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We study the decay of a helium/neon dimer after ionization and simultaneous excitation of either the neon or the helium atom using Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS). We find that, depending on the decaying state, either direct Interatomic Coulombic Decay (ICD) (i.e. mediated by a virtual photon exchange), exchange ICD (mediated by electron exchange) or radiative charge transfer occurs. The corresponding channels are identified.

Summary Background Sporicidal surface disinfection is recommended to control transmission of Clostridium difficile in healthcare facilities. EN 17126 provides a method to determine the sporicidal activity in suspension and has been approved as a European standard. In addition, a sporicidal surface test has been proposed. Aim To determine the interlaboratory reproducibility of a test method for evaluating the susceptibility of a C. difficile spore preparation to a biocidal formulation following the 4-field test (EN 16615 methodology). Methods Nine laboratories participated. C. difficile NCTC 13366 spores were used. Glutaraldehyde (1% and 6%; 15 min) and peracetic acid (PAA; 0.01% and 0.04%; 15 min) were used to determine the spores' susceptibility in suspension in triplicate. Findings One-percent glutaraldehyde revealed a mean decimal log10 reduction of 1.03 with variable results in the nine laboratories (0.37–1.49) and a reproducibility of 0.38. The effect of 6% glutaraldehyde was stronger (mean: 2.05; range: 0.96–4.29; reproducibility: 0.86). PAA revealed similar results. An exemplary biocidal formulation based on 5% PAA was used at 0.5% (non-effective concentration) and 4% (effective concentration) to determine the sporicidal efficacy (4-field test) under clean conditions in triplicate with a contact time of 15 min. When used at 0.5% it demonstrated an overall log10 reduction of 2.68 (range: 2.35–3.57) and at 4% of 4.61 (range: 3.82–5.71). The residual contamination on the three primarily uncontaminated test fields was Conclusion The interlaboratory reproducibility seems to be robust.

Laser-driven electron recollision is at the heart of the rapidly growing field of attosecond science. The recollision wavepacket is qualitatively described within the strong-field approximation, which commonly assumes tunnelling ionization and plane-wave propagation of the liberated electron in the continuum. However, with increasing experimental sophistication, refinements to this simple model have become necessary. Through careful modelling and measurements of laser-induced recollision holography using aligned N 2 molecules, we demonstrate that the continuum electron wavepacket already carries a non-trivial spatial phase structure immediately following ionization. This effect is of rather general character: any molecule and any non-isotropic system that is ionized by a strong laser field will exhibit an offset in the phase of the continuum electron wavepacket. Specifically, this has important implications for any coherent scattering process in molecules, such as high-harmonic generation or laser-induced electron holography.

Figure S1. Quality control of [68Ga]DOTAZOL by means of cross checked radio-HPLC and radio-TLC, as a representative of 68Ga-labelled bisphosphonates. A: After 15 min reaction time. B: After SPE purification. A(HPLC): Rt([68Ga]DOTAZOL) = 0.6 min. (88 %), Rt([68Ga]DFO) = 4.1 min. (12 %). B(HPLC): Rt([68Ga]DOTAZOL) = 0.6 min. (98 %). A(TLC): Rf([68Ga]DOTAZOL) = 0.1 (85 %), Rf([68Ga]acetylacetonate) = 0.9 (15 %). B(TLC): Rf([68Ga]DOTAZOL) = 0.1 (99 %). Control(TLC): Rf([68Ga] acetylacetonate) = 0.9 (99 %). Figure S2. Radio-HPLC of [177Lu]DOTAZOL on a Zorbax 300SB-C18 9,4 × 250 mm 5 μ, A = 100 mM TEAP pH = 2,24, isocratic flow: 1 ml/min. Figure S3. Radio-HPLC of urine and blood samples after administration of [177Lu]DOTAZOL. The HPLC method used for analysing the Lu-177 complexes is also suitable for the Ga-68 complexes of DOTA-Bisphosphonates. The Ga-68 complexes showed a different retention time based on the different character of the DOTA complex. This is also known for other DOTA-Compounds like DOTATOC or DOTATATE. Figure S4. Radio-HPLC of [68Ga]DOTAZOL on a Zorbax 300SB-C18 9,4 × 250 mm 5 μ, A = 100 mM TEAP pH = 2,24, isocratic flow: 1 ml/min. (DOCX 742 kb)

Analysis of the electrons ionized from water dimers suggests that the energy absorbed by one molecule is rapidly transmitted to the second molecule from which the electron is ejected. This process, referred to as intermolecular Coulombic decay, is a qualitatively different source of low-energy electrons to conventional direct ionization processes. At the transition from the gas to the liquid phase of water, a wealth of new phenomena emerge, which are absent for isolated H2O molecules. Many of those are important for the existence of life, for astrophysics and atmospheric science. In particular, the response to electronic excitation changes completely as more degrees of freedom become available. Here we report the direct observation of an ultrafast transfer of energy across the hydrogen bridge in (H2O)2 (a so-called water dimer). This intermolecular coulombic decay leads to an ejection of a low-energy electron from the molecular neighbour of the initially excited molecule. We observe that this decay is faster than the proton transfer that is usually a prominent pathway in the case of electronic excitation of small water clusters and leads to dissociation of the water dimer into two H2O+ ions. As electrons of low energy (∼0.7–20 eV) have recently been found to efficiently break-up DNA constituents1,2, the observed decay channel might contribute as a source of electrons that can cause radiation damage in biological matter.

