| 1. |
- Fang, Qiu, et al.
(författare)
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Photodissociation of phosgene : Theoretical evidence for the ultrafast and synchronous concerted three-body process
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131:16
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Tidskriftsartikel (refereegranskat)abstract
- The potential energy surfaces for Cl2CO dissociation into CO+Cl+Cl in the lowest two electronic singlet states (S-0 and S-1) have been determined by the complete active space self-consistent field, coupled-cluster method with single and double excitations (CCSD), and equation-of-motion CCSD calculations, which are followed by direct ab initio molecular dynamics simulations to explore its photodissociation dynamics at 230 nm. It is found that the C-O stretching mode is initially excited upon irradiation and the excess internal energies are transferred to the C-Cl symmetric stretching mode within 200 fs. On average, the first and the second C-Cl bonds break completely within subsequent 60 and 100 fs, respectively. Electronic structure and dynamics calculations have thus provided a strong evidence that the photoinitiated dissociation of Cl2CO at 230 nm or shorter wavelengths is an ultrafast, adiabatic, and concerted three-body process. Since the two C-Cl bonds begin to break at the same time and the time interval between the two C-Cl bond broken fully is very short (similar to 40 fs), the photoinitiated dissociation of Cl2CO to CO+2Cl can be considered as the synchronous concerted process.
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| 2. |
- Lin, Li-Li, et al.
(författare)
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Effect of Aromatic Coupling on Electronic Transport in Bimolecular Junctions
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:32, s. 14474-14477
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Tidskriftsartikel (refereegranskat)abstract
- We have performed a systematic first-principles study on conductance-voltage characteristics of bioligo(phenylene ethynylene)-monothiol molecular junctions as recently reported by Wu et al.[Nalure Nanotech. 2008, 3, 569]. It is found that the molecular conductance is very sensitive to the vertical distance between two molecules as well as the titled angle between two molecular planes. By comparing with experimental results, key structure parameters for bimolecular junction are determined, indicating that in the experimental devices, the vertical distance between two molecules is around 0.30 mn, the two planar molecules have a cofacial arrangement, and the length of the molecular bridge is about 2.88 nm. The underlying mechanism for electron transport in these aromatically coupled bimolecular junctions has also been discussed.
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| 3. |
- Lin, Na, 1981-
(författare)
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Theoretical Studies on Electronic and Vibrationally Resolved Multi-Photon Absorption and Dichroism
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents time-dependent density functional theory studies on electronic and vibronically resolved linear and nonlinear optical absorption and dichroism spectra of organic molecules. Special attention has been paid to the influence of solvent environment and molecular vibrations on one-, two- and three-photon absorption and one- and two-photon circular dichroism. It is found that dielectric medium as described by polarizable continuum model can enhance remarkably three-photon absorption cross section of a highly conjugated fluorene derivative, for which the simplified two-state model is shown to be largely inadequate. Origin-invariant density functional calculations on one- and two-photon circular dichroisms of a chiral molecule confirm that the recently developed CAMB3LYP functional performs better than the popular B3LYP functional for Rydberg-states. The first experimental measurement of TPCD spectra is performed on an axial chiral system in tetrahydrofunan, where the double L-scan technique is applied. Theoretical calculations well reproduce the experimental profiles when both the electron correlation and the solvent effect are taken into account. Vibronically resolved one- and two-photon absorption spectra of charge-transfer molecules have been obtained using a Linear Coupling model, where the 'borrowing mechanism' for the so-called Herzberg-Teller contribution is analyzed in detail. It is shown that Herzberg-Teller contribution can introduce a change of sign to the chiral responses of a molecule without the involvement of different electronic states, which has important consequences for the assignment of absolute configurations of chiral molecules. Adiabatic harmonic Franck-Condon model is also applied to simulate vibronically resolved one- and two-photon circular dichroism spectra of the same chiral system, where the sign-inversion and the interference between Franck-Condon and Herzberg-Teller contributions are also observed.
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| 4. |
- Lin, Na, et al.
(författare)
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Theory for Vibrationally Resolved Two-Photon Circular Dichroism Spectra : Application to(R)-(R)-(R)-(+)-3-Methylcyclopentanone
- 2009
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 113:16, s. 4198-4207
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Tidskriftsartikel (refereegranskat)abstract
- A harmonic adiabatic approach in combination with density functional response theory for computing twophotonvibronically resolved circular dichroism spectra of chiral molecules is presented. It includes bothFranck-Condon and Herzberg-Teller contributions and it takes fully into account frequency changes andDuschinsky effects. Model calculations have been performed for two dominant conformers of (R)-(+)-3-methylcyclopentanone in the gas phase. It is found that the Herzberg-Teller contribution can introduce asign change in two-photon circular dichroism of a single excited electronic state of a conformer. The changesurvives after Boltzmann averaging, and it might be amenable to experimental verification. Interestinginterference effects between Franck-Condon and Herzberg-Teller contributions are revealed and analyzedin detail. Results obtained within the more approximate and less computationally intensive linear couplingvibronic model are also given for comparison.
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| 5. |
- Tsai, Dun-Hou, et al.
(författare)
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Stories within and behind the story: A representation of entrepreneurial process
- 2009
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Ingår i: Critical Management Studies, Warwick 2009.
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Konferensbidrag (refereegranskat)abstract
- This paper uses a narrative approach to represent entrepreneurial process. It is a story about a specific process taking place in Yan-shuei, Taiwan, which is built upon a single entrepreneur and the people around him; what they did when they were“ entrepreneuring.” Within the story there are also other stories representing the researchers’ own experiences of entrepreneurial processes. As well, behind the story there is a story about The Moon Port City which relates to ancient times. Theories inspiring a process theory of entrepreneurship mark the beginning of the story. The middle is made up by the three main stories within the story as a whole. At the end the authors explain in what ways the narrative approach has emphasized entrepreneurial process.
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| 6. |
- Yuesheng, Ning, et al.
(författare)
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Single molecule's conductance depending on its orientation
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:1, s. 26-30
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Tidskriftsartikel (refereegranskat)abstract
- Single molecules of 1,1,2,3,4,5-hexaphenylsilole adsorbed on Cu(111) have been investigated using low-temperature scanning tunneling microscopy, scanning tunneling spectroscopy, and quantum chemistry calculations. Two adsorption states have been identified, showing distinctive tunneling conductance. The molecules can switch their states under tip influence. Theoretical calculations indicate that the two states are associated with molecules adsorbed at two 90°-rotated orientations, and the tunneling conductance is attributed to molecular orbitals that spatially bridge tip-to-substrate gap. Our findings demonstrate a decisive dependence of single-molecule conductance on the molecular orientation with respect to electrodes.
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