bluuebunny/crossref_metadata_2025 huggingface dataset:
Suppression of the AC-Stark shift by vortex light beams
Authors: Schulz S A-L , Muller R A , Surzhykov A
Published: June 2020

Synopsis

In this work, we present how the AC-Stark shift can be suppressed by using twisted light beams for photoexcitations. Twisted light beams carry a non-zero projection of orbital angular momentum (OAM) onto their propagation direction, have a helical phase front and an intensity minimum in the beam center. Atoms located in this minimum experience a reduced AC-Stark shift and, therefore, twisted beams may be considered as valuable tool to drive atomic clock transitions. In this contribution, particular emphasis is paid to the electric-octupole (E3) transition 2
S1/2
→ 2
F7/2
in the 171 Yb+ ion.
Heavy metal spectroscopy in extremely metal rich subdwarfs
Authors: Fernández-Menchero L , Ballance C P , Ramsbottom C A
Published: June 2020

Synopsis

Helium-rich subdwarf B stars represent a small group of low-mass hot stars. A number of significant but unfamiliar absorption lines have been identified of heavy-metal ions, such as germanium, strontium, yttrium and zirconium. The abundances in the photosphere of theses element was estimated between 1000 and 10 000 times the solar. We calculate the collision-radiative data for the ions Sr+, Y2+ and Zr3+. Comparing with measured spectra we can determine these abundances. We compare the obtained results with the RMATRX and DARC methods.
Time-dependent perturbation theory beyond the dipole approximation for two-photon ionization of atoms
Authors: Wang M , Liang H , Xiao X , Chen S , Peng L
Published: June 2020

Synopsis

We develop a time-dependent perturbation theory beyond the dipole approximation to analyze the two-photon ionization dynamics of atoms exposed to short laser pulses with an arbitrary polarization. Subse-quent applications of the PT method in the nonresonant regime allow us to analyze one of the most important nondipole effects, i.e., the linear-momentum-transfer law in the two-photon ionization process and to unveil the important role of the interferences between the dipole and nondipole transition pathways to the photoelectron momentum shift along the laser-propagation direction.
Water molecule ionization by proton impact experiment and GTO-First Born theory
Authors: Della Picca R , Cariatore D , Fiol J , Fregenal D , Bernardi G
Published: June 2020

Synopsis

In this communication we present calculations and measurements of water ionization by protons at intermediate and high impact energies. The main goal of the present theoretical approach is the development of a method to routinely incorporate sophisticated wavefunctions for small and medium-sized molecules in the determination of ionization cross-sections.
Kinetic energy release in dissociation of NH3
q+ under ion impact
Authors: Safvan C P , Sairam T , Bhatt P
Published: June 2020

Synopsis

The dynamics of the dissociation of multiply charged ammonia ions is investigated. The pathways for sequential and concerted dissociation are separated, and the kinetic energy released along the different pathways is measured. The measured values are compared with ab-initio quantum chemical calculations to identify the repulsive states of the molecular ion which are responsible for the two pathways.
Nonlinear Cooper minimum as a precise tool for understanding multiphoton photoionization
Authors: Hofbrucker J , Volotka A V , Fritzsche S
Published: June 2020

Synopsis

A new approach to accurately assess multiphoton ionization is suggested. Vanishing of the dominant ionization channel in nonresonant (direct) multiphoton ionization is predicted for a specific incident photon energy. The exact energy position of such nonlinear Cooper minimum can be accurately measured and requires calculations of the complete electronic spectrum. Measurements of various observables at these photon energies are desirable for further evaluation of theoretical calculations at hitherto unreachable accuracy.
The importance of energy-differential cross sections highlighted in a benchmark for positronium formation in the Galaxy
Authors: Cocks D G , Chaudhary H , Machacek J R
Published: June 2020

Synopsis

We detail a benchmark model aimed at improving the implementation of Monte Carlo codes for simulations of positrons propagating through interstellar media. The benchmark highlights the key features of cross sections sets which lead to major differences in astronomical observables. One of these is the energy-differentiation of the ionisation cross section. This leads us to call for improved cross section sets for all constituents of interstellar media.
Projectile coherence effects analyzed using impact parameters determined by classical trajectory Monte Carlo calculations
Authors: Nagy L. , Járai-Szabó F. , Borbély S. , Tőkési K.
Published: June 2020

Synopsis

We analyze the dependence of the fully differential ionization cross section on the coherence width of the wave packet associated to the projectile. The wave packet beside its size is characterized by the closest distance of its center relative to the target (the impact parameter). We determine the distribution of the possible impact parameters by classical trajectory Monte Carlo calculations.
Auger decay of Rubidum atom after 3d-shell ionization
Authors: Palaudoux J , Penent F , Khalal M , Jänkälä K , Keskinen J , Huttula M , Bizau J-M , Cubaynes D , Guilbaud S , Zitnik M , Bucar K , Ito K , Andric L , Lablanquie P
Published: June 2020

Synopsis

We present here the different Auger decay paths following 3d inner-shell ionization of Rubidium atom and we observe the peculiar behaviour and correlation effects due to the outer, unpaired 5s electron. This electron can be submitted to shake-up during 3d ionization. Also shake-up and shake-down of the outer electron are observed in the Auger decay. Cascade double Auger decay is the dominant process leading to Rb3+ ion.
Differential cross sections for ionisation of helium by proton impact
Authors: Alladustov S U , Abdurakhmanov I B , Kadyrov A S , Bray I , Bartschat K
Published: June 2020

