| 1. |
- Minaev, Boris, et al.
(författare)
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Density functional theory study of vibronic structure of the first absorption Qx band in free-base porphin
- 2006
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Ingår i: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - : Elsevier BV. - 1386-1425 .- 1873-3557. ; 65:2, s. 308-323
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Tidskriftsartikel (refereegranskat)abstract
- Harmonic vibrational frequencies and vibronic intensities in the first S-0 -> S-1 (pi pi*) absorption band of free-base porphin (H2P) are investigated by hybrid density functional theory (DFT) with the standard B3LYP functional. The S-0-S-1 transition probability is calculated using time-dependent DFT with account of Franck-Condon (FC) and Herzberg-Teller (HT) contributions to the electric-dipole transition moments including displacements along all 108 vibrational modes. Two weak wide bands observed in the gas phase absorption spectra of the H2P molecule at 626 and 576 nm are interpreted as the 0-0 band of the X(1)A(g)-> B-3u transition and the 0-1 band with largest contributions from the nu(10)(a(g)) = 1610 cm(-1) and nu(19)(b(1g)) = 1600 cm(-1) modes, respectively, in agreement with previous tentative assignments. Both bands are induced by the HT mechanism, while the FC contributions are negligible. A number of fine structure bands, including combination of two vibrational quanta, are obtained and compared with available spectra from supersonic jet and Shpolskij matrices. Both absorption and fluorescence spectra are interpreted on ground of the linear coupling model and a good fulfillment of the mirror-symmetry rule.
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| 2. |
- Wang, Chuankui, et al.
(författare)
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Solvent dependence of solvatochromic shifts and the first hyperpolarizability of para-nitroaniline : a nonmonotonic behaviour
- 2003
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 119:8, s. 4409-
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Tidskriftsartikel (refereegranskat)abstract
- Solvent dependence of the electronic structure and nonlinear optical properties of the para-nitroaniline (pNA) molecule on the polarity of the solutions has been studied using the polarizable continuum model in combination with the hybrid density functional theory. With a supermolecular approach, specific hydrogen bonding effects have also been fully considered. Good agreement between theory and experiments are obtained for both solvatochromic shifts of the charge transfer state and the solvent-induced first hyperpolarizability of pNA.
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| 3. |
- Wang, Yanhua, et al.
(författare)
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Solvent effects on the vibronic one-photon absorption profiles of dioxaborine heterocycles
- 2005
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 123:19, s. 194311-1-194311-7
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Tidskriftsartikel (refereegranskat)abstract
- The vibronic profiles of one-photon absorption spectra of dioxaborine heterocycles in gas phase and solution have been calculated at the Hartree-Fock and density-functional-theory levels. The polarizable continuum model has been applied to simulate the solvent effect, while the linear coupling model is used to compute the Franck-Condon and Herzberg-Teller contributions. It is found that a good agreement between theory and experiment can be achieved when the solvent effect and electron correlation are taken into account simultaneously. For the first excited charge-transfer state, the maximum of its Herzberg-Teller profile is blueshifted from that of the Franck-Condon profile. The shifted energy is found to be around 0.2 eV, which agrees well with the measured energy difference between two- and one-photon absorptions of the first excited state.
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| 4. |
- Wang, Yanhua, et al.
(författare)
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Vibrational contributions to nonlinear optical properties of methanol, ethanol and propanol
- 2005
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Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0166-1280. ; 717:1-3, s. 223-230
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Tidskriftsartikel (refereegranskat)abstract
- Static and dynamic vibrational contributions to the linear polarizability and the first and second nonlinear hyperpolarizabilities of methanol, ethanol and propanol have been calculated. Both the pure vibrational contribution and the zero-point vibrational averaging contribution have been determined by adopting the perturbation treatment of Bishop and Kirtman at the Hartree-Fock level. The pure vibrational contribution is quite important at the static limit, while in the optical region it varies for different nonlinear optical processes. The zero-point vibrational averaging contribution is a quite large correction to the electronic nonlinear optical (NLO) properties, especially for the second hyperpolarizability at finite fundamental frequencies. Vibrational analysis shows that the swinging modes at around 300 cm(-1) and the C-H stretching modes at around 3160 cm(-1) often give large contributions.
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| 5. |
- Liu, Jicai, et al.
(författare)
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Auger effect in the presence of strong x-ray pulses
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 81:4, s. 043412-
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Tidskriftsartikel (refereegranskat)abstract
- We study the role of propagation of strong x-ray free-electron laser pulses on the Auger effect. When the system is exposed to a strong x-ray pulse the stimulated emission starts to compete with the Auger decay. As an illustration we present numerical results for Ar gas with the frequency of the incident x-ray pulse tuned in the 2p(3/2)-4s resonance. It is shown that the pulse propagation is accompanied by two channels of amplified spontaneous emission, 4s-2p(3/2) and 3s-2p(3/2), which reshape the pulse when the system is inverted. The population inversion is quenched for longer propagation distances where lasing without inversion enhances the Stokes component. The results of simulations show that the propagation of the strong x-ray pulses affect intensively the Auger branching ratio.
