• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1783-1792
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• 2009

Although overlapping resonances have been studied extensively in conventional resonance theories, there have not been many studies on them in multichannel quantum defect theories (MQDT). In MQDT, overlapping resonances occur between the channels instead of states, which pose far greater difficulty. Their systematic treatment was obtained for cases involving degenerate closed channels by applying our previous theory, which decouples background scattering from the resonance scattering in the MQDT formulation. The use of mathematical theory on con-diagonalization and con-similarity was essential for handling the non-Hermitian symmetric complex matrix. Overlapping resonances in rare gas spectra of Ar, Kr and Xe were analyzed using this theory and the results were compared with the ones of the previous alternative parameterizations of MQDT which make the open-open part $K^{oo}$ and closed-closed part $K^{cc}$ of reactance submatrices zero. The comparison revealed that separation of background and resonance scatterings achieved in our formulation in a systematic way was not achieved in the representation of $K^{oo}\;=\;0\;and\;K^{cc}$ = 0 when overlapping resonances are present.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.315-326
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• 2010

This study examined the overlapping resonances in the systems involving 1 open and 2 closed channels using the phase-shifted version of multichannel quantum-defect theory (MQDT). The results showed that 21 patterns for the q reversals in the autoionization spectra are possible depending on the relative arrangements of the two simple poles and roots of the quadratic equations. Complete cases could be generated easily using the q zero planes determined using only 3 asymmetric spectral line profile indices. The transition of the spectra of the coarse interloper Rydberg series from the lines into a structured continuum by being dispersed onto the entire Rydberg series was found. The overall behavior of the time delays was found to be governed by the dense Rydberg series, which is quite different from the one of the autoionization cross sections that is governed by an interloper, indicating that different dynamics prevail for them. This is in contrast to the two channel system where both quantities behave similarly. The dynamics obtained in the presence of overlapping resonances is as follows. The absorption process is instant and dominated by a transition to the interloper line. This process is followed by rapid leakage into the dense Rydberg series, which has a longer residence time before ionization than that of the interloper state. This is because the orbiting period is proportional to $\upsilon^3$ so that an excited electron has a shorter lifetime in the interloper state belonging to a lower member of the Rydberg series.

• Bulletin of the Korean Chemical Society
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• v.21 no.5
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• pp.497-502
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• 2000

Quantum mechanical analysis is presented for the photodissociation dynamics of the v'=4 levels of the $A^2Σ^+$ state of the OH molecule. We focus on the effects of the multichannel interactions between the asymptotically degenerate states in the recoupling region to see how they affect the dynamics near the predissociating resonances. Both the scalar (total cross section and branching ratios) and the vector properties (angular distributions and alignment parameters) of O($^3P_j, j=0, 1, 2) are treated. The resonances are predicted to be highly Lorentzian, and the branching ratios do not change much across them. Vector properties, however, show very delicate effects of the multichannel interactions and overlapping near the isolated and overlapping resonances. Computed resonance lifetimes agree reasonably well with experimental results.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1519-1526
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• 2011

A previous study (Lee, C. W. J. Phys. B 2010, 43, 175002) that isolated the overlapping resonances in the photoionization spectra using multichannel quantum defect theory (MQDT) in systems involving a single open channel was extended to manage many open channels when the closed channels are degenerate. The theory was applied to the dipole allowed J = 1$^{\circ}$ spectra from the ground state with excitation energies lying between the lowest ionization thresholds for rare gas atoms, Ar, Kr, and Xe, and also for group IV elements, Ge, Sn and Pb.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3201-3211
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• 2010

Previous work on the phase-shifted version of the multichannel quantum-defect theory (MQDT) for a system involving 2 closed and many open channels (Lee, C.-W. Bull. Korean Chem. Soc. 2010, 31, 1669) was extended to obtain the formulae of the spectral shape parameters with the structure of a pole extracted explicitly for general cases only limited by 2 non-degenerate closed channels. The theory was applied to the narrow $6p_{1/2,3/2}np$ J = 1 autoionizing Rydberg series in barium perturbed by the $6p_{3/2}nf$ states obtained by de Graaff et al.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1669-1680
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• 2010

