bluuebunny/crossref_metadata_2025 huggingface dataset:
Foreign investor reactions to risk and uncertainty in antitrust: U.S. merger policy investigations and the deterrence of foreign acquirer presence
Authors: Clougherty Joseph A. , Zhang Nan
Published: June 2020

Motivated by the potential for antitrust and competition policies to be protectionist in effect, we formulate the theoretical prior that merger policy deters foreign acquirer participation in local M&A markets. The policy risk and policy uncertainty characteristic of merger review may negatively affect foreign acquirers more so than domestic acquirers, thereby disadvantaging foreign acquisitions of local firms and deterring future cross-border investment activities. We test this prior by employing sector-level data on U.S. merger policy investigations and foreign acquirer presence in U.S. M&A markets over the 2002–2017 period. Our panel-data methodological approach indicates that the risk and uncertainty characteristic of U.S. merger policy disproportionately deters the acquisition activities of foreign investors. The empirical results also suggest that the application of competition and merger policies in other national jurisdictions – where there is less of a strong commitment to antitrust principles – might also be effectively protectionist.
“Le Grand absent Européen”: solidarity in the politics of European integration
Authors: Grimmel Andreas
Published: June 2020

The appeal for more solidarity is a recurring pattern in political discussions of how to cope with the crises the European Union (EU) confronts. This became most palpable in two major challenges—the Eurozone crisis and the refugee and migrant crisis. However, there is a yawning gap between the rhetorical commitment to solidarity and member states’ practices of solidarity: Even though the EU and its members regularly refer to solidarity as one of their fundamental values, the concept regularly fails to translate into concrete and common action. This lack of solidarity when it comes to problem resolution not only renders solidarity a weak principle within the EU’s political framework; it also precludes more effective crisis management. Drawing on the works of Ludwig Wittgenstein as well as (neo)pragmatism, this paper argues that a language- and practice-based reading can offer a new perspective on solidarity as one of the EU’s fundamental values. It can also explain why solidarity does not play a more vital role in the EU today, especially in times of crisis, when it is most needed.
Improving shape memory alloys for solid-state cooling
Authors: Frank Jodi Ackerman
Published: June 2020

The freestanding multilayer thin films fabricated by sputtering deposition can withstand more than 20 million cycles.
Size-tunable electroluminescence characteristics of quantum confined Si nanocrystals embedded in Si-rich oxide matrix
Authors: Sarkar Arijit , Bar Rajshekhar , Singh Sudarshan , Chowdhury Rup Kumar , Bhattacharya Sekhar , Das Amal Kumar , Ray Samit K.
Published: June 2020

Tunable electroluminescence properties of size-controlled Si nanocrystals embedded in silicon rich oxide films are demonstrated at room temperature, using an active light emitting layer in the metal oxide semiconductor device structure. Plasma enhanced chemical vapor deposited Si-rich oxide films were annealed at elevated temperatures to form Si nanocrystals of varying diameters. A typical redshift in the photoluminescence peak is observed with increasing annealing temperature, confirming the formation of quantum confined Si nanocrystals. The carrier transport and light emission mechanism have been studied in detail through current–voltage characteristics and ultrafast transient spectroscopy, respectively. The origin of electroluminescence and the size-tunable emission peak have been analyzed and attributed to the radiative recombination of carriers within Si nanocrystal quantum wells. The fabricated Si nanocrystal-based metal oxide semiconductor light emitting diode and the resultant size-dependent tunable electroluminescence are very attractive as a potential CMOS compatible optical source for future photonic integrated chips.
Effect of spin–orbit coupling on decay widths of electronic decay processes
Authors: Fasshauer Elke
Published: June 2020

Auger–Meitner processes are electronic decay processes of energetically low-lying vacancies. In these processes, the vacancy is filled by an electron of an energetically higher lying orbital, while another electron is simultaneously emitted to the continuum. In low-lying orbitals, relativistic effects can not, even for light elements, be neglected. At the same time, lifetime calculations are computationally expensive. In this context, we investigate which effect spin–orbit coupling has on Auger–Meitner decay widths and aim for a rule of thumb for the relative decay widths of initial states split by spin–orbit coupling. We base this rule of thumb on Auger–Meitner decay widths of Sr4p−1 and Ra6p−1 obtained by relativistic FanoADC–Stieltjes calculations and validate it against Auger–Meitner decay widths from the literature.
The ORCA quantum chemistry program package
Authors: Neese Frank , Wennmohs Frank , Becker Ute , Riplinger Christoph
Published: June 2020

In this contribution to the special software-centered issue, the ORCA program package is described. We start with a short historical perspective of how the project began and go on to discuss its current feature set. ORCA has grown into a rather comprehensive general-purpose package for theoretical research in all areas of chemistry and many neighboring disciplines such as materials sciences and biochemistry. ORCA features density functional theory, a range of wavefunction based correlation methods, semi-empirical methods, and even force-field methods. A range of solvation and embedding models is featured as well as a complete intrinsic to ORCA quantum mechanics/molecular mechanics engine. A specialty of ORCA always has been a focus on transition metals and spectroscopy as well as a focus on applicability of the implemented methods to “real-life” chemical applications involving systems with a few hundred atoms. In addition to being efficient, user friendly, and, to the largest extent possible, platform independent, ORCA features a number of methods that are either unique to ORCA or have been first implemented in the course of the ORCA development. Next to a range of spectroscopic and magnetic properties, the linear- or low-order single- and multi-reference local correlation methods based on pair natural orbitals (domain based local pair natural orbital methods) should be mentioned here. Consequently, ORCA is a widely used program in various areas of chemistry and spectroscopy with a current user base of over 22 000 registered users in academic research and in industry.
Trielectrode plasma reactor for water treatment
Authors: Giuliani L. , De Angelis L. , Diaz Bukvic G. , Zanini M. , Minotti F. , Errea M. I. , Grondona D.
Published: June 2020

