Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailIntramolecular dynamics by photoelectron spectroscopy. I. Application to N2 +, HBr+, and HCN+
Lorquet, Andrée; Lorquet, Jean-Claude ULg; Delwiche, Jacques ULg et al

in Journal of Chemical Physics (1982), 76

The Fourier transform of an optical electronic spectrum leads to an autocorrelation function C(t) which describes the evolution in time of the wave packet created by the Franck-Condon transition, as it ... [more ▼]

The Fourier transform of an optical electronic spectrum leads to an autocorrelation function C(t) which describes the evolution in time of the wave packet created by the Franck-Condon transition, as it propagates on the potential energy surface of the electronic upper state. This correlation function is equal to the modulus of the overlap integral between the initial position of the wave packet and its instantaneous position at time. The original data resulting from an experimentally determined spectral profile must be corrected for finite energy resolution, rotational, and spin-orbit effects. The behavior of the system can then be followed up to a time of the order of 10 -l3 s, i.e., during the first few vibrations which follow immediately the electronic transition. The method is applied to photoelectron spectra and the results are compared to the available information on potential energy surfaces of ionized molecules, in order to study their unimolecular dissociation dynamics. In the case of the X 2Σg +, A 2Πu, and B 2Σu + states of N2 +, an oscillatory pattern is obtained for the correlation function. This indicates that the nuclear motion is taking place in a bound potential. Effects due to anharmonicity are visible in the case of the A 2Πu state. The study of the X 2Π state of HBr+ demonstrates the overwhelming importance of spin-orbit coupling when heavy atoms are present in the molecule. Finally, the method is applied to a polyatomic molecule. The potential energy surface of the B̃ 2Σ+ state of HCN+ is characterized by two energy minima separated by a saddle point. The corresponding band in the photoelectron spectrum is characterized by an irregular vibrational structure superimposed upon a broad continuum. A study of the correlation function shows that the wave packet undergoes a complicated, two-component motion: while oscillating across the saddle point, it spreads away at the same time along the dissociative degree of freedom. This gives information on the rate of energy redistribution within the molecule. © 1982 American Institute of Physics. [less ▲]

Detailed reference viewed: 16 (2 ULg)
Full Text
Peer Reviewed
See detailIntramolecular dynamics by photoelectron spectroscopy. II. Nonadiabatic processes.
Dehareng, Dominique ULg; Leyh, Bernard ULg; Desouter-Lecomte, Michèle ULg et al

in Journal of Chemical Physics (1983), 79(8), 3719-3724

The Fourier transform of an electronic spectrum leads to an autocorrelation function which provides information on the propagation of the wave packet on the potential energy surface of the electronic ... [more ▼]

The Fourier transform of an electronic spectrum leads to an autocorrelation function which provides information on the propagation of the wave packet on the potential energy surface of the electronic state reached in the transition. The formula is valid even when nonadiabatic interaction is present, i.e., when the wave packet splits at a particular surface crossing with one part branching off to another potential energy surface. An explicit expression of the correlation function is given for a model of several discrete states interacting with a continuum. Closed-form solutions are given in the case of one and two resonances. A very simple formula valid in the strong coupling limit is also derived. The method is applied to the photoelectron spectrum of state A 2Sigma+ of HBr+, which is shown to correspond to the strong couplig case. [less ▲]

Detailed reference viewed: 24 (5 ULg)
Full Text
Peer Reviewed
See detailIntramolecular dynamics by photoelectron spectroscopy. III.Predissociation of the B 2B2 state of H2O+ and D2O+ by a semiclassical approach
Dehareng, Dominique ULg

in Chemical Physics (1986), 110

The initial wave packets and H2O+ and D2O+ in their B 2B2 /2A' states are expanded in the frozen gaussian basis set proposed by Heller. The gaussian functions are propagated on the adiabatic and diabatic ... [more ▼]

The initial wave packets and H2O+ and D2O+ in their B 2B2 /2A' states are expanded in the frozen gaussian basis set proposed by Heller. The gaussian functions are propagated on the adiabatic and diabatic potential energy surfaces resulting from the conical intersection with the A 2A1/2A' states. Autocorrelation functions are calculated separately for the adiabatic and the diabatic motions of the nuclei. These autocorrelation functions are compared with their experimental counterparts. The agreement is qualitatively good and the isotope effects are well accounted for. [less ▲]