The phase-shifted version of the multichannel quantum-defect theory (MQDT) was reformulated by disentangling the interloper spectrum from the perturbed dense Rydberg series for a systems involving 2 closed and more than 1 open channel. The theory was applied successfully to Martins and Zimmermann's photoionization spectra of the Rydberg series Cu I $3d^9\;4s(^1D_2)\;nd^2G_{9/2}$ perturbed by the interloper, $3d^9\;4p^2\;^4F_{9/2}$, for which Cohen's 4 channel QDT had failed. The zero surface graphic of the perturbed Fano's asymmetry parameter q of the autoionization spectrum of dense Rydberg series by the interloper was determined by only two parameters for this system. It was used as a map to trace the transformation route of the 3 channel autoionization spectra to the 4 channel spectra when the channel coupling of the closed channels with a newly added open channel was turned on progressively.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.809-817
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• 2012

The resonance structure of the preionization spectrum of $H_2$ in the region immediately above its ionization threshold, ($^2{\sum}_{g}^{+}$, $\nu^+=0$, $N^+=0$) converging toward its rotationally excited ($\nu^+=0$, $N^+=2$) limit, is complicated due to perturbation by the vibrationally excited levels $7_{p\pi}\;v=1$ and $57_{p\pi}\;v=2$. The spectra of interlopers are separated from the rotationally preionizing Rydberg series to allow analysis of this complex resonance structure. Although only two vibrationally excited levels perturb the rotational preionization spectrum, at least 6 interloper Rydberg series participate in the complex spectrum over most of its energy range and more interloper series participate at a narrow range around $124500cm^{-1}$ in the spectrum. To allow handling of an arbitrary number of interloper series, MATLAB$^{(R)}$'s symbolic operation is used to perform on-the-fly formulation.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2657-2668
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• 2012

We obtain the general formulation which can handle the rotational preionization spectrum of $H_2$ in the region above its ${H_2}^+$ ionization threshold, ($^2{\sum}_g^+$, ${\nu}^+=0$, $N^+=0$) converging toward its rotationally excited (${\nu}^+=0$, $N^+=2$) limit and perturbed by the vibrationally excited levels $7p{\pi}$ ${\nu}=1$ and $5p{\pi}$ ${\nu}^=2$. The formulation is based on phase-shifted multichannel quantum-defect theory. With this formulation, resonance structures are analyzed in detail.

• Journal of the Korean Magnetic Resonance Society
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• v.8 no.1
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• pp.55-61
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• 2004

Biosupramolecular systems such as biological membranes usually fluid under physiological conditions$^1$. Therefore, solid-state NMR has been used to investigate biosupramolecular systems. But solid-state NMR spectra contain a large number of overlapping resonances and are rather difficult to analyze. These problem has to be overcome by selective isotope labeling. We constructed a deuterium NMR probe for AM400 NMR spectrometer, which is mainly used for liquid samples. To overcome the fluidity problem, a saddle type coil was designed. The efficiency was systematically investigated for two kinds of coil geometry, solenoid and saddle types. Our results suggest that solenoids are superior to saddle type coils in the sensitivity. However, the letter fits better to fluid samples such as biosupramolecular systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.3 s.118
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• pp.288-297
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• 2007

The novel internal monopole chip antenna of penta-band operation for GSM850/GSM900/DCS/USPCS/WCDMA bands for mobile phones is proposed. This antenna occupies a small volume $8\times3.2\times20mm^3$ and is suitable to be embedded in a mobile phone as an internal antenna. The minimization of the proposed antenna was realized by using spiral line structure and meander line structure on FR-4 of dielectric$(\varepsilon_r=4.4)$. The designed antenna has the wide-band operation in the upper band by overlapping high order resonances. The measured bandwidth of this antenna (VSWR>3) is 150MHz$(1,030\sim1,180\;MHz)$ in the lower band operation and 650 MHz$(1,760\sim2,410\;MHz)$ in higher band operation. The measured radiation efficiency within bandwidth(VSWR 3:1) is over 50 %. The antenna has been designed by a commercial software HFSS.