| 1. |
- Andersson, LM, et al.
(författare)
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Vibrational wave packet dynamics in NaK : The A (1)Sigma(+) state
- 1999
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 241:1, s. 43-54
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Tidskriftsartikel (refereegranskat)abstract
- A combined experimental and theoretical study of the vibrational wave packet dynamics for the NaK molecule in the A (1)Sigma(+) state is presented. The experiment utilises a 790 nm one-colour femtosecond pump-probe scheme with detection of a previously nor reported dissociation pathway of the 3 (1)Pi(+) state, leading to the Na(3p) + K(4s) product channel. The dissociation is suggested to proceed via either collisionally mediated processes or a molecular cascading process via the 4 (1)Sigma(+) state, which crosses several states correlating to the Na(3p) + K(4s) limit. Time-dependent quantum mechanical calculations are used for studying the dynamics in detail. Simulations are performed both for 790 nm and for 766 nm, to relate also to earlier studies. The previous interpretations of the probe processes are revised. Inclusion of vibrational and rotational temperature effects are shown to be crucial for explaining the shape of the signal and the vibrational period, and leads to excellent agreement with the experiments.
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| 2. |
- Antzutkin, Oleg, et al.
(författare)
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Molecular motion of the Morpholin-1-yl radical in CF2 ClCFCl2 as studied by ESR : use of residual anisotrophy of powder spectra to extract dynamics
- 1993
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 169:2, s. 195-205
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of the deprotonated neutral morpholin-1-yl radical, trapped in a halocarbon matrix, CF2ClCFCl2, has been studied utilizing electron spin resonance (ESR) spectroscopy. The experimental lineshapes of the radical exhibit an alterating line-width effect in the temperature range 105-144 K. The major changes of the ESR lineshape were governed by the averaging of the nitrogen hyperfine anisotropy while no exchange of the isotropic hyperfine coupling constants was observed. Geometrical parameters specifying the restricted anisotropic rotation of the whole radical trapped in the matrix could be extracted. Two methods for simulating anisotropic exchange broadened ESR spectra, the secular and non-perturbative, were utilized to investigate the dynamics of the radical. A surprisingly simple ''three-site'' jump model with a barrier of almost-equal-to 3.6 kcal/mol can be applied in the simulation of the experimental spectra. It has been shown that the secular method cannot reproduce the exchange broadened ESR spectra of systems with large hyperfine anisotropy undergoing large internal reorganisation.
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| 3. |
- Baev, A, et al.
(författare)
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Picturing molecular femtosecond processes through an ultra-fast controllable X-ray shutter
- 2003
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 289, s. 51-56
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Tidskriftsartikel (refereegranskat)abstract
- We show that frequency detuning in a resonant X-ray scattering experiment acts as an X-ray camera shutter by regulating the duration time of the scattering process. The camera shutter can be used to select processes at different time scales for observation. This is illustrated by a resonant Auger study of the ultra-fast dissociation of the core-excited HF molecule. We present experimental results and first principle simulations of the molecular fraction in the resonant Auger spectra of HF which is a dynamical parameter that well illustrates X-ray shutter controlled dissociation.
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| 4. |
- Bustad, Johnny, et al.
(författare)
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C1s and O1s gas phase shake-up spectra from Mo(CO)6
- 1994
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104 .- 1873-4421. ; 179:3, s. 303-312
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Tidskriftsartikel (refereegranskat)abstract
- Experimental high-resolution core photoelectron C1s and O1s shake-up spectra of molybdenum hexacarbonyl, Mo(CO)(6), are reported and compared with results of semiempirical INDO/CI calculations. Several hitherto unobserved peaks are identified and assigned. It is found that an intra- and inter-group classification can be used to describe the transitions. The transitions of lowest energy have Mo-CO inter-group character. Dynamical effects on the line widths of the experimental shake-up peaks are discussed. A discussion of the relevance of experimental results obtained for the Mo(CO)(6)e for CO adsorption on metal surfaces is presented.
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| 5. |
- Carravetta, V., et al.
(författare)
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A screened static-exchange potential for core electron excitations
- 2001
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 263:03-feb, s. 231-242
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Tidskriftsartikel (refereegranskat)abstract
- We explore the use of a screened potential for static exchange calculations of core electron excitations, and to which extent this potential can relieve the main limitation of the static exchange method, namely the non-account of the residual screening in the presence of the excited electron. The screened potential is obtained by projecting the target state on a set of polarized orbitals, giving origin to a fully screened potential. Applications are presented and discussed for X-ray absorption spectra of a set of molecules of different size and type. It is found that with the little extra computational effort using the screened potential, the low-energy part of the spectra is generally improved, while the error in the term values are roughly of equal magnitude but of different sign compared to the normal static-exchange calculation. Various aspects of the screened and un-screened static-exchange approximations are analyzed in comparison with other techniques.
