Interferometry of quantum revivals.

It has recently been shown that an interferometric approach can be used to obtain Auger lifetimes in molecules in certain point groups. Here, we extend this concept to those molecular states for which Auger decay is energetically forbidden and which exhibit initial quasi-exponential decay followed by quantum revivals. We demonstrate that this allows us to extract the quasi-exponential decay rate and the revival timescale. We solve analytically a model containing a state coupled to the idealized Bixon-Jortner quasicontinuum, and we obtain an interferometric signature of revival, which can be easily generalized to realistic systems. Moreover, we analyze how this revival signature is influenced by the system parameters, and we suggest optimal conditions for its observation. We, therefore, show that our new approach allows population revivals of a molecular state to be detected interferometrically.

[Features of sleependoscopy in children]. / Osobennosti slipendoskopii v detskom vozraste.

OBJECTIVE: To describe the technique and determine the indications for sleep endoscopy in children. MATERIAL AND METHODS: This study included 35 children, the average age of 5 years 1 month ± 3 years 4 months (from 1 year 6 months to 14 years 5 months). All children underwent standard polysomnography and sleep endoscopy. RESULTS: According to polysomnography, severe obstructive sleep apnea (OSA) was diagnosed in 21 children, moderate - in 8 children and mild - in 6 children. Sleep endoscopy revealed that in most cases in unoperated children (about 70%), adenoids and palatine tonsils were the cause of obstruction. In the group of children, who previously underwent surgery for OSA, the causes of residual apnea more often were soft palate and palatine tonsils. In 5 of 8 children, tonsils pharyngoscopy size did not exceed the 1st degree. In 1 child after adenotonsillectomy, the hypertrophic tori tubarii were the cause of obstruction. Another rare cause of upper airway obstruction, lingual tonsil hypertrophy, was found in 2 primary patients. CONCLUSION: Sleep endoscopy is a safe and useful method that makes it possible to determine the level of obstruction in children and to plan the optimal amount of surgical treatment.

Fano-ADC(2,2) method for electronic decay rates.

Fano-ADC is a family of ab initio methods for the prediction of electronic decay widths in excited, singly and doubly ionized systems. It has been particularly successful in elucidating the geometry dependence of the inter-atomic decay widths in clusters and facilitated the prediction of new electronic decay phenomena. However, the available Fano-ADC schemes are limited to the second-order treatment of the initial state and the first-order treatment of the final states of the decay. This confines the applicability of the Fano-ADC approach to first-order decay processes, e.g., normal but not double Auger decay (DAD), and compromises the numerical accuracy of the schemes through the unbalanced treatment of electronic correlation. Here, we introduce the ADC(2,2) approximation for singly ionized states, which describes both initial and final states of the decay up to second order. We use the new scheme to construct the Fano-ADC(2,2) approximation for the decay widths and show that it provides superior accuracy for the decay widths of a series of processes. Moreover, the Fano-ADC(2,2) method provides access to second-order decay processes, such as DAD, which are qualitatively beyond the reach of the previously available Fano-ADC implementations.

Molecular Auger Interferometry.

We introduce and present a theory of interferometric measurement of a normal Auger decay lifetime in molecules. Molecular Auger interferometry is based on the coherent phase control of Auger dynamics in a two-color (ω/2ω) laser field. We show that, in contrast to atoms, in oriented molecules of certain point groups the relative ω/2ω phase modulates the total ionization yield. A simple analytical formula is derived for the extraction of the lifetimes of Auger-active states from a molecular Auger interferogram, circumventing the need in either high-resolution or attosecond spectroscopy. We demonstrate the principle of the interferometric Auger lifetime measurement using inner-valence decay in CH_{3}F.

Full Ab Initio Many-Electron Simulation of Attosecond Molecular Pump-Probe Spectroscopy.

Here, we present an ab initio approach to full simulation of an attosecond molecular pump-probe experiment. Sequential molecular double ionization by the pump and probe laser pulses with controlled delay is described from first-principles with a full account of the continuum dynamics of the photoelectrons. Many-electron bound-continuum dynamics is simulated using the time-dependent (TD) molecular B-spline algebraic diagrammatic construction (ADC) method. Our calculations give a quantitative prediction about the creation of a coherent superposition of molecular ionic states in the photoionization process and simulate the probe of the ensuing attosecond dynamics by a second ionizing pulse within a single first-principles many-electron framework. We therefore demonstrate the capability to simulate and interpret the results of a prototypical molecular pump-probe experiment of interest in attoscience. As a particular example, we simulate and elucidate the interpretation of a pump-probe experiment in CO2 aimed at measuring strong field-induced hole dynamics via photoionization yields.