Detailed reference viewed: 26 (2 ULg)
Full Text
Peer Reviewed
See detailIntramolecular Dynamics of Molecular Ions.
Lorquet, Jean-Claude ULg; Lorquet, Andrée ULg; Dehareng, Dominique ULg et al

in Bulletin de la Société Chimique Belge (1983), 92(6/7), 609-611

The Fourier transform of an electronic spectrum gives a direct dynamic information on the nuclear motion of a wavepacket on the potential energy surface of the final state reached in the electronic ... [more ▼]

The Fourier transform of an electronic spectrum gives a direct dynamic information on the nuclear motion of a wavepacket on the potential energy surface of the final state reached in the electronic transition, at least during the first few molecular vibrations. The method is valid for both adiabatic and non-adiabatic situations. It has proved its usefulness in the study of molecular processes such as Duchinsky effect, fast predissociations and internal conversions. [less ▲]

Detailed reference viewed: 57 (17 ULg)
Full Text
Peer Reviewed
See detailIntramolecular excited-state processes of a halato-telechelic polymer, evaluated by global compartmental analysis of the fluorescence decay surface with the use of model coumpounds
van Stam, Jan; De Schryver, Frans C; Boens, Noël et al

in Macromolecules (1997), 30(19), 5582-5590

The excited-state processes of the halato-telechelic polymer bis[(N,N-dimethyl-N-[3-(1-pyrenyl)propyl]ammonio)trifluoromethanesulfonate]-end-capped poly(tetrahydrofuran) at low concentrations are ... [more ▼]

The excited-state processes of the halato-telechelic polymer bis[(N,N-dimethyl-N-[3-(1-pyrenyl)propyl]ammonio)trifluoromethanesulfonate]-end-capped poly(tetrahydrofuran) at low concentrations are investigated by time-resolved fluorescence. The photophysical processes can be described by an intramolecular three-state excited-state model. Such a system is not identifiable in the absence of a priori information. It is possible to perform a global compartmental analysis of the fluorescence decay surface using the scanning technique, based on model compound data previously obtained [Hermans et al., J. Phys. Chem. 1994, 98, 13583 and Hermans et al. Macromolecules 1995, 28, 3380]. The value boundaries on the rate constant for ring closure of the chain ends show that this process is close to diffusion-controlled. [less ▲]

Detailed reference viewed: 23 (2 ULg)
Full Text
Peer Reviewed
See detailIntramolecular vibrational energy relaxation seen as expansion in phase space. I. Some experimental results for H2O+(X̃ 2B1), C2H4 +(X̃ 2B3), and HCN+(B̃2Σ +)
Lorquet, Jean-Claude ULg; Pavlov-Verevkin, V. B.

in Journal of Chemical Physics (1990), 93

It has been shown by Heller that a nonstationary wave packet resulting from a Franck-Condon transition evolves on the potential energy surface of the final electronic state and propagates through phase ... [more ▼]