Water pollution due to emerging organic pollutants, such as agrochemicals, has become a topic of growing interest worldwide. The increase of pollutants in aquatic systems stimulated the development of new strategies for water remediation. Plasma technology is an advanced oxidation process which has proved to be an efficient method for organic matter degradation. In this work, a novel design of a trielectrode plasma reactor based on a dielectric barrier discharge extended to a third electrode operated in ambient air is presented. The water to be treated flows through a gutter with low impedance and far from the electrodes connected to the voltage sources. The reactor operates in ambient air, and it does not rely on the use of expensive inert gases. The design of the reactor is easily scalable. The performance of the reactor, in terms of the removal efficiency and the energy yield, was tested in an aqueous solution of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), one of the most widely used around the world. The reactor presents a good efficiency in the removal of the herbicide 2,4-D and values of energy yield of about 240 mg/kW h.
Controlling the crystallization of Nd-doped Bi4Ti3O12 thin-films for lead-free energy storage capacitors
Authors: Song D. P. , Yang J. , Sun J. X. , Chen L.-Y. , Chu Y. Q. , Wang Y. , Lee J.-K.
Published: June 2020

Environmentally benign non-lead-based dielectric thin film capacitors with high electrostatic energy density, long-term stability, and fast charge/discharge capability are strongly demanded in advanced electrical and pulsed power devices. Here, we propose that insufficient crystallization is an effective method to achieve high energy storage performance. A high efficiency of 84.3%, together with a good energy density of 41.6J/cm3 and an excellent fatigue endurance, is obtained in a lead-free Nd-doped Bi4Ti3O12 film of low crystallization. An increase in the annealing temperature increases the crystallinity and grain size, which improves the ferroelectric polarization of a thin film. A narrow hysteresis loop with large maximum polarization and small remnant polarization is obtained in the insufficiently crystallized film, which is annealed in the intermediate temperature. This film also shows a lower leakage current compared with the fully crystallized counterpart due to the less defective microstructure. This work provides a straightforward and executable method to design ferroelectric materials for the applications of energy storage capacitors.
Cu-rich Ti52.8Ni22.2Cu22.5Co2.5 shape memory alloy films with ultra-low fatigue for elastocaloric applications
Authors: Bumke Lars , Zamponi Christiane , Jetter Justin , Quandt Eckhard
Published: June 2020

Elastocaloric cooling demands for ultra-low functional and structural fatigue in combination with a high effect size and low energy input. Recent advances in fine-grained sputtered Ti-rich Ti54Ni34Cu12 and Ti54.7Ni30.7Cu12.3Co2.3 alloys show that a high fatigue resistance can be achieved. Ti54Ni34Cu12 shows a good compatibility (λ2 ∼ 0.9905) with coherent Ti2Cu precipitates, whereas Ti54.7Ni30.7Cu12.3Co2.3 shows a near perfect compatibility (λ2 ∼ 1.00083) but no Ti2Cu and lower transition temperatures. To differentiate whether the crystallographic compatibility or Ti2Cu precipitates influence the functional properties more, a TiNiCuCo alloy with a large expected fraction of Ti2Cu precipitates was chosen. In this work, freestanding Ti52.8Ni22.2Cu22.5Co2.5 films are fabricated by a multilayer sputter deposition approach. They show stable superelasticity for more than 2 × 107 cycles with almost no degradation. Temperature-dependent x-ray diffraction and scanning transmission electron microscopy-high-angle annular dark-field imaging investigations identify that a perfect crystallographic compatibility (λ2 ∼ 0.994 instead of 1) is not needed for high cyclic stability when combined with a small grain size (∼300 nm) and Ti2Cu precipitates. In situ x-ray diffraction studies of the stress-induced transformation reveal the presence of non-transformed austenite well above the superelastic plateau and an eased transformation perpendicular to the loading direction. In agreement with XRD studies, the adiabatic temperature change shows an increase with increasing strain up to −12.2 K for the reverse transformation. The material shows a stable isothermal entropy change of −21.8 J kg−1 K−1 over a wide range of 40 K. The average COPmat reaches a value of 11.2, which makes Ti52.8Ni22.2Cu22.5Co2.5 highly suitable for elastocaloric cooling applications.
Conditional spatially averaged turbulence and dispersion characteristics in flow over two-dimensional dunes
Authors: Dey Subhasish , Paul Prianka , Padhi Ellora
Published: June 2020