Multi-channel dynamics in high harmonic generation of aligned CO2: ab initio analysis with time-dependent B-spline algebraic diagrammatic construction.

Here we present a fully ab initio study of the high-order harmonic generation (HHG) spectrum of aligned CO2 molecules. The calculations have been performed by using the molecular time-dependent (TD) B-spline algebraic diagrammatic construction (ADC) method. We quantitatively study how the sub-cycle laser-driven multi-channel dynamics, as reflected in the position of the dynamical minimum in the HHG spectrum, is affected by the full inclusion of both correlation-driven and laser-driven dipole interchannel couplings. We calculate channel-resolved spectral intensities as well as the phase differences between contributions of the different ionization-recombination channels to the total HHG spectrum. Our results show that electron correlation effectively controls the relative contributions of the different channels to the total HHG spectrum, leading to the opening of the new ones (12Πu, 12Σ), previously disregarded for the aligned molecular setup. We conclude that inclusion of many-electron effects into the theoretical interpretation of molecular HHG spectra is essential in order to correctly extract ultrafast electron dynamics using HHG spectroscopy.

[The possibility of using tranexamic acid for the treatment of bleeding in otorhinolaryngology].

This article is focused on the analysis of the literature publications pertaining to the problem of bleeding in otorhinolaryngology. It reports the epidemiological data on the structure of bleeding and the main methods used to arrest it. Special attention is given to the possibilities of application of tranexamic acid as an effective hemostatic agent not only for systemic but also for topical administration.

[The silent sinus syndrome in the patients presenting with the uncinate process apposed to the orbital wall].

The objective of the present study was to analyze the frequency of the silent sinus syndrome (SSS) based on the results of computed tomography of the paranasal sinuses (PNS) in the patients presenting with the uncinate process (UP) apposed to the orbital wall. The study included 35 patients with the uncinate process apposed to the orbital wall who had been operated in the Clinic of ENT Diseases of I.M. Sechenov First Moscow State Medical University. The examination of the nasal cavity with the use of computed tomography and PNS endoscopy revealed the silent sinus syndrome in 14 patients. Ten of them had endoscopically confirmed type 2 hypoplasia of maxillary sinuses (MS). This finding suggests the necessity of computed tomography of paranasal sinuses in the patients with this condition in order to exclude the diagnosis of silent sinus syndrome even in the absence of exophthalmos. All the patients included in the present study underwent endoscopic surgery on maxillary sinuses that resulted in the adequate widening of the ostium and comprehensive sanation of the sinuses.

B-spline algebraic diagrammatic construction: application to photoionization cross-sections and high-order harmonic generation.

We present the first implementation of the ab initio many-body Green's function method, algebraic diagrammatic construction (ADC), in the B-spline single-electron basis. B-spline versions of the first order [ADC(1)] and second order [ADC(2)] schemes for the polarization propagator are developed and applied to the ab initio calculation of static (photoionization cross-sections) and dynamic (high-order harmonic generation spectra) quantities. We show that the cross-section features that pose a challenge for the Gaussian basis calculations, such as Cooper minima and high-energy tails, are found to be reproduced by the B-spline ADC in a very good agreement with the experiment. We also present the first dynamic B-spline ADC results, showing that the effect of the Cooper minimum on the high-order harmonic generation spectrum of Ar is correctly predicted by the time-dependent ADC calculation in the B-spline basis. The present development paves the way for the application of the B-spline ADC to both energy- and time-resolved theoretical studies of many-electron phenomena in atoms, molecules, and clusters.

Total photoionization cross-sections of excited electronic states by the algebraic diagrammatic construction-Stieltjes-Lanczos method.

