Isotope effects in dynamics of water isotopologues induced by core ionization at an x-ray free-electron laser.

Dynamical response of water exposed to x-rays is of utmost importance in a wealth of science areas. We exposed isolated water isotopologues to short x-ray pulses from a free-electron laser and detected momenta of all produced ions in coincidence. By combining experimental results and theoretical modeling, we identify significant structural dynamics with characteristic isotope effects in H2O2+, D2O2+, and HDO2+, such as asymmetric bond elongation and bond-angle opening, leading to two-body or three-body fragmentation on a timescale of a few femtoseconds. A method to disentangle the sequences of events taking place upon the consecutive absorption of two x-ray photons is described. The obtained deep look into structural properties and dynamics of dissociating water isotopologues provides essential insights into the underlying mechanisms.

Attosecond timing of electron emission from a molecular shape resonance.

Shape resonances in physics and chemistry arise from the spatial confinement of a particle by a potential barrier. In molecular photoionization, these barriers prevent the electron from escaping instantaneously, so that nuclei may move and modify the potential, thereby affecting the ionization process. By using an attosecond two-color interferometric approach in combination with high spectral resolution, we have captured the changes induced by the nuclear motion on the centrifugal barrier that sustains the well-known shape resonance in valence-ionized N2. We show that despite the nuclear motion altering the bond length by only 2%, which leads to tiny changes in the potential barrier, the corresponding change in the ionization time can be as large as 200 attoseconds. This result poses limits to the concept of instantaneous electronic transitions in molecules, which is at the basis of the Franck-Condon principle of molecular spectroscopy.

Accuracy and precision of the RABBIT technique.

One of the most ubiquitous techniques within attosecond science is the so-called reconstruction of attosecond beating by interference of two-photon transitions (RABBIT). Originally proposed for the characterization of attosecond pulses, it has been successfully applied to the accurate determination of time delays in photoemission. Here, we examine in detail, using numerical simulations, the effect of the spatial and temporal properties of the light fields and of the experimental procedure on the accuracy of the method. This allows us to identify the necessary conditions to achieve the best temporal precision in RABBIT measurements. This article is part of the theme issue 'Measurement of ultrafast electronic and structural dynamics with X-rays'.

Time-Stretched Spectroscopy by the Quantum Zeno Effect: The Case of Auger Decay.

A tenet of time-resolved spectroscopy is "faster laser pulses for shorter timescales". Here, we suggest turning this paradigm around, and slowing down the system dynamics via repeated measurements, to do spectroscopy on longer timescales. This is the principle of the quantum Zeno effect. We exemplify our approach with the Auger process, and find that repeated measurements increase the core-hole lifetime, redistribute the kinetic energy of Auger electrons, and alter entanglement formation. We further provide an explicit experimental protocol for atomic Li, to make our proposal concrete.

[Blood management in geriatric hospitalized population]. / Épargne transfusionnelle dans la population âgée hospitalisée.

INTRODUCTION: In France, nearly 50% of patients transfused in packed red blood cells are 75 or older. The benefit of restrictive transfusion policies is no longer to be demonstrated, but the practices are still far from it. The objective of our study was to show the impact of a decision support tool on transfusion practices, specifically in a hospitalized elderly population. METHOD: A clinical decision support, validated in the improvement of practices, was created, based on the latest transfusion recommendations of 2014. Our study was interventional, monocentric, within the departments of internal medicine and geriatrics of a university hospital from February to July 2016. The clinical decision support was available for any request of transfusion of packed red blood cells for 75 years old or older patient who was hospitalized in one of these two services. RESULTS: There were 134 transfusions out of 173 for which the prescriber used our tool. Comparing 2016 with the previous two years, our tool decreased the rate of packed red blood cells delivered by 11% compared to 2014 (P<0.005), but there was no significant difference compared to 2015. It has also reduced the transfusion rate of multi-unit transfusions by 35% compared with 2014 and by 29% compared with 2015 (P<0.005). CONCLUSION: Our tool, applied specifically to the elderly, is useful to improve transfusion practices and requires to be validated on a larger scale.

Photoionization in the time and frequency domain.

Ultrafast processes in matter, such as the electron emission after light absorption, can now be studied using ultrashort light pulses of attosecond duration (10-18 seconds) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses has raised issues in the interpretation of the experimental results and the comparison with theoretical calculations. We determine photoionization time delays in neon atoms over a 40-electron volt energy range with an interferometric technique combining high temporal and spectral resolution. We spectrally disentangle direct ionization from ionization with shake-up, in which a second electron is left in an excited state, and obtain excellent agreement with theoretical calculations, thereby solving a puzzle raised by 7-year-old measurements.

Spectral phase measurement of a Fano resonance using tunable attosecond pulses.