Conditional turbulence and dispersion characteristics in flow over a series of two-dimensional dunes are analyzed by applying the spatial averaging methodology. To this end, the flow data measured over an array of points on the vertical central plane were used. The manifestation of the wake-interference flow over dunes, including the boundary layer diffusion, flow separation, and flow reattachment, is demonstrated by overlapping the vorticity contours on the velocity vector diagram. The vertical distributions of the spatially averaged (SA) streamwise velocity, Reynolds shear and normal stresses, dispersive shear and normal stresses, turbulent kinetic energy (TKE) fluxes, and dispersive kinetic energy (DKE) fluxes are analyzed. It is recognized that the dominance of the conditional SA streamwise velocity associated with the temporal sweep events causes the flow to accelerate temporally. The conditional SA Reynolds stresses and TKE fluxes associated with the temporal ejection events are dominant above the dune crest, whereas those associated with the temporal sweep events are the governing mechanism below the crest. An examination of the conditional dispersive normal stresses and the DKE fluxes reveals that within the upper portion of the roughness sublayer, the dispersive ejection events are the key flow dispersion mechanism, whereas near the dune trough, the dispersive outward interaction events prevail. Furthermore, the temporal ejection events are found to be more persistent, but less frequent, than the temporal sweep events. Besides, the frequencies of the occurrences of the temporal bursting events are higher below the crest than those above it, suggesting the flow to be more turbulent below the crest.
A novel gradient composition spreading and nanolayer stacking process for combinatorial thin-film materials library fabrication
Authors: Yan Zongkai , Wu Shuai , Song Yu , Xiang Yong , Zhu Jun
Published: June 2020

A novel magnetron sputtering process is proposed to fabricate a combinatorial thin-film materials library with highly precise composition spreading. In order to produce a gradient composition spreading for a specific target, a moving shutter is used to cover the deposition substrate step by step with a fixed step-length. By rotating the substrate and repeating the step-by-step masked deposition with different targets in turn, a heterogeneous precursor structure is obtained with alternate stacking of different material layers, each of which is in a step-by-step wedge-shaped thickness cross section. By controlling the thickness of each layer at the nanometer scale, a multilayer structure is formed to facilitate the interlayer diffusion between different precursor layers. It may also define the boundaries of individual sample pixels, resulting in improved composition spreading resolutions for the prepared materials library. A combinatorial magnetron sputtering system is designed with reciprocating rectangular targets, a narrow slit between the substrate and the target, and a quartz crystal microbalance feedback to control the deposition uniformity, resulting in a variation better than 3% across a 76 × 76 mm substrate. Three individual deposition chambers are designed in an annular distribution with 90° angle between each other. Moreover, a step-by-step moving shutter and a rotating substrate holder are incorporated. Combinatorial materials libraries with more than 10 000 individual compositions could be obtained using this system. A Ti–Zr–Ni ternary alloy library was fabricated for demonstration in which the sheet resistance spreading diagram of the Ti–Zr–Ni library was studied as a function of the composition.
Experimental formation of monolayer group-IV monochalcogenides
Authors: Chang Kai , Parkin Stuart S. P.
Published: June 2020

Monolayer group-IV monochalcogenides (MX, M=Ge, Sn, Pb; X=S, Se, Te) are a family of novel two-dimensional (2D) materials that have atomic structures closely related to that of the staggered black phosphorus lattice. The structure of most monolayer MX materials exhibits a broken inversion symmetry and many of them exhibit ferroelectricity with a reversible in-plane electric polarization. A further consequence of the noncentrosymmetric structure is that when coupled with strong spin–orbit coupling, many MX materials are promising for the future applications in non-linear optics, photovoltaics, spintronics, and valleytronics. Nevertheless, because of the relatively large exfoliation energy, the creation of monolayer MX materials is not easy, which hinders the integration of these materials into the fast-developing field of 2D material heterostructures. In this Perspective, we review recent developments in experimental routes to the creation of the monolayer MX, including molecular beam epitaxy and two-step etching methods. Other approaches that could be used to prepare the monolayer MX are also discussed, such as liquid phase exfoliation and solution-phase synthesis. A quantitative comparison between these different methods is also presented.
Combined transcriptome sequencing and prokaryotic expression to investigate the key enzyme in the 2-C-methylerythritol-4-phosphate pathway of Osmanthus fragrans
Authors: Xiong Rui , Chen Zhu , Wang Weiyu , Jiang Li , Xiang Yan , Fan Jun
Published: June 2020

Terpenoids are one of the main components of plant aromas. In the present study we investigated these compounds in Osmanthus fragrans Lour., which is a fragrant plant widely used for the production of essential oils. Quantitative real-time PCR (qRT-PCR) results of enzymes associated with the 2-C-methylerythritol-4-phosphate pathway confirmed that the TPS is a key enzyme for terpenoid synthesis in O. fragrans. In a series of experiments, we identified the TPS candidate genes in O. fragrans and revealed the underlying catalytic activity and subcellular localisation of the encoded proteins. Because there is no available O. fragrans reference genome, we sequenced and analysed its transcriptome and identified two putative TPS genes, OfTPS1 and OfTPS2. According to qRT-PCR analysis, both genes were most highly expressed at the full-bloom stage, suggesting that OfTPS1 and OfTPS2 contribute to O. fragrans terpenoid synthesis. To verify this hypothesis, we constructed prokaryotic expression vectors to obtain protein. In order to study the function of OfTPS1 and OfTPS2 in the synthesis of monoterpenes, the obtained proteins were reacted with geranyl pyrophosphate. As a result, two kinds of monoterpenes, (E)-β-ocimene and linalool, were detected from reaction products, respectively. In conclusion, OfTPS1 and OfTPS2 are both monoterpene synthases.
Factors affecting the embedding of integrated primary–secondary care into a health district
Authors: Mitchell Geoffrey K. , Young Charlotte E. , Janamian Tina , Beaver Kylie M. , Johnson Joanne L. K. , Hannan-Jones Clare , Mutch Allyson J.
Published: June 2020

