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| 2. |
- Cronstrand, P., et al.
(author)
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Ab initio calculations of three-photon absorption
- 2003
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In: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 375:1-2, s. 233-239
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Journal article (peer-reviewed)abstract
- We present large scale ab initio calculations of three-photon absorption of a series of dithienothiophene based charge transfer molecules using response theory within the random phase approximation. The structure-to-property relations obtained for the three-photon absorption cross-sections are discussed and compared with those for one- and two-photon absorption. © 2003 Published by Elsevier Science B.V.
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| 3. |
- Cronstrand, P., et al.
(author)
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Ab initio modeling of excited state absorption of polyenes
- 2001
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 3:13, s. 2567-2575
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Journal article (peer-reviewed)abstract
- Vertical excitation energies and transition dipole moments between excited electronic states have been calculated for the trans-polyenes series C4H6-C12H14 in order to study the formation of excited state absorption spectra of these species. Quadratic response theory is applied in conjunction with the self-consistent field method and a hierarchical set of coupled-cluster methods. The convergence of the excited state absorption, with respect to wavefunction and treatment of electron correlation and also the length of the oligomer unit, is studied, revealing a considerable demand on the computational effort in order to predict the excited state spectra with precision. The organization of the excited states is found to change in character along the polyene series. The inflexion point for the vertical excitation energies between the one-photon allowed 1(1)B(u) and the two-photon 2(1)A(g) state is predicted to occur between hexatriene and octatetraene. Good agreement with experiment is obtained for butadiene and hexatriene for which the most accurate calculations have been carried out.
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| 4. |
- Frazer, MB, et al.
(author)
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The effects of job rotation on the risk of reporting low back pain
- 2003
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In: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 46:9, s. 904-919
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Journal article (peer-reviewed)abstract
- Job rotation has been widely recommended as an administrative control to reduce the risk of developing work-related musculoskeletal disorders. However, evidence of its benefits are hard to find in the literature. The effect of job rotation on predictions for the risk of reporting low back pain was estimated using Low Back Pain Reporting (LBPR) and Time Weighted Average (TWA) approaches. Index scores calculated using the peak hand force, the peak L4/L5 shear force and the L4/L5 moment cumulated over the entire shift were used to estimate the effects of job rotation on the probability of reporting low back pain. Simulations of realistic rotations between two jobs showed that workers in low demand jobs who rotate into higher demand jobs experience a linear increase in reporting probability using the TWA approach. With the LBPR approach a step increase in reporting probability occurred because of the immediate exposure to the peak loading parameters associated with the more demanding job. With a 50-50 rotation the TWA and LBPR index scores increased by 39% and 57%, respectively. With the LBPR approach the redistribution of risk was not uniform with job rotation. The increase was greater for those who rotated into the demanding job compared to the reduction experienced by those who rotated out of the demanding job. The effects of job rotation are not easily estimated because of the complex effect that mixing jobs has on peak and cumulative tissue loading.
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| 5. |
- Jansik, B., et al.
(author)
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Relativistic effects on linear and non-linear polarizabilities of the furan homologues
- 2003
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In: Journal of Molecular Structure. - 0166-1280. ; 633:2-3, s. 237-246
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Journal article (peer-reviewed)abstract
- First principles calculations including relativistic effects are carried out for dipole moments, polarizabilities, first- and second-order hyperpolarizabilities for the series of furan homologues XC4H 4, X = O, S, Se, Te, at three different levels of theory, time-dependent Dirac-Hartree-Fock (DHF), time-dependent Hartree-Fock with a Douglas-Kroll transformed one-component Hamiltonian, and time-dependent Hartree-Fock using effective-core potentials. By comparison with the corresponding non-relativistic results, the influence of relativistic effects on the properties as well as the accuracy of previously reported calculations on these molecules using effective-core potentials for selenium and tellurium can be addressed. The obtained results indicate that relativistic effects can be described with comparable accuracy at all three employed levels, and that non-scalar effects, which are explicitly treated only at the time-dependent DHF level, are of minor importance. Frequency dispersion and relativity are found to be additive at the single-determinant level. We find that relativistic effects cannot make up for the earlier identified mismatch between theory and experiment for the non-linear polarizabilities of the heavier homologues. A Bishop-Kirtman analysis of vibrational effects indicates that the same can be said about these. © 2003 Elsevier B.V. All rights reserved.