Electron dynamics induced by resonant absorption of light is of fundamental importance in nature and has been the subject of countless studies in many scientific areas. Above the ionization threshold of atomic or molecular systems, the presence of discrete states leads to autoionization, which is an interference between two quantum paths: direct ionization and excitation of the discrete state coupled to the continuum. Traditionally studied with synchrotron radiation, the probability for autoionization exhibits a universal Fano intensity profile as a function of excitation energy. However, without additional phase information, the full temporal dynamics cannot be recovered. Here we use tunable attosecond pulses combined with weak infrared radiation in an interferometric setup to measure not only the intensity but also the phase variation of the photoionization amplitude across an autoionization resonance in argon. The phase variation can be used as a fingerprint of the interactions between the discrete state and the ionization continua, indicating a new route towards monitoring electron correlations in time.

[Radiation therapy for elderly patients]. / Quelles sont les spécificités de la prise en charge d'une personne âgée en radiothérapie ?

Cancer is a disease that predominantly occurs in older patients who represent a quarter of the population in western countries. Numerous types of cancer are observed in elderly people. Radiotherapy is one of the most powerful treatments against cancer. Most of published studies have demonstrated feasibility of radiotherapy in curative or palliative intent whatever cancer types are considered. Complete geriatric assessment and a multidisciplinary approach are the key points. The purpose of this review is to highlight sights of radiation oncology specifically related to aging. Particular emphasis is placed on logistic and technical aspects of radiation, as dose, irradiated volume, fractionation and the potential usefulness of new technologies.

Attosecond pulse walk-off in high-order harmonic generation.

We study the influence of the generation conditions on the group delay of attosecond pulses in high-order harmonic generation in gases. The group delay relative to the fundamental field is found to decrease with increasing gas pressure in the generation cell, reflecting a temporal walk-off due to the dispersive properties of the nonlinear medium. This effect is well reproduced using an on-axis phase-matching model of high-order harmonic generation in an absorbing gas.

[Lung cancer in the elderly: what about surgery?]. / Cancer du poumon en oncogériatrie : quelles possibilités chirurgicales dans le grand âge ?

Geriatric oncology is a rapidly expanding domain because of the deep epidemiological changes of the last decades related to the ageing of the population. Lung cancer treatment in patients 75 years and over is a major issue of thoracic oncology. Curative surgery remains the treatment offering the best survival rates to the patient whatever his age. The important variability observed within the elderly forces us to take into account their specificities, in particular for ageing physiology and associated comorbidities. Thus, preoperative workup permitting to assess the resectability of the tumor but also the operability of the patient is all the more essential in the advanced age that it must be adapted to the particular characteristics of the elderly. Thanks to recent data of the literature, morbidity and mortality associated to surgical treatment are now better characterized and considered as acceptable in accordance with long-term survival. Clinical investigation remains essential to acquire a better knowledge of potential benefit of multimodal treatments in the elderly, for which very few data are available.

Probing time-dependent molecular dipoles on the attosecond time scale.

Photoinduced molecular processes start with the interaction of the instantaneous electric field of the incident light with the electronic degrees of freedom. This early attosecond electronic motion impacts the fate of the photoinduced reactions. We report the first observation of attosecond time scale electron dynamics in a series of small- and medium-sized neutral molecules (N(2), CO(2), and C(2)H(4)), monitoring time-dependent variations of the parent molecular ion yield in the ionization by an attosecond pulse, and thereby probing the time-dependent dipole induced by a moderately strong near-infrared laser field. This approach can be generalized to other molecular species and may be regarded as a first example of molecular attosecond Stark spectroscopy.

Development and characterization of a multiple-coincidence ion-momentum imaging spectrometer.

The design and performance of a high-resolution momentum-imaging spectrometer for ions which is optimized for experiments using synchrotron radiation is presented. High collection efficiency is achieved by a focusing electrostatic lens; a long drift tube improves mass resolution and a position-sensitive detector enables measurement of the transverse momentum of ions. The optimisation of the lens for particle momentum measurement at the highest resolution is described. We discuss the overall performance of the spectrometer and present examples demonstrating the momentum resolution for both kinetics and for angular measurements in molecular fragmentation for carbon monoxide and fullerenes. Examples are presented that confirm that complete space-time focussing is possible for a two-field three-dimensional imaging spectrometer.

Role of the Renner-Teller effect after core hole excitation in the dissociation dynamics of carbon dioxide dication.

The fragmentation of the doubly-charged carbon dioxide molecule is studied after photoexcitation to the C 1s(1)2π(u) and O 1s(1)2π(u) states using a multicoincidence ion-imaging technique. The bent component of the Renner-Teller split states populated in the 1s→ π* resonant excitation at both the carbon and oxygen 1s ionization edges opens pathways to potential surfaces in highly bent geometries in the dication. Evidence for a complete deformation of the molecule is found in the coincident detection of C(+) and O(2)(+) ions. The distinct alignment of this fragmentation channel indicates rapid deformation and subsequent fragmentation. Investigation of the complete atomization dynamics in the dication leading to asymmetric charge separation shows that the primary dissociation mechanisms, sequential, concerted, and asynchronous concerted, are correlated to specific fragment kinetic energies. The study shows that the bond angle in fragmentation can extend below 20°.

