Browsing by Author "Wu, Yu-Jong"

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A new method for investigating infrared spectra of protonated benzene (C6H7+) and cyclohexadienyl radical (c-C6H7) using para-hydrogen
(2012-04-21)
Bahou, Mohammed
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Wu, Yu-Jong
;
Lee, Yuan-Pern
;
應用化學系
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應用化學系分子科學碩博班
We use protonated benzene (C6H7+) and cyclohexadienyl radical (c-C6H7) to demonstrate a new method that has some advantages over other methods currently used. C6H7+ and c-C6H7 were produced on electron bombardment of a mixture of benzene (C6H6) and para-hydrogen during deposition onto a target at 3.2 K. Infrared (IR) absorption lines of C6H7+ decreased in intensity when the matrix was irradiated at 365 nm or maintained in the dark for an extended period, whereas those of c-C6H7 increased in intensity. Observed vibrational wavenumbers, relative IR intensities, and deuterium isotopic shifts agree with those predicted theoretically. This method, providing a wide spectral coverage with narrow lines and accurate relative IR intensities, can be applied to larger protonated polyaromatic hydrocarbons and their neutral species which are difficult to study with other methods. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3703502]
Absorption spectra in the vacuum ultraviolet region of methanol in condensed phases
(2007-10-15)
Kuo, Yu-Ping
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Lu, Hsiao-Chi
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Wu, Yu-Jong
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Cheng, Bing-Ming
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Ogilvie, J. F.
With radiation from a synchrotron we measured the spectra of pure solid methanol and of methanol dispersed in solid argon (molar ratio 200) and krypton (molar ratio 250) at 10 K from the onset of absorption in the vacuum ultraviolet region until the limits imposed by LiF windows or the Ar or Kr dispersant. We fitted the total absorption profile divided by wavenumber to gaussian curves of minimal number. and made tentative assignments of electronic transitions and vibrational structure by comparison with spectra of gaseous methanol and with energies and intensities from our published quantum-chemical calculations. (C) 2007 Elsevier B.V. All rights reserved.
Blue/near UV light emission from hybrid InN/TiO(2) nanoparticle films
(2011-01-01)
Wu, Chih-Wei
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Lu, Chih-Wei
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Lee, Yuan-Pern
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Wu, Yu-Jong
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Cheng, Bing-Ming
We report on the enhancement of photoluminescence (PL) from anatase TiO(2) thin films covered by InN nanoparticles prepared using plasma enhanced chemical vapor deposition (PECVD). The SEM images and X-ray diffraction spectra illustrate the strong interaction between the InN particles and the TiO(2) films. UV-Vis absorption spectra indicate that the InN particles have an increased absorption in the visible light region and may sensitize the TiO(2) films. The strong PL band observed in the anatase TiO(2) thin films with the addition of InN may have been due to an increased localization of impurities and/or defect-trapped excitons.
Blue/near UV light emission from hybrid InN/TiO2 nanoparticle films
(2011-01-01)
Wu, Chih-Wei
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Lu, Chih-Wei
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Lee, Yuan-Pern
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Wu, Yu-Jong
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Cheng, Bing-Ming
We report on the enhancement of photoluminescence (PL) from anatase TiO2 thin films covered by InN nanoparticles prepared using plasma enhanced chemical vapor deposition (PECVD). The SEM images and X-ray diffraction spectra illustrate the strong interaction between the InN particles and the TiO2 films. UV-Vis absorption spectra indicate that the InN particles have an increased absorption in the visible light region and may sensitize the TiO2 films. The strong PL band observed in the anatase TiO2 thin films with the addition of InN may have been due to an increased localization of impurities and/or defect-trapped excitons.
Direct infrared observation of hydrogen chloride anions in solid argon
(2017-09-21)
Huang, Tzu-Ping
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Chen, Hui-Fen
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Liu, Meng-Chen
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Chin, Chih-Hao
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Durrant, Marcus C.
To facilitate direct spectroscopic observation of hydrogen chloride anions (HCl-), electron bombardment of CH3Cl diluted in excess Ar during matrix deposition was used to generate this anion. Subsequent characterization were performed by IR spectroscopy and quantum chemical calculations. Moreover the band intensity of HCl fi decays slowly when the matrix sample is maintained in the dark for a prolonged time. High-level ab inito calculation suggested that HCl fi is only weakly bound. Atom-in-molecule charge analysis indicated that both atoms of HCl fi are negatively charged and the Cl atom is hypervalent. Published by AIP Publishing.
