• Bulletin of the Korean Chemical Society
• /
• v.27 no.9
• /
• pp.1377-1380
• /
• 2006

The technique of corona-excited supersonic expansion was applied to produce electronically excited but rovibrationally cooled m-tolunitrile. The well-resolved vibronic emission spectrum of the jet-cooled m-tolunitrile in the $S_1\;\rightarrow \;S_0$ transition was recorded in the uv region using a Fourier transform spectrometer equipped with a Quartz-uv beam splitter. From an analysis of the spectrum observed, it was confirmed that the electronic transition and vibrational mode frequencies in the ground electronic state were accurately determined.

• Journal of the Korean Chemical Society
• /
• v.52 no.3
• /
• pp.322-327
• /
• 2008

The geometrical structure, binding energy and vibrational frequencies of HOOCl-H2O cluster were investigated with MP2/6-311G(d,p) and MP2/6-311G(2d,2p) methods. The most stable conformer is skew HOOCl-H2O cluster and the binding energy was 46~48kJ/mol. The trans HOOCl-H2O cluster is less stable than skew form, but the binding energy is big enough to stablize the complex. The vibrational frequencies of skew and trans HOOCl-H2O cluster were calculated and compared with the spectrum of HOOCl.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11b
• /
• pp.1055-1060
• /
• 2001

Springing phenomena of ships is introduced with its concept, research history and approach methodology. Being a hydroelasticity problem, non-linear vibration and stochastic process, springing was formulated and modeled in vibration point of view separating hydrodynamic force into system properties and excitation force. Both RAO and response spectrum as well as wave spectrum were presented as a case study of springing analysis for a flexible vessel with wide breadth. The effect of advance speed, heading angle and loading condition were investigated as parametric study. The results and observations showed availability of analysis for the prediction of the ship springing behavior.

• Journal of The Korean Astronomical Society
• /
• v.29 no.2
• /
• pp.223-243
• /
• 1996

We have constructed a line-by-line model of the A-X system of CO in order to analyze the CO bands appearing in the UV spectra of comets. The model includes electronic, rotational, vibrational transitions, excitations by solar UV radiation, and effects of neutral and electron collisions. The major bands of the A-X system occur in the $1200 - 1800{\AA}$ range where the temporal variation of solar irradiation is significant. The solar spectrum in this spectral range shows many emission lines, which cause a significant Swings effect. We derived fluorescence efficiencies of the bands as functions of heliocentric velocity and cometocentric distance using a high resolution spectrum of the sun. We compared our model with a spectrum of comet P/Halley obtained with the IUE, and estimated that the UV Swings effects are less than 20 fluorescence efficiencies for the most bands of the A-X system. We discuss the temporal variation of solar UV irradiation and its effects on the fluorescence efficiencies. The study of the A-X system also requites knowledge of vibrational and rotational fluorescent processes in the infrared and radio regions because the majority of CO molecules in the coma is in the ground rotational states. The solar infrared spectrum near 5 microns, where the fundamental band of CO occurs, contains strong absorption lines of the fundamental band and hot bands of CO and its isotopes. We derived fluorescence efficiencies of the infrared band as functions of heliocentric velocity and cometrocentric distance. The solar absorption lines near 5 microns cause a 20 reduction of the g-factor of the fundamental band at heliocentric velocities close to 0 km/sec. We discuss the effects of neutral and electron collisions on the fluorescence efficiencies of the infrared and UV bands.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.10
• /
• pp.3391-3396
• /
• 2012

Two-dimensional infrared (2D-IR) spectroscopy can probe the fast structural evolution of molecules under thermal equilibrium. Vibrational frequency fluctuation caused by structural evolution produced the time-dependent line shape change in 2D-IR spectrum. A variety of methods has been used to connect the evolution of 2D-IR spectrum with Frequency-Frequency Correlation Function (FFCF), which connects the experimental observables to a molecular level description. Here, a new method to extract FFCF from 2D-IR spectra is described. The experimental observable is the time-dependent frequency shift of maximum peak position in the slice spectrum of 2D-IR, which is taken along the excitation frequency axis. The direct relation between the 2D-IR peak shift and FFCF is proved analytically. Observing the 2D-IR peak shift does not need the full 2D-IR spectrum which covers 0-1 and 1-2 bands. Thus data collection time to determine FFCF can be reduced significantly, which helps the detection of transient species.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.8
• /
• pp.2175-2179
• /
• 2010

