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Fragmentation of gas-phase chloro- and bromoacetic acid samples, particularly its dependency on the atomic site of the initial core ionization, was studied in photoelectron-photoion-photoion coincidence (PEPIPICO) measurements. The fragmentation was investigated after ionizing carbon Is and bromine 3d or chlorine 2p core orbitals. It was observed that the samples had many similar fragmentation pathways and that their relative weights depended strongly on the initial ionization site. Additional Auger PEPIPICO measurements revealed a clear dependence of fragment pair intensities on the kinetic energy of the emitted Auger electrons. The modeled and measured Auger electron spectra indicated that the average internal energy of the molecule was larger following the carbon Is core-hole decay than after the decay of the halogen core hole. This difference in the internal energies was found to be the source of the site-dependent photofragmentation behavior. [ABSTRACT FROM AUTHOR]

The Auger decay processes from the 1s-core-hole state of Ne have been investigated with a multielectron coincidence method. We have observed the double and triple Auger decays, in which both cascade and direct processes are identified from different ways in energy sharing between the Auger electrons. Branching ratios for the different electronic configurations of the Auger final states are determined from the corresponding electron coincidence yields. Particularly for the double Auger decay, the branching ratios are divided into the individual contributions from direct and cascade paths. [ABSTRACT FROM AUTHOR]

A detailed experimental and theoretical investigation of the dynamics leading to fragmentation of doubly ionized molecular thiophene is presented. Dissociation of double-ionized molecules was induced by S 2p core photoionization and the ionic fragments were detected in coincidence with Auger electrons from the core-hole decay. Rich molecular dynamics was observed in electron-ion-ion coincidence maps exhibiting ring breaks accompanied by hydrogen losses and/or migration. The probabilities of various dissociation channels were seen to be very sensitive to the internal energy of the molecule. Theoretical simulations were performed by using the semiempirical self-consistent charge-density-functional tight-binding method. By running thousands of these simulations, the initial conditions encountered in the experiment were properly taken into account, including the systematic dependencies on the internal (thermal) energy. This systematic approach, not affordable with first-principle methods, provides a good overall description of the complex molecular dynamics observed in the experiment and shows good promise for applicability to larger molecules or clusters, thus opening the door to systematic investigations of complex dynamical processes occurring in radiation damage. [ABSTRACT FROM AUTHOR]

We theoretically investigate the effects of strong couplings in resonant Auger processes under the combination of strong resonant x-ray and nearly resonant optical pulses. The x-ray field couples the ground state with a core-excited state, while the optical field couples the core-excited state with another core-excited state of opposite parity. The Auger electron spectrum changes its shape as the intensities of the x-ray and/or optical fields increase, and at sufficiently high intensities we observe that the splitting, which is induced by the optical field, is superposed on the asymmetric splitting induced by the x-ray field in the Auger electron spectra. The asymmetric splitting itself, which is induced by the strong x-ray pulse, is persistent but modified due to the presence of the strong optical field. Moreover, through the systematic study by including or excluding the individual photoionization processes from the core-excited states and the direct photoionizaton process from the ground state, we clarify the contribution of the respective processes to the total electron yield and the Auger electron spectra. These results show that we can manipulate the resonant Auger processes through the introduction of the second core-excited state and the strong optical field. [ABSTRACT FROM AUTHOR]

We examine the archetype of an interference experiment for Auger electrons: two electron wave packets are launched by inner-shell ionizing a krypton atom using two attosecond light pulses with a variable time delay. This setting is an attosecond realization of the Ramsey method of separated oscillatory fields. Interference of the two ejected Auger-electron wave packets is predicted, indicating that the coherence between the two pulses is passed to the Auger electrons. For the detection of the interference pattern an accurate coincidence measurement of photo- and Auger electrons is necessary. The method allows one to control inner-shell electron dynamics on an attosecond timescale and represents a sensitive indicator for decoherence. [ABSTRACT FROM AUTHOR]

A four-body semiclassical model is developed to describe interferences observed in the angular distribution of Auger electrons emitted after double capture in 30-keV He2+ + H2 collisions. The present model is based on both the corpuscular and wave behaviors of the emitted electron. The corpuscular aspect is used to determine the trajectories of the collision partners, while the wave behavior occurs only in the determination of the phase shift. The results of the calculation are found to reproduce the experiment remarkably well. Series of maxima and minima are found in the angular distribution, with periods that are close to the experimental values. In addition, at a fixed angle, oscillations in the energy distribution are clearly evidenced in both the experiment and calculation. [ABSTRACT FROM AUTHOR]

Abstract: Numerical values of the Chandrasekhar function are needed with high accuracy in evaluations of theoretical models describing electron transport in condensed matter. An algorithm for such calculations should be possibly fast and also accurate, e.g. an accuracy of 10 decimal digits is needed for some applications. Two of the integral representations of the Chandrasekhar function are prospective for constructing such an algorithm, but suitable transformations are needed to obtain a rapidly converging quadrature. A mixed algorithm is proposed in which the Chandrasekhar function is calculated from two algorithms, depending on the value of one of the arguments. Program summary: Program title: CHANDRAS Catalogue identifier: AEMC_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMC_v1_0.html Program obtainable from: CPC Program Library, Queenʼs University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 567 No. of bytes in distributed program, including test data, etc.: 4444 Distribution format: tar.gz Programming language: Fortran 90 Computer: Any computer with a FORTRAN 90 compiler Operating system: Linux, Windows 7, Windows XP RAM: 0.6 Mb Classification: 2.4, 7.2 Nature of problem: An attempt has been made to develop a subroutine that calculates the Chandrasekhar function with high accuracy, of at least 10 decimal places. Simultaneously, this subroutine should be very fast. Both requirements stem from the theory of electron transport in condensed matter. Solution method: Two algorithms were developed, each based on a different integral representation of the Chandrasekhar function. The final algorithm is edited by mixing these two algorithms and by selecting ranges of the argument ω in which performance is the fastest. Restrictions: Two input parameters for the Chandrasekhar function, x and ω (notation used in the code), are restricted to the range: and , which is sufficient in numerous applications. Unusual features: The program uses the Romberg quadrature for integration. This quadrature is applicable to integrands that satisfy several requirements (the integrand does not vary rapidly and does not change sign in the integration interval; furthermore, the integrand is finite at the endpoints). Consequently, the analyzed integrands were transformed so that these requirements were satisfied. In effect, one can conveniently control the accuracy of integration. Although the desired fractional accuracy was set at , the obtained accuracy of the Chandrasekhar function was much higher, typically 13 decimal places. Running time: Between 0.7 and 5 milliseconds for one pair of arguments of the Chandrasekhar function. [Copyright &y& Elsevier]

Modern x-ray sources enable the production of coherent x-ray pulses with a pulse duration in the same order as the characteristic lifetimes of core-hole states of atoms and molecules. These pulses enable the manipulation of the core-hole population during Auger-decay processes, modifying the line shape of the electron spectra. In this work, we present a theoretical model to study those effects in neon. We identify effects in the Auger-electron-photoelectron coincidence spectrum due to the duration and intensity of the pulses. The normal Auger line shape is recovered in Auger-electron spectra integrated over all photoelectron energies. [ABSTRACT FROM AUTHOR]