Synopsis

A wave-packet convergent close-coupling approach is applied to study differential ionisation in proton-helium collisions. The fully differential cross sections for electrons ejected with energy of 5.4 eV are investigated in 75 keV proton-helium collisions. We also study the doubly differential cross sections for electrons ejected with energies up to 65 eV at intermediate projectile energies (50-150 keV). The results are converged regarding the number of pseudostates included and are in fairly good agreement with the available experimental data.
Classical calculations of differential electron emission in fast heavy-ion collisions with water molecules
Authors: Jorge A , Horbatsch M , Illescas C , Kirchner T
Published: June 2020

Synopsis

We present a classical study of differential electron emission cross sections for highly-charged projectiles at υp
∼ 10 a.u. impinging on water molecules [1, 2]. Comparisons with Continuum Distorted Wave Eikonal Initial State theoretical results and with experimental data are presented. We implement a time-dependent screening effect in our model and account for the molecular target structure by means of a three-center potential.
Three body dissociation of

SO2q+
Authors: Rajput J , Kumar H , Bhatt P , Safvan C P
Published: June 2020

Synopsis

Multiply charged ion impact induced three body fragmentation pathways of

SO

2

q
+

(q=3, 4) molecular ions have been studied using the technique of recoil ion momentum spectroscopy. An attempt has been made to distinguish the three-body breakup based on mechanism of dissociation, whether sequential or concerted.
Angular distribution in two-body dissociation of

SO2q+
Authors: Rajput J , Kumar H , Bhatt P , Safvan C P
Published: June 2020

Synopsis

The two-body dissociation of multiply charged SO2 molecules is studied using a recoil ion momentum spectrometer. These molecular ions were generated in collision of the neutral parent with an energetic highly charged ion. From the measured momenta of the recoil ions, angular distributions are generated with respect to the incoming beam direction and are found to vary strongly with kinetic energy release.
The interaction of 355nm laser light on Adenine and Uracil
Authors: Hallado L , Prieto E , Álvarez I , Guerrero A , Cisneros C
Published: June 2020

Synopsis

Dissociation and ionization of adenine and uracil were investigated in the multiphoton absorption re-gime using laser pulse at 355nm in conjunction with TOF mass spectrometry in reflectron mode (R-TOF). In contrast of previous investigations where a notorious amount of low mass ions was detected arising from both molecules.
Ion induced fragmentation of diatomic molecular clusters
Authors: Méry A , Agnihotri A N , Douady J , Fléchard X , Gervais B , Guillous S , Iskandar W , Jacquet E , Kumar V , Matsumoto J , Rangama J , Ropars F , Safvan C P , Shiromaru H , Zanuttini D , Cassimi A
Published: June 2020

Synopsis

Weakly bound atomic or molecular clusters are of growing interest in the fields of atmospheric science, hadron-therapy or astrophysics. We will present our recent experimental results on the fragmentation of diatomic molecular dimers after irradiation by highly charged ions. For (N2)2 dimers, the measured KER spectrum is very similar to the one of the N2 monomers but is globally shifted towards higher energies. Moreover, sequential dissociation of the (CO)2 dimers has been observed when metastable states of the CO2+ dications are populated.
Electron–beam ion trap/source for ion–molecule collisions in the non-perturbative regime
Authors: Bapat B , Sharma D , Srivastav S
Published: June 2020

Synopsis

An Electron Beam Ion Trap and Source has been installed at the Indian Institute of Science Education and Research Pune. The source, manufactured by Dreebit GmbH, will provide ions up to Ar16+ at energies up to 30 keV/q. These will be used for studying ion-molecule collisions in the non-perturbative regime.
Dissociative multiple ionization of the H2O molecule induced by ion impact: experimental and theoretical results
Authors: Kovaćs S T S , Herczku P , Juhász Z , Sarkadi L , Gulyás L , Chesnel J-Y , Sulik B
Published: June 2020

Synopsis

Fragment energy spectra of the water molecule impacted by singly charged (SCI) and highly charged (HCI) ions have been measured in crossed beam experiments. Double differential fragmentation cross sections (DDCS) have been determined. Similarities and differences of the measured DDCSs induced by the medium- and low-energy projectiles have been analyzed. Multiple target ionization cross sections have been deduced and they were further analyzed through the results of the CTMC and CDW-EIS models.
Angle-resolved Auger spectroscopy of K-shell ionized molecules
Authors: Fuchs S , Paul D , Buhr T , Ricz S , Schippers S
Published: June 2020

Synopsis

We report on measured oxygen K-LL Auger spectra induced by 1.5-keV electron impact on O2, CO2, and N2O gaseous targets. An ESA-22-type electron spectrometer was employed which is capable of simultaneous energy and angular analysis covering a polar angular range of 15° to 345°. The measurements were carried out in preparation for future experiments with more complex chiral molecular targets and a spin-polarized electron source. The present experimental data are compared with results from earlier experimental studies.
Li-like carbon Auger KLL measurements of mixed-state C4+(1s2
1S, 1s2s 3S) ions in 6-15 MeV collisions with He and comparison to 3eAOCC calculations
Authors: Madesis I , Laoutaris A , Benis E P , Zouros T J M , Dubois A
Published: June 2020