With the aging population, the tide of chronic disease is rising with attendant increases in health service need. Integrated care and patient-centred approaches, which established partnerships between a regional Hospital and health service (HHS), the local primary health network and local general practitioners (GPs), were identified as exemplars of an approach needed to support growing community health needs. This paper summarises the findings from a process evaluation of four GP–specialist care integration programs with the aim of identifying recommendations for embedding integrated GP–specialist care into routine practice within the HHS. The process evaluation of the integration programs drew on input from a multidisciplinary expert advisory group and data collected through face-to-face semi-structured interviews with key stakeholders, as well as surveys of participating GPs and patients. Overarching findings were identified and grouped under six themes: interdisciplinary teamwork; communication and information exchange; the use of shared care guidelines or pathways; training and education; access and accessibility; and funding. Within each theme, key challenges and enablers emerged. The findings of this study highlight benefits and challenges associated with the establishment of integrated care between primary and secondary care providers, leading to the development of key recommendations for routine integration.
Management of acute low back pain: the practices and perspectives of primary care clinicians in Australia
Authors: Ahern Malene , Dean Catherine M. , Dear Blake F. , Willcock Simon M. , Hush Julia M.
Published: June 2020

Low back pain (LBP) is the highest cause of years lived with a disability in Australia and the most frequent musculoskeletal condition for which patients seek primary care. The aims of this study were to: (1) evaluate the current practices and perspectives of Australian GPs and physiotherapists managing acute back pain; and (2) explore alignment of care with clinical guidelines. This was a prospective cross-sectional Internet survey conducted from March 2018 to May 2018 of experienced Australian GPs and physiotherapists. Descriptive statistics were used to analyse all quantitative outcomes. Two hundred primary care practitioners (72% physiotherapists and 28% GPs) from all States and Territories of Australia completed the survey. Most primary care practitioners were familiar with clinical guidelines for acute back pain management and reported delivery of many of the core components of guideline-based care, including education, advice about favourable prognosis, encouraging activity and self-management and discouraging prolonged bed rest. Deviations from guideline-based care were common, including provision of analgesic medication, passive therapies and using radiological imaging. Australian primary care clinicians in this sample were aware of back pain guidelines and typically implement care that is consistent with guideline-based recommendations. Divergences from these guidelines may indicate that primary care practitioners are delivering evidence-based and person-centred care that integrates clinicians’ judgement with patients’ preferences and guideline-based evidence.
Sustained representation of perspectival shape
Authors: Morales Jorge , Bax Axel , Firestone Chaz
Published: June 2020

Arguably the most foundational principle in perception research is that our experience of the world goes beyond the retinal image; we perceive the distal environment itself, not the proximal stimulation it causes. Shape may be the paradigm case of such “unconscious inference”: When a coin is rotated in depth, we infer the circular object it truly is, discarding the perspectival ellipse projected on our eyes. But is this really the fate of such perspectival shapes? Or does a tilted coin retain an elliptical appearance even when we know it’s circular? This question has generated heated debate from Locke and Hume to the present; but whereas extant arguments rely primarily on introspection, this problem is also open to empirical test. If tilted coins bear a representational similarity to elliptical objects, then a circular coin should, when rotated, impair search for a distal ellipse. Here, nine experiments demonstrate that this is so, suggesting that perspectival shapes persist in the mind far longer than traditionally assumed. Subjects saw search arrays of three-dimensional “coins,” and simply had to locate a distally elliptical coin. Surprisingly, rotated circular coins slowed search for elliptical targets, even when subjects clearly knew the rotated coins were circular. This pattern arose with static and dynamic cues, couldn’t be explained by strategic responding or unfamiliarity, generalized across shape classes, and occurred even with sustained viewing. Finally, these effects extended beyond artificial displays to real-world objects viewed in naturalistic, full-cue conditions. We conclude that objects have a remarkably persistent dual character: their objective shape “out there,” and their perspectival shape “from here.”
Chinese Reading Rooms, Print Culture, and Overseas Chinese Nationalism in Colonial Singapore and Malaya
Authors: Han Ming Guang
Published: June 2020

While recent research has given deeper understanding of libraries, the print culture ofo the English-speaking residents of colonial Singapore and Malaya, the majority, non-English-speaking population, has been largely neglected. To give a more complete and nuanced understanding of the role that libraries and reading and writing cultures played in colonial Singapore and Malaya, this paper will situate the three aspects among the overseas Chinese community in pre-war Singapore and Malaya. It will demonstrate that Chinese reading rooms, along with Chinese print culture, had a major role in shaping overseas Chinese nationalism in colonial Singapore and Malaya. They were important avenues for the Kuomintang to propagate ideologies that helped fostered an imagined community: a sense of nationhood among the overseas Chinese in Singapore and Malaya, whose loyalty lay with China and not the British. This was unacceptable to the British, who responded with surveillance, suppression, and censorship to contain the threat to their rule.
Hyperbolic cosine function in physics
Authors: Bonnet Isabelle , Gabelli Julien
Published: June 2020