We present an experimental investigation into the angular and energy distributions of electrons set free by the interaction of hydrogen molecular ions with strong laser fields. The results extend on those presented previously [M. Odenweller et al., Phys. Rev. Lett. 107, 143004 (2011)] for circularly polarized light. Pulses of laser light ($\ensuremath{\lambda}=780$ nm, $I\ensuremath{\approx}6\ifmmode\times\else\texttimes\fi{}{10}^{14}$ W cm${}^{\ensuremath{-}2}$, $\ensuremath{\tau}\ensuremath{\approx}40$ fs) of both linear and circular polarization are focused onto an H${}_{2}$${}^{+}$ molecular ion beam. The momenta of the proton and electron fragments are determined in a coincidence experiment, enabling electron momentum emission patterns in the molecular frame to be deduced for specific values of internuclear distances.

Electron correlation is one of the main frontiers of modern science and of fundamental importance to such diverse fields as, e.g., many body systems, superconductivity and quantum computing. At the ultrafast laser frontier electron correlation has found prominence in the dramatic enhancement of multiple ionization and high harmonic generation. The underlying mechanism, called recollision, forms the foundation of attosecond science. However, above a certain threshold intensity the laser field-electron coupling dominates electron correlation and recollision is no longer important. Hence, electron correlation was assumed to be restricted to lower laser intensities. Only recently experimental evidence has corroborated the notion that the creation of a continuum electron wave packet by laser pulses often entails a correlated electronic hole wave packet in the ion in particular at those higher laser intensities., 2012 IEEE Photonics Conference (IPC), 2012-09-23 - 2012-09-27, Burlingame, CA, USA

We measure the angular distribution of an electron emitted by a strong elliptically polarized two-color laser field from exploding doubly charged molecular nitrogen. This angular distribution is vastly different for emission of the electron from the up-field core of the molecule as compared to that from the down-field core. The emission from the down-field core leads to a slight rotation with respect to the internuclear axis in the direction expected by the Coulomb effect of the remaining ion, while, for the emission from the up-field core, this direction is inversed. Our semiclassical simulations suggest that this unexpected angular distribution is caused by an initial longitudinal momentum of the electron freed by over-the-barrier ionization above the inner barrier in the molecule. The initial kinetic energy is in the range of the potential energy of the Stark-shifted orbital above the barrier.

Radiation damage to living tissue stems not only from primary ionizing particles but to a substantial fraction from the dissociative attachment of secondary electrons with energies below the ionization threshold. We show that the emission yield of those low energy electrons increases dramatically in ion–atom collisions depending on whether or not the target atoms are isolated or embedded in an environment. Only when the atom that has been ionized and excited by the primary particle impact is in immediate proximity of another atom is a fragmentation route known as interatomic Coulombic decay (ICD) enabled. This leads to the emission of a low energy electron. Over the past decade ICD was explored in several experiments following photoionization. Most recent results show its observation even in water clusters. Here we show the quantitative role of ICD for the production of low energy electrons by ion impact, thus approaching a scenario closer to that of radiation damage by alpha particles: We choose ion energies on the maximum of the Bragg peak where energy is most efficiently deposited in tissue. We compare the electron production after colliding He + ions on isolated Ne atoms and on Ne dimers (Ne 2 ). In the latter case the Ne atom impacted is surrounded by a most simple environment already opening ICD as a deexcitation channel. As a consequence, we find a dramatically enhanced low energy electron yield. The results suggest that ICD may have a significant influence on cell survival after exposure to ionizing radiation.

We demonstrated that the weak van der Waals–force-bound argon dimer can be nonadiabatically aligned by nonresonant femtosecond laser pulses, showing periodic alignment and anti-alignment revivals after the extinction of the laser pulse. Based on the measured nonadiabatic alignment trace, the rotational constant of the argon dimer ground state is determined to be B0 = 0.05756 ± 0.00004 cm −1 . Noticeable alignment dependence of frustrated tunneling ionization and bond-softening induced dissociation of the argon dimer are observed.

We observe multiply frustrated tunneling ionization-induced dissociation of the argon dimers by intense linearly polarized ultrashort laser pulses. By measuring the kinetic energy release and angular distribution of the Coulomb explosion of up to eightfold ionized argon dimers, we can trace the recapture of up to two electrons to Rydberg states of the highly charged compound at the end of the laser pulse. Upon dissociation of the dimer, the Rydberg electron prefers to localize at the atomic ion with the higher charge state. We probe the electron recapture dynamics by a time-delayed weak pulse.

