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Sensitivity of entanglement decay of quantum-dot spin qubits to the external magnetic field
PublicationWe study the decay of entanglement of quantum-dot electron-spin qubits under hyperfine-interaction-mediated decoherence.We show that two-qubit entanglement of a single entangled initial state may exhibit decay characteristic of two disentanglement regimes in a single sample, when the externalmagnetic field is changed. The transition is manifested by the suppression of time-dependent entanglement oscillations which are superimposed...
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Free randomness amplification using bipartite chain correlations
PublicationA direct analysis of the task of randomness amplification from Santha-Vazirani sources using the violation of the chained Bell inequality is performed in terms of the convex combination of no-signaling boxes required to simulate quantum violation of the inequality. This analysis is used to find the exact threshold value of the initial randomness parameter from which perfect randomness can be extracted in the asymptotic limit of...
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Quantum-state transfer in spin chains via isolated resonance of terminal spins
PublicationWe propose a quantum-state transfer protocol in a spin chain that requires only the control of the spins at the ends of the quantum wire. The protocol is to a large extent insensitive to inhomogeneity caused by local magnetic fields and perturbation of exchange couplings. Moreover, apart from the free evolution regime, it allows one to induce an adiabatic spin transfer, which provides the possibility of performing the transfer...
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Static electric multipole susceptibilities of the relativistic hydrogenlike atom in the ground state: Application of the Sturmian expansion of the generalized Dirac-Coulomb Green function
PublicationThe ground state of the Dirac one-electron atom, placed in a weak, static electric field of definite $2^{L}$ polarity, is studied within the framework of the first-order perturbation theory. The Sturmian expansion of the generalized Dirac-Coulomb Green function [R. Szmytkowski, J. Phys. B: At. Mol. Opt. Phys. 30, 825 (1997); erratum R. Szmytkowski, J. Phys. B: At. Mol. Opt. Phys. 30, 2747 (1997)] is used to derive closed-form analytical...
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Conjectured strong complementary-correlations tradeoff
PublicationWe conjecture uncertainty relations that restrict correlations between the results of measurements performed by two separate parties on a shared quantum state. The first uncertainty relation bounds the sum of two mutual informations when one party measures a single observable and the other party measures one of two observables. The uncertainty relation does not follow from the Maassen-Uffink uncertainty relation and is much stronger...
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Separability in terms of a single entanglement witness
PublicationThe separability problem is formulated in terms of a characterization of a single entanglement witness. More specifically, we show that any (in general multipartite) state rho is separable if and only if a specially constructed entanglement witness W-rho is weakly optimal, i.e., its expectation value vanishes on at least one product vector. Interestingly, the witness can always be chosen to be decomposable. Our result changes the...
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Anomalous decay of quantum correlations of quantum-dot qubits
PublicationWe study the evolution of quantum correlations, quantified by the geometric discord, of two excitonic quantum-dot qubits under the influence of the phonon environment. We show that the decay of these correlations differs substantially from the decay of entanglement. Instead of displaying sudden-death-type behavior, the geometric discord shows a tendency to undergo transitions between different types of decay, is sensitive to nonlocal...
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Properties of dimension witnesses and their semidefinite programming relaxations
PublicationIn this paper we develop a method for investigating semi-device-independent randomness expansion protocols that was introduced in Li et al. [H.-W. Li, P. Mironowicz, M. Pawłowski, Z.-Q. Yin, Y.-C. Wu, S. Wang, W. Chen, H.-G. Hu, G.-C. Guo, and Z.-F. Han, Phys. Rev. A 87, 020302(R) (2013)]. This method allows us to lower bound, with semi-definite programming, the randomness obtained from random number generators based on dimension...
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Quantum metrology: Heisenberg limit with bound entanglement
PublicationQuantum entanglement may provide a huge boost in the precision of parameter estimation. However, quantum metrology seems to be extremely sensitive to noise in the probe state. There is an important still open question: What type of entanglement is useful as a resource in quantum metrology? Here we raise this question in relation to entanglement distillation. We provide a counterintuitive example of a family of bound entangled states...
