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1.
Psychother Res ; : 1-16, 2024 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-38412334

RESUMO

OBJECTIVE: Patients with posttraumatic stress disorder (PTSD) report changes in what they think of the world and themselves, referred to as posttraumatic cognitions, and changes in how they think, reflected in increased perseverative thinking. We investigated whether pre-post therapy changes in the two aspects of thinking were associated with pre-post therapy changes in posttraumatic symptom severity. METHOD: 219 d clinic patients with posttraumatic stress symptoms received trauma-focused psychotherapy with cognitive behavioral and metacognitive elements. The posttraumatic cognitions inventory (PTCI), the perseverative thinking questionnaire (PTQ), and the Davidson trauma scale (DTS) were applied at two occasions, pre- and post-therapy. Using latent change score models, we investigated whether change in PTCI and change in PTQ were associated with change in DTS and its subscales. We then compared the predictive value of PTQ and PTCI in joint models. RESULTS: When jointly modeled, change in overall DTS score was associated with change in both PTCI and PTQ. Concerning DTS subscales, reexperiencing and avoidance were significantly associated with change in PTCI, but not in PTQ. CONCLUSION: Results indicate that both aspects of cognition may be valuable targets of psychotherapy. A focus on posttraumatic cognitions might be called for in patients with severe reexperiencing and avoidance.

2.
Artigo em Inglês | MEDLINE | ID: mdl-36898634

RESUMO

BACKGROUND: In bipolar disorder (BD), the alternation of extreme mood states indicates deficits in emotion processing, accompanied by aberrant neural function of the emotion network. The present study investigated the effects of an emotion-centered psychotherapeutic intervention on amygdala responsivity and connectivity during emotional face processing in BD. METHODS: In a randomized controlled trial within the multicentric BipoLife project, euthymic patients with BD received one of two interventions over 6 months: an unstructured, emotion-focused intervention (FEST), where patients were guided to adequately perceive and label their emotions (n = 28), or a specific, structured, cognitive behavioral intervention (SEKT) (n = 31). Before and after interventions, functional magnetic resonance imaging was conducted while patients completed an emotional face-matching paradigm (final functional magnetic resonance imaging sample of patients completing both measurements: SEKT, n = 17; FEST, n = 17). Healthy control subjects (n = 32) were scanned twice after the same interval without receiving any intervention. Given the focus of FEST on emotion processing, we expected FEST to strengthen amygdala activation and connectivity. RESULTS: Clinically, both interventions stabilized patients' euthymic states in terms of affective symptoms. At the neural level, FEST versus SEKT increased amygdala activation and amygdala-insula connectivity at postintervention relative to preintervention time point. In FEST, the increase in amygdala activation was associated with fewer depressive symptoms (r = 0.72) 6 months after intervention. CONCLUSIONS: Enhanced activation and functional connectivity of the amygdala after FEST versus SEKT may represent a neural marker of improved emotion processing, supporting the FEST intervention as an effective tool in relapse prevention in patients with BD.


Assuntos
Transtorno Bipolar , Humanos , Mapeamento Encefálico , Vias Neurais , Tonsila do Cerebelo , Emoções/fisiologia , Psicoterapia
3.
J Behav Ther Exp Psychiatry ; 81: 101841, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-36827946

RESUMO

BACKGROUND AND OBJECTIVES: The Affect Intolerance Scale (AIS) assesses two core concepts of emotion regulation: appraisals of negative emotions as threatening and proneness to emotional avoidance. Maladaptive emotion regulation is associated with various psychopathologies. We translated and validated the AIS in a German student and clinical sample of patients with trauma-related disorders. METHODS: 340 patients, 161 with post-traumatic stress disorder and 179 with adjustment disorder, and 322 students were enrolled. We employed exploratory and confirmatory factor analyses in a cross-validation design to investigate construct validity, convergent and discriminant validity, and reliability. RESULTS: We replicated the originally described two-factor structure in both samples. Cronbach's α was 0.947 in the student and 0.950 in the clinical sample. AIS subscales showed moderate to high correlations with convergent and low correlations with discriminant measures. AIS total scores were significantly larger in the clinical sample, controlled for gender and age. LIMITATIONS: This study provides a unified cross-validation model in a clinical and a student sample at the cost of reduced sample sizes. CONCLUSIONS: The AIS is a valid measure of affect intolerance with the discriminative ability to distinguish between patients with trauma-related disorders and students. Test redundancy within both sub-constructs of the AIS might lead to biased estimates but allows for increased test precision, rendering the AIS a tool suitable for individual treatment monitoring.


