• Journal of the Korean Chemical Society
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• v.45 no.5
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• pp.436-441
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• 2001

The emission and excitation spectra of mer-[Cr(dien)(glygly)]ClO$_4$(glygly=glycylglycinate;dien=N-(2-aminoethyl)-1,2-ethanediamine) taken at 77 K are reported. The infrared and visible spectra at 298 K are also measured. The twelve electronic bands due to spin-allowed and spin-forbidden transitions are assigned. Using the observed transitions, a ligand field analysis has been performed to determine the bonding property of coordinated atoms in the chromium(III) complex. It is confirmed that the amine nitrogen atoms of the dien and glygly have strong $\sigma$-donor characters, but the peptide nitrogen of glygly has weak $\pi$-donor property toward chromium(III) ion.

• Bulletin of the Korean Chemical Society
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• v.26 no.6
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• pp.903-908
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• 2005

The sharp-line absorption and emission spectra of $(H_{13}O_6)${$trans-[Cr(Me_2tn)_2Br_2]$}$_2Br_2(ClO_4)\;(Me_2$tn = 2,2-dimethyl-1,3-diaminopropane) have been measured between 13000 $cm^{-1}$ and 16000 $cm^{-1}$ at 5 K. The 298 K infrared and visible absorption spectra have also been measured. The nine electronic bands due to spin-allowed and spin-forbidden transitions were assigned. Using observed transitions, a ligand field analysis has been performed to probe the ligand field properties of coordinated atoms in the title chromium(III) complex ion. The zero-phonon line in the sharp-line absorption spectrum splits into two components by 286 $cm^{-1}$, and the large $^2E_g$ splitting can be reproduced by the modern ligand field theory. It is confirmed that nitrogen atoms of the Me2tn ligand have a strong $\sigma$-donor character, but the bromide has weak $\sigma$- and $\pi$-donor properties toward chromium(III) ion.

• Bulletin of the Korean Chemical Society
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• v.27 no.3
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• pp.363-367
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• 2006

The structure-property relations of ternary copper chalcogenides, $TlCu_{3-x}S_2$ and $\alpha-BaCu_{2-x}S_2$ are examined. The density of states, band dispersions, and Fermi surfaces of these compounds are investigated to verify the reason of the metal-insulator transitions by extended Huckel tight-binding band calculations. The origin of the metalinsulator transitions of non-stoichiometric $TlCu_{3-x}S_2$ and $\alpha-BaCu_{2-x}S_2$ is thought to be the electronic instability induced by their Fermi surface nesting.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05c
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• pp.3-7
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• 2004

$HgGa_2S_4:CO^{2+}$ single crystal were grown by the chemical transport reaction(CTR) method. 1n the optical absorption spectrum of the $HgGa_2S_4:CO^{2+}$ single crystal measured at 298K, three groups of impurity optical absorption peaks consisting of three peaks, respectively, were observed at 673nm, 734nm, and 760nm, 1621nm, 1654nm, and 1734nm, and 2544nm, 2650nm, and 2678nm. At 10K, the three peaks(673nm, 734nm, and 760nm) of the first group were split to be twelve peaks. These impurity optical absorption peaks are assigned to be due to the electronic transitions between the split energy levels of $Co^{2+}$ sited in the $S_4$ symmetry point.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.7
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• pp.579-583
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• 2003

HgGa$_2$S$_4$: Co$^{2＋}$ single crystal were grown by the chemical transport reaction(CTR) method. In the optical absorption spectrum of the HgGa$_2$S$_4$: Co$^{2＋}$ single crystal measured at 298K, three groups of impurity optical absorption peaks consisting of three peaks, respectively, were observed at 673nm, 734nm, and 760nm, 1621nm, 1654nm, and 1734nm, and 2544nm, 2650nm, and 2678nm. At 10K, the three peaks(673nm, 734nm, and 760nm) of the first group were split to be twelve peaks. These impurity optical absolution peaks are assigned to be due to the electronic transitions between the split energy levels of Co$^{2＋}$ sited in the S$_4$ symmetry point.