Synopsis

New state-resolved Li-like carbon Auger KLL measurements of mixed-state C4+(1s2
1S, 1s2s 3S) ions in 6-15 MeV collisions with He are presented. Results of three-electron semiclassical atomic orbital AOCC coupled channel (3eAOCC) calculations are also presented and compared.
Radiative double electron capture for 2.11 MeV/u F9+,8+ + N2, Ne
Authors: La Mantia D S , Kumara P N S , Buglione S L , McCoy C P , Taylor C J , White J S , Kayani A , Tanis J A
Published: June 2020

Synopsis

The first successful observation of radiative double electron capture for gas targets is reported. RDEC has been observed for 2.11 MeV/u F9+,8++N2, Ne collisions. Cross sections for both projectile charge states and targets were determined and compared with previous results and theory. This abstract gives an overview of the results found for both gas targets.
The low energy beamline of the FISIC experiment: current status of construction and performance
Authors: Schury D , Méry A , Ramillon J M , Adoui L , Chesnel J-Y , Lévy A , Macé S , Prigent C , Rangama J , Rousseau P , Steydli S , Trassinelli M , Vernhet D , Gumberidze A , Stöhlker Th , Bräuning-Demian A , Hahn C , Spillmann U , Lamour E
Published: June 2020

Synopsis

Ion-ion collisions between slow (kev/u) and fast (MeV/u) ions play an important role in for example astrophysical or inertial fusion plasmas as well as in ion-matter interaction. In this regime the energy transfer is maximum, as all primary electronic processes reach their maximum. At the same time up to today no reliable experimental data exists while being difficult to treat accurately by theory. We present the current status and performance of the low energy beam-line of the FISIC experiment which aims at filling in the blanks in this regime.
Kinetic energy release (KER) of vibrationally cold HeH+: experiments at the reaction microscope in the Frankfurt low-energy storage ring (FLSR)
Authors: Müller J C , Dörner R , Schmidt L Ph H , Schöffler M S , Stiebing K E
Published: June 2020

Synopsis

The installation of a reaction microscope (COLTRIMS [1]) in the electrostatic Frankfurt Low Energy Storage Ring (FLSR) [2] has been completed. A first experiment, exploring the KER for dissociative electron transfer to HeH+ ions at 20 keV from a cold supersonic He gas target have been carried. Even at the moderate vacuum of 10−8 mbar a change of the KER and the Q value distribution due to cooling of the molecular ions during the storage time can be observed. In this contribution the final experiment, performed after heating the ring will be discussed.
Dissociative recombination and vibrational excitation of molecular cations with electrons: application to H2
+, BeH+ and their isotopomers
Authors: Pop N , Iacob F , Mezei J Zs , Niyonzima S , Motapon O , Schneider I F
Published: June 2020

Synopsis

Cross sections and Maxwell rate coefficients for the low-energy reactive collisions of electrons with Hydrogen and Beryllium hydride cations will be presented, as well as a discussion on the major relevant mechanisms and features – direct/indirect process, ro-vibronic couplings, ro-vibrational dependence.
Electron dissociative attachement to ArH+, HD+, N2
+ and CO2
Authors: Abdoulanziz A , Djuissi E , Argentin C , Moulane Y , Bultel A , Mezei J Zs , Tennyson J , Chakrabarti K , Laporta V , Schneider I
Published: June 2020

Synopsis

We will present our recent results in the study of electron-induced reactivity of ionized and neutral molecules. The Configuration Interaction method and the Multichannel Quantum Defect Theory have been employed in order to obtain cross sections for collisions of electrons with ArH+, HD+, N2 and CO2.
On-the-fly dynamics simulation of dissociative electron attachment to chloroethane
Authors: Kossoski F , Barbatti M
Published: June 2020

Synopsis

We present a novel theoretical approach for describing dissociative electron attachment. It is is based on classically propagating the nuclei on the potential surface of the resonant anion, which is described by bound state methods, while electron autodetachment is taken into account with an ad-hoc model built from scattering calculation results. As a first application, we considered the electron induced dissociation of chloroethane. Comparison to experimental data is very encouraging. The simulations reveal further details on the underlying dynamics of the dissociation.
Methylation effect in e−— scattering on methyl-substituted ethylenes
Authors: Stefanowska-Tur S , Szmytkowski Cz , Ptasińska-Denga E , Możejko P
Published: June 2020

Synopsis

Methylation effect has been observed and studied in electron-scattering from selected hydrocarbon molecules. In measured total cross section (TCS) functions we have noticed energy shifts and changes in the intensity of observed structures.
Time delay in slow electron elastic scattering by potentials with arising levels
Authors: Amusia M Ya , Baltenkov A S
Published: June 2020

Synopsis

We study Wigner time delay of slow electrons by spherically symmetric square potential well as a function of the well parameters. We show that the electron interaction with scattering center qualitatively depends on presence of discrete levels in the well. Electron retention mode by a potential well with no discrete level is replaced by the mode at which after level appears the incident electron hardly enters the scatterer. This behavior of time delay is universal since it is typical not only for the first but also for following arising s-levels.
On the e− – C60 elastic angle-differential scattering cross section
Authors: Dolmatov V K , Amusia M Ya , Chernysheva L V
Published: June 2020

Synopsis

We study theoretically the experimental angle-differential elastic electron scattering off a C60 fullerene with the aim to elucidate whether its features depend primarily on the details of the full molecular potential of C60 or they can be understood without reference to the full nature of the potential. We demonstrate the success of the latter option.
Halogen loss induced by electron collisions in halouracils at low energies
Authors: Cornetta L M , Varella M T do N
Published: June 2020

