Disentangling Spectral Phases of Interfering Autoionizing States from Attosecond Interferometric Measurements.

We have determined spectral phases of Ne autoionizing states from extreme ultraviolet and midinfrared attosecond interferometric measurements and ab initio full-electron time-dependent theoretical calculations in an energy interval where several of these states are coherently populated. The retrieved phases exhibit a complex behavior as a function of photon energy, which is the consequence of the interference between paths involving various resonances. In spite of this complexity, we show that phases for individual resonances can still be obtained from experiment by using an extension of the Fano model of atomic resonances. As simultaneous excitation of several resonances is a common scenario in many-electron systems, the present work paves the way to reconstruct electron wave packets coherently generated by attosecond pulses in systems larger than helium.

Abdomen agudo secundario a torsión de bazo ectópico como causa inusual de dolor abdominal en urgencias / Acute Abdomen After Ectopic Spleen Torsion as an Unusual Cause of Abdominal Pain in the Emergency Department

RESUMEN El bazo ectópico es una enfermedad infrecuente, que se caracteriza por el aumento de la movilidad del bazo debido a la ausencia o laxitud de sus ligamentos suspensorios, lo que puede dar lugar a una torsión de su pedículo, y provocar un abdomen agudo. Se presenta el caso de una mujer de 29 años que acude al servicio de urgencias por presentar dolor abdominal de 7 meses de evolución, localizado en fosa ilíaca izquierda, que ha empeorado en las últimas 48 horas. Se realizó ecografía en el servicio de urgencias (point-of-care) que mostró una imagen compatible con bazo ectópico junto a su hilio, localizado en tercio inferior del abdomen cerca de la vejiga y del útero, y líquido libre. La tomografía axial computarizada confirmó el diagnóstico de torsión del pedículo. Se realizó laparotomía de urgencia y se localizó el bazo dentro de la pelvis con torsión del pedículo; ante un bazo no viable se realizó esplenectomía. La histología demostró cambios trombóticos difusos con infartos isquémicos y hemorrágicos del bazo. A pesar de su baja prevalencia, el bazo ectópico se debe tener en cuenta a la hora de realizar el diagnóstico diferencial en aquellas mujeres en edad fértil que consultan por dolor abdominal o masa pélvica(AU)

ABSTRACT Ectopic spleen is a rare disease, characterized by increased mobility of the spleen due to the absence or laxity of its suspensory ligaments, which can lead to torsion of its pedicle and cause acute abdomen. We present the case of a 29-year-old woman who attends the emergency department with abdominal pain of seven months of evolution and located in the left iliac fossa, which has worsened in the last 48 hours. An ultrasound was performed in the emergency department (point-of-care), which showed, next to its hilum, an image consistent with ectopic spleen, located in the lower third of the abdomen near the bladder and uterus, and free fluid. Computed axial tomography confirmed the diagnosis of pedicle torsion. Emergency laparotomy was performed and the spleen was located inside the pelvis with torsion of the pedicle. Splenectomy was performed before a non-viable spleen. Histology showed diffuse thrombotic changes with ischemic and hemorrhagic infarcts of the spleen. Despite its low prevalence, the ectopic spleen should be taken into account when making the differential diagnosis in those women at childbearing age who come to the clinic for abdominal pain or pelvic mass(AU)

Anisotropic photoemission time delays close to a Fano resonance.

Electron correlation and multielectron effects are fundamental interactions that govern many physical and chemical processes in atomic, molecular and solid state systems. The process of autoionization, induced by resonant excitation of electrons into discrete states present in the spectral continuum of atomic and molecular targets, is mediated by electron correlation. Here we investigate the attosecond photoemission dynamics in argon in the 20-40 eV spectral range, in the vicinity of the 3s-1np autoionizing resonances. We present measurements of the differential photoionization cross section and extract energy and angle-dependent atomic time delays with an attosecond interferometric method. With the support of a theoretical model, we are able to attribute a large part of the measured time delay anisotropy to the presence of autoionizing resonances, which not only distort the phase of the emitted photoelectron wave packet but also introduce an angular dependence.

Electron Correlation in the Ionization Continuum of Molecules: Photoionization of N2 in the Vicinity of the Hopfield Series of Autoionizing States.

Direct measurement of autoionization lifetimes by using time-resolved experimental techniques is a promising approach when energy-resolved spectroscopic methods do not work. Attosecond time-resolved experiments have recently provided the first quantitative determination of autoionization lifetimes of the lowest members of the well-known Hopfield series of resonances in N2. In this work, we have used the recently developed XCHEM approach to study photoionization of the N2 molecule in the vicinity of these resonances. The XCHEM approach allows us to describe electron correlation in the molecular electronic continuum at a level similar to that provided by multireference configuration interaction methods in bound state calculations, a necessary condition to accurately describe autoionization, shakeup, and interchannel couplings occurring in this range of photon energies. Our results show that electron correlation leading to interchannel mixing is the main factor that determines the magnitude and shape of the N2 photoionization cross sections, as well as the lifetimes of the Hopfield resonances. At variance with recent speculations, nonadiabatic effects do not seem to play a significant role. These conclusions are supported by the very good agreement between the calculated cross sections and those determined in synchrotron radiation and attosecond experiments.

Hybrid-Basis Close-Coupling Interface to Quantum Chemistry Packages for the Treatment of Ionization Problems.

The theoretical description of observables in attosecond pump-probe experiments requires a good representation of the system's ionization continuum. For polyelectronic molecules, however, this is still a challenge, due to the complicated short-range structure of correlated electronic wave functions. Whereas quantum chemistry packages (QCP) implementing sophisticated methods to compute bound electronic molecular states are well-established, comparable tools for the continuum are not widely available yet. To tackle this problem, we have developed a new approach that, by means of a hybrid Gaussian-B-spline basis, interfaces existing QCPs with close-coupling scattering methods. To illustrate the viability of this approach, we report results for the multichannel ionization of the helium atom and of the hydrogen molecule that are in excellent agreement with existing accurate benchmarks. These findings, together with the versatility of QCPs to describe a broad range of chemical systems, indicate that this is a valid approach to study the ionization of polyelectronic systems in which correlation and exchange symmetry play a major role.