Browsing by Author "Chin, Chih-Hao"

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Ab initio studies of excited electronic state S(2) of pyrazine and Franck-Condon simulation of its absorption spectrum
(2009-07-07)
He, Rongxing
;
Zhu, Chaoyuan
;
Chin, Chih-Hao
;
Lin, Sheng Hsien
;
應用化學系分子科學碩博班
The equilibrium geometry and 24 vibrational-normal-mode frequencies of the excited state S(2)((1)B(2u))of pyrazine are calculated and characterized using the complete active space self-consistent field method in the adiabatic representation. The displaced harmonic oscillator approximation is used to simulate the absorption spectrum of the S(2)((1)B(2u)) state along with the Franck-Condon approximation. It is found that the totally symmetric mode v(1) plays the most important role and this exactly agrees with the experimental observations. The simulated absorption spectrum agrees well with those experimentally observed. This indicates that the present S(2)((1)B(2u)) state calculated in the adiabatic representation effectively includes contribution from the diabatic vibronic coupling through the conical intersection. (C) 2009 Elsevier B.V. All rights reserved.
Ab initio studies of excited electronic state S-2 of pyrazine and Franck-Condon simulation of its absorption spectrum
(2009-07-07)
He, Rongxing
;
Zhu, Chaoyuan
;
Chin, Chih-Hao
;
Lin, Sheng Hsien
;
應用化學系分子科學碩博班
The equilibrium geometry and 24 vibrational-normal-mode frequencies of the excited state S-2(B-1(2u))of pyrazine are calculated and characterized using the complete active space self-consistent field method in the adiabatic representation. The displaced harmonic oscillator approximation is used to simulate the absorption spectrum of the S-2(B-1(2u)) state along with the Franck-Condon approximation. It is found that the totally symmetric mode v(1) plays the most important role and this exactly agrees with the experimental observations. The simulated absorption spectrum agrees well with those experimentally observed. This indicates that the present S-2(B-1(2u)) state calculated in the adiabatic representation effectively includes contribution from the diabatic vibronic coupling through the conical intersection. (C) 2009 Elsevier B.V. All rights reserved.
Direct infrared observation of hydrogen chloride anions in solid argon
(2017-09-21)
Huang, Tzu-Ping
;
Chen, Hui-Fen
;
Liu, Meng-Chen
;
Chin, Chih-Hao
;
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
;
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.
Exploring the dynamics of reaction N((2)D) + C(2)H(4) with crossed molecular-beam experiments and quantum-chemical calculations
(2011-01-01)
Lee, Shih-Huang
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Chin, Chih-Hao
;
Chen, Wei-Kan
;
Huang, Wen-Jian
;
Hsieh, Chu-Chun
We conducted the title reaction using a crossed molecular-beam apparatus, quantum-chemical calculations, and RRKM calculations. Synchrotron radiation from an undulator served to ionize selectively reaction products by advantage of negligibly small dissociative ionization. We observed two products with gross formula C(2)H(3)N and C(2)H(2)N associated with loss of one and two hydrogen atoms, respectively. Measurements of kinetic-energy distributions, angular distributions, low-resolution photoionization spectra, and branching ratios of the two products were carried out. Furthermore, we evaluated total branching ratios of various exit channels using RRKM calculations based on the potential-energy surface of reaction N((2)D) + C(2)H(4) established with the method CCSD(T)/6-311+G(3df,2p)//B3LYP/6-311G(d,p)+ZPE[B3LYP/6-311G(d,p)]. The combination of experimental and computational results allows us to reveal the reaction dynamics. The N((2)D) atom adds to the C=C pi-bond of ethene (C(2)H(4)) to form a cyclic complex c-CH(2)(N)CH(2) that directly ejects a hydrogen atom or rearranges to other intermediates followed by elimination of a hydrogen atom to produce C(2)H(3)N; c-CH(2)(N)CH+H is the dominant product channel. Subsequently, most C(2)H(3)N radicals, notably c-CH(2)(N)CH, further decompose to CH(2)CN+H. This work provides results and explanations different from the previous work of Balucani et al. [J. Phys. Chem. A, 2000, 104, 5655], indicating that selective photoionization with synchrotron radiation as an ionization source is a good choice in chemical dynamics research.
Exploring the dynamics of reaction N(D-2) + C2H4 with crossed molecular-beam experiments and quantum-chemical calculations
(2011)
Lee, Shih-Huang
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Chin, Chih-Hao
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Chen, Wei-Kan
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Huang, Wen-Jian
;
Hsieh, Chu-Chun
We conducted the title reaction using a crossed molecular-beam apparatus, quantum-chemical calculations, and RRKM calculations. Synchrotron radiation from an undulator served to ionize selectively reaction products by advantage of negligibly small dissociative ionization. We observed two products with gross formula C2H3N and C2H2N associated with loss of one and two hydrogen atoms, respectively. Measurements of kinetic-energy distributions, angular distributions, low-resolution photoionization spectra, and branching ratios of the two products were carried out. Furthermore, we evaluated total branching ratios of various exit channels using RRKM calculations based on the potential-energy surface of reaction N(D-2) + C2H4 established with the method CCSD(T)/6-311+G(3df,2p)//B3LYP/6-311G(d,p)+ZPE[B3LYP/6-311G(d,p)]. The combination of experimental and computational results allows us to reveal the reaction dynamics. The N(D-2) atom adds to the C=C pi-bond of ethene (C2H4) to form a cyclic complex c-CH2(N)CH2 that directly ejects a hydrogen atom or rearranges to other intermediates followed by elimination of a hydrogen atom to produce C2H3N; c-CH2(N)CH+H is the dominant product channel. Subsequently, most C2H3N radicals, notably c-CH2(N)CH, further decompose to CH2CN+H. This work provides results and explanations different from the previous work of Balucani et al. [J. Phys. Chem. A, 2000, 104, 5655], indicating that selective photoionization with synchrotron radiation as an ionization source is a good choice in chemical dynamics research.