A catenary is the shape that an electric cable takes under its own weight if suspended only at its ends between two pylons. A rope hung between two masts is also described with a catenary equation which is based on the hyperbolic cosine function. We propose here to approach the hyperbolic cosine function with two simple experiments using a beaded chain. We first study the static form of a chain whose ends are suspended between two poles, when the distance between the two poles varies. Then, we study the dynamics of the same chain falling from the edge of a table. The simplicity of these two experiments, which can be done at home, makes them appropriate for undergraduate students interested in practicals.
Stratified equatorial flows in cylindrical coordinates
Authors: Henry D , Martin C I
Published: June 2020

We construct an exact solution modelling the geophysical dynamics of an inviscid and incompressible fluid which possesses a variable density stratification, where the fluid density may vary with both the depth and latitude. Our solution pertains to the large-scale equatorial dynamics of a fluid body with a free surface propagating steadily in a purely azimuthal direction, and is expressed in terms of cylindrical coordinates. Allowing for general fluid stratification greatly complicates the Bernoulli relation—which relates the imposed pressure to the reciprocal fluid distortion at the free-surface—thereby acting as a constraint on the existence of a solution. Employing the implicit function theorem, we establish the existence of solutions and determine that the requisite monotonicity properties hold for the flow solutions we found. Furthermore, since the fluid velocity and pressure are prescribed by explicit formulae in the framework of cylindrical coordinates, our solution is amenable to analysis by the short-wavelength stability approach, which we investigate.
tP40 carbon: A novel superhard carbon allotrope*
Authors: Liu Heng , Fan Qing-Yang , Yang Fang , Yu Xin-Hai , Zhang Wei , Yun Si-Ning
Published: June 2020

In this work, a novel carbon allotrope tP40 carbon with space group P4/mmm is proposed. The structural stability, mechanical properties, elastic anisotropy, and electronic properties of tP40 carbon are investigated systematically by using density functional theory (DFT). The calculated elastic constants and phonon dispersion spectra indicate that the tP40 phase is a metastable carbon phase with mechanical stability and dynamic stability. The B/G ratio indicates that tP40 carbon is brittle from 0 GPa to 60 GPa, while tP40 carbon is ductile from 70 GPa to 100 GPa. Additionally, the anisotropic factors and the directional dependence of the Poisson’s ratio, shear modulus, and Young’s modulus of tP40 carbon at different pressures are estimated and plotted, suggesting that the tP40 carbon is elastically anisotropic. The calculated hardness values of tP40 carbon are 44.0 GPa and 40.2 GPa obtained by using Lyakhov–Oganov’s model and Chen’s model, respectively, which means that the tP40 carbon can be considered as a superhard material. The electronic band gap within Heyd–Scuseria–Ernzerhof hybrid functional (HSE06) is 4.130 eV, and it is found that the tP40 carbon is an indirect and wider band gap semiconductor material.
Weakly nonlinear multi-mode Bell–Plesset growth in cylindrical geometry*
Authors: Guo Hong-Yu , Cheng Tao , Li Ying-Jun
Published: June 2020

Bell–Plesset (BP) effect caused perturbation growth plays an important role in better understanding of characteristics of the convergence effect. Governing equations for multi-mode perturbation growth on a cylindrically convergent interface are derived. The second-order weakly nonlinear (WN) solutions for two-mode perturbations at the interface which is subject to uniformly radical motion are obtained. Our WN theory is consistent with the numerical result in terms of mode-coupling effect in converging Richtmyer–Meshkov instability. Nonlinear mode-coupling effects will cause irregular deformation of the convergent interface. The mode-coupling behavior in convergent geometry depends on the mode number, Atwood number A and convergence ratio C
r. The A = –1.0 at the interface results in larger perturbation growth than A = 1.0. The growth of generated perturbation modes from two similar modes at the initial stage are smaller than that from two dissimilar modes.
Polarization phenomena in bichromatic ionization of Ne and Ar induced by circularly polarized VUV femtosecond pulses
Authors: Grum-Grzhimailo A N , Gryzlova E V , Popova M M
Published: June 2020

Synopsis

Interference effects resulting from direct single-photon and resonant two-photon ionization of neon and argon by bichromatic circularly polarized radiation were investigated in the framework of the perturbation theory. Analytical formulas are obtained for the differential cross section of the process in multielectron noble gas atoms. The possibility of coherent control of the photoelectron angular distribution and spin polarization will be discussed.
Measurements of spatial correlations in quantum gases using ultralong-range strontium Rydberg molecules
Authors: Whalen J D , Ding R , Kanungo S K , Dunning F B , Killian T C , Yoshida S , Burgdörfer J
Published: June 2020

Synopsis

The photoexcitation of ultralong-range Rydberg molecules is demonstrated as a probe of spatial cor-relations in a quantum gas on previously inaccessible length scales of 1400-3200 a
0. Measurements using cold (∼1 μK) (fermionic) 87Sr and (bosonic) 84Sr reveal the effects of quantum statistics on the pair correlation function g
(2)(R).
Optical shielding for ultracold 39K-Cs binary collisions
Authors: Xie T , Orbán A , Dulieu O , Bouloufa-Maafa N
Published: June 2020

Synopsis

The optical shielding efficiency in ultracold collisions is investigated for the first time with atoms of different species (39K-Cs) with a close-coupling approach. The spontaneous emission is taken into account through a complex optical potential. The results show that an efficient shielding can be achieved in the presence of a blue-detuned laser. The role of the light polarization on the shielding efficiency is carefully investigated.
Non-adiabatic quantum dynamics of the ultracold Li+LiNa→ Li2+Na chemical reaction
Authors: Kendrick B K , Li M , Li H , Kotochigova S , Croft J F E , Balakrishnan N
Published: June 2020