Quantum mechanical properties of unsymmetrical and unfunctionalized trans-stilbene derivatives 1-3, which had been prepared by solid-phase parallel syntheses, were characterized using mPW1PW91/6-311G(d,p) (hybrid HF-DF) calculations. The total electronic energies, normal vibrational modes, Gibbs free energies, and HOMOs and LUMOs of sixteen different structures from three different groups were analyzed. The energy differences between the HOMOs and LUMOs of the various unsymmetrical trans-stilbenes are in accord with the maximum absorption peaks of the experimental UV spectra of 1-3. The calculated normal vibrational modes of 21 were comparable with its experimental IR spectrum. The $\pi$-conjugation in the para-connected biphenyl group of 2 is better than the one in the metaconnected biphenyl group on the shorter side of 3.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.12
• /
• pp.3771-3776
• /
• 2010

The dynamics of the $CN^-$-ligated ferric cytochrome c (CytcCN) in $D_2O$ at 283 K following Q-band photoexcitation at 575 nm was observed using femtosecond time-resolved vibrational spectroscopy. The equilibrium vibrational spectrum of the CN stretching mode of CytcCN shows two overlapping bands: one main band (82%) at $2122\;cm^{-1}$ with $23\;cm^{-1}$ full width at half maximum (fwhm) and the other band (18%) at $2116\;cm^{-1}$ with $7\;cm^{-1}$ fwhm. The time-resolved spectra show bleaching of the CN fundamental mode of CytcCN and two absorption features at lower energies. The bleach signal and both absorption features are all formed within the time resolution of the experiment (< 200 fs) and decay with a life time of 1.9 ps. One transient absorption feature, appearing immediately red to the bleach signal, results from the thermal excitation of low-frequency modes of the heme that anharmonically couple to the CN fundamental mode, thereby shifting the CN mode to lower energies. The shift of the CN mode decays with a lifetime of 2 ps, equivalent to the time scale for vibrational cooling of the low-frequency heme modes. The other transient absorption feature, which is 3.3 times weaker than the bleach signal and shifted $27\;cm^{-1}$ toward lower energies, is attributed to the CN mode in an electronically excited state where the CN bond is weakened with a lowered extinction coefficient. These observations suggest that photoexcited CytcCN mainly undergoes ultrafast radiationless relaxation, causing photo-deligation of $CN^-$ from CytcCN highly inefficient. As also observed in $CN^-$-ligated myoglobin, inefficient ligand photodissociation might be a general property of $CN^-$-ligated ferric hemes.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.8
• /
• pp.2751-2755
• /
• 2011

The visible vibronic emission spectrum was recorded from the corona discharge of precursor 1,2,3,4-tetramethylbenzene with a large amount of inert carrier gas helium using a pinhole-type glass nozzle coupled with corona excited supersonic expansion. The spectrum showed a series of vibronic bands in the $D_1{\rightarrow}D_0$ electronic transition of jet-cooled benzyl-type radicals formed from the precursor in a corona excitation. The analysis confirmed that two isomeric radicals, 2,3,4- and 2,3,6-trimethylbenzyl radicals, were produced as a result of removal of a hydrogen atom from the methyl group at different substitution positions. For each isomeric product, the electronic transition and a few vibrational mode frequencies were determined in the ground electronic state.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.1
• /
• pp.68-74
• /
• 2013

The surface enhanced Raman spectrum of juglone, a traditional natural dye, has been observed by a custom-built micro-Raman setup. The spectral features of juglone significantly differ from those of lawsone, a structural isomer of juglone; only small red shifts of the double bond stretching bands are observed, and strong SERS bands are observed in the lower frequency regions as well. The DFT computations reveal that juglone coordinated to an $Ag^+$ adatom with $H^+$ release best correlates with the observed vibrational characteristics in the SERS spectrum among the plausible configurations of juglone coordinated to an adatom on the Ag surface, in line with the previously studied lawsone case. The differences in the SERS spectra of juglone and lawsone are attributed to the different locations of the hydroxyl group in the two isomers.

• Bulletin of the Korean Chemical Society
• /
• v.17 no.5
• /
• pp.461-463
• /
• 1996

The laser-induced fluorescence excitation spectrum of 7-amino-4-(trifluoromethyl)coumarin in a supersonic jet has been recorded in the 340-352 nm region. The electronic band origin was observed at 28622.8 cm-1. Vibrational assignments for the three fundamental low-frequency modes and eight combination bands have been made for the S1 electronic excited state. The out-of-plane vibrations of this molecule have been characterized from the low-frequency assignments of the spectrum. The periodic potential energy function for the CF3 torsion, which satisfactorily fits the observed data, were also determined to be V(Φ)=95X(1-cos3Φ)-32X(1-cos6Φ) where Φ is the torsional angle. The relatively low torsional barrier of 99 cm-1 in S1 state could be explained by the small steric interactions between the functional groups attached to a bicyclic ring.