It has been shown by Heller that a nonstationary wave packet resulting from a Franck-Condon transition evolves on the potential energy surface of the final electronic state and propagates through phase space at a rate which can be determined from the autocorrelation function \C(t)\2 = | 〈∅(0) |∅(t) ) |2. Since C(t) can be obtained by Fourier transformation of an optical spectrum S(E), i.e., from an observable quantity, it is possible to derive from an experimental measurement information concerning the density operator of a so-called dynamical statistical ensemble (DSE). This density operator, denoted ρav, represents a statistical mixture of the eigenstates of the system with weights determined by the dynamics of the system. It becomes diagonal after a so-called break time Script T sign;B. Its measure, according to a definition due to Stechel, can be interpreted as an effective number of states (denoted script N) that significantly contribute to the dynamics. The break time Script T sign;B represents the finite period of time allowed to expand in the phase space and after which no further progress can be made. Therefore, the number script N∞ of phase space cells which are accessed after a very long interval of time (or in practice after the break time) remains limited. Information on the validity of statistical theories of unimolecular reactions is contained in the fraction ℱ of the available phase space which is eventually explored. In order to assess the representativity of the sampling, it is necessary to account for the selection rule which requires all the states counted in script N ∞ to belong to the totally symmetric representation. It is also appropriate to estimate the role played by Fermi resonances and similar vibrational interactions which bring about energy flow into zero-order antisymmetric modes. A method to carry out the necessary partitionings is suggested. The functions script N T and ℛ T, and the quantities Script T signB, script N ∞, t script N, and ℱ have been determined from experimental data in three cases. In each case, the rate ℛT = d script N r/dT starts from an initial value of zero, increases up to a maximum which is reached after a time of the order of 10-14 s, and then exhibits an overall decrease upon which oscillations are superimposed. For state X̃ 2B1 of H2O+, Script T signB ≃a 2.4×10-14 s and Script T sign ≃ 0.3. The wave packet never accesses that part of the phase space that corresponds to the excitation of antisymmetric vibrations. For state X̃ 2B3u of C2 H4 +, Script T signB ≃1.6 × 10-13 s and Script T sign ≃ * 5×10-4. This fraction raises to 6 × 10 -3 if measured with respect to the effectively available phase space. When the spectrum consists of a discrete part followed by a dissociation continuum, the method can be extended to study the behavior of the bound part of the wave packet only. This has been applied to state B̃ 2Σ+ of HCN+ which is characterized by a very irregular spectrum. This case offers an example of complete occupation of phase space after a break time which is of the order of 2 ×10 -13 s. © 1990 American Institute of Physics. [less ▲]

Detailed reference viewed: 18 (0 ULg)
Full Text
Peer Reviewed
See detailIntramolecular vibrational relaxation seen as expansion in phase space. 4. Generic relaxation laws for a spectroscopic clump profile
Pavlov-Verevkin, V. B.; Lorquet, Jean-Claude ULg

in Journal of Physical Chemistry A (2002), 106(29), 6694-6701

We examine the volume of phase space sampled by a nonstationary wave packet when the spectral function consists of a single clump or of a series of them. The relaxation laws are expressed in terms of ... [more ▼]

We examine the volume of phase space sampled by a nonstationary wave packet when the spectral function consists of a single clump or of a series of them. The relaxation laws are expressed in terms of reduced time variables tau, whose definition involves either the average density of states (for a single clump) or appropriately weighted average densities of states (when the spectrum consists of many clumps). Introducing reasonable approximations, very simple generic relaxation laws are derived for the ratio N(tau)/N-infinity which measures the fraction of available phase space that has been sampled by time tau. Under certain assumptions, these laws are found to depend neither on the number nor on the individual features (shapes and widths) of the clumps. However, they strongly depend on the nature (regular or chaotic) of the underlying dynamics. When the dynamics is regular, the relaxation law is expressed in terms of tau(-1), whereas the corresponding equation in the chaotic limit is slightly more complicated and involves terms in tau(-2) and tau(-2) ln tau. Phase space is thus explored according to essentially different relaxation laws in the regular and chaotic limits, the difference being appreciable during the entire relaxation. These laws reflect in the time domain the difference in the distribution of nearest-neighbor level spacings observed in the energy domain (Poisson or Wigner statistics). [less ▲]

Detailed reference viewed: 15 (0 ULg)
Full Text
Peer Reviewed
See detailIntramolecular vibrational relaxation seen as expansion in phase space. II. Reference ergodic systems
Pavlov-Verevkin, V. B.; Lorquet, Jean-Claude ULg

in Journal of Chemical Physics (1996), 104(4), 1362-1369

The aim of the paper is to estimate the volume of phase space that is, in principle, available to a nonstationary wave packet during its intramolecular vibrational relaxation. For that purpose, use is ... [more ▼]