Synopsis

We report non-adiabatic dynamics of the Li+LiNa→Li2+Na chemical reaction at cold and ultracold temperatures employing accurate ab initio electronic potential energy surfaces in a quantum dynamics formulation employing a diabatic representation. Results are compared against those from a single adiabatic ground state potential energy surface and a universal model based on the long-range interaction potential. We discuss signatures of non-universal behavior in the total rate coefficients as well as strong non-adiabatic effects in the state-to-state rotationally resolved rate coefficients.
Coincident detection of recoil ions and photoelectrons after multiphoton-ionisation of cold 6Li atoms trapped in a dipole trap
Authors: Kurz N , Mootheril D T M , Mezinska S , Pfeifer T , Dorn A
Published: June 2020

Synopsis

We report on performing high resolution recoil ion momentum spectroscopy in a reaction microscope (ReMi) on a target of dipole-force trapped cold 6Li atoms in a non-interacting |1〉-|2〉 spin mixture and coincident detection of recoil ions and photoelectrons. Photo-ionization occurs from the electronic ground state of the 6Li atoms and IR photons significantly contribute to the ion yield via 3-photon resonances. High resolution time-of-flight spectra are obtained by modulating the trap depth synced with the arrival of the fs laser pulses.
Low-energy scattering properties of ground-state and excited-state positronium collisions
Authors: Higgins M D , Daily K M , Greene C H
Published: June 2020

Synopsis

Low-energy elastic and inelastic scattering in the Ps(1s)-Ps(2s) channel is treated in a four-body hyperspherical coordinate calculation. Adiabatic potentials are calculated for triplet-triplet, singlet-singlet, and singlet-triplet spin symmetries of coupled electrons and coupled positrons, with total angular momentum L = 0 and positive parity. Preliminary estimates of the s-wave scattering length in the elastic Ps(1s)-Ps(2s) channel were obtained. Spin recoupling is implemented to obtain calculations of experimentally relevant scattering properties for different Ps spin states.
Tunnelling of the Bose-Einstein condensates in a tilted shallow trap
Authors: Jian Y , Xue J K
Published: June 2020

Synopsis

Using variational method and numerical simulation, the tunnelling of Bose-Einstein condensates (BECs) in a tilted shallow trap is studied. The stable bound state, the quasi-bound state and the diffusion state are predicted. For a driven shallow trap, the resonance tunnelling phenomenon is observed.
Understanding the formation of metastable furan dication in collisions with ions
Authors: Erdmann E , Indrajith S , Chiarinelli J , Díaz-Tendero S , Aguirre N F , Alcamí M , Domaracka A , Rousseau P , Huber B A , Bolognesi P , Avaldi L , Łabuda M
Published: June 2020

Synopsis

This work relies on complementary theoretical and experimental studies of the processes induced by ion-furan collisions. Results of the Molecular Dynamics simulations and exploration of the energy profiles combined with coincidence mass spectrometry provide complete picture of the fragmentation of furan dication.
A resonant ionization spectroscopy scheme for photodetachment studies
Authors: Welander J , Navarrete J E Navarro , Kodambattil M , Sundberg J , Lu D , Hanstorp D
Published: June 2020

Synopsis

A refined Resonant Ionization Spectroscopy (RIS) scheme for high resolution Laser Photodetachment Threshold Spectroscopy (LPTS). In this work the scheme is used to measure the electron affinity of cesium.
Model potential parameters for alkali metal atomic lithium
Authors: Zhao S F , Tang Z F , Jiao Z H , Li W , Wang G L , Zhou X X
Published: June 2020

Synopsis

The model potential proposed by Laughlin (Phys.Rev.A 64,013406 (2001)) can give accurate bound-state energies of atoms, which is very useful in atomic physics. We determine model potential parameters for alkali metal atomic lithium (Li) by comparing the present calculated bound-state energies with both the experimental singlet energy values and quantum defect calculations.
Electron-impact excitation of the (4p55s5p)4S3/2 quasimetastable state in Rb
Authors: Roman V , Demes S
Published: June 2020

Synopsis

The ejected-electron excitation function of the (4p55s5p)4S3/2 quasimetastable state in rubidium was experimentally investigated by electron-impact in the energy range from the excitation threshold at 16.64 eV to 100 eV. The obtained data at 0.12 eV energy resolution indicate the presence of negative-ion resonances just above excitation threshold. A comparison is made with the optical excitation function of the (4p55s5p)4S3/2 → (4p65p)2P3/2 transition (λ = 82.37 nm), measured earlier with a lower energy resolution of ≈ 1.5 eV.
Infrared laser spectroscopy measurement of the electron affinity of thallium
Authors: Walter C W , Gibson N D , Patel K R , Spielman S E
Published: June 2020

Synopsis

The electron affinity of thallium, Tl, has been measured using tunable infrared laser photodetachment threshold spectroscopy. The relative cross section for neutral atom production following photodetachment from Tl− was measured with a crossed laser-ion beam apparatus over the photon energy range 300 - 900 meV. A single s-wave threshold was observed near 320 meV due to the opening of the ground state phodetachment channel, yielding a preliminary value for the electron affinity of thallium. The present results are compared to previous experimental and theoretical results.
Coexistence of cubic and tetragonal phase with colored excitonic emissions in mixed halide Perovskite CH3NH3PbI3-xClx thin film
Authors: Tanveer Karim A M M , Hossain M S , Khan M K R
Published: June 2020