Assuntos
Emoções , Estudantes , Humanos , Reprodutibilidade dos Testes , Estudantes/psicologia , Psicometria , Inquéritos e Questionários
4.
Artigo em Inglês | MEDLINE | ID: mdl-36087699

RESUMO

BACKGROUND: In bipolar disorder, impaired affective theory of mind (aToM) performance and aberrant neural activation in the ToM brain network partly explain social functioning impairments. However, it is not yet known whether psychotherapy of bipolar disorder influences neuroimaging markers of aToM. METHODS: In this study, conducted within the multicentric randomized controlled trial of the BipoLife consortium, patients with euthymic bipolar disorder underwent 2 group interventions over 6 months (mean = 28.45 weeks): 1) a specific, cognitive behavioral intervention (specific psychotherapeutic intervention [SEKT]) (n = 31) targeting impulse regulation, ToM, and social skills and 2) an emotion-focused intervention (FEST) (n = 28). To compare the effect of SEKT and FEST on neural correlates of aToM, patients performed an aToM task during functional magnetic resonance imaging before and after interventions (final functional magnetic resonance imaging sample of pre- and postcompleters, SEKT: n = 16; FEST: n = 17). Healthy control subjects (n = 32) were scanned twice with the same time interval. Because ToM was trained in SEKT, we expected an increased ToM network activation in SEKT relative to FEST postintervention. RESULTS: Both treatments effectively stabilized patients' euthymic state in terms of affective symptoms, life satisfaction, and global functioning. Confirming our expectations, SEKT patients showed increased neural activation within regions of the ToM network, bilateral temporoparietal junction, posterior cingulate cortex, and precuneus, whereas FEST patients did not. CONCLUSIONS: The stabilizing effect of SEKT on clinical outcomes went along with increased neural activation of the ToM network, while FEST possibly exerted its positive effect by other, yet unexplored routes.


Assuntos
Transtorno Bipolar , Teoria da Mente , Humanos , Teoria da Mente/fisiologia , Encéfalo , Transtorno Ciclotímico , Psicoterapia
5.
J Phys Chem A ; 125(47): 10138-10143, 2021 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-34788037

RESUMO

We performed a time-resolved spectroscopy experiment on the dissociation of oxygen molecules after the interaction with intense extreme-ultraviolet (XUV) light from the free-electron laser in Hamburg at Deutsches Elektronen-Synchrotron. Using an XUV-pump/XUV-probe transient-absorption geometry with a split-and-delay unit, we observe the onset of electronic transitions in the O2+ cation near 50 eV photon energy, marking the end of the progression from a molecule to two isolated atoms. We observe two different time scales of 290 ± 53 and 180 ± 76 fs for the emergence of different ionic transitions, indicating different dissociation pathways taken by the departing oxygen atoms. With regard to the emerging opportunities of tuning the central frequencies of pump and probe pulses and of increasing the probe-pulse bandwidth, future pump-probe transient-absorption experiments are expected to provide a detailed view of the coupled nuclear and electronic dynamics during molecular dissociation.

6.
J Intell ; 9(2)2021 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-34207993

RESUMO

The study of socio-cognitive abilities emerged from intelligence research, and their specificity remains controversial until today. In recent years, the psychometric structure of face cognition (FC)-a basic facet of socio-cognitive abilities-was extensively studied. In this review, we summarize and discuss the divergent psychometric structures of FC in easy and difficult tasks. While accuracy in difficult tasks was consistently shown to be face-specific, the evidence for easy tasks was inconsistent. The structure of response speed in easy tasks was mostly-but not always-unitary across object categories, including faces. Here, we compare studies to identify characteristics leading to face specificity in easy tasks. The following pattern emerges: in easy tasks, face specificity is found when modeling speed in a single task; however, when modeling speed across multiple, different easy tasks, only a unitary factor structure is reported. In difficult tasks, however, face specificity occurs in both single task approaches and task batteries. This suggests different cognitive mechanisms behind face specificity in easy and difficult tasks. In easy tasks, face specificity relies on isolated cognitive sub-processes such as face identity recognition. In difficult tasks, face-specific and task-independent cognitive processes are employed. We propose a descriptive model and argue for FC to be integrated into common taxonomies of intelligence.