Direct IR Absorption Spectra of Propargyl Cation Isolated in Solid Argon
(2018-09-26)
Chin, Chih-Hao
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Lin, Meng-Yeh
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Huang, Tzu-Ping
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Wu, Pei-Zhen
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Wu, Yu-Jong
The direct infrared (IR) absorption spectra of propargyl cations were recorded. These cations were generated via the electron bombardment of a propyne/Ar matrix sample during matrix deposition. Secondary photolysis with selected ultraviolet (UV) light was used for grouping the observed bands of various products. The band assignment of the propargyl cation in solid Ar was performed according by referring to the previous infrared photodissociation (IRPD) and velocity-map imaging photoelectron (VMI-PE) data, and via theoretical predictions of the anharmonic vibrational wavenumbers, band intensities, and deuterium-substituted isotopic ratios. Almost all the IR active bands with an observable intensity were recorded and the nu(11) mode was reported for the first time.
Direct spectral evidence of single-axis rotation and ortho-hydrogen-assisted nuclear spin conversion of CH(3)F in solid para-hydrogen
(2008-09-14)
Lee, Yuan-Pern
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Wu, Yu-Jong
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Hougen, Jon T.
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應用化學系
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應用化學系分子科學碩博班
Observation of two weak absorption lines from the E (K=1) level and one intense feature from A (K=0) for degenerate modes v(4) and v(6) of CH(3)F provides direct spectral evidence that CH(3)F isolated in p-H(2) rotates about only its symmetry axis, and not about the other two axes. An interaction between A and E vibrational levels caused by the partially hindered spinning rotation is proposed. Conversion of nuclear spin between A and E components of CH(3)F is rapid when p-H(2) contains some o-H(2), but becomes slow when the proportion of o-H(2) is much decreased. (c) 2008 American Institute of Physics.
Experimental and theoretical investigation of rate coefficients of the reaction S(P-3)+OCS in the temperature range of 298-985 K
(2006-10-28)
Lu, Chih-Wei
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Wu, Yu-Jong
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Lee, Yuan-Pern
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Zhu, R. S.
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Lin, M. C.
The reaction S(P-3)+OCS in Ar was investigated over the pressure range of 50-710 Torr and the temperature range of 298-985 K with the laser photolysis technique. S atoms were generated by photolysis of OCS with light at 248 nm from a KrF excimer laser; their concentration was monitored via resonance fluorescence excited by atomic emission of S produced from microwave-discharged SO2. At pressures less than 250 Torr, our measurements give k(298 K)=(2.7 +/- 0.5)x10(-15) cm(3) molecule(-1) s(-1), in satisfactory agreement with a previous report by Klemm and Davis [J. Phys. Chem. 78, 1137 (1974)]. New data determined for 407-985 K connect rate coefficients reported previously for T >= 860 and T <= 478 K and show a non-Arrhenius behavior. Combining our results with data reported at high temperatures, we derived an expression k(T)=(6.1 +/- 0.3)x10(-18) T-1.97 +/- 0.24 exp[-(1560 +/- 170)/T] cm(3) molecule(-1) s(-1) for 298 <= T/K <= 1680. At 298 K and P >= 500 Torr, the reaction rate was enhanced. Theoretical calculations at the G2M(CC2) level, using geometries optimized with the B3LYP/6-311+G(3df) method, yield energies of transition states and products relative to those of the reactants. Rate coefficients predicted with multichannel Rice-Ramsperger-Kassel-Marcus (RRKM) calculations agree satisfactorily with experimental observations. According to our calculations, the singlet channel involving formation of SSCO followed by direct dissociation into S-2(a (1)Delta(g))+CO dominates below 2000 K; SSCO is formed via intersystem crossing from the triplet surface. At low temperature and under high pressure the stabilization of OCS2, formed via isomerization of SSCO, becomes important; its formation and further reaction with S atoms partially account for the observed increase in the rate coefficient under such conditions. (c) 2006 American Institute of Physics.
Formation and identification of borane radical anions isolated in solid argon
(2018-02-21)
Lin, Meng-Yeh
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Huang, Tzu-Ping
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Chin, Chih-Hao
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Wu, Yu-Jong
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應用化學系
The infrared (IR) spectrum of borane(3) anions (BH3-) isolated in solid Ar was recorded; two vibrational modes were observed at 2259.4 and 606.6 cm(-1), which were assigned to the BH2 stretching (nu(3)) and out-of-plane large-amplitude (nu(2)) modes, respectively. These anions were produced by the electron bombardment of an Ar matrix sample containing a small proportion of B2H6 and H-2 during matrix deposition or by the photolysis of single-bridged-B2H5 fi in an Ar matrix with the selected ultraviolet light. The band positions, relative intensity ratios, isotopic splitting pattern, and isotopic shift ratios of the observed IR features of BH3- are generally in good agreement with those predicted by the B2PLYP/aug-cc-pVTZ method.