Synopsis

CH3NH3PbI3-xClx crystalline film composed of cuboids and polyhedral structure was prepared by dipping and withdrawing method at ambient. X-ray diffraction shows the presence of tetragonal and cubic phases having high absorption coefficient of 106 m-1. Photoluminescence study confirms shallow and deep level emissions. Temperature dependent-cathodoluminescence shows a green luminescence at 2.51 eV accompanied by weak red and ultraviolet luminescence at 80 and 300 K.
Resonance contribution to electron-impact excitation rate coefficients of helium-like S14+ ions
Authors: Wu Z W , Ren C , Jiang J , Xie L Y , Zhang D H , Dong C Z
Published: June 2020

Synopsis

Electron-impact excitation rate coefficients of S14+ ions have been studied by using a relativistic flexible atomic code that can account systematically for configuration interactions. Moreover, we also considered the resonance excitation contributions to the rate coefficients. It is found that the contributions of resonance excitation on rate coefficients is very important.
Accurate electron affinity of lanthanum atom
Authors: Lu Y , Tang R , Fu X , Ning C
Published: June 2020

Synopsis

Atomic lanthanum anion La− is the best candidate for laser cooling of any atomic anions by far. The previous theoretical studies showed that La− has very a complicated electronic structure, which cannot be well resolved by the traditional photoelectron spectroscopy. In the present work, we used the slow-electron velocity-map imaging method in combination with an ion trap to measure the electronic structure of La−. The electron affinity of La is accurately determined to be 4496.97(20) cm−1 or 0.557553(25) eV.
Ab initio investigation of the line-shape parameters for atmosphere-relevant molecular systems
Authors: Jóźwiak H , Thibault F , Cybulski H , Stolarczyk N , Gancewski M , Wcisło P
Published: June 2020

Synopsis

We demonstrate the results of the first ab initio investigation of the line-shape parameters for two molecular systems important for atmospheric studies: CO-N2 and O2-N2. We provide the pressure broadening and shift coefficients with their speed dependencies for purely rotational lines, calculated from highly accurate potential energy surfaces with the close-coupling scheme. This is the first, fully quantum approach to the problem of determination of the spectral line shapes for the systems important for terrestrial atmospheric measurements.
Pressure manipulation of exciton dynamics in few-layered MoS2
Authors: Li Q , Sui L , Jiang Y , Chen A , Jin W , Liu H , Yuan K , Jin M
Published: June 2020

Synopsis

Transition metal dichalcogenides have recently attracted great interest as an important class of two-dimensional semiconductors because of their distinctive electronic, optical and catalytic properties. Here we demonstrate the first experimental study on ultrafast excited state dynamics of few-layered molybdenum disulfide under high pressure by means of broadband transient absorption spectroscopy combined with diamond anvil cell devices.
Probing functional group dependence in dissociative electron attachment using negative ion momentum imaging
Authors: Gokhale S , Gope K , Tadsare V , Bain M , Raghav A , Ashfold M N R , Krishnakumar E , Prabhudesai V S
Published: June 2020

Synopsis

Dissociative electron attachment (DEA) is the most efficient way to explore the structure and dynam-ics of excited states of molecular negative ions. More importantly, DEA has been shown to be a tool for chemical control. One crucial aspect of the chemical control using DEA is the functional group dependence present in this process. Here we present cases on the effect of delocalized electrons on DEA patterns observed in simple aromatic compounds.
Uncertainty assessment of Rydberg and doubly-excited molecular states ab initio calculations using Quantum Defect Theory scaling laws
Authors: Telmini M , Jungen Ch
Published: June 2020

Synopsis

We discuss the accuracy of various published ab initio calculations of highly excited Born-Oppenheimer bound and doubly excited states in diatomic molecules. We show that some of these results appear questionable and in a few cases even clearly unreliable, a fact which may also affect the prediction of collision cross sections based on such data. Our analysis uses Quantum Defect Theory scaling laws and is supported by variational R-matrix calculations. Some simple recipes are discussed, which may help users of ab initio quantum chemistry packages to assess the quality of their results.
Electron emission from CH4 molecule induced by 5.5 MeV/u bare C ions
Authors: Mandal A , Bagdia C , Roychowdhury M , Monti J M , Rivarola R D , Tribedi L C
Published: June 2020

Synopsis

We present the experimental and theoretical study of electron emission from methane (CH4) in collisions with 5.5 MeV/u bare carbon projectiles. We have measured double differential cross section of electron emission and compared the data with the prior form of the continuum distorted wave – eikonal initial state (CDW-EIS) model calculation. The CDW-EIS calculations are in very good agreement with the data.
Impact parameter sensitive study of inner-shell atomic processes in Xe54+, Xe52+ → Xe collisions
Authors: Gumberidze A , Kozhuharov C , Zhang R T , Trotsenko S , Kozhedub Y S , Du R D , Bois H , Beyer F. , Blumenhagen K-H , Brandau C , Bräuning-Demian A , Chen W , Forstner O , Gao B , Gassner T , Grisenti R E , Hagmann S , Hillenbrand P-M , Indelicato P , Kumar A , Lestinsky M , Litvinov Yu A , Petridis N , Schury D , Spillmann U , Trageser C , Trassinelli M , Tu X , Stöhlker Th
Published: June 2020

