1 symmetry resulting from the n- π* transition, while the first excited triplet state is of 3 B2 symmetry resulting from the π- π* transition. The harmonic vibrational frequencies have been calculated at the optimized geometry of each electronic state, and the scaled frequencies have been compared with the experimental frequencies available. The adiabatic and vertical transition energies from the ground electronic state to the low-lying electronic states have been estimated by means of multireference methods based on the CASSCF wavefunctions, i.e., the multiconfigurational quasidegenerate second order perturbation (MCQDPT2) theory and the CASSCF second-order configuration interaction (CASSCF-SOCI) theory. The vertical transition energies have also been calculated by the CIS method for comparison. The computed transition energies, particularly by MCQDPT2, agree well with the experimental observations, and the electronic structures of the molecules have been discussed, particularly in light of the controversy over the existence of the so-called second electronic state.

• 대한화학회지
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• 제20권3호
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• pp.198-205
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• 1976

Parr의 Integral Hellmann-Feynman이론을 비대각꼴에 까지 일반화하여 의의를 갖도록 하였으며 그 특징을 논하였다. 그리하여 이 비대각꼴을 결정장론에 미치는 배치작용의 효과를 검토하는데 적용함으로서, 모든 차의 섭동 에너지를 하나의 묶음으로서 도입하였다. 그 결과 ${\Gamma}$, S 및 m로 특징지워지는 상태들에게, 파라미터화 할 수 있는 공통적인 동경적분이 존재하지 않음을 밝혔다. 그러나 만일 각 성분에 변형이 없고 동경성분에게 동등한 변형만이 있는 여기된 배치들의 작용만을 허락한다면, 이는 고전적인 결정장론에서 결정장 파라메터 10 Dq와 Condon-Slater 적분 $F^n$의 척도를 변경시키는 결과를 초래함을 알게 되었다.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.976-981
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• 1997

The magnetic susceptibilities of molybdenum ions with 4d1 electronic configuration in the octahedral crystal field were calculated on the basis of ligand field theory. The experimental magnetic susceptibilities for molybdenum ions, which are stabilized at the octahedral site in the perovskite lattice of Ba2ScMoⅤO6 and Sr2YMoⅤO6, were compared with the theoretical ones. We have tried to fit their temperature dependence of magnetic susceptibility with ligand field parameters, spin-orbit coupling constant ζSO, and orbital reduction parameter κ according to intermediate field coupling and strong field theory. Strong field coupling theory could not explain experimental curves without unrealistically large axial ligand field, since it ignores the mixing up between different state via spin-orbit interaction and ligand field. On the other hand, the intermediate field coupling theory could successfully reproduce experimental data in octahedral and trigonal ligand field. The fitting result demonstrates not only the fact that spin-orbit interaction is primarily responsible for the variation of magnetic behavior but also the fact that effective orbital overlap, enhanced by cubic crystal structure, reduces significantly orbital angular momentum as indicated by κ parameter.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3261-3266
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• 2011

The interaction of bilobalide (BB) and ginkgolides B (GB) with bovine serum albumin (BSA) was investigated by fluorescent technique and UV/vis absorption spectroscopy. The results showed that BB and GB could intensively quench the fluorescence of BSA through a static quenching procedure. The binding constants (Ka) and the average binding distance between the donor (BSA) and the acceptor (ginkgolides) were obtained ($r_{BB}$ = 5.33 nm and $r_{GB}$ = 4.20 nm) by the theory of non-radiation energy transfer, and then the thermodynamic parameters such as ${\Delta}S^0$ (0.17-0.32 kJ/mol), ${\Delta}G^0$ (-20.76 ~ -17.79 kJ/mol) and ${\Delta}H^0$ (32.47-76.52 kJ/mol) could be calculated, respectively. All these results revealed that the interaction of BB and GB with BSA were driven mainly by hydrophobie force. The synchronous fluorescence spectroscopy was applied to examine the effect of two ginkgolides on the configuration of BSA. The configuration alteration of BSA could be induced by the hydrophobicitv environment of tyrosine with the increase of the drug concentration.

• 대한화학회지
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• 제21권1호
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• pp.23-31
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• 1977

Octahedral symmetry 를 지닌 리간드에 의한 영향 아래있는 하나의 d전자를 갖는 금속 착물을 대상으로, 결정장 분리계수 10Dq를 결정장이론에 의하여 이론적으로 계산하였다. 점전하 모형을 쓰되, Shull-Lowdin 함수를 사용하여 배치간 작용을 고려하고, Integral Hellmann-Feynman Theorem을 써서 고차섭동의 영향을 추출하였다. 고차섭동의 영향이 일차섭동의 약 $50{\%}$가 됨을 알았다. Octahedral potential에 의해 3d 함수의 각 성분의 변화가 없고, $E_g\;와\;T_{2g}$상태에서, 동경성분의 변화가 일정하므로 10Dq는 유일한 파라미터로 남을 것이라는 결론을 얻었다.

• Bulletin of the Korean Chemical Society
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• 제11권1호
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• pp.34-41
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• 1990

The second order ab initio effective valence shell Hamiltonian is calculated for the valence state potential energy curves of NH and $NH^+$. From the potential energy curves various spectroscopic constants of valence states are determined. The results are in good agreement with experiments and configuration interaction calculations. They show the composite picture of potential energy curves and also indicate that the second order effective Hamiltonian theory is adequate for describing various valence states of a molecule and its ions simultaneously.

• Bulletin of the Korean Chemical Society
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• 제7권4호
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• pp.262-266
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• 1986

A multi-reference many-body perturbation theory (MRMBPT) method is critically tested in second order by comparing with the corresponding configuration interaction (CI) calculations. Excitation energies of the four-valence-electron states of transition metal atoms and ions are used for the comparison. The agreement between the second order MRMBPT and CI calculations is very reasonable, confirming the reliability of the second order MRMBPT method. The reliability of calculations with the present second order MRMBPT method was only been inferred empirically in the past since most results have been gauged by the agreement with experiment and/or with other MRMBPT calculations based upon different sets of orbitals and configuration spaces. The present MRMBPT method appears to be an efficient ab initio multi-reference method for the calculation of electron correlation effects in atoms and molecules, and it is shown how MRMBPT can be used to estimate core-core and core-valence correlation effects which are often omitted in CI calculations because too many configurations and correlating electrons are involved.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1231-1236
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• 2011

Chiral discrimination is the ability to distinguish one enantiomeric form over another. The differential binding interaction between two molecules with the same helicity and those with the opposite helicity was investigated by using dispersion-corrected density functional theory. [5]helicene, tetrahydro[5]helicene and the polar D-${\pi}$-A compounds, 3,12-dimethoxy-7,8-dicyano-[5]helicene and 3,12-dimethoxy-7,8-dicyano-tetrahydro[5]helicene were the monomers considered in this study. In gas phase, the dimeric interaction from two helical molecules with the opposite handedness is greater than from those with the same handedness. The stable configurations of such dimers were identified. The most stable configuration tends to be the one with maximum contact between monomers.