FORMATION AND IDENTIFICATION OF INTERSTELLAR MOLECULE LINEAR C(5)H FROM PHOTOLYSIS OF METHANE DISPERSED IN SOLID NEON
(2009-08-10)
Wu, Yu-Jong
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Chen, Hui-Fen
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Camacho, Cristopher
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Witek, Henryk A.
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Hsu, Sheng-Chuan
Photolysis of methane dispersed (1/1000) in solid Ne at 3 K with vacuum-ultraviolet light from a synchrotron produced infrared absorption lines of several products, including new lines at 3319.3 and 1955.5 cm(-1). Based on experiments with isotopic labeling and results of quantum-chemical calculations, these lines are assigned to the C-H stretching and C=C stretching modes, respectively, of interstellar molecule linear C(5)H radicals.
FORMATION AND IDENTIFICATION OF INTERSTELLAR MOLECULE LINEAR C5H FROM PHOTOLYSIS OF METHANE DISPERSED IN SOLID NEON
(2009-08-10)
Wu, Yu-Jong
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Chen, Hui-Fen
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Camacho, Cristopher
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Witek, Henryk A.
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Hsu, Sheng-Chuan
Photolysis of methane dispersed (1/1000) in solid Ne at 3 K with vacuum-ultraviolet light from a synchrotron produced infrared absorption lines of several products, including new lines at 3319.3 and 1955.5 cm(-1). Based on experiments with isotopic labeling and results of quantum-chemical calculations, these lines are assigned to the C-H stretching and C=C stretching modes, respectively, of interstellar molecule linear C5H radicals.
Formation and infrared absorption of protonated naphthalenes (1-C10H9+ and 2-C10H9+) and their neutral counterparts in solid para-hydrogen
(2013)
Bahou, Mohammed
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Wu, Yu-Jong
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Lee, Yuan-Pern
;
應用化學系
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應用化學系分子科學碩博班
Protonated naphthalene (C10H9+) and its neutral counterparts (hydronaphthyl radicals, C10H9) are important intermediates in the reactions of aromatic compounds and in understanding the unidentified infrared (IR) emissions from interstellar media. We report the IR spectra of 1-C10H9+, 2-C10H9+, 1-C10H9, and 2-C10H9 trapped in solid para-hydrogen (p-H-2); the latter three are new. These species were produced upon electron bombardment of a mixture of naphthalene (C10H8) and p-H-2 during matrix deposition. The intensities of IR features of 1-C10H9+ decreased after the matrix was maintained in darkness for 19 h, whereas those of 1-C10H9 and 2-C10H9 increased. Irradiation of this matrix sample with light at 365 nm diminished lines of 1-C10H9+ and 2-C10H9 and enhanced lines of 1-C10H9 and 2-C10H9+; the latter species was unstable and converted to 1-C10H9+ in less than 30 min and 2-C10H9 was converted to 1-C10H9 at 365 nm. Observed wavenumbers and relative intensities of these species agree satisfactorily with the anharmonic vibrational wavenumbers and IR intensities predicted with the B3PW91/6-311++G(2d,2p) method. Compared with spectra recorded previously with IR photodissociation of Ar-tagged C10H9+ or IR multiphoton dissociation of C10H9+, our method has the advantages of producing high-resolution IR spectra with a wide spectral coverage, true IR intensity and excellent ratio of signal to noise; both protonated species and their neutral counterparts are produced with little interference from other fragments. With these advantages, the IR spectra of 1-C10H9+, 2-C10H9+, 1-C10H9, and 2-C10H9 are here clearly characterized.