Synopsis

We employed both eletronic scattering techniques and ab initio quantum dynamics to study electron-driven reactions in halouracils at low energies. Particularly, it was addressed halogen dissociation and H-loss probabilities in anionic 5-BrU and 5-IU. Besides, we also propose a model of how to include auto-ionization probabilities during the dynamics.
Electron elastic scattering from Ho, Er, Tm, Yb, Lu and Hf atoms
Authors: Felfli Z , Msezane A Z
Published: June 2020

Synopsis

We carefully investigate negative ion formation in the large lanthanide atoms Ho, Er, Tm, Yb and Lu as well as in atomic Hf through the electron elastic total cross sections (TCSs) calculation using the robust Regge-pole methodology. The TCSs are found to be characterized generally by ground, metastable and excited states negative ion formation. The extracted from the TCSs anionic binding energies (BEs), with those for the ground states corresponding to the definitive and unambiguous electron affinities (EAs), are contrasted with the measured and/or calculated EAs.
Diagnosing the lightning plasma temperature based on the collisional-radiative model
Authors: Zhang W , Jiang J , Yuan P
Published: June 2020

Synopsis

The atomic parameters of the NII ion, including the energy levels, transition probabilities, collision sections, and collision excitation rate coefficients, have been calculated based on the multi-configuration Dirac-Fock method by implementing Flexible Atomic Code. The ratios of line intensity, I567.96nm/I500.52nm
, have been calculated by using the collisional-radiative model. The temperatures of six lightning plasma channels were then obtained, and they are consistent with temperatures obtained by using the multi-spectral lines method.
EUV spectroscopy of optically thin germanium plasmas in the 9-18 nm region
Authors: Maguire O , Kos D , O’Sullivan G , Sokell E
Published: June 2020

Synopsis

EUV spectra have been recorded from optically-thin germanium laser produced plasmas created using a high-powered TEA CO2 laser. The Cowan suite of atomic codes has been used to identify previously unidentified lines in Ge VI-XI. The absence in the spectra of Δn=0 transitions for ion stages lower than Ge9+ has been interpreted by calculating line strength ratios for of Δn=0 to Δn=1 transitions for the relevant ion stages.
Effective modulation of the terahertz radiation force
Authors: Zhang X B , Qiao X , Zhang A X , Xue J K
Published: June 2020

Synopsis

The radiation force of the terahertz field is realized and highly modulated by changing the spatial distribution of the THz field, which is controlled by the coupling effects of the laser field, external magnetic field, and self-generated plasma channel. Moreover, the stability of the terahertz radiation is also discussed.
Programmable plasma structure generated by the laser-plasma interaction
Authors: Zhang X B , Qiao X , Zhang A X , Xue J K
Published: June 2020

Synopsis

The programmable plasma structure generated by the laser-plasma interaction is discussed theoretically. The multiple plasma density distribution patterns which includes single channel, double channel and slow-wave plasma structure is achieved by modulating the ponderomotive force controlled by the laser’s beam profile and pulse width.
Ammonia ices under low-energy electron irradiation - Towards quantitative desorption rates and effective cross sections
Authors: Sala L , Amiaud L , Dablemont C , Lafosse A
Published: June 2020

Synopsis

Low-energy (< 20 eV) electron processing of NH3 multilayer films, systems of interest in astrochemistry, leads to significant NH3 desorption, fragmentation, and to a complex chemistry arising from recombination and secondary processes induced by reactive products. Quantitative desorption rates of neutral species and effective cross sections for selected processes were obtained by combining three surface-sensitive techniques: High Resolution Electron-Energy Loss Spectroscopy (HREELS), Temperature Programmed Desorption (TPD) and Electron Stimulated Desorption (ESD) of neutral species.
Low energy electron induced chemistry in CO2:NH3:CH4 ices
Authors: Esmaili S , Bass A D , Cloutier P , Lemelin V , Sanche L , Huels M A
Published: June 2020

Synopsis

We report measurements of the electron stimulated desorption of anions from thin (nanometer scale) films of CO2, NH3, CH4, and mixtures thereof.
Resonant anionic states of organic molecules adsorbed on metal surfaces
Authors: Aguilar-Galindo F , Díaz-Tendero S , Borisov A G
Published: June 2020

Synopsis

The interaction of organic molecules with metal surfaces induces drastic changes in the electronic structure of the adsorbate. In particular, properties such as the energy and the lifetime of anionic states are strongly modified. Decay into the metal continuum must be considered in the electron dynamics, since in many cases it dominates over the decay through the vacuum. We present a generalized methodology to study this kind of systems in order to obtain the energy of the states, as well as their lifetime and decay paths.
Many body phenomenon within multiple scattering approach in PEELS
Authors: Mandal A , Kochetov V , Dhankhar N , Sébilleaut D , Choubisa R
Published: June 2020

Synopsis

Plasmon excitation within multiple scattering approach is being explored. The plasmon loss is described within the so-called quasi-boson approximation, originally proposed by Hedin and further extended by Fujikawa. We compare the different fluctuation potentials i.e. Plasmon-pole model, Bechstedt model and other available potentials based on beyond-RPA dielectric functions and use either the exact core state wave function or more accurate model than a simple delta function used previously for total energy loss in Aluminium targets.
Photoionization of endohedrals: complete semi-phenomenological approach
Authors: Amusia M Ya , Chernysheva L V
Published: June 2020