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 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
;
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
;
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
;
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 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
;
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 isotopomers of chloromethylene in solid argon
(2018-03-01)
Lin, Meng-Yeh
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Huang, Tzu-Ping
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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
;
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.
Novel conjugated polymers based on bis-dithieno [3,2-b;2 ',3 '-d] pyrrole vinylene donor and diketopyrrolopyrrole acceptor: side chain engineering in organic field effect transistors
(2018-01-07)
Lin, Fang-Ju
;
Lin, Song-Di
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Chin, Chih-Hao
;
Chuang, Wei-Tsung
;
Hsu, Chain-Shu
Two new donor-acceptor conjugated polymers, i.e. PB(C12DTP) V-DTDPP-C-12 and PB(C12DTP) V-DTDPP-C12C8, were prepared by the Stille coupling of (E)-1,2-bis(4-dodecyl-6-(trimethylstannyl)-4H-dithieno[ 3,2-b: 2', 3'-d] pyrrol-2-yl) ethene (Sn-B(C12DTP)V) with 3,6-bis(5-bromothiophen-2-yl)-2,5-didodecylpyrrolo[ 3,4-c] pyrrole-1,4-dione (Br-DTDPP-C-12) and 3,6-bis(5-bromo-thiophen-2-yl)-2,5-bis(2octyldodecyl) pyrrolo[ 3,4-c] pyrrole-1,4-dione (Br-DTDPP-C8C12), respectively. The molecular weight and thermal properties of the obtained polymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetry (TG). Their optical and electrochemical properties were analyzed by UV-vis-NIR spectroscopy and cyclic voltammetry (CV). The morphological and molecular-packing features of the polymers were characterized by optical microscopy and atomic force microscopy (AFM), UV polarization spectroscopy and grazing incidence X-ray diffraction (GIXD) to determine the relationship between the structural morphology and the performance. PB (C12DTP) V-DTDPP-C12C8 with branched C12C8 side chains on DPP units shows much higher hole mobility (1.2 cm(2) V-1 s(-1)) than 0.69 cm(2) V-1 s(-1) of PB(C12DTP) V-DTDPP-C-12.
Photochemistry and infrared spectrum of single-bridged diborane(5) anion isolated in solid argon
(2016-08-21)
Liu, Meng-Chen
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Chen, Hui-Fen
;
Huang, Wei-Jie
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Chin, Chih-Hao
;
Chen, Sian-Cong
Three-center two-electron bonds are important for understanding electron-deficient molecules. To examine such a molecule, we produced a diborane(5) anion with a single-bridged structure upon electron bombardment during matrix deposition of Ar containing a small proportion of diborane(6). The diborane(5) anion was destroyed upon photolysis at 180, 220, 385, and 450 nm, but not at 532 nm. Moreover, the possible formation of neutral diborane(5) was observed upon photolysis at 385 and 450 nm, whereas neutral diborane(3) was observed upon photolysis at 180 and 220 nm. The observed line wavenumbers, relative intensities, and isotopic ratios of the diborane(5) anion agreed satisfactorily with those predicted by density functional theory calculations at the B3LYP/aug-cc-pVTZ level of theory. Thus, this method produced the boron hydride anion of interest with few other fragments, which enabled us to clearly identify the IR spectrum of the diborane(5) anion. Published by AIP Publishing.
Theoretical investigations of absorption and fluorescence spectra of protonated pyrene
(2016-06-07)
Chin, Chih-Hao
;
Lin, Sheng Hsien
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應用化學系
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Department of Applied Chemistry
The equilibrium geometry and 75 vibrational normal-mode frequencies of the ground and first excited states of protonated pyrene isomers were calculated and characterized in the adiabatic representation by using the complete active space self-consistent field (CASSCF) method. Electronic absorption spectra of solid neon matrixes in the wavelength range 495-415 nm were determined by Maier et al. and they were analyzed using time-dependent density functional theory calculations (TDDFT). CASSCF calculations and absorption and emission spectra simulations by one-photon excitation equations were used to optimize the excited and ground state structures of protonated pyrene isomers. The absorption band was attributed to the S0 -> S1 electronic transition in 1H-Py+, and a band origin was used at 20580.96 cm(-1). The displaced harmonic oscillator approximation and Franck-Condon approximation were used to simulate the absorption spectrum of the (1) (1)A\' <- (X) over tilde (1)A\' transition of 1H-Py+, and the main vibronic transitions were assigned for the first pi pi(star) state. It shows that the vibronic structures were dominated by one of the eight active totally symmetric modes, with v(15) being the most crucial. This indicates that the electronic transition of the S-1((1)A\')state calculated in the adiabatic representation effectively includes a contribution from the adiabatic vibronic coupling through Franck-Condon factors perturbed by harmonic oscillators. The present method can adequately reproduce experimental absorption and fluorescence spectra of a gas phase.
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.