The aim of the paper is to estimate the volume of phase space that is, in principle, available to a nonstationary wave packet during its intramolecular vibrational relaxation. For that purpose, use is made of the maximum entropy method, together with the concept of constrained ergodicity to construct two so-called reference ergodic systems. The first one concerns thermal excitation processes. In that case, the only two constraints that are imposed on the intramolecular dynamics arise from the normalization of the wave function and from the conservation of. energy. These constraints affect the zeroth and first moments of the spectrum. The second reference system concerns a situation where, as an additional constraint, use is made of the information that the system has been prepared spectroscopically, i.e., by a specific .excitation process, consisting in the coherent excitation of an initial pure state. Then, the second moment of the spectrum, denoted cr, is shown to provide the appropriate additional constraint. Translated into the time domain, the prior knowledge of the dynamics used as a constraint is limited to an infinitesimally brief period of time [0,dt] with the remaining evolution determined by the maximum entropy method. The spectroscopic reference system constructed in that way can be understood as the one that samples the maximal volume of phase space available to a wave packet having a specified average energy and being put in motion by a specified initial force. Closed-form expressions are obtained for the phase space volumes occupied by these two reference systems for various simple parametrizations of the function D(E) that expresses the density of states as a function of the internal energy (power laws or exponential increase). Thermal reference systems are found to sample a larger volume of phase space than their spectroscopic counterparts. The difference between these two cases depends critically on the value of σ, and also on the symmetry characteristics of the excitation process. In general, the volumes occupied by the reference systems, thermal as well as spectroscopic, can be expressed as ηE avD(E av), where E av is the (conserved) average energy of the wave packet and η is a correcting factor that depends on the functional form of D(E) and on the nature of the imposed constraints. In all cases studied, the value of η was found not to greatly differ from 1. The method has been applied to the analysis of three experimental photoelectron spectra presenting different spectral characteristics (X̃ 2A 1 state of NH 3 +, X̃ 2B 3 state of C 2H 4 +, and the X̃ 2A″ state of C 2H 3F +). The fractional occupancy index F defined by Heller as the fraction of the available phase space eventually explored up to the break time T B could be determined. After a time of the order of 100 fs, F was found to be of the order of a few percent for thermal excitation. When the molecule presents some symmetry, the expansion of the wave packet is restricted to that part of phase space spanned by the totally symmetric wave functions. The use of this additional a priori knowledge increases the fractional index F. © 1996 American Institute of Physics. [less ▲]

Detailed reference viewed: 26 (2 ULg)
Full Text
Peer Reviewed
See detailIntramolecular vibrational relaxation seen as expansion in phase space. III. The long-time limit
Pavlov-Verevkin, V. B.; Lorquet, Jean-Claude ULg

in Journal of Chemical Physics (1997), 107(17), 6677-6680

Asymptotic formulas that describe the behavior of the function N(T) measuring the phase space volume sampled by a nonstationary wave packet during its time evolution are derived. It is shown that, in the ... [more ▼]

Asymptotic formulas that describe the behavior of the function N(T) measuring the phase space volume sampled by a nonstationary wave packet during its time evolution are derived. It is shown that, in the long-time limit, N(T)∼T-1 when the dynamics is regular, whereas N(T)∼T-2 In T for the chaotic case. © 1997 American Institute of Physics. [less ▲]

Detailed reference viewed: 20 (0 ULg)
Full Text
Peer Reviewed
See detailIntramyocardial synthesis of pro- and anti-inflammatory cytokines in infants with congenital cardiac defects.
Qing, Ma; Schumacher, Kathrin; Heise, Ruth et al

in Journal of the American College of Cardiology (2003), 41(12), 2266-74

OBJECTIVES: We sought to test the hypothesis that cytokines would be expressed in the myocardium of infants with congenital cardiac defects and to identify the signaling pathways involved. BACKGROUND ... [more ▼]

OBJECTIVES: We sought to test the hypothesis that cytokines would be expressed in the myocardium of infants with congenital cardiac defects and to identify the signaling pathways involved. BACKGROUND: Mechanical stress upregulates pro-inflammatory cytokines in the myocardium. METHODS: Fifteen infants with tetralogy of Fallot (TOF) (n = 7) or with ventricular septal defects (VSDs) (n = 8) were investigated. Concentrations of pro- and anti-inflammatory cytokines and of the inducible nitric oxide synthase (iNOS) were measured by enzyme-linked immunosorbent assay and/or Western blotting in the right ventricular myocardium taken during cardiac surgery. Activation of the nuclear factor-kappa-B (NF-kappa-B) and p38 mitogen-activated protein kinase (MAPK) pathways was assessed by electrophoretic mobility shift assay with supershift and/or Western blotting, respectively. RESULTS: The pro-inflammatory cytokines tumor necrosis factor (TNF)-alpha, interleukin (IL)-1-beta, and IL-6 and the anti-inflammatory cytokine IL-10 were detected in the myocardium of all patients. Concentrations of the pro-inflammatory cytokines and also of phosphorylated p38 MAPK were higher in patients with TOF than in those with VSD and correlated with the degree of pressure overload of the right ventricle. Levels of phosphorylated I-kappa-B-alpha, iNOS, and IL-10 were similar in patients with TOF and in those with VSD. CONCLUSIONS: Our results show intramyocardial synthesis of pro-inflammatory cytokines in infants with congenital cardiac defects. This is associated with activation of both the NF-kappa-B and p38 MAPK pathways. The latter could be particularly important for the transduction of mechanical signals in the infant's myocardium. Synthesis of IL-10 indicates an intramyocardial anti-inflammatory potential in this age group. [less ▲]

