Browsing by Author "Lin, Meng-Yeh"

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Direct IR Absorption Spectra of Propargyl Cation Isolated in Solid Argon
(2018-09-26)
Chin, Chih-Hao
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Lin, Meng-Yeh
;
Huang, Tzu-Ping
;
Wu, Pei-Zhen
;
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.
Formation and identification of borane radical anions isolated in solid argon
(2018-02-21)
Lin, Meng-Yeh
;
Huang, Tzu-Ping
;
Chin, Chih-Hao
;
Wu, Yu-Jong
;
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
;
Chen, Hui-Fen
;
Camacho, Cristopher
;
Witek, Henryk A.
;
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
;
Chen, Hui-Fen
;
Camacho, Cristopher
;
Witek, Henryk A.
;
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 IR spectrum of monobridged Si2H4 isolated in solid argon
(2020-05-29)
Lin, Shu-Yu
;
Chou, Sheng-Lung
;
Lin, Meng-Yeh
;
Huang, Wen-Jian
;
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
;
Wu, Pei-Zhen
;
Chin, Chih-Hao
;
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
;
Wu, Pei-Zhen
;
Chin, Chih-Hao
;
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.
Infrared absorption spectra of vinyl radicals isolated in solid Ne
(2008-05-28)
Wu, Yu-Jong
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Lin, Meng-Yeh
;
Cheng, Bing-Ming
;
Chen, Hui-Fen
;
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 spectra of isotopomers of chloromethylene in solid argon
(2018-03-01)
Lin, Meng-Yeh
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Huang, Tzu-Ping
;
Chin, Chih-Hao
;
Lee, Yin-Yu
;
Wu, Yu-Jong
We measured the IR spectra of the solid Ar-trapped chloromethylene (HCCl) prepared by electron bombardment of a CH3Cl/Ar mixture during matrix deposition. Irradiation of matrix samples at 210 nm decreased the intensity of lines corresponding to HCCl, whereas irradiation at 385 nm had an opposite effect. The above behavior allowed an unambiguous identification of all vibrational modes of HCCl, and the obtained assignments were further confirmed by quantum chemical calculations and C-13/H-2 isotopic labeling experiments. (C) 2017 Elsevier Inc. All rights reserved.
Infrared Spectra of the 1-Methylvinoxide Radical and Anion Isolated in Solid Argon
(2019-06-06)
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 1-methylvinoxy radical (1-MVO) is an important intermediate in the combustion and tropospheric reaction of OH. However, the vibrational structures of this species and its anionic form, 1-methylvinoxide anion (1-MVO-), are not fully known. Thus, in this study, we obtained the infrared (IR) absorption spectra of 1-MVO and 1-MVO- trapped in a solid Ar matrix. 1-MVO- anions were produced by electron bombardment during matrix deposition of Ar containing a small amount of acetone. The anions were destroyed upon irradiation at 675, 365, and 160 nm, although the formation of 1-MVO was only observed upon irradiation at 675 nm. The assignment of the IR bands of 1-MVO- and 1-MVO was based on the expected chemistry upon photoexcitation and comparison of line wavenumbers, relative IR intensities, and D-isotopic shift ratios with those predicted at the B3LYP/aug-cc-pVTZ level of theory.
UV absorption spectrum of allene radical cations in solid argon
(2018-05-05)
Chin, Chih-Hao
;
Lin, Meng-Yeh
;
Huang, Tzu-Ping
;
Wu, Yu-Jong
;
應用化學系
Electron bombardment during deposition of an Ar matrix containing a small proportion of allene generated allene cations. Further irradiation of the matrix sample at 385 nm destroyed the allene cations and formed propyne cations in solid Ar. Both cations were identified according to previously reported IR absorption bands. Using a similar technique, we recorded the ultraviolet absorption spectrum of allene cations in solid Ar. The vibrationally resolved progression recorded in the range of 266-237 nm with intervals of about 800 cm(-1) was assigned to the A E-2 <- X E-2 transition of allene cations, and the broad continuum absorption recorded in the region of 229-214 nm was assigned to their B (2)A(1) <- X E-2 transition. These assignments were made based on the observed photolytic behavior of the progressions and the vertical excitation energies and oscillator strengths calculated using time-dependent density functional theory. (C) 2018 Elsevier B.V. All rights reserved.
Vacuum ultraviolet photolysis of CH4:O-2 ice mixtures and the formation of CO and CO2
(2020-06-05)
Chou, Sheng-Lung
;
Lin, Meng-Yeh
;
Huang, Tzu-Ping
;
Wu, Yu-Jong
;
應用化學系
Vacuum ultraviolet (VUV) photolysis of CH4:O-2 ice mixtures at 10 K using 121.6, 157, and 170-nm wavelengths was performed to examine photochemical reactions for the oxidation of hydrocarbon species. Ice samples with three component ratios were prepared: CH4-dominated (CH4:O-2 = 100:1), mixed (CH4:O-2 = 1:1), and O-2-dominated (CH4:O-2 = 1:100) ice samples. Photochemical behavior with dependence on the photolysis wavelength and component ratio was observed. In addition, the column densities of CO and CO2 formed by the VUV photolysis of the three ice samples and the abundance ratios of CO and CO2 as a function of the photon dosage and photolysis wavelength were examined. The results may imply a correlation between the unknown depletion of interstellar oxygen and the formation of CO and CO2. (C) 2020 Elsevier B.V. All rights reserved.