Formation and infrared spectra of monohydrogenated pyrenes 2-C16H11 and 4-C16H11 trapped in solid para-hydrogen
(2020-06-05)
Bahou, Mohammed
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Chou, Sheng-Lung
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Wu, Yu-Jong
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應用化學系
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應用化學系分子科學碩博班
We recorded the IR spectra of 2-C16R11 and 4-C16R11 trapped in solid para-hydrogen (p-H-2). These species were produced on the electron bombardment of p-H-2 containing pyrene (C16H10) in a small proportion during matrix deposition. IR absorption features of 1-C16H11+ and 1-C16H11 in solid p-H-2 were previously identified [J. Phys. Chem. Lett. 4 (2013) 1989]. Here, the irradiation of a similar matrix sample at 365 nm depleted 1-C(16)H(11)(+ )and 2-C16H11 and produced 1-C16H11 and 4-C16H11. In contrast, irradiation at 405 nm decreased 1-C16H11+, 2-C16H11 and 4-C16H11. The identification of the observed lines of 2-C16H11, and 4-C16H11 was supported by predictions of the vibrational wavenumbers and relative IR intensities at the B3PW91/6-311++G(2d,2p) level of theory. (C) 2020 Elsevier B.V. All rights reserved.
Formation and IR spectrum of monobridged Si2H4 isolated in solid argon
(2020-05-29)
Lin, Shu-Yu
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Chou, Sheng-Lung
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Lin, Meng-Yeh
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Huang, Wen-Jian
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Huang, Tzu-Ping
The infrared (IR) spectrum of monobridged Si2H4 (denoted as mbr-Si2H4) isolated in solid Ar was recorded, and a set of lines (in the major matrix site) observed at 858.3 cm(-1), 971.5 cm(-1), 999.2 cm(-1), 1572.7 cm(-1), 2017.7 cm(-1), 2150.4 cm(-1), and 2158.4 cm(-1) were characterized. The species was produced by the electron bombardment of an Ar matrix sample containing a small proportion of SiH4 during matrix deposition. Upon photolysis of the matrix samples using 365 nm and 160 nm light, the content of mbr-Si2H4 increased. The band positions, relative intensity ratios, and D-isotopic shift ratios of the observed IR features are generally in good agreement with those predicted by the B3LYP/aug-cc-pVTZ method. In addition, the photochemistry of the observed products was discussed.
Formation of Halogen-bearing Species. I. Irradiation of Methyl Fluorides in Carbon Monoxide Ice with VUV Light and Electrons
(2019-08-01)
Lin, Meng-Yeh
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Huang, Tzu-Ping
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Wu, Pei-Zhen
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Chin, Chih-Hao
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Wu, Yu-Jong
We studied the synthesis of fluorine-bearing species by the irradiation of CO ice containing a small proportion of CH3F at 10 K with vacuum ultraviolet (VUV) light and energetic electrons. Photolysis of the ice sample with VUV light with a wavelength of 121.6 nm produced mainly fragments of CH3F, whereas both carbon oxides and fragments of CH3F were generated by irradiation with broadband VUV light. In contrast, electron irradiation of a similar ice sample generated not only those products observed in the photolysis experiments, but also complex organic hydrocarbons and fluorinated (carbon) oxides. This observation of the distinctive effect of the formation of different products by different excitation sources provides an insight into the energetic processes occurring in interstellar icy dust grains.
Formation of Halogen-bearing Species. II. Irradiation of Chloromethane in Carbon Monoxide Ice with VUV Light and Electrons
(2020-01-01)
Lin, Meng-Yeh
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Huang, Tzu-Ping
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Wu, Pei-Zhen
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Chin, Chih-Hao
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Wu, Yu-Jong
The synthesis of chlorine-bearing species in CO ice was studied by the irradiation of CH3Cl:CO ice at 10 K with vacuum-ultraviolet (VUV) light and energetic electrons. In contrast to the photochemical behavior of CH3F:CO ice, photolysis of CH3Cl:CO ice with Ly alpha or broadband VUV light afforded various products. This discrepancy was attributed to the abundant absorption bands of CH3Cl in the VUV region, particularly in the Ly alpha region. The Cl-bearing species including Cl2O, ClCO, C3Cl2, C3HCl, and HOOCl were characterized by observing their IR features. In contrast, electron bombardment of ice mixtures produced various carbon oxides and primary products, such as CH2Cl and HCO. In addition, the mechanism of energetic processes in electron bombardment was discussed.
Identification of a Simplest Hypervalent Hydrogen Fluoride Anion in Solid Argon
(2017-06-07)
Liu, Meng-Chen
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Chen, Hui-Fen
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Chin, Chih-Hao
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Huang, Tzu-Ping
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Chen, Yu-Jung
Hypervalent molecules are one of the exceptions to the octet rule. Bonding in most hypervalent molecules is well rationalized by the Rundle-Pimentel model (three-center four-electron bond), and high ionic bonding between the ligands and the central atom is essential for stabilizing hypervalent molecules. Here, we produced one of the simplest hypervalent anions, HF-, which is known to deviate from the Rundle-Pimentel model, and identified its ro-vibrational features. High-level ab inito calculations reveal that its bond dissociation energy is comparable to that of dihalides, as supported by secondary photolysis experiments with irradiation at various wavelengths. The charge distribution analysis suggested that the F atom of HF-is negative and hypervalent and the bonding is more covalent than ionic.