Synopsis

We developed a semi-phenomenological approach that permits to calculate the photoionization cross section of an endohedral A@CN. We take, along with the static pseudopotential of atom A and fullerene CN also the static and dynamic polarization of A and CN by the incoming photons and outgoing electrons. The approach is general and applicable to any spherically-symmetric endohedrals. Concrete results are obtained for Ar@C60 and Xe@C60. We take into account the multi-electron correlations in the frame of the random phase approximation with exchange (RPAE).
Profile of energy-loss spectrum in collisions of ions with heteronuclear diatomic molecules
Authors: Nakamura M , Ichimura A
Published: June 2020

Synopsis

Profile of energy-loss spectrum in collisions of low velocity ions with heteronuclear diatomic molecules is theoretically investigated. With changing mass asymmetry in a target diatomic molecule, energy-loss spectrum is calculated with the classical trajectory calculation. Rotational excitation plays an essential role for energy-loss. The shape of the spectrum is found to show a drastic variation with mass asymmetry.
Diffraction of 80 eV hydrogen through suspended graphene
Authors: Brand C , Susi T , Kotakoski J , Arndt M , Debiossac M , Aguillon F , Roncin P
Published: June 2020

Synopsis

We have investigated theoretically the possibility to diffract hydrogen atoms through a suspended graphene single layer. Using quantum and semi classical approaches we evaluate the momentum and energy exchange to the electronic and vibrational system and estimate their influence on the coherence and spot size.
On the mechanisms of formation and decomposition of peptide bonds
Authors: Bolognesi P , Chiarinelli J , Richter R , Stockett M H , Indrajith S , Nicolafrancesco C , Eklund G , Zettergren H , Sa’adeh H , Domaracka A , Rousseau P , Avaldi L
Published: June 2020

Synopsis

The electronic structure and the fragmentation dynamics of a series of isolated cyclic-dipeptides (cyclo-Ala-Ala; cyclo-Gly-Ala; cyclo-Gly-Gly) have been studied by mass spectrometry, photoemission and photoelectron-photoion coincidence spectroscopy.
Path integral molecular dynamics simulations for muoniated and hydrogenated thioacetone radicals
Authors: Okano S , Oba Y , Tachikawa M
Published: June 2020

Synopsis

Theoretical understanding of hyperfine coupling constant (HFCC) is important to analyze muon spin rotation/relaxation/resonance (μSR) spectrum. We performed ab initio path integral molecular dynamics simula-tions to predict and analyze the reduced HFCCs of muoniated thioacetone radical (Mu-TACE) and hydrogenated thioacetone radical (H-TACE). Our predicted HFCC value of Mu in Mu-TACE was larger than that of H in H-TACE, because of the larger nuclear quantum effect of positive muon.
Vibrational and rotational cooling dynamics of the triatomic molecular ion N2O+ stored in RICE
Authors: Igosawa R , Hirota A , Yamaguchi T , Lindley M , Chartkunchand K , Nakano Y , Kuma S , Azuma T
Published: June 2020

Synopsis

We studied radiative cooling dynamics of the triatomic molecular ion N2O+ stored in RICE. We observed the evolution of the populations at vibrational and rotational levels up to several 100 s by measuring neutral fragments from the laser-induced predissociation process. We found clear evidence of radiative cooling of the vibrational level populations with a time constant of several seconds. In contrast, absence of significant changes in the rotational levels revealed that the time scale of the rotational cooling is far longer, which is consistent to our simulation.
State-selected ion-molecule reactions with VUV synchrotron radiation : the O2
+ + C3H6 case
Authors: Thissen R , Romanzin C , Lemaire J , Thomas S , Alcaraz C
Published: June 2020

Synopsis

O2
+ molecular ion is produced by photoionization close to threshold at SOLEIL, DESIRS beam line. By means of coincidence methods, ions are prepared in selected vibrational and electronic states (X, v=0,3,15 and a, v=3). Their reactivity with the propene in single collision regime is studied in the guided ion beam in-strument CERISES, adding ability to vary the collision energy. Absolute reaction cross section and branching ratio are recorded for the 5 most intense reactive channels, described as dissociative charge transfer. Contrasted effects of internal and collision energy are observed.
Radiative cooling dynamics of anthracene cations stored in DESIREE studied via the time evolution of 2-photon-absorption induced dissociation rate
Authors: Bernard J , Ji M C , Martin S , Wenzel G , Al-Mogeeth A , Stockett M H , Schmidt H T , Zettergren H , Joblin C
Published: June 2020

Synopsis

Anthracene cations (C14H10
+) have been stored in the cryogenic (13 K) electrostatic storage ring DESIREE in Stockholm to study their radiative cooling dynamics on a long time scale up to 2 s. By monitoring the laser-induced delayed dissociation curves during the storage, the evolution of the dissociation rate was obtained. Its decrease as a function of time is closely related to the time evolution of the internal energy distribution of the stored anthracene cations and consequently to the energy loss due to radiative cooling, including both Poincaré and infrared fluorescences.
DAVIS: a direct algorithm for velocity-map imaging system
Authors: Harrison G R , Vaughan J C , Hidle B , Laurent G M
Published: June 2020

Synopsis

Recently, we reported a direct (non-iterative) algorithm to reconstruct the three-dimensional momentum-space picture of any charged particles collected with a velocity-map imaging system from the two-dimensional projected image captured by a position-sensitive detector. The method consists of fitting the measured image with an analytical 2D projection of a model 3D velocity distribution defined by the physics of the light-matter interaction. In this work, we present a systematic comparison of the level of performance (accuracy and speed) of our method with others well-known techniques for inverting experimental images.
The attoclock and tunnelling time
Authors: Bray A.W.
Published: June 2020