7.
Cortex ; 134: 114-133, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33276306

RESUMO

Given the crucial role of face recognition in social life, it is hardly surprising that cognitive processes specific for faces have been identified. In previous individual differences studies, the speed (measured in easy tasks) and accuracy (difficult tasks) of face cognition (FC, involving perception and recognition of faces) have been shown to form distinct abilities, going along with divergent factorial structures. This result has been replicated, but remained unexplained. To fill this gap, we first parameterized the sub-processes underlying speed vs. accuracy in easy and difficult memory tasks for faces and houses in a large sample. Then, we analyzed event-related potentials (ERPs) extracted from the EEG by using residue iteration decomposition (RIDE), yielding a central (C) component that is comparable to a purified P300. Structural equation modeling (SEM) was applied to estimate face specificity of C component latencies and amplitudes. If performance in easy tasks relies on purely general processes that are insensitive to stimulus content, there should be no specificity of individual differences in the latency recorded in easy tasks. However, in difficult tasks specificity was expected. Results indicated that, contrary to our predictions, specificity occurred in the C component latency of both speed-based and accuracy-based measures, but was stronger in accuracy. Further analyses suggested specific relationships between the face-related C latency and FC ability. Finally, we detected specificity in RTs of easy tasks when single tasks were modeled, but not when multiple tasks were jointly modeled. This suggests that the mechanisms leading to face specificity in performance speed are distinct across tasks.


Assuntos
Potenciais Evocados , Reconhecimento Facial , Cognição , Eletroencefalografia , Humanos , Individualidade , Tempo de Reação
8.
Neuroimage ; 204: 116229, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31563519

RESUMO

Face cognition, the ability to perceive faces and interpret facial information, is a crucial skill in human social interactions. At the neurobiological level, several functionally specialized brain regions constitute a network of face processing. However, the evidence whether functional specialization within the face network is also reflected in the white matter structural connectivity patterns is yet limited. Based on imaging data from 1051 young healthy adult women and men, we investigated individual differences in the integrity of fibre tracts connecting face-processing regions relative to brain-general tract integrity. We analyzed individual tract-averaged fractional anisotropy (FA) values with structural equation modeling (SEM). Our results show that beyond the variance explained by a general factor indicating the quality of global tracts, the specificity of white matter integrity within the face network can be accounted for by additional factors. These factors correspond to the core and extended networks suggested in classic neuro-functional models of face processing. The right-hemisphere dominance, as commonly found in face cognition studies, is also reflected in this factorial structure. Overall, our results extend the structural brain substrate of the classic functional face processing system to the network of fibre tracts connecting these brain areas, and shed light on a structure-function correspondence from the perspective of individual differences.


Assuntos
Encéfalo , Imagem de Tensor de Difusão/métodos , Reconhecimento Facial/fisiologia , Lateralidade Funcional/fisiologia , Fibras Nervosas Mielinizadas/ultraestrutura , Rede Nervosa , Percepção Social , Adulto , Encéfalo/anatomia & histologia , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Feminino , Humanos , Individualidade , Masculino , Rede Nervosa/anatomia & histologia , Rede Nervosa/diagnóstico por imagem , Rede Nervosa/fisiologia , Vias Neurais/diagnóstico por imagem , Adulto Jovem
9.
Phys Rev Lett ; 123(16): 163201, 2019 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-31702368

RESUMO

We report on the experimental observation of a strong-field dressing of an autoionizing two-electron state in helium with intense extreme-ultraviolet laser pulses from a free-electron laser. The asymmetric Fano line shape of this transition is spectrally resolved, and we observe modifications of the resonance asymmetry structure for increasing free-electron-laser pulse energy on the order of few tens of Microjoules. A quantum-mechanical calculation of the time-dependent dipole response of this autoionizing state, driven by classical extreme-ultraviolet (XUV) electric fields, evidences strong-field-induced energy and phase shifts of the doubly excited state, which are extracted from the Fano line-shape asymmetry. The experimental results obtained at the Free-Electron Laser in Hamburg (FLASH) thus correspond to transient energy shifts on the order of a few meV, induced by strong XUV fields. These results open up a new way of performing nonperturbative XUV nonlinear optics for the light-matter interaction of resonant electronic transitions in atoms at short wavelengths.