Infrared absorption spectra of vinyl radicals isolated in solid Ne
(2008-05-28)
Wu, Yu-Jong
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Lin, Meng-Yeh
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Cheng, Bing-Ming
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Chen, Hui-Fen
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Lee, Yuan-Pern
Irradiation of samples of solid Ne near 3.0 K containing ethene (C(2)H(4)) with vacuum ultraviolet radiation at 120 nm from synchrotron yielded new spectral lines at 3141.0, 2953.6, 2911.5, 1357.4, 677.1, 895.3, and 857.0 cm(-1). These features are assigned to alpha-CH stretching (nu(1)), CH(2) antisymmetric stretching (nu(2)), CH(2) symmetric stretching (nu(3)), CH(2)-bending (nu(5)), HCCH cis bending (nu(7)), CH(2) out-of-plane bending (nu(8)), and alpha-CH out-of-plane bending (nu(9)) modes of C(2)H(3), respectively, based on results of (13)C- and D-isotopic experiments and quantum-chemical calculations. These calculations using density-functional theory (B3LYP and PW91PW91/aug-cc-pVTZ) predict vibrational wavenumbers, IR intensities, and isotopic ratios of vinyl radical that agree satisfactorily with our experimental results. (C) 2008 American Institute of Physics.
INFRARED AND ULTRAVIOLET SPECTRA OF METHANE DILUTED IN SOLID NITROGEN AND IRRADIATED WITH ELECTRONS DURING DEPOSITION AT VARIOUS TEMPERATURES
(2016-06-01)
Chin, Chih-Hao
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Chen, Sian-Cong
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Liu, Meng-Chen
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Huang, Tzu-Ping
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Wu, Yu-Jong
We recorded the infrared and ultraviolet absorption spectra of CH4:N-2 matrix samples that underwent electron bombardment during deposition in the temperature range of 10-44 K. In contrast to a previous experiment on the IR spectroscopy of electron-bombarded icy samples, methyl and azide radicals became the main products upon electron bombardment during deposition; furthermore, reduced production of nitrile species was observed for deposition at 10 and 20 K. On the other hand, for deposition above 33 K, the observed bands of the radical species (such as methyl and azide) decreased, and bands of large nitriles appeared. This observation may suggest that radical species easily diffuse and recombine to form more complex molecules in solid nitrogen at higher temperatures. Further measurements of similar samples at 10-33 K in the UV region revealed the intense band of azide radicals at 272.5 nm and weak, broad, overlapping features of methyl and azide radicals in the 225-197 nm region. For deposition at 44 K, only a broad feature centered at 219.4 nm was observed, and the possible carriers of nitrile species were proposed based on the corresponding IR spectrum and theoretical predictions of excitation energy. This band is similar to the observed absorption feature of Pluto's surface recorded by the Hubble telescope in terms of both band position and bandwidth. Our findings therefore further support the suggestion that complex nitrile species may exist on the surface of Pluto.
Infrared spectra of free radicals and protonated species produced in para-hydrogen matrices
(2014)
Bahou, Mohammed
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Das, Prasanta
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Lee, Yu-Fang
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Wu, Yu-Jong
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Lee, Yuan-Pern
The quantum solid para-hydrogen (p-H-2) has emerged as a new host for matrix isolation experiments. Among several unique characteristics, the diminished cage effect enables the possibility of producing free radicals via either photolysis in situ or bimolecular reactions of molecules with atoms or free radicals that are produced in situ from their precursors upon photo-irradiation. Many free radicals that are unlikely to be produced in noble-gas matrices can be produced readily in solid p-H-2. In addition, protonated species can be produced upon electron bombardment of p-H-2 containing a small proportion of the precursor during deposition. The application of this novel technique to generate protonated polycyclic aromatic hydrocarbons (PAH) and their neutral counterparts demonstrates its superiority over other methods. The technique of using p-H-2 as a matrix host has opened up many possibilities for the preparation of free radicals and unstable species and their spectral characterization. Many new areas of applications and fundamental understanding concerning the p-H-2 matrix await further exploration.