Attosecond transient absorption spectroscopy of helium above the N=2 ionization threshold

Attosecond transient absorption spectroscopy (ATAS) allows for the study of electron dynamics in atoms and molecules with attosecond time resolution. Previous works reported in the literature have made use of ATAS to image and control such dynamics in the single-channel ionization continuum of helium; in particular, in the vicinity of the doubly excited autoionizing states lying between the N=1 and N=2 thresholds. In this work, we have extended these studies to autoionizing states lying above the N=2 threshold, where several ionization channels are open. From an accurate solution of the time-dependent Schrödinger equation, we predict the appearance of pronounced one-photon beatings between the 3snp states and the adjacent 1Se and 1De resonances, as well as, more surprisingly, two-photon beatings between the 3s3p doubly excited state and the 1Po nonresonant continuum. Both effects lead to a significant distortion of the 3snp Fano profiles and to a strong variation of these profiles with the pump-probe delay, thus demonstrating control of the corresponding multichannel two-electron correlated wave packets, in the same way as reported for resonances lying below the N=2 thresholdWe would like to acknowledge allocation of computer time at Mare Nostrum BSC and CCC-UAM. This work was supported by the European Research Council Advanced Grant No. XCHEM 290853, the MINECO Projects No. FIS2013-42002-R and No. FIS2016-77889-R, the European COST Action XLIC CM1204, and the CAM project NANOFRONTMAG. L.A. acknowledges support from the TAMOP NSF Grant No. 1607588, as well as UCF funding

Attosecond Transient Absorption Spectroscopy Of Helium Above The N=2 Ionization Threshold

Attosecond transient absorption spectroscopy (ATAS) allows for the study of electron dynamics in atoms and molecules with attosecond time resolution. Previous works reported in the literature have made use of ATAS to image and control such dynamics in the single-channel ionization continuum of helium; in particular, in the vicinity of the doubly excited autoionizing states lying between the N=1 and N=2 thresholds. In this work, we have extended these studies to autoionizing states lying above the N=2 threshold, where several ionization channels are open. From an accurate solution of the time-dependent Schrödinger equation, we predict the appearance of pronounced one-photon beatings between the 3snp states and the adjacent 1Se and 1De resonances, as well as, more surprisingly, two-photon beatings between the 3s3p doubly excited state and the 1Po nonresonant continuum. Both effects lead to a significant distortion of the 3snp Fano profiles and to a strong variation of these profiles with the pump-probe delay, thus demonstrating control of the corresponding multichannel two-electron correlated wave packets, in the same way as reported for resonances lying below the N=2 threshold

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 -1 np 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

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

The clinical role of glutamine supplementation in patients with multiple trauma: a narrative review

Glutamine is considered an essential amino acid during stress and critical illness. Parenteral glutamine supplementation in critically ill patients has been shown to improve survival rate and minimise infectious complications, costs and hospital length-of-stay. However, glutamine supplementation in patients receiving enteral nutrition and the best method of administration are still controversial. The purpose of this article is to provide a narrative review of the current evidence and trials of enteral and parenteral glutamine supplementation in multiple trauma patients. A search in PubMed and EMBASE was conducted and relevant papers that investigated the effect of enteral or parenteral glutamine supplementation in patients with multiple trauma were reviewed. Although recent nutritional guidelines recommend that glutamine supplementation should be considered in these patients, further well-designed trials are required to provide a confirmed conclusion. Due to the inconclusive results of enteral glutamine supplementation trials in patients receiving enteral nutrition, future trials should focus on intravenous glutamine supplementation in patients requiring enteral nutrition and on major clinical outcome measures (e.g. mortality rate, infectious complications)