| 1. |
- Rolles, D., et al.
(författare)
-
Femtosecond x-ray photoelectron diffraction on gas-phase dibromobenzene molecules
- 2014
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 47:12
-
Tidskriftsartikel (refereegranskat)abstract
- We present time-resolved femtosecond photoelectron momentum images and angular distributions of dissociating, laser-aligned 1,4-dibromobenzene (C6H4Br2) molecules measured in a near-infrared pump, soft-x-ray probe experiment performed at an x-ray free-electron laser. The observed alignment dependence of the bromine 2p photoelectron angular distributions is compared to density functional theory calculations and interpreted in terms of photoelectron diffraction. While no clear time-dependent effects are observed in the angular distribution of the Br(2p) photoelectrons, other, low-energy electrons show a pronounced dependence on the time delay between the near-infrared laser and the x-ray pulse.
|
|
| 2. |
- Stern, S., et al.
(författare)
-
Toward atomic resolution diffractive imaging of isolated molecules with X-ray free-electron lasers
- 2014
-
Ingår i: Faraday Discussions. - : Royal Society of Chemistry (RSC). - 1364-5498. ; 171, s. 393-418
-
Tidskriftsartikel (refereegranskat)abstract
- We give a detailed account of the theoretical analysis and the experimental results of an X-ray-diffraction experiment on quantum-state selected and strongly laser-aligned gasphase ensembles of the prototypical large asymmetric rotor molecule 2,5-diiodobenzonitrile, performed at the Linac Coherent Light Source [Phys. Rev. Lett. 112, 083002 (2014)]. This experiment is the first step toward coherent diffractive imaging of structures and structural dynamics of isolated molecules at atomic resolution, i.e., picometers and femtoseconds, using X-ray free-electron lasers.
|
|
| 3. |
- Aidas, Kestutis, et al.
(författare)
-
The Dalton quantum chemistry program system
- 2014
-
Ingår i: WIREs Computational Molecular Science. - : Wiley. - 1759-0876 .- 1759-0884. ; 4:3, s. 269-284
-
Tidskriftsartikel (refereegranskat)abstract
- Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from for a number of UNIX platforms.
|
|
| 4. |
- Boll, Rebecca, et al.
(författare)
-
Imaging molecular structure through femtosecond photoelectron diffraction on aligned and oriented gas-phase molecules
- 2014
-
Ingår i: Faraday Discussions. - : Royal Society of Chemistry (RSC). - 1364-5498. ; 171, s. 57-80
-
Tidskriftsartikel (refereegranskat)abstract
- This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray free-electron laser. We present results of two experiments aimed at measuring photoelectron angular distributions of laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) and dissociating, laser-aligned 1,4-dibromobenzene (C6H4Br2) molecules and discuss them in the larger context of photoelectron diffraction on gas-phase molecules. We also show how the strong nanosecond laser pulse used for adiabatically laser-aligning the molecules influences the measured electron and ion spectra and angular distributions, and discuss how this may affect the outcome of future time-resolved photoelectron diffraction experiments.
|
|
| 5. |
- Lindwall, Magnus, 1975, et al.
(författare)
-
Method Effects: The Problem With Negatively Versus Positively Keyed Items
- 2012
-
Ingår i: Journal of Personality Assessment. - 0022-3891. ; 94:2, s. 196-204
-
Tidskriftsartikel (refereegranskat)abstract
- Using confirmatory factor analyses, we examined method effects on Rosenberg's Self-Esteem Scale (RSES; Rosenberg, 1965) in a sample of older European adults. Nine hundred forty nine community-dwelling adults 60 years of age or older from 5 European countries completed the RSES as well as measures of depression and life satisfaction. The 2 models that had an acceptable fit with the data included method effects. The method effects were associated with both positively and negatively worded items. Method effects models were invariant across gender and age, but not across countries. Both depression and life satisfaction predicted method effects. Individuals with higher depression scores and lower life satisfaction scores were more likely to endorse negatively phrased items.
|
|
| 6. |
- Thogersen, L., et al.
(författare)
-
The trust-region self-consistent field method : Towards a black-box optimization in Hartree-Fock and Kohn-Sham theories
- 2004
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:1, s. 16-27
-
Tidskriftsartikel (refereegranskat)abstract
- The trust-region self-consistent field (TRSCF) method is presented for optimizing the total energy E-SCF of Hartree-Fock theory and Kohn-Sham density-functional theory. In the TRSCF method, both the Fock/Kohn-Sham matrix diagonalization step to obtain a new density matrix and the step to determine the optimal density matrix in the subspace of the density matrices of the preceding diagonalization steps have been improved. The improvements follow from the recognition that local models to E-SCF may be introduced by carrying out a Taylor expansion of the energy about the current density matrix. At the point of expansion, the local models have the same gradient as E-SCF but only an approximate Hessian. The local models are therefore valid only in a restricted region-the trust region-and steps can only be taken with confidence within this region. By restricting the steps of the TRSCF model to be inside the trust region, a monotonic and significant reduction of the total energy is ensured in each iteration of the TRSCF method. Examples are given where the TRSCF method converges monotonically and smoothly, but where the standard DIIS method diverges.
|
|
| 7. |
- Thogersen, L., et al.
(författare)
-
The trust-region self-consistent field method in Kohn-Sham density-functional theory
- 2005
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 123:7
-
Tidskriftsartikel (refereegranskat)abstract
- The trust-region self-consistent field (TRSCF) method is extended to the optimization of the Kohn-Sham energy. In the TRSCF method, both the Roothaan-Hall step and the density-subspace minimization step are replaced by trust-region optimizations of local approximations to the Kohn-Sham energy, leading to a controlled, monotonic convergence towards the optimized energy. Previously the TRSCF method has been developed for optimization of the Hartree-Fock energy, which is a simple quadratic function in the density matrix. However, since the Kohn-Sham energy is a nonquadratic function of the density matrix, the local energy functions must be generalized for use with the Kohn-Sham model. Such a generalization, which contains the Hartree-Fock model as a special case, is presented here. For comparison, a rederivation of the popular direct inversion in the iterative subspace (DIIS) algorithm is performed, demonstrating that the DIIS method may be viewed as a quasi-Newton method, explaining its fast local convergence. In the global region the convergence behavior of DIIS is less predictable. The related energy DIIS technique is also discussed and shown to be inappropriate for the optimization of the Kohn-Sham energy.
|
|
| 8. |
- Thogersen-Ntoumani, C, et al.
(författare)
-
Health and well-being profiles of older European adults
- 2011
-
Ingår i: EUROPEAN JOURNAL OF AGEING. - : Springer Science and Business Media LLC. - 1613-9372 .- 1613-9380. ; 8:2, s. 75-85
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to identify health and well-being typologies among a sample of older European adults. Further, we examined various demographic, social, and health behaviour characteristics that were used to discriminate between such groups. The participants were 1,381 community-dwelling adults aged 65 years and above (M age = 73.65; SD = 7.77) from six European Union (EU) countries who completed self-reported questionnaires. Hierarchical cluster analysis was initially conducted followed by a k means analysis to confirm cluster membership. Four clusters were identified and validated: ‘good health and moderate functioning’ (38.40%), ‘moderate health and functioning’ (30.84%), ‘obese and depressed’ (20.24%) and ‘low health and functioning’ (10.51%). The groups could be discriminated based on age, gender, nationality, years of education, social isolation and health behaviours (alcohol consumption and walking behaviour). The results of the study demonstrate heterogeneity with regard to the relationships between the variables examined. The information can be used in targeting older Europeans for health promotion interventions.
|
|