We doubly ionize H(2)O by single photon absorption at 43 eV leading to H(+) + OH(+). A direct double ionization and a sequential process in which single ionization is followed by rapid dissociation into a proton and an autoionizing OH(*) are identified. The angular distribution of this delayed autoionization electron shows a preferred emission in the direction of the emitted proton. From this diffraction feature we obtain internuclear distances of 700 to 1100 a.u. at which the autoionization of the OH(*) occurs. The experimental findings are in line with calculations of the excited potential energy surfaces and their lifetimes.

We propose a new approach to obtain molecular frame photoelectron angular distributions from molecules ionized by intense laser pulses. With our method we study the angular tunnel ionization probability of H2 at a wavelength of 800 nm over an intensity range of 2-4.5 x 10(14) W/cm2. We find an anisotropy that is stronger than predicted by any existing model. To explain the observed anisotropy and its strong intensity dependence we develop an analytical model in the framework of the strong-field approximation. It expresses molecular ionization as a product of atomic ionization rate and a Fourier transform of the highest occupied molecular orbital filtered by the strong-field ionization process.

Molecular structure is usually determined by measuring the diffraction pattern the molecule impresses on x-rays or electrons. We used a laser field to extract electrons from the molecule itself, accelerate them, and in some cases force them to recollide with and diffract from the parent ion, all within a fraction of a laser period. Here, we show that the momentum distribution of the extracted electron carries the fingerprint of the highest occupied molecular orbital, whereas the elastically scattered electrons reveal the position of the nuclear components of the molecule. Thus, in one comprehensive technology, the photoelectrons give detailed information about the electronic orbital and the position of the nuclei.

We have investigated the correlated momentum distribution of both electrons from nonsequential double ionization of helium in a 800 nm, 4.5×1014W/cm2 laser field. Using very high resolution coincidence techniques, we find a so-far unobserved fingerlike structure in the correlated electron momentum distribution. The structure can be interpreted as a signature of the microscopic dynamics in the recollision process. We identify features corresponding to the binary and recoil lobe in field-free (e,2e) collisions. This interpretation is supported by analyzing ab initio solutions of a fully correlated three-dimensional helium model. © 2007 The American Physical Society.

Using H2+ and D2+, we observe two-surface population dynamics by measuring the kinetic energy of the correlated ions that are created when H2+ (D2+) ionize in short (40-140 fs) and intense (10(14) W/cm2) infrared laser pulses. Experimentally, we find a modulation of the kinetic energy spectrum of the correlated fragments. The spectral progression arises from a hitherto unexpected spatial modulation on the excited state population, revealed by Coulomb explosion. By solving the two-level time-dependent Schrödinger equation, we show that an interference between the net-two-photon and the one-photon transition creates localized electrons which subsequently ionize.

We have investigated the full three-dimensional momentum correlation between the electrons emitted from strong field double ionization of neon when the recollision energy is of the order of the ionization potential. The momentum correlation in the direction perpendicular to the laser field depends on the time difference between the two electrons leaving the ion. Our results are consistent with double ionization proceeding through transient double excited states that field ionize., Photonics North 2004: International Conference on Applications of Photonic Technology, ICAPT, September 26-29, 2004, Ottawa, ON, Canada, Series: Proceedings of SPIE

Eine neue Technik ermoglicht es, in einem einzigen Experiment Informationen uber das hochste besetzte Molekulorbital sowie den Bindungsabstand eines Molekuls zu gewinnen. Damit sind Physiker der J.W. Goethe-Universitat Frankfurt in Zusammenarbeit mit Kollegen am National Research Council of Canada dem Ziel naher gekommen, in Echtzeit zu beobachten, wie sich sowohl das atomare Gerust als auch die Elektronenwolke eines Molekuls wahrend einer chemischen Reaktion verandern.

We doubly ionize H2O by single photon absorption at 43 eV leading to H+ + OH+. A direct double ionization and a sequential process in which single ionization is followed by rapid dissociation into a proton and an autoionizing OH* are identified. We obtain information about the internuclear distance at which the decay of the OH* occurs from the angular distribution of the autoionization electron.

We present a systematic study of the molecular-frame photo-electron angular distributions produced by multiphoton double ionization of H2 using circularly polarized 800 nm, femtosecond laser pulses. We compare experimental results to numerical results obtained from a reduced-dimensionality time-dependent Schr¨ odinger equation (TDSE) model. In addition, we implement a TDSE-like version of the strong-field approximation to isolate the effect of the parent ion’s Coulomb potential on the continuum electron in our simulations. Thereby we identify the contributions of the parent ion potential, and light induced sub-optical cycle electron dynamics on the observable energy and angular distributions.