Probing single-photon ionization on the attosecond time scale.

We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the 3s(2) and from the 3p(6) shell, at different excitation energies ranging from 32 to 42 eV. The determination of photoemission time delays requires taking into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using a universal formula and is found to account for a substantial fraction of the measured delay.

What the specific tools of geriatrics and oncology can tell us about the role and status of geriatricians in a pilot geriatric oncology program.

BACKGROUND: Pilot Oncogeriatric Coordination Units (UPCOGs) were created by the French National Cancer Institute (INCA) in order to implement routine geriatric assessment of all cancer patients over 75 years of age. This article examines the role of geriatric and oncologic tools in the organization of medical oncogeriatric activities, focusing on the role and place of geriatricians. METHODS: We conducted a qualitative sociological survey in the West Paris Oncogeriatric Program (POGOP), one of the Pilot Oncogeriatric Coordination Units (UPCOGs) recently created in France. Various qualitative methods were used including a review of the literature, participative observational surveys, and semidirective interviews with medical staff managing elderly cancer patients. RESULTS: The results show that the way in which geriatric assessment procedures are implemented confirms the role of the geriatrician in the diagnosis and prevention of vulnerabilities and fragility at the time of initial diagnosis and medical decision making. Nevertheless, the articulation of these different working methods gives rise to various organizational configurations. CONCLUSIONS: The POGOP has largely contributed to clarifying medical activity in oncogeriatrics: identification of physicians, definition of shared goals, initiation, and structuring of new partnerships. Nevertheless, the geriatrician's tools, expertise, and know-how are often perceived ambiguously.

Nuclear motion in carbonyl sulfide induced by resonant core electron excitation.

The angular anisotropy for selected dissociation channels is measured at resonantly excited states of Σ and Π symmetries at the C and O K-shell ionization edges of carbonyl sulfide. While the kinetic energy released in the reaction is mainly independent of the excitation energy, the angular anisotropy and momentum correlation clearly show deformation of the OCS molecule in the C 1s(-1)π(∗1) state. The discovery of a two-body fragmentation channel SO(+)/C(+) with a well defined angular anisotropy indicates the rapid formation of the CSO isomeric species.

Phase measurement of resonant two-photon ionization in helium.

We study resonant two-color two-photon ionization of helium via the 1s3p (1)P(1) state. The first color is the 15th harmonic of a tunable Ti:sapphire laser, while the second color is the fundamental laser radiation. Our method uses phase-locked high-order harmonics to determine the phase of the two-photon process by interferometry. The measurement of the two-photon ionization phase variation as a function of detuning from the resonance and intensity of the dressing field allows us to determine the intensity dependence of the transition energy.

[Radiation therapy in elderly patients]. / Radiothérapie et sujet âgé

Cancer is a disease that predominantly occurs in older patients who represent a quarter of the population in western countries. Numerous types of cancer are observed in elderly people. Radiotherapy is one of the most powerful treatment against cancer. Most of published studies have demonstrated feasibility of radiotherapy in curative or palliative intent whatever cancer types are considered. Complete geriatric assessment and a multidisciplinary approach are the key points. The purpose of this review is to highlight sights of radiation oncology specifically related to aging. Particular emphasis is placed on logistic and technical aspects of radiation, as dose, irradiated volume and fractionation.

Dynamics of proton migration and dissociation in core-excited ethyne probed by multiple ion momentum imaging.

The study focuses on the rapid geometry change in ethyne excited near the carbon 1s edge. Core excitation and ionization lead to population of dicationic states in ethyne. We study three competing dissociation pathways associated with deprotonation in the linear ethyne molecule, and two cases of rapid proton migration. We investigate the alignment of the molecule in the excited state and find startling differences in these three cases. We present evidence for a strong anisotropy in the production of H(2)(+)/C(2)(+) fragments through a rapid deformation of the molecule to a dibridged conformation with the transition dipole moment parallel to the polarization of the exciting radiation.

Physical interpretation of the "kinetic energy release" effect in the double photoionization of H(2).

A physical interpretation is given for the variation with internuclear separation of the fully differential cross section for double photoionization of H2. This effect is analyzed in a geometry where the fourbody interaction is completely probed. Excellent agreement is found between experiment and time-dependent close-coupling theory after convoluting the latter over the relevant solid angles. We show the observed variations are purely due to the epsilon(Sigma) component of the polarization vector epsilon along the molecular axis, a conclusion which is supported through calculations of the photoionization of H2(+).