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| 6. |
- Jonsson, D., et al.
(author)
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The Cotton-Mouton effect of gaseous CO2, N2O, OCS, and CS2. A cubic response multiconfigurational self-consistent field study
- 2001
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 114:19, s. 8372-8381
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Journal article (peer-reviewed)abstract
- The hypermagnetizability and the hypermagnetizability anisotropy of CO2, N2O, OCS, and CS2 are computed at a wavelength of 632.8 nm using cubic response theory with multiconfigurational self-consistent field wave functions. The anisotropies of the electric dipole polarizability and of the magnetizability are also obtained. This allows us to study the temperature dependence of the Cotton-Mouton constant for all four molecules and thus to compare to the results of the experimental study by Kling and Huttner [Chem. Phys. Lett. 90, 207 (1984)]. We also assess the importance of pure and zero-point vibrational effects on the relevant molecular properties. In particular, we show that for CO2, OCS, and CS2, the pure vibrational effects to the hypermagnetizability anisotropy can be even more important than the electronic contribution.
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| 7. |
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| 8. |
- Macak, Peter, et al.
(author)
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Two-photon excitations in molecules
- 2003
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In: Non-linear optical responses of molecules,solids and liquids: Methods and applications. - : Plenum Publishing.
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Book chapter (peer-reviewed)abstract
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| 9. |
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| 10. |
- Neumann, Patrick, et al.
(author)
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Trunk posture: reliability, accuracy, and risk estimates for low back pain from a video based assessment method
- 2001
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In: International Journal of Industrial Ergonomics. - 0169-8141. ; 28, s. 355-365
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Journal article (peer-reviewed)abstract
- It has been recently reported that both dynamic movement characteristics, as well as the duration of postures adopted during work, are important in the development of low back pain (LBP). This paper presents a video-based posture assessment method capable of measuring trunk angles and angular velocities in industrial workplaces. The interobserver reliability, system accuracy, and the relationship of the measured exposures to the reporting of low back pain are reported. The video analysis workstation consisted of a desktop computer equipped with digital video capture and playback technology, a VCR, and a computer game type joystick. The operator could then use a joystick to track trunk flexion and lateral bending during computer-controlled video playback. The joystick buttons were used for binary input of twisting. The inter-observer reliability for peak flexion and percentage of time spent in posture category variables were excellent (ICC>0.8). Lower reliability levels were observed for peak and average velocity and movement related variables. The video analysis system time series data showed very high correlation to the criterion optoelectronic imaging system (r ¼ 0:92). Root mean square errors averaged 5.81 for the amplitude probability distribution function data. Trunk flexion variables including peak level, peak velocity, average velocity indicators, and percent time in flexion category indicators all showed significant differences between cases and controls in the epidemiological study. A model consisting of the measures peak trunk flexion, percent time in lateral bend and average lateral bending velocity emerged after multivariable analysis for relationship to low back pain.
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| 11. |
- Norman, Patrick, et al.
(author)
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Density-functional theory calculations of optical rotatory dispersion in the nonresonant and resonant frequency regions
- 2004
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In: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 120:11, s. 5027-5035
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Journal article (peer-reviewed)abstract
- The complex linear response function is extended to mixed electric-dipole-magnetic-dipole properties using London atomic orbitals which ensures gauge-origin independent properties. The optical rotation is determined by mixed electric-dipole-magnetic-dipole polarizability. The anomalous optical rotatory dispersion (ORD) spectra of chiral molecules is calculated using first-principle quantum-chemical methods when absorption is considered. This methodology of ORD is applied to hydrogen peroxide, 3R-methylcyclohexanone, 4R-1,1-dimethyl-[3]-(1,2)-ferrocenophan-2-on, and D2 isomer of C 84 fullerene.
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| 12. |
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| 13. |
- Norman, Patrick, et al.