• Applied Science and Convergence Technology
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• v.24 no.5
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• pp.167-171
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• 2015

Quantum-confined nanostructures open up additional perspectives in engineering materials with different electronic and optical properties. We have fabricated unique cation-exchanged CdS and CdS/CdSe quantum dots and measured their first four exciton transitions. We demonstrate that the relationship between electronic transitions and charge-carrier distributions is generalized for a broad range of core-shell nanostructures. These nanostructures can be used to further improve the performance in the fields of bio-imaging, light-emitting devices, photovoltaics, and quantum computing.

• Journal of Photoscience
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• v.7 no.1
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• pp.21-26
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• 2000

The photoemission and excitation spectra of cis-[Cr(cyclam)F$_2$]ClO$_4$ (cyclam = 1,4,8,11-tetraazacy-clotetradecane) taken at 77 K are reported. The 298 K mid- and far-infrared spectra are also measured. The vibrational intervals of the electronic ground state are extracted from the far-infrared and emission spectra. The ten electronic bands due to spin-allowed and spin-forbidden transitions are assigned. The zero-phonon line In the excitation spectrum splits into two components by 169 cm$^{1}$, and the large $^2$E$_{g}$ splitting can be reproduced by the ligand field theory. According to the ligand field analysis, we can confirm that nitrogen atoms of the cyclam ligand have a strong c-donor character, and fluoride ligand also has strong $\sigma$- and $\pi$-donor properties toward chromium(III) ion.n.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.1
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• pp.21-27
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• 2000

We used the surface photovoltage spectroscopy(SPVS) for characterization of GaAs/Al\ulcornerGa\ulcornerAs multi-quantum well(MQW) structures grown by molecular beam epitaxy(MBE) method. Energy gap related transitions in GaAs and AlGaAs were observed. The Al composition(x=0.3) was determined by Sek's composition formula. Transition energies in MQW were determined using the differential surface photo-volatage spectroscopy)DSPVS) of the measured resonanced. In order to indentify the transitions, the experimentally observed energies were compared with results of the envelope function approximation for a rectangular quantum well. We have observed and interesting behavior of the temperature dependence(80K~300K) of the 11Hand 11L transition for sample.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.850-858
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• 2010

The electronic absorption spectra of five Schiff bases derived from 2-hydroxy-1-naphthaldehyde with glycine, alanine, leucine, valine and phenylalanine have been measured in various solvents. The observed bands were assigned to the proper electronic transitions and compared with the predicted transitions at the semiempirical level of theory. The calculated equilibrium constants are in agreement with the experimental results, predicting the existence of all studied compounds predominantly or completely in keto-imine tautomerism. On the other hand, a correlation between $\nu\;(cm^{-1})$ (main frequency of each compound) and the well known solvent parameters $E_T$ (30), $\varepsilon_T$, $\pi^*$ been made. Furthermore, the acid dissociation constants, $pK_a$, were determined by using three different spectrophotometric methods.

• Bulletin of the Korean Chemical Society
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• v.20 no.1
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• pp.81-84
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• 1999

The emission and excitation spectra of [Cr(NH3)5(imH)](ClO4)3·H2O (imH=imidazole) taken at 77 K are reported. The 298 K visible and far-infrared spectra are also measured. The vibrational intervals of the electronic ground state are extracted from the far-infrared and emission spectra. The ten electronic bands due to spin-allowed and spin-forbidden transitions are assigned. Using the observed transitions, a ligand field analysis has been performed to determine the bonding properties of coordinated imidazole in the title chromium(Ⅲ) complex. It is confirmed that nitrogen atom of the imidazole ligand has a medium it-acceptor property toward chromium(Ⅲ) ion. The zero-phonon line in the excitation spectrum splits into two components by 181 cm-1, and the large 2Eg splitting can be reproduced by the ligand field theory.