10.
Phys Rev Lett ; 123(10): 103001, 2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31573300

RESUMO

We demonstrate time-resolved nonlinear extreme-ultraviolet absorption spectroscopy on multiply charged ions, here applied to the doubly charged neon ion, driven by a phase-locked sequence of two intense free-electron laser pulses. Absorption signatures of resonance lines due to 2p-3d bound-bound transitions between the spin-orbit multiplets ^{3}P_{0,1,2} and ^{3}D_{1,2,3} of the transiently produced doubly charged Ne^{2+} ion are revealed, with time-dependent spectral changes over a time-delay range of (2.4±0.3) fs. Furthermore, we observe 10-meV-scale spectral shifts of these resonances owing to the ac Stark effect. We use a time-dependent quantum model to explain the observations by an enhanced coupling of the ionic quantum states with the partially coherent free-electron laser radiation when the phase-locked pump and probe pulses precisely overlap in time.

11.
R Soc Open Sci ; 6(7): 180857, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31417686

RESUMO

Face cognition (FC) is a specific ability that cannot be fully explained by general cognitive functions. Cortical thickness (CT) is a neural correlate of performance and learning. In this registered report, we used data from the Human Connectome Project (HCP) to investigate the relationship between CT in the core brain network of FC and performance on a psychometric task battery, including tasks with facial content. Using structural equation modelling (SEM), we tested the existence of face-specific interindividual differences at behavioural and neural levels. The measurement models include general and face-specific factors of performance and CT. There was no face-specificity in CT in functionally localized areas. In post hoc analyses, we compared the preregistered, small regions of interest (ROIs) to larger, non-individualized ROIs and identified a face-specific CT factor when large ROIs were considered. We show that this was probably due to low reliability of CT in the functional localization (intra-class correlation coefficients (ICC) between 0.72 and 0.85). Furthermore, general cognitive ability, but not face-specific performance, could be predicted by latent factors of CT with a small effect size. In conclusion, for the core brain network of FC, we provide exploratory evidence (in need of cross-validation) that areas of the cortex sharing a functional purpose did also share morphological properties as measured by CT.

12.
J Exp Psychol Hum Percept Perform ; 45(1): 16-38, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30475024

RESUMO

Faces are a major source of information in social interaction. The ability to perceive and interpret faces thus carries paramount importance in people's social lives. However, this crucial ability is not yet fully understood. Individual differences studies show that the speed and accuracy of face cognition (including perception and memory/recognition), the two facets targeted when measuring cognitive performance, are relatively independent traits. Unlike accuracy data, individual differences in reaction times (RTs) measured in perceptual decision tasks with or without memory load using faces and objects, do not show face-specific variance. Here, we applied the diffusion model to RT and accuracy data captured by simple perceptual decision tasks to improve understanding of the lack of face specificity. If performance speed in face cognition tasks is truly a global, nonspecific individual ability, no parameter of the diffusion model should hold face specificity. In a study on adults (N = 217), we administered two tasks of face and object perception. We used individually estimated diffusion model parameters as manifest variables to study face specificity in drift rate (ν), boundary separation (a), and nondecision time (Ter) using structural equation modeling. Furthermore, to study differential relationships between diffusion model parameters and measures of cognitive abilities, we regressed factors of face and object cognition accuracy on factors of diffusion model parameters. The results revealed face specificity only in boundary separation. This suggests face-specific adjustment in the cautiousness of information processing. (PsycINFO Database Record (c) 2018 APA, all rights reserved).


Assuntos
Reconhecimento Facial/fisiologia , Individualidade , Modelos Psicológicos , Desempenho Psicomotor/fisiologia , Tempo de Reação/fisiologia , Percepção Social , Adolescente , Adulto , Feminino , Humanos , Masculino , Adulto Jovem
13.
Neuroreport ; 27(14): 1031-6, 2016 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-27489099