(author)
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First principle calculations of dipole-dipole dispersion coefficients for the ground and first π → π∗ excited states of some azabenzenes
- 2004
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In: Journal of Computational Methods in Sciences and Engineering. - : IOS Press. - 1472-7978 .- 1875-8983. ; 4:3, s. 321-332
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Journal article (peer-reviewed)abstract
- The complex polarization propagator method has been applied to the calculation of dipole-dipole dispersion coefficients (also known as C6 coefficients) of pyridine, pyrazine, and s-tetrazine. These calculations refer to the electronic ground states as well as the first excited states of π → π∗ character. It is argued that accurate ground state dispersion coefficients are obtained with density functional theory using the B3LYP exchange-correlation functional. The proposed values for the C6 coefficients of pyridine, pyrazine, and s-tetrazine in their ground states are 1543 a.u., 1398 a.u., and 1014 a.u., respectively. Multi-configurational complete active space calculations are performed on these compounds in their respective π → π∗ excited state. The isotropic averages of the frequency-dependent polarizabilities are smaller in the excited states, but the effective frequencies-defined in the London-van der Waals dispersion relation-are on the other hand larger.
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| 14. |
- Norman, Patrick, et al.
(author)
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First-principle quantum modeling of optical power limiting materials
- 2004
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In: Journal of Computational and Theoretical Nanoscience. - : American Scientific Publishers. - 1546-1955 .- 1546-1963. ; 1:4, s. 343-366
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Research review (peer-reviewed)abstract
- We highlight the course of development of a project initiated 1998 by the authors and concerned with quantum modeling of optical power limiting materials. The methodological development has involved various quantum mechanical technologies for a description of multi-photon excitations within the framework of wave function and density function theories, with relativistic effects being addressed at rigorous as well as more approximate levels of theory. The method development has also involved models for vibronic and solvent contributions to the multi-photon excitations as well as pulse propagation based on the solution of the classical wave equations. Our review of these issues is completely nonmathematical. Results from sample applications are discussed in order to illustrate different aspects of concern for choosing materials with good optical limiting capabilities. Some focus is given to organic and organometallic push-pull compounds, including metallo-porphyrin compounds and platinum complexes. Copyright © 2004 American Scientific Publishers. All rights reserved.
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| 15. |
- Norman, Patrick, et al.
(author)
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Quadratic response functions in the time-dependent four-component Hartree-Fock approximation
- 2004
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:13, s. 6145-6154
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Journal article (peer-reviewed)abstract
- The implementation of quadratic response function in the four-component Hartree-Fock approximation was discussed. It was implemented based on the Dirac-Coulomb Hamiltonian. The second-order response function enabled the calculation of non-linear, time-dependent, corrections of the molecular polarization and magnetization. The first order response function was determined to evaluate the second-order response function.
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| 16. |
- Souza De Almeida, J., et al.
(author)
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Optical properties of donor-triad cluster in GaAs and GaN
- 2002
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:17, s. 3158-3160
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Journal article (peer-reviewed)abstract
- The effect of the transition energy of three-donor clusters on far infrared absorption in n-type semiconductor materials has been investigated by a multiconfigurational self-consistent-field model calculation and applied to GaAs and GaN systems. We show that it is crucial to consider the many-particle correlation effects within three-donor clusters. With electron correlation taken into account, the present results support the interpretation of a very recent unidentified peak energy observed in absorption measurement of GaN as due to electronic transitions in these clusters. We also corroborate the suggestion that the X line in GaAs arises from such transitions.
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| 17. |
- Sylvester-Hvid, K. O., et al.
(author)
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Sign change of hyperpolarizabilities of solvated water, revised : Effects of equilibrium and nonequilibrium solvation
- 2004
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In: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 108:41, s. 8961-8965
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Journal article (peer-reviewed)abstract
- The second harmonic and electro-optical responses for the water molecule in its liquid state are theoretically revised. The continuum, semicontinuum, and supermolecular solvation models are employed using quadratic response theory at the Hartree-Fock level, either in the equilibrium or nonequilibrium implementation. The experimentally observed sign change of the second harmonic response of water on liquefaction is reproduced using the supermolecular and semicontinuum model for both equilibrium and nonequilibrium solvation. The conclusions of a previous study, which rested upon linear response theory in an equilibrium implementation, are confirmed. Also, the assumption of Kleinman symmetry and dispersion is addressed.
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