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| 6. |
- Liu, Ji-Cai, et al.
(författare)
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Coherent control of population and pulse propagation beyond the rotating wave approximation
- 2008
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Ingår i: Journal of Physics B. - : Institute of Physics Publishing (IOPP). - 0953-4075 .- 1361-6455. ; 41:7
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of populations of the vibrational states in a NO molecule ( one-photon absorption) and of the electronic states in a 4,4'-bis( dimethylamino) stilbene molecule ( two-photon absorption) is studied versus the frequency, intensity and shape of the laser pulse. We show that specially designed infrared laser pulses can build selective populations of certain vibrational states. A detuning of light frequency from the vibrational resonance qualitatively changes the dynamics of populations. It is found out that the populations of the nonresonant levels follow the pulse shape adiabatically if the detuning significantly exceeds the inverse characteristic time of the change of the pulse. Depopulation of the nonresonant vibrational states leads to a high population of the resonant state at the end of the pulse. Complete breakdown of the standard rotating wave approximation for a two-photon absorption process is observed even for a rather small intensity of the laser pulse. An analytical solution for the interaction of a pulse with a three-level system beyond the rotating wave approximation is obtained, and it is in close agreement with the strict numerical solution of the amplitude equations. Special attention is paid to the population dynamics of randomly oriented molecules. The orientational disorder as well as the vibrations limit the coherent population transfer. Calculations show the strong role of the anisotropy of photoexcitation in the coherent control of populations which can affect the anisotropy of photobleaching.
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| 7. |
- Ma, Yong, et al.
(författare)
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The equilibrium geometry of A@C60 : A test case for conventional density functional theory
- 2014
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 591, s. 312-316
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Tidskriftsartikel (refereegranskat)abstract
- Potential energy surfaces (PESs) along the reaction pathway towards the center of CC bond between two six membered rings for ten different endohedral fullerenes A@C60 (A = H, C, O, S, N, P, He, Ne, Ar, Kr) have been studied by density functional theory (DFT) and Hartree-Fock (HF) method. The results show that no suitable method can consistently describe the interaction between atom A and carbon cage. The dispersion corrected DFT methods fail to describe the equilibrium geometry and PES of the complexes with light atoms. Nevertheless, the inclusion of the dispersion stabilizes the system as reflected by interaction energies (IEs) between atom A and C60.
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| 8. |
- Song, Xiuneng, et al.
(författare)
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Effects of Protonation, Hydrogen Bonding, and Photodamaging on X-ray Spectroscopy of the Amine Terminal Group in Aminothiolate Monolayers
- 2012
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:23, s. 12649-12654
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Tidskriftsartikel (refereegranskat)abstract
- The amine head group, NH2, in aminothiolate monolayers can often generate unexpectedly rich structures in its N K-edge X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra that are difficult to assign. We have carried out density functional theory (DFT) calculations to study the XPS and NEXAFS of amine head group in four different aminothiolate monolayers, namely aliphatic 11-aminoundecane-1-thiol (AUDT), aromatic 4-aminobenzenethiol (ABT) and araliphatic 4-aminophenylbutane-1-thiol (APBT) and 3-(4”-amino-1,1’:4’,1”-terphenyl-4-yl)propane-1-thiol (ATPT), with the focus on structure changes caused by protonation, hydrogen bonding and X-ray damaging. Spectra of all possible saturated and unsaturated species, as well as X-ray damage products, such as imine, nitrile, azo species and cumulative double bonds, have been thoroughly examined. It is found that extra spectral structures observed in the experimental XPS spectra are not resulted from protonation, but from the formation of a primary ammonium. The X-ray excitation can induce cross linking between two neighboring molecules to form different complexes that contribute to the π features in NEXAFS spectra.
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| 9. |
- Song, Xiuneng, et al.
(författare)
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Energy landscape inside the cage of neutral and charged N@C60
- 2011
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 517:4-6, s. 199-203
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Tidskriftsartikel (refereegranskat)abstract
- Potential energy surfaces along different escaping paths of the nitrogen atom inside the neutral and charged endohedral fullerene N@C60 have been constructed at the density functional theory level. It is found that the dispersion force plays an important role in determining the equilibrium geometry of the neutral system. The most energetic favorable escaping path is towards the center of C = C/C–C bond connecting two neighboring rings for all three systems. The rate determining potential energy surface shows a very small dependence on the charging state. The presented theoretical results should be useful for the practical applications of N@C60 in quantum computing and information.
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| 10. |
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