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| 6. |
- Chiu, D T, et al.
(författare)
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Manipulating the biochemical nanoenvironment around single molecules contained within vesicles
- 1999
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Ingår i: Chemical Physics. - Univ Gothenburg, Dept Chem, SE-41296 Gothenburg, Sweden. Stanford Univ, Dept Chem, Stanford, CA 94305 USA. : ELSEVIER. - 0301-0104 .- 1873-4421. ; 247:1, s. 133-139
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Tidskriftsartikel (refereegranskat)abstract
- A method to study single-molecule reactions confined in a biomimetic container is described. The technique combines rapid vesicle preparation, optical trapping and fluorescence confocal microscopy for performing simultaneous single-vesicle trapping and single-molecule detection experiments. The collisional environment between a single enzyme and substrate inside a vesicle is characterized by a Brownian dynamics Monte Carlo simulation. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 7. |
- Edholm, Olle, et al.
(författare)
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Stretched exponentials and barrier distributions
- 2000
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 252:02-jan, s. 221-225
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Tidskriftsartikel (refereegranskat)abstract
- Non exponential relaxation in complex macromolecular systems may be the consequence of dispersedness giving rise to different free energy barriers for different molecules. An approximate analytic formula that relates the time derivative of the decaying function to a probability distribution for the barrier is derived. From this, so called stretched exponentials, e(-t beta),are obtained from barrier distributions with width k(B)T/beta in energy and some asymmetry towards low energies. They may be represented as double exponential functions. An exact general formula that relates the Fourier transforms of the barrier height distribution and the time decaying function is also derived. This is gives a much more stable method for the numerical determination of the barrier height distribution than direct inversion of the Laplace transform.
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| 8. |
- Engström, Maria, et al.
(författare)
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Hartree-Fock linear response calculations of g-tensors of substituted benzene radicals
- 1999
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Ingår i: Chemical Physics. - : Elsevier. - 0301-0104 .- 1873-4421. ; 243:3, s. 263-271
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Tidskriftsartikel (refereegranskat)abstract
- Linear response theory has been applied for calculations of g-tensors of organic radicals in order to test the range of validity of restricted Hartree-Fock reference states. The g-values were calculated for the benzene cation (C6H6+), the benzene anion (C6H6-), hydropyrazine (C4H5N2), the dihydropyrazine cation (C4H6N2+), the aniline radical (C6H5NH), the p-benzoquinone anion (C6H4O2-), phenoxyl (C6H5O), the nitrobenzene anion (C6H5NO2-), and the nitropyridine anion (C5H4N2O2-). Influence of variations of structural parameters on the g-tensor components were investigated. Calculated g-values were in excellent agreement with experiment for six out of nine radicals. Two radicals - the p-benzoquinone anion and aniline radical - showed minor discrepancies, while the g-tensor of the phenoxyl radical was incorrect. The problem with the phenoxyl radical was traced to a complex electronic structure and optical spectrum. Results consistent with experiment could in that case only be obtained with electron correlated calculations.
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| 9. |
- Engström, Maria, et al.
(författare)
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Linear response calculations of electronic g-factors and spin-rotational coupling constants for diatomic molecules with a triplet ground state
- 1998
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Ingår i: Chemical Physics. - : Elsevier. - 0301-0104 .- 1873-4421. ; 237:1-2, s. 149-158
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Tidskriftsartikel (refereegranskat)abstract
- Electronic g-factors for ESR spectra of a number of diatomic molecules with a ground X3Σ- state and their electronic spin-rotational coupling constants have been calculated by a linear response method. General expressions are used for the second order correction to the electronic g-factor which account for spin-orbit coupling induced admixtures from all excited triplet states to the ground state orbital magnetism. First order corrections - the spin-Zeeman kinetic energy contribution and the one-electron spin-Zeeman gauge contribution - to the g-factor are also accounted for. Calculated g-factors and spin-rotational coupling constants are in a good agreement with available experimental data. In particular, the positive, anomalous, sign of the spin-rotational coupling constant of the PF radical is reproduced.
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| 10. |
- García, Emilio Melero, et al.
(författare)
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Neutral dissociation of superexcited states in nitric oxide
- 2003
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 293:1, s. 65-73
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Tidskriftsartikel (refereegranskat)abstract
- Near-infrared dispersed fluorescence measurements of 13 different atomic multiplets of neutral atomic fragments from photon induced neutral dissociation processes in NO are reported. For excitation of the molecules narrow band synchrotron photons of energy 17.2-25.8 eV were used. Neither Rydberg series nor other molecular states in NO known so far can account for the collected data. From ab initio calculations we try to obtain more information regarding the NO precursor states, and the mechanism behind the observed neutral dissociation.
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