RESUMO

Prolonged periods of demanding cognitive tasks lead to an exhausted feeling known as mental fatigue. The neural underpinnings of mental fatigue are still under exploration. In the present study, we aimed to identify neurophysiological indicators of mental fatigue by studying the time-frequency distribution of the event-related potentials (ERPs) measured in N=26 adults in nonfatigued versus fatigued states. We were interested in the frontal theta and occipital alpha variations, which have shown consistent relationships with mental fatigue in previous studies. Furthermore, we expected differential changes in left and right electrodes, in line with previously detected lateralization effects in cognitive tasks. Mental fatigue was induced by a sustained two-back verbal visual memory task for 125 min and assessed using the Chalder Fatigue Scale. We applied a high-resolution time-frequency analysis method called smoothed pseudo Wigner Ville distribution and used regional integrals as indicators for changing trends of signal energy. Results showed an increase in ERP frontal theta energy (P=0.03) and a decrease in occipital alpha energy (P=0.028) when participants became mentally fatigued. The change in frontal theta was more pronounced in left electrode sites (P=0.032), hinting toward a differential fatigue effect in the two hemispheres. The results were discussed on the basis of previous lateralization studies with memory tasks and interpreted as an indicator of a causal relationship between the sustained task execution and the physiological changes. Our findings also suggest that the ERP signal energy variations in frontal theta and occipital alpha might be used as neural biomarkers to assess mental fatigue.


Assuntos
Potenciais Evocados/fisiologia , Lobo Frontal/fisiopatologia , Memória/fisiologia , Fadiga Mental/patologia , Fadiga Mental/fisiopatologia , Tempo de Reação/fisiologia , Adulto , Ritmo alfa/fisiologia , Análise de Variância , Eletroencefalografia , Feminino , Análise de Fourier , Humanos , Masculino , Estimulação Luminosa/efeitos adversos , Fatores de Tempo , Adulto Jovem
14.
Opt Lett ; 41(4): 709-12, 2016 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-26872169

RESUMO

Noncollinear four-wave-mixing (FWM) techniques at near-infrared (NIR), visible, and ultraviolet frequencies have been widely used to map vibrational and electronic couplings, typically in complex molecules. However, correlations between spatially localized inner-valence transitions among different sites of a molecule in the extreme ultraviolet (XUV) spectral range have not been observed yet. As an experimental step toward this goal, we perform time-resolved FWM spectroscopy with femtosecond NIR and attosecond XUV pulses. The first two pulses (XUV-NIR) coincide in time and act as coherent excitation fields, while the third pulse (NIR) acts as a probe. As a first application, we show how coupling dynamics between odd- and even-parity, inner-valence excited states of neon can be revealed using a two-dimensional spectral representation. Experimentally obtained results are found to be in good agreement with ab initio time-dependent R-matrix calculations providing the full description of multielectron interactions, as well as few-level model simulations. Future applications of this method also include site-specific probing of electronic processes in molecules.

15.
Appl Opt ; 55(36): 10318-10322, 2016 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-28059252

RESUMO

In time-resolved spectroscopy, it is a widespread belief that the temporal resolution is determined by the laser pulse duration. Recently, it was observed and shown that partially coherent laser pulses as they are provided by free-electron-laser (FEL) sources offer an alternative route to reach a temporal resolution below the average pulse duration. Here, we demonstrate the generation of partially coherent light in the laboratory like we observe it at FELs. We present the successful implementation of such statistically fluctuating pulses by using the pulse-shaping technique. These pulses exhibit an average pulse duration about 10 times larger than their bandwidth limit. The shaped pulses are then applied to transient-absorption measurements in the dye IR144. Despite the noisy characteristics of the laser pulses, features in the measured absorption spectra occurring on time scales much faster than the average pulse duration are resolved, thus proving the universality of the described noisy-pulse concept.

16.
Proc Natl Acad Sci U S A ; 112(51): 15613-8, 2015 Dec 22.
Artigo em Inglês | MEDLINE | ID: mdl-26647182

RESUMO

Controlling chemical reactions by light, i.e., the selective making and breaking of chemical bonds in a desired way with strong-field lasers, is a long-held dream in science. An essential step toward achieving this goal is to understand the interactions of atomic and molecular systems with intense laser light. The main focus of experiments that were performed thus far was on quantum-state population changes. Phase-shaped laser pulses were used to control the population of final states, also, by making use of quantum interference of different pathways. However, the quantum-mechanical phase of these final states, governing the system's response and thus the subsequent temporal evolution and dynamics of the system, was not systematically analyzed. Here, we demonstrate a generalized phase-control concept for complex systems in the liquid phase. In this scheme, the intensity of a control laser pulse acts as a control knob to manipulate the quantum-mechanical phase evolution of excited states. This control manifests itself in the phase of the molecule's dipole response accessible via its absorption spectrum. As reported here, the shape of a broad molecular absorption band is significantly modified for laser pulse intensities ranging from the weak perturbative to the strong-field regime. This generalized phase-control concept provides a powerful tool to interpret and understand the strong-field dynamics and control of large molecules in external pulsed laser fields.