Ultrafast laser pulses have enabled experiments probing the temporal dynamics of an electron tunnelling out of an atom. A quintessential example of such is known as the ‘attoclock’. While the investigation is ongoing, the window for non-zero ‘tunnelling times’ in this context appears to have largely closed.
XUV+IR photoionization of argon atoms: selection of sideband orders
Authors: Picca R Della , Gramajo A A , López S , Arbó D G
Published: June 2020

We present a theoretical study of atomic ionization due to an XUV pulse in the presence of an infrared laser. Within the strong field approximation and considering the periodicity and symmetry of the transition matrix we show that the photoelectron spectrum can be described from the contribution during only one (or half) infrared cycle. These symmetry and periodicity properties impress selection rules which destructively cancel certain sideband orders favoring others. In particular, we analyze the photoionization of Argon in four geometrical arrangements of the polarization vector and the photoelectron momentum direction.
Photo-processing of astro-PAHs
Authors: Joblin C , Wenzel G , Rodriguez Castillo S , Simon A , Sabbah H , Bonnamy A , Toublanc D , Mulas G , Ji M , Giuliani A , Nahon L
Published: June 2020

Polycyclic aromatic hydrocarbons (PAHs) are key species in astrophysical environments in which vacuum ultraviolet (VUV) photons are present, such as star-forming regions. The interaction with these VUV photons governs the physical and chemical evolution of PAHs. Models show that only large species can survive. However, the actual molecular properties of large PAHs are poorly characterized and the ones included in models are only an extrapolation of the properties of small and medium-sized species. We discuss here experiments performed on trapped ions including some at the SOLEIL VUV beam line DESIRS. We focus on the case of the large dicoronylene cation,

C

48

H

20

+

, and compare its behavior under VUV processing with that of smaller species. We suggest that C2 H2 is not a relevant channel in the fragmentation of large PAHs. Ionization is found to largely dominate fragmentation. In addition, we report evidence for a hydrogen dissociation channel through excited electronic states. Although this channel is minor, it is already effective below 13.6 eV and can significantly influence the stability of astro-PAHs. We emphasize that the competition between ionization and dissociation in large PAHs should be further evaluated for their use in astrophysical models.
Merged beam studies of mutual neutralization at subthermal collision energies
Authors: Urbain X. , de Ruette N. , Dochain A. , Launoy T. , Nascimento R.F. , Kaminska M. , Stockett M.H. , Loreau J. , Liévin J. , Vaeck N. , Thomas R.D. , Schmidt H.T. , Cederquist H.
Published: June 2020

We have measured the kinetic energy distributions for the mutual neutralization of a large ensemble of atomic anions and cations. Ions are accelerated to equal velocities in a merged beam setup, enabling measurements at collision energies as low as 5 meV. Three-dimensional momentum imaging is performed with two position sensitive detectors located several meters downstream from the few centimeter long region where the beams overlap. An unprecedented resolution in the kinetic energy release (KER) spectra allows us to identify the states of both reactants and products down to their fine structure. Knowing the angular distribution of the products in the laboratory and center-of-mass frame, allows for total, partial, and differential cross sections to be retrieved.
On the highly charged ion transmission spectroscopy applied to 2D materials
Authors: Wilhelm Richard A.
Published: June 2020

The interaction of ions with solid materials may lead to charge exchange. Previous results show that charge exchange is confined to the uppermost surface layers of a solid or to the thickness of a freestanding 2D material, even when initially highly charged ions are used. Several processes are active during charge exchange and a clear distance or impact parameter dependence is observed. Here I show, that highly charged ion transmission can be used to determine the material structure of 2D materials especially when atomically resolved electron microscopy cannot be applied. The method is based on measurement of energy-, charge-, and angle-resolved ion transmission spectra in coincidence and a comparison with a local model for a time-dependent change in the projectile’s electron occupation and consequently the scattering potential. Also necessary experimental procedures are discussed.
Polarisation Effects in Above-Threshold Ionisation of Excited Helium
Authors: Bray A C , Maxwell A S , de Morisson Faria C Figueira , Kissin Y , Ruberti M , Khokhlova M , Averbukh V
Published: June 2020

Synopsis

We present work on the disentanglement of core dynamics and binding potential influences for Above-Threshold Ionisation in Helium prepared in an excited p state, interacting with a mid-IR field. This was formed by comparing the Coulomb Quantum-Orbit Strong-Field Approximation (CQSFA) with B-spline Algebraic Diagrammatic Construction (ADC) simulations. This may lead to the identification of initial momentum distributions, for tunneling and re-scattering instances, from the CQSFA perspective. The latter method is an inverse approach; thus, the ADC simulations will allow comparison of findings.
Atomic RABBITT-like experiments assisted by a circularly polarized laser
Authors: Boll D I R , Fojón O A
Published: June 2020

Synopsis

We study theoretically the single ionization of atoms by the combined action of an attosecond pulse train with linear polarization and an assistant laser field with circular polarization. By means of a non-perturbative model, we obtain closed-form expressions for the angular distributions of photoelectrons. We show that such a configuration of light fields is similar to the usual polarization control technique where both the attosecond pulse train and the assistant laser field are linearly polarized with a controlled relative orientation.
RABBITT attoclock for the direct measurement of ionization phases
Authors: Donsa S , Douguet N , Burgdörfer J , Březinová I , Argenti L
Published: June 2020