Detailed reference viewed: 11 (0 ULg)
Full Text
Peer Reviewed
See detailIntranasal infusion of enilconazole for treatment of sinonasal aspergillosis in dogs.
Zonderland, Jean-Luc; Stork, Christoph; Saunders, Jimmy et al

in Journal of the American Veterinary Medical Association [=JAVMA] (2002), 221

Detailed reference viewed: 44 (9 ULg)
Full Text
Peer Reviewed
See detailIntranasal oxytocin in obsessive-compulsive disorder
Ansseau, Marc ULg; Legros, Jean-Jacques ULg; Mormont, Christian ULg et al

in Psychoneuroendocrinology (1987), 12

A 55 years patient with obsessive-compulsive disorder showed clear improvement during four weeks of treatment with intranasal oxytocin compared to four weeks of intranasal placebo. This improvement was ... [more ▼]

A 55 years patient with obsessive-compulsive disorder showed clear improvement during four weeks of treatment with intranasal oxytocin compared to four weeks of intranasal placebo. This improvement was concurrent with the development of severe memory disturbances, supporting the amnestic properties of the peptide. However, the patient also developped psychotic symptoms and a marked decrease in plasma sodium and osmolality, which may have masked the obsessive symptomatology. The case highlights the need for careful monitoring in long-term oxytocin therapy. [less ▲]

Detailed reference viewed: 51 (16 ULg)
Full Text
Peer Reviewed
See detailIntranasal oxytocine as an adjunct to escitalopram in major depression.
Scantamburlo, Gabrielle ULg; Ansseau, Marc ULg; Geenen, Vincent ULg et al

in Journal of Neuropsychiatry and Clinical Neurosciences (The) (2011), 23(2), 5

Detailed reference viewed: 54 (22 ULg)
See detailIntransigeantisme, intégralisme et réformisme social. Structure et longue durée dans l'histoire du catholicisme contemporain (XIXe - XXe s.): réflexions historiographiques et méthodologiques
Jadoulle, Jean-Louis ULg

in G. BRAIVE et J.-M. CAUCHIES (Ed.) La critique historique à l'épreuve. Liber discipulorum Jacques Paquet (1989)

Detailed reference viewed: 39 (0 ULg)
Full Text
Peer Reviewed
See detailThe Intranuclear Cascade and the Collision Dynamics
Cugnon, Joseph ULg; L'Hôte, Denis

in Csernaï, L. P.; Strottmann, D. D. (Eds.) Relativistic Heavy Ion Collisions (1991)

Detailed reference viewed: 4 (0 ULg)
Full Text
See detailThe Intranuclear Cascade for Heavy Ion Relativistic Collisions
Cugnon, Joseph ULg; Vandermeulen, Jacques

in Dietrich, Klaus; di Toro, M.; Mang, H. J. (Eds.) Winter College on Fundamental Nuclear Physics, vol. 3, (World Scientific, Singapore, 1985), pp. 1373-1418 (1985)

Detailed reference viewed: 13 (1 ULg)
Full Text
Peer Reviewed
See detailIntranuclear Cascade Model. A Review
Cugnon, Joseph ULg

in Nuclear Physics A (1982), 389

Detailed reference viewed: 4 (0 ULg)
Full Text
Peer Reviewed
See detailIntranuclear Cascade Models Lack Dynamic Flow
Cugnon, Joseph ULg; L'Hôte, Denis; Molitoris, J.-J. et al

in Physical Review. C : Nuclear Physics (1986), 33

Detailed reference viewed: 12 (1 ULg)