Synopsis

In this work, we present a pilot experiment in the experimental storage ring (ESR) at GSI devoted to impact parameter sensitive studies of inner shell atomic processes for bare and He-like xenon ions (Xe54+, Xe52+) colliding with neutral xenon gas atoms. The projectile and target x-rays have been measured at different observation angles for all impact parameters as well as for the impact parameter range of ∼35 - 70 fm.
Energetic processing of hydrocarbons molecular species by ionizing radiation towards the formation of cyclic species
Authors: Indrajith S , Kočišekt J , Domaracka A , Rousseau P , Huber B A
Published: June 2020

Synopsis

Here we report on experimental studies of the collisions between butadiene clusters and three different ionizing radiation sources: 70 eV electrons, 270 nm photons and 3 keV Ar+ ions. New molecular species are produced by growth mechanism inside of clusters.
Energy deposit by electron excitation in CnN+ projectiles (n=1-3) colliding at in termediate velocity with He atoms : semi-empirical estimates and calculations
Authors: Mahajan T , Béroff K , Pons B , Illescas C , Chabot M , Idbarkach T , Jorge A , Aguirre N F , Diaz-Tendero S
Published: June 2020

Synopsis

Using measured dissociation branching ratios and theoretical dissociation energies, we extracted semi-empirical estimates of the energy deposit due to electron excitation in CnN+-He collisions at v=2.2 a.u. We compared these estimates to calculations based on the IAE (Independent Atom and Electron) model where the atom(ion)-atom excitation is treated within the Classical Trajectory Monte Carlo (CTMC) approach. A good agreement has been found. This atomic approach is also able to reproduce the experimental Kinetic Energy Release (KER) in CN+ dissociation measured in 3.5 a.u CN+-He collision.
Femtosecond nonadiabatic cascade and subsequent photofragmentation of XUV excited caffeine molecule
Authors: Yamazaki K , Marciniak A , Maeda S , Reduzzi M , Despré V , Hervé M , Meziane M , Niehaus T , Loriot V , Kuleff A , Schindler B , Compagnon I , Sansone G , Lépine F
Published: June 2020

Synopsis

We found that the XUV excited caffeine undergoes nondadabatic cascade via more than 100 shake-up states within the time constant of 40 fs by using femtosecond XUV-NIR pump-probe photo-ion spectroscopy and the SAC-CI level of ab-initio many-body theory. This nonadiabatic cascade results in the photofragmentation to specific large fragments. Furether ionization by NIR probe during the cascade increases the small fragments CH3
+, CO+
etc. This results show that both vibronic coupling and electron correlation are the keys for the femtochemistry in the highly-correlated electronic excited states.
L-changing through very-long-range interactions in high-n, n∼300, Rydberg-Rydberg collisions
Authors: Yoshida S , Burgdörfer J , Fields G , Brienza R , Dunning F B
Published: June 2020

Synopsis

State-changing in thermal-energy collisions between strontium atoms in high-n, n∼300, n1F3 Rydberg states is studied in an atomic beam and analyzed using classical trajectory Monte Carlo simulations. The L-changing cross section is large, ∼10-4 cm2, much greater than the corresponding “hard-sphere” cross section.
Model for vibronic excitation of CH+ by resonant scattering of electron
Authors: Jiang X , Yuen C , Cortona P , Kokoouline V , Ayouz M
Published: June 2020

Synopsis

A new model for theoretical study of vibronic (de-)excitation (including vibrational (de-)excitation) cross sections of CH+ by electron impact was developed based on the multichannel quantum defect theory (MQDT) close-channel-elimination procedure and vibrational-frame-transformation theory of Chang and Fano. The successful application of this model suggested a promising calculation method for vibronic (de-)excitation of diatomic ion core by resonant scattering of electron.
Ionization cross-sections of L-shell and L-subshells by electron impact
Authors: Patoary M A R , Shorifuddoza M , Haque A K F , Uddin M A
Published: June 2020

Synopsis

Vaisburd and Evdokimov proposed an empirical VE model to calculate the electron impact single ionization cross-sections of atoms and molecules. The extension of the modified VE model (MVE) has been proposed incorporating the relativistic effects. This model is applied to investigate the total L-shell as well as L1-, L2- and L3-subshells ionization cross-sections of various atomic targets with atomic numbers Z =1892 for incident energies up to 1 GeV. The results from the MVE model are compared with the available experimental data and theoretical findings.
Quantum vortex surfaces: a dizzying new effect in single ionization collisions
Authors: Navarrete F , Barrachina R O
Published: June 2020

Synopsis

We study the appearance of quantum vortices in the transition matrix element of single ionization collisions. We relax all the usual geometrical restrictions on the momenta of the final-state, and demonstrate that previously observed vortex points and lines correspond to 2D and 3D intersections of a much more complex structure: a quantum vortex surface. Finally, we theoretically evaluate this complex structure for the single ionization of hydrogen by positron impact.
Improvement of the target continuum state in distorted wave theories: a dynamic-depending charge
Authors: Rojas M F , Monti J M , Quinto M A , Rivarola R D
Published: June 2020

Synopsis

In order to improve the representation of the residual-target final state whilst maintaining low computational times, a dynamic-depending charge defined by the emission energy and angle of the ionized electron is considered in the residual-target continuum state.