Here, we extend the L2 ab initio method for molecular photoionization cross-sections introduced in Gokhberg et al. [J. Chem. Phys. 130, 064104 (2009)] and benchmarked in Ruberti et al. [J. Chem. Phys. 139, 144107 (2013)] to the calculation of total photoionization cross-sections of molecules in electronically excited states. The method is based on the ab initio description of molecular electronic states within the many-electron Green's function approach, known as algebraic diagrammatic construction (ADC), and on the application of Stieltjes-Chebyshev moment theory to Lanczos pseudospectra of the ADC electronic Hamiltonian. The intermediate state representation of the dipole operator in the ADC basis is used to compute the transition moments between the excited states of the molecule. We compare the results obtained using different levels of the many-body theory, i.e., ADC(1), ADC(2), and ADC(2)x for the first two excited states of CO, N2, and H2O both at the ground state and the excited state equilibrium or saddle point geometries. We find that the single excitation ADC(1) method is not adequate even at the qualitative level and that the inclusion of double electronic excitations for description of excited state photoionization is essential. Moreover, we show that the use of the extended ADC(2)x method leads to a substantial systematic difference from the strictly second-order ADC(2). Our calculations demonstrate that a theoretical modelling of photoionization of excited states requires an intrinsically double excitation theory with respect to the ground state and cannot be achieved by the standard single excitation methods with the ground state as a reference.

Total molecular photoionization cross-sections by algebraic diagrammatic construction-Stieltjes-Lanczos method: benchmark calculations.

In [K. Gokhberg, V. Vysotskiy, L. S. Cederbaum, L. Storchi, F. Tarantelli, and V. Averbukh, J. Chem. Phys. 130, 064104 (2009)] we introduced a new L(2) ab initio method for the calculation of total molecular photoionization cross-sections. The method is based on the ab initio description of discretized photoionized molecular states within the many-electron Green's function approach, known as algebraic diagrammatic construction (ADC), and on the application of Stieltjes-Chebyshev moment theory to Lanczos pseudospectra of the ADC electronic Hamiltonian. Here we establish the accuracy of the new technique by comparing the ADC-Lanczos-Stieltjes cross-sections in the valence ionization region to the experimental ones for a series of eight molecules of first row elements: HF, NH3, H2O, CO2, H2CO, CH4, C2H2, and C2H4. We find that the use of the second-order ADC technique [ADC(2)] that includes double electronic excitations leads to a substantial systematic improvement over the first-order method [ADC(1)] and to a good agreement with experiment for photon energies below 80 eV. The use of extended second-order ADC theory [ADC(2)x] leads to a smaller further improvement. Above 80 eV photon energy all three methods lead to significant deviations from the experimental values which we attribute to the use of Gaussian single-electron bases. Our calculations show that the ADC(2)-Lanczos-Stieltjes technique is a reliable and efficient ab initio tool for theoretical prediction of total molecular photo-ionization cross-sections in the valence region.

Time-resolved measurement of interatomic coulombic decay in Ne2.

The lifetime of interatomic Coulombic decay (ICD) [L. S. Cederbaum et al., Phys. Rev. Lett. 79, 4778 (1997)] in Ne2 is determined via an extreme ultraviolet pump-probe experiment at the Free-Electron Laser in Hamburg. The pump pulse creates a 2s inner-shell vacancy in one of the two Ne atoms, whereupon the ionized dimer undergoes ICD resulting in a repulsive Ne+(2p(-1))-Ne+(2p(-1)) state, which is probed with a second pulse, removing a further electron. The yield of coincident Ne+-Ne2+ pairs is recorded as a function of the pump-probe delay, allowing us to deduce the ICD lifetime of the Ne2(+)(2s(-1)) state to be (150±50) fs, in agreement with quantum calculations.

Ab initio interatomic decay widths of excited states by applying Stieltjes imaging to Lanczos pseudospectra.

Electronically excited states of atoms and molecules in an environment may decay in interatomic processes by transferring excess energy to neighboring species and ionizing them. The corresponding interatomic decay width is the most important characteristic of the decay allowing to calculate its efficiency and the final states' distribution. In this paper we present calculations of interatomic widths by the Fano-Stieltjes method applied to Lanczos pseudospectra, which has been previously shown to provide accurate autoionization widths in atoms and molecules. The use of Lanczos pseudospectra allows one to avoid the full diagonalization bottleneck and makes the method applicable to larger systems. We apply the present method to the calculation of interatomic decay widths in NeMg, NeAr and HCN[middle dot]Mg(n), n = 1, 2 clusters. The results are compared with widths obtained analytically and by other ab initio methods where available.

Autoionization widths by Stieltjes imaging applied to Lanczos pseudospectra.