Synopsis

We use a circularly polarized attosecond pulse train (APT) together with a weak replica of the fundamental circularly polarized infra-red (IR) field to reconstruct the ionization phase of the dipole allowed (2s2p)1P° resonance in atomic helium by analyzing the momentum distribution of the ionized photoelectrons within the polarization plane.
Can we break the symmetry along the polarization axis in photoionization?
Authors: Cheng Y-C , Mikaelsson S , Nandi S , Rämisch L , Guo C , Harth A , Vogelsang J , Miranda M , Arnold C L , L’Huillier A , Gisselbrecht M
Published: June 2020

Synopsis

Photoionization is a fundamental process in which an electron is emitted from an atom. The emission is traditionally considered to be symmetric with respect to the polarization axis, unless it is temporally confined to a period shorter than an optical cycle time. We demonstrate that this symmetry can still be broken by combining a train of a few attosecond pulses and a dressing laser field. The light fields act as temporal slits and phase modulator that releases electron wavepackets. The resulting photoelectron spectra differ for electrons emitted in opposite direction along the polarization.
Attosecond XUV-pump/XUV-probe spectroscopy of glycine
Authors: Lara-Astiaso M , Palacios A , Delgado J , González-Vázquez J , Decleva P , Martín F
Published: June 2020

Synopsis

We theoretically describe the outcome of an attosecond XUV pump-probe experiment in the smallest amino acid, glycine. We accurately evaluate the ionization amplitudes for the pump and the probe pulses. The molecular wave packet is then time-propagated using a trajectory-based Surface Hopping approach, accouting for the momentum distributions of the nuclei. Experimentally measurable photoelectron spectra are retrieved.
H2 photoionization induced by XUV pulses and X-ray free electron lasers
Authors: Sopena A , Palacios A , Martín F , Catoire F , Bachau H
Published: June 2020

Synopsis

We present a theoretical study on H2 photionization taking into account coupled electron-nuclear motion and non-dipole effects. In the first part we study the effects of harmonic filtering in a pump-probe scheme using attosecond train pulses (ATP) in dipole approximation. In the second part we investigate nondipole effects in XUV and soft X-ray regimes.
Dynamical origin of below-threshold harmonic generation of diatomic molecules
Authors: Li P-C , Zhou X-X , Chu S-I
Published: June 2020

Synopsis

We present an ab initio quantum study of below-threshold harmonic generation (BTHG) from H2
+ molecules in the presence of an intense laser field by solving the time-dependent Schrödinger equation accurately in space and time. We find that multiple channels contribute to BTHG of H2
+ molecules, which are related to the electron driven initially at specific time of the laser pulse from one nuclear core to another nuclear core or back to the parent core itself. The distinct contributions of these channels are distinguished by using a novel synchro squeezing time-frequency analysis.
Ultrafast imaging of the Renner-Teller effect in a field-dressed molecule
Authors: Amini K , Steinle T , Sclafani M , Shaikh M , Sanchez A , Liu X , Le A T , Steinmetzer J , Pfeiffer T , Moshammer R , Ullrich J , Lewenstein M , Moszynski R , de Abajo J G , Lin C D , Gräfe S , Biegert J
Published: June 2020

Synopsis

We present experimental results of linear-to-bent transition of field-dressed molecules, mediated by Renner-Teller effect. Using the state-of-the-art laser-induced electron diffraction (LIED) technique, we image a bent and symmetrically stretched carbon disulfide (CS2) molecule populating an excited electronic state under the influence of strong laser field. Our findings are well-supported by ab initio quantum mechanical calculations.
Experimental comparison of frustrated tunnel ionisation in multi-cycle and few-cycle pulses
Authors: Chetty D , Glover R D , Xu H , Palmer A J , deHarak B A , Light P S , Luiten A N , Litvinyuk I V , Sang R T
Published: June 2020

Synopsis

We present the first experimental evidence which qualitatively shows that frustrated tunnel ionization results in a larger number of excited neutrals per a tunnelling event for 6 fs pulses compared to 30 fs pulses. In addition, we also observe a less severe dependence on elliptical polarization for the 6 fs pulses. Furthermore, by varying the carrier envelope phase of the shorter pulse, we observe a modulation in the yield of excited neutrals which indicates possible control of electron trajectories.
Real-time reconstruction of the strong-field driven dipole response
Authors: Stooß V , Cavaletto S M , Donsa S , Blättermann A , Birk P , Keitel C H , Březinová I , Burgdörfer J , Ott C , Pfeifer T
Published: June 2020

Synopsis

Using ultrashort and phase-locked laser pulses, combined with an in situ measurement of a reference pulse, we present a method capable of retrieving the nonlinearly perturbed time-dependent response function of a quantum system driven by strong electric fields directly from spectroscopic absorption data with high precision.
Revealing the multiorbital and excitation effects in dissociative double ionization of CO molecules with angular streaking measurement
Authors: Li X , Yu J , Yu X , Yang Y , Wang C , Luo S , Ding D
Published: June 2020

Synopsis

We investigate the sequential double ionization dynamics for the dissociative channel C+ + O+ of CO molecules in strong circularly polarized laser fields. By using four-particle coincident measurement, the obtained ionic angular emissions and molecular frame photoelectron angular distributions of each ionization steps for various pathways reveals the significant effects of multiorbital ionization and laser-driven excitation.
Classical theory of laser-assisted spontaneous bremsstrahlung
Authors: Ambalampitiya H B , Fabrikant I I
Published: June 2020

