• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.815-820
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• 2014

We applied the two-color resonant two-photon ionization and mass-analyzed threshold ionization techniques to record the vibronic and cation spectra of 2,4-difluorophenol. As supported by our theoretical calculations, only the cis form of 2,4-difluorophenol involves in the two-photon photoexcitation and pulsed field ionization processes. The band origin of the $S_1{\leftarrow}S_0$ electronic transition of cis-2,4-difluorophenol appears at 35 647 ${\pm}2cm^{-1}$ and the adiabatic ionization energy is determined to be 70 $030{\pm}5cm^{-1}$, respectively. Most of the observed active vibrations in the electronically excited $S_1$ and cationic ground $D_0$ states mainly involve in-plane ring deformation vibrations. Comparing these data of cis-2,4-difluorophenol with those of phenol, cis-2-fluorophenol, and 4-fluorophenol, we found that there is an additivity rule associated with the energy shift resulting from the additional fluorine substitution.

• Journal of the Korean Chemical Society
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• v.59 no.6
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• pp.541-544
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• 2015

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.277-280
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• 2002

Mass-analyzed threshold ionization (MATI) spectra of 2-hydroxypyridines existing as lactims (2-pyridinol) in a molecular beam are obtained via (1+1') two-photon process to give accurate ionization energies of 8.9344${\pm}$0.0005 and 8.9284${\pm}$0.0005 eV for 2-pyridinol (2Py-OH) and its deuterated analogue (2Py-OD), respectively. Resonantly-enhanced two-photon ionization spectra of these compounds are also presented to give vibrational structures of their $S_1$ states. Vibrational frequencies of 2Py-OH and 2Py-OD in ionic ground states are accurately determined from MATI spectra taken via various $S_1$ intermediate states, and associated vibrational modes are assigned with the aid of ab initio calculations.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.212-217
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• 2005

Desorption/ionization on silicon mass spectrometry (DIOS-MS) is a relatively new laser desorption/ionization technique for mass spectrometry without employing an organic matrix. This present study was carried to survey the experimental factors to improve the efficiency of DIOS-MS through electrochemical etching condition in structure and morphological properties of the porous silicon. The porous structure of silicon structure and its properties are crucial for the better performance of DIOS-MS and they can be controlled by the suitable selection of electrochemical conditions. The fabrication of porous silicon and ion signals on DIOS-MS were examined as a function of silicon orientation, etching time, etchant, current flux, irradiation, pore size, and pore depth. We have also examined the effect of pre- and post-etching conditions for their effect on DIOS-MS. Finally, we could optimize the electrochemical conditions for the efficient performance of DIOS-MS in the analysis of small molecule such as amino acid, drug and peptides without any unknown noise or fragmentation.

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.1996-2000
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• 2009

Alkali metal salts were introduced to enhance the ionization efficiency of glucose and maltooligoses in electrospray ionization-mass spectrometry (ESI-MS). A mixture of the same moles of glucose, maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose, and maltoheptaose was used. Salts of lithium, sodium, potassium, and cesium were employed as the cationizing agent. The ionization efficiency varied with the alkali metal cation types as well as the analyte sizes. Ion abundance distribution of the [M+$cation]^+$ ions of the carbohydrates varied with the fragmentor voltage. The maximum ion abundance at low fragmentor voltage was observed at maltose, while the maximum ion abundance at high fragmentor voltage shifted to maltotriose or maltotetraose for Na, K, and Cs. Variation of the ionization efficiency was explained with the hydrated cation size and the binding energy of the analyte and alkali metal cation.

• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1247-1252
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• 2002

Mass-analyzed threshold ionization (MATI) technique is optimized to generate substantial amount of state-selected molecular ions sufficient for dynamics study. The main strategy is to stabilize intermediate (n = 100- 200) Rydberg states by l,m-mix ing induced by AC field. Electrical jitter inherent in high voltage switching is utilized for this purpose. A related technique to locate the MATI onset is also described.

• Bulletin of the Korean Chemical Society
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• v.16 no.7
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• pp.578-582
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• 1995

The resonance ionization mass spectrometry (RIMS) system with angular reflectron type time-of-flight mass spectrometer (AREF-TOFMS) has been developed and characterized. The system is applied for the ultratrace determination of Pb element. The 2-color 3-photon laser ionization scheme is adopted for the study and the mass resolution of the system is determined as T/ΔT=1680. The calibration curve for Pb is obtained in the range of 100 ppb to 0.01 ppb by using standard solutions. The minimal amount of detection for the present RIMS system is determined as less than 100 femtograms (10-13 gram).

• Bulletin of the Korean Chemical Society
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• v.32 no.11
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• pp.3941-3946
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• 2011

The specific rates of sovolysis of 1-piperidincarbonyl chloride (1) have been determined in 26 pure and binary solvents at $25.0^{\circ}C$. Comparison of the specific rates of solvolyses of 1 with those for p-methoxybenzoyl chloride and those for 4-morpholinecarbonyl chloride in terms of linear free energy relationships (LFER) are helpful in mechanistic considerations, as is also treatment in terms of the extended Grunwald-Winstein equation. It is proposed that the solvolyses of 1 in binary aqueous solvent mixtures proceed through an ionization [I] pathway rather than through an $S_N1/S_N2$ and/or ionization/(ionization-elimination) = [I/(I-E)] pathway.

• Tribology and Lubricants
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• v.37 no.6
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• pp.208-212
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• 2021

Chemical mechanical polishing (CMP) is a key technology used for the global planarization of thin films in semiconductor production and smoothing the surface of substrate materials. CMP is a type of hybrid process using a material removal mechanism that forms a chemically reacted layer on the surface of a material owing to chemical elements included in a slurry and mechanically removes the chemically reacted layer using abrasive particles. Sapphire is known as a material that requires considerable time to remove materials through CMP owing to its high hardness and chemical stability. This study introduces a technology using electrolytic ionization and ultraviolet (UV) light in sapphire CMP and compares it with the existing CMP method from the perspective of the material removal rate (MRR). The technology proposed in the study experimentally confirms that the MRR of sapphire CMP can be increased by approximately 29.9, which is judged as a result of the generation of hydroxyl radicals (·OH) in the slurry. In the future, studies from various perspectives, such as the material removal mechanism and surface chemical reaction analysis of CMP technology using electrolytic ionization and UV, are required, and a tribological approach is also required to understand the mechanical removal of chemically reacted layers.

• Bulletin of the Korean Chemical Society
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• v.27 no.4
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• pp.581-583
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• 2006