Excited states of atoms and molecules lying above the ionization threshold can decay by electron emission in a process commonly known as autoionization. The autoionization widths can be calculated conveniently using Fano formalism and discretized atomic and molecular spectra by a standard procedure referred to as Stieltjes imaging. The Stieltjes imaging procedure requires the use of the full discretized spectrum of the final states of the autoionization, making its use for poly-atomic systems described by high-quality basis sets impractical. Following our previous work on photoionization cross-sections, here we show that also in the case of autoionization widths, the full diagonalization bottleneck can be overcome by the use of Lanczos pseudospectra. We test the proposed method by calculating the well-documented autoionization widths of inner-valence-excited neon and apply the new technique to autoionizing states of hydrofluoric acid and benzene.

Calculation of resonant interatomic Coulombic decay widths of inner-valence-excited states delocalized due to inversion symmetry.

Inner-valence-excited states of clusters can decay by electron emission via several of mechanisms, the leading ones being intra-atomic autoionization and resonant interatomic Coulombic decay. Recently, we have derived the Wigner-Weisskopf theory for the calculation of the decay widths of the inner-valence excitations [J. Chem. Phys. 124, 144315 (2006)]. While the new method has been successful in producing the decay rates of heteronuclear diatomic clusters, it cannot be applied to systems possessing inversion symmetry, e.g., to homonuclear diatoms, due to delocalization of the molecular orbitals involved in the decay processes. In the present work, we show that the Wigner-Weisskopf theory of the decay of inner-valence-excited states can be generalized to systems with inversion symmetry using a technique of adapted final states [J. Chem. Phys. 125, 094107 (2006)]. The same technique can be employed when going beyond the Wigner-Weisskopf theory. We consider the experimentally relevant case of competing resonant interatomic Coulombic decay and autoionization in neon dimer and calculate the rates of these processes for a series of inner-valence-excited states which has been measured by Aoto et al. [Phys. Rev. Lett. 97, 243401 (2006)].

Molecular photoionization cross sections by Stieltjes-Chebyshev moment theory applied to Lanczos pseudospectra.

Stieltjes imaging technique is widely used for the ab initio computation of photoionization cross sections and decay widths. The main problem hampering the application of the standard Stieltjes imaging algorithms in conjunction with high-level ab initio methods to polyatomic molecules is the requirement of full diagonalization of excessively large Hamiltonian matrices. Here we show that the full diagonalization bottleneck can be overcome by applying the Stieltjes imaging procedure to Lanczos pseudospectrum of the atomic or molecular Hamiltonian. Using the helium and neon atoms as examples, we demonstrate that the Lanczos pseudospectrum obtained after only a relatively small number of iterations can be used for Stieltjes-type calculations of photoionization cross sections essentially without loss of accuracy. The new technique is applied to the calculation of the total photoionization cross section of benzene within an ab initio approach explicitly taking into account single and double electronic excitations. Good agreement with experimental results is obtained.

Decay rates of inner-valence excitations in noble gas atoms.

A Fano - algebraic diagrammatic construction - Stieltjes method has been recently developed for ab initio calculations of nonradiative decay rates [V. Averbukh and L. S. Cederbaum, J. Chem. Phys. 123, 204107 (2005)] of singly ionized states. In the present work this method is generalized for the case of electronic decay of excited states. The decay widths of autoionizing inner-valence-excited states of Ne, Ar, and Kr are calculated. Apart from the lowest excitation of Kr, they are found to be in good to excellent agreement with the experimental values. Comparison with the other theoretical studies shows that in many cases the new method performs better than the previously available techniques.

On the interatomic Coulombic decay in the Ne dimer.

The interatomic Coulombic decay (ICD) in the Ne dimer is discussed in view of the recent experimental results. The ICD electron spectrum and the kinetic energy release of the Ne+ fragments resulting after Coulomb explosion of Ne2 (2+) are computed and compared to the measured ones. A very good agreement is found, confirming the dynamics predicted for this decay mechanism. The effect of the temperature on the electron spectrum is briefly investigated.

High harmonic generation of soft X-rays by carbon nanotubes

We extend the method for the formulation of selection rules for high harmonic generation spectra [Phys. Rev. Lett. 80, 3743 (1998)] beyond the dipole approximation and apply it to single-walled carbon nanotubes interacting with a circularly polarized laser field. Our results show that the carbon nanotubes can be excellent systems for a selective generation of high harmonics, up to the soft x-ray regime.