Synopsis

At low energies the classical trajectories for electron motion in a combined Coulomb and ac fields are affected by the Coulomb focusing. This leads to a strong enhancement of the laser-assisted bremsstrahlung cross section as compared to the field-free case.
Laser-assisted electron scattering and ionization processes in a quasi-Sturmian-Floquet approach
Authors: Zaytsev S A , Zaytsev A S , Ancarani L U , Kouzakov K A
Published: June 2020

Synopsis

We demonstrate the robustness and efficiency of our recently formulated quasi-Sturmian-Floquet method to treat light-dressed electron states. For this purpose we study the archetypical processes such as laser-modified electron scattering on a Coulomb potential and laser-assisted electron-impact ionization of atomic hydrogen. For both processes we explore various regimes of laser radiation and identify the differences with respect to the corresponding laser-free situations.
Complex permittivity and permeability properties analysis of NiCuZn Ferrite-Polymer nanocomposites for EMI suppressor applications
Authors: Raju P , Shankar J , Anjaiah J , Kalyani Ch , Neeraja Rani G
Published: June 2020

The complex permittivity and permeability studies of NiCuZn ferrite-paraformaldehyde (NCZ-PFD) nanocomposites for electromagnetic interference (EMI) suppressor applications are presented. The NCZ Ferrite and nanocomposites were prepared via microwave hydrothermal and ball-milling, respectively. The nanocomposites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) the results indicate that the NCZ-PFD nanocomposites were successfully prepared without impurities. The complex permittivity and permeability were measured over frequency range of 8.2-12.4 GHz and 12.4–18 GHz. The results show that for nanocomposites, the values of the real (ε′) and imaginary permittivity (ε″) and imaginary permeability (μ″) increase, while the value of real permeability (μ′) decreases as the polymer content increases. Dielectric relaxations were studied using cole-cole plots of complex permittivity. Magnetic relaxation dispersions were analyzed using cole-cole plots of complex permeability. The possibility to modulate the electromagnetic properties of the composite materials is of a great interest to fabricate microwave absorbing and electromagnetic shielding materials with high performances.
Dielectric, Magnetic and Spectral studies of gel grown Mg2+ Doped Copper Cadmium Oxalate Single Crystals
Authors: Rohith P S , Jagannatha N , Pradeepkumar K V , Mangala M S
Published: June 2020

Mg2+ doped Copper Cadmium oxalate (MCuCO) single crystals were grown by a single diffusion method in silica hydrogel at room temperature. Powder X-ray diffraction (XRD) studies show the triclinic nature of the crystals. The dielectric constant, ac resistivity and ac conductivity have been measured as a function of frequency. The dielectric constant of MCuCO crystal decreases as the frequency of applied field increases; at the end it gives the diminishing value of dielectric constant. AC conductivity increases with the increase of frequency. Absorbance, transmittance, reflectance, refractive index, and energy gap of MCuCO crystal were determined by UV-Visible spectroscopy. A high bandgap corresponds to the dielectric behavior of the crystal.
Synthesis, Characterization and Studies on Polyaniline/Nanocomposites Thin Films
Authors: Husain Jakeer , Raghu Nagalli , Reddy Narsappa , Sagar Jaisheel , Ambika Prasad M V N , anjum Bushara
Published: June 2020

Nanocomposites of Polyaniline/Copper oxide were prepared by in-situ polymerization method. These composites were characterized by employing Scanning Electron Microscope (SEM), Transmission Electron microscopy (TEM), Thermal study by (TGA). The dc conductivity of prepared composites was measured as a function of temperature which shows the strong interaction between Pani and copper oxide particles and exhibits semiconducting behavior. The prepared composites show better Electrical& Thermal properties which may be useful for Potential applications.
Structural, microstructural and optical property studies on sol-gel synthesized Cr/Fe-doped CuO nanoparticles
Authors: Kumar J Praveen , Chandra Sekhar K S K R , Paila Anantharao , Kandula Kumara Raja , Suryanarayana B , Patri Tirupathi
Published: June 2020

Here with we reported a detailed synthesis of Fe/Cr co-doped Copper oxide nano particles with a simple and inexpensive wet chemical method. The pure and Fe, Cr substituted CuO nanoparticles was prepared with sol-gel chemical method are expedient for industrial application. The preliminary X – ray diffraction and Rietveld refinement study revealed a pure crystallinity nature with monoclinic crystal with C2/c phase. The average crystallite size was calculated by Scherrer’s formula in order of 21 nm and further observation indicates with increase concentration crystalline size increases. The scanning electron microscopy (SEM) images indicate particles are in 20-30 nm range. The Raman spectroscopic study indicates the existence of molecular groups in the CuO nanoparticles with the doping of Cr and Fe.
An Overview on Types of White Cast Irons and High Chromium White Cast Irons
Authors: Ngqase Mbulelo , Pan Xiaowei
Published: June 2020

Crushing and grinding are widely used in mining, mineral processing, cement making, and coal power generation. The mechanical components that contact with materials being processed are working under the conditions of high abrasion and impact. How to reduce the wearing damages and prevent from the cracking failure of the mechanical parts is one of the crucial challenges facing the operations of many industries, involved crushing and grinding processes. Whit cast irons, and specifically high chromium white cast irons, have been developed and deployed worldwide for making mechanical components of crushing and grinding machines due to the combination of high wear resistance and good mechanical strength. The paper is aimed to give an overview on the white cast iron alloys, and particularly high chromium white cast iron alloys, including their classifications, their standard specifications in USA, China and Australia, their main usages and the new developments.