17.
Phys Rev Lett ; 115(3): 033003, 2015 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-26230787

RESUMO

The evolution of a V-type three-level system is studied, whose two resonances are coherently excited and coupled by two ultrashort laser pump and probe pulses, separated by a varying time delay. We relate the quantum dynamics of the excited multilevel system to the absorption spectrum of the transmitted probe pulse. In particular, by analyzing the quantum evolution of the system, we interpret how atomic phases are differently encoded in the time-delay-dependent spectral absorption profiles when the pump pulse either precedes or follows the probe pulse. This scheme is experimentally applied to atomic Rb, whose fine-structure-split 5s (2)S{1/2}→5p(2)P{1/2} and 5s(2)S_{1/2}→5p(2)P{3/2} transitions are driven by the combined action of a pump pulse of variable intensity and a delayed probe pulse. The provided understanding of the relationship between quantum phases and absorption spectra represents an important step towards full time-dependent phase reconstruction (quantum holography) of bound-state wave packets in strong-field light-matter interactions with atoms, molecules, and solids.

18.
Psychiatry Res ; 232(1): 130-3, 2015 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-25800218

RESUMO

In schizophrenia, reduced orbitofrontal cortex (OFC) volume is inconsistently reported. To investigate the impact of genetic load on OFC volume, manual MRI-tracing in 23 first-episode schizophrenia patients (FE-SZ) and 23 controls was performed. FE-SZ with genetic load showed a decrease in OFC volume compared to FE-SZ without load and controls.


Assuntos
Carga Genética , Córtex Pré-Frontal/patologia , Esquizofrenia/genética , Esquizofrenia/patologia , Adulto , Estudos de Casos e Controles , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Adulto Jovem
19.
Nature ; 516(7531): 374-8, 2014 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-25519135

RESUMO

The concerted motion of two or more bound electrons governs atomic and molecular non-equilibrium processes including chemical reactions, and hence there is much interest in developing a detailed understanding of such electron dynamics in the quantum regime. However, there is no exact solution for the quantum three-body problem, and as a result even the minimal system of two active electrons and a nucleus is analytically intractable. This makes experimental measurements of the dynamics of two bound and correlated electrons, as found in the helium atom, an attractive prospect. However, although the motion of single active electrons and holes has been observed with attosecond time resolution, comparable experiments on two-electron motion have so far remained out of reach. Here we show that a correlated two-electron wave packet can be reconstructed from a 1.2-femtosecond quantum beat among low-lying doubly excited states in helium. The beat appears in attosecond transient-absorption spectra measured with unprecedentedly high spectral resolution and in the presence of an intensity-tunable visible laser field. We tune the coupling between the two low-lying quantum states by adjusting the visible laser intensity, and use the Fano resonance as a phase-sensitive quantum interferometer to achieve coherent control of the two correlated electrons. Given the excellent agreement with large-scale quantum-mechanical calculations for the helium atom, we anticipate that multidimensional spectroscopy experiments of the type we report here will provide benchmark data for testing fundamental few-body quantum dynamics theory in more complex systems. They might also provide a route to the site-specific measurement and control of metastable electronic transition states that are at the heart of fundamental chemical reactions.

20.
Phys Rev Lett ; 112(10): 103001, 2014 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-24679285

RESUMO

Fano line shapes observed in absorption spectra encode information on the amplitude and phase of the optical dipole response. A change in the Fano line shape, e.g., by interaction with short-pulsed laser fields, allows us to extract dynamical modifications of the amplitude and phase of the coupled excited quantum states. We introduce and apply this physical mechanism to near-resonantly coupled doubly excited states in helium. This general approach provides a physical understanding of the laser-induced spectral shift of absorption-line maxima on a sub-laser-cycle time scale as they are ubiquitously observed in attosecond transient-absorption measurements.

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