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Method for universal detection of two-photon polarization entanglement
PublicationDetecting and quantifying quantum entanglement of a given unknown state poses problems that are fundamentally important for quantum information processing. Surprisingly, no direct (i.e., without quantum tomography) universal experimental implementation of a necessary and sufficient test of entanglement has been designed even for a general two-qubit state. Here we propose an experimental method for detecting a collective universal...
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Bound on Bell inequalities by fraction of determinism and reverse triangle inequality
PublicationIt is an established fact that entanglement is a resource. Sharing an entangled state leads to nonlocal correlations and to violations of Bell inequalities. Such nonlocal correlations illustrate the advantage of quantum resources over classical resources. In this paper, we quantitatively study Bell inequalities with 2 × n inputs. As found in Gisin et al. [Int. J. Quantum. Inform. 05, 525 (2007)], quantum mechanical correlations...
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Device-independent quantum key distribution based on measurement inputs
PublicationWe provide an analysis of a family of device-independent quantum key distribution (QKD) protocols that has the following features. (a) The bits used for the secret key do not come from the results of the measurements on an entangled state but from the choices of settings. (b) Instead of a single security parameter (a violation of some Bell inequality) a set of them is used to estimate the level of trust in the secrecy of the key....
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Distributed correlations and information flows within a hybrid multipartite quantum-classical system
PublicationUnderstanding the non-Markovian mechanisms underlying the revivals of quantum entanglement in the presence of classical environments is central in the theory of quantum information. Tentative interpretations have been given by either the role of the environment as a control device or the concept of hidden entanglement. We address this issue from an information-theoretic point of view. To this aim, we consider a paradigmatic tripartite...
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Quantum origins of objectivity
PublicationIn spite of all of its successes, quantum mechanics leaves us with a central problem: How does nature create a bridge from fragile quanta to the objective world of everyday experience? Here we find that a basic structure within quantum mechanics that leads to the perceived objectivity is a so-called spectrum broadcast structure. We uncover this based on minimal assumptions, without referring to any dynamical details or a concrete...
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Directed percolation effects emerging from superadditivity of quantum networks
PublicationEntanglement-induced nonadditivity of classical communication capacity in networks consisting of quantum channels is considered. Communication lattices consisting of butterfly-type entanglement-breaking channels augmented, with some probability, by identity channels are analyzed. The capacity superadditivity in the network is manifested in directed correlated bond percolation which we consider in two flavors: simply directed and...
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Elastic electron scattering and vibrational excitation of isoxazole molecules in the energy range from 2 to 20 eV
PublicationDifferential cross sections for elastic electron scattering and the excitation of the C-H vibrational modes of isoxazole molecules were measured in the energy range from 2 to 20 eV and over the scattering angle range from 10◦ to 180◦. The cross sections at the scattering angles of and above 90◦ were accessible with the use of a magnetic angle changer. The differential cross sections were integrated to yield integral and momentum...
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Analytical progress on symmetric geometric discord: Measurement-based upper bounds
PublicationQuantum correlations may be measured by means of the distance of the state to the subclass ofstates having well defined classical properties. In particular, a geometric measure of asymmetricdiscord [Daki´c et al., Phys. Rev. Lett. 105, 190502 (2010)] was recently defined as the Hilbert-Schmidt distance of a given two-qubit state to the closest classical-quantum (CQ) correlated state.We analyze a geometric measure of symmetric...
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Quantum privacy witness
PublicationWhile it is usually known that the mean value of a single observable is enough to detect entanglement or its distillability, the counterpart of such an approach in the case of quantum privacy has been missing. Here we develop the concept of a privacy witness, i.e., a single observable that may detect the presence of the secure key even in the case of bound entanglement. Then we develop the notion of secret-key estimation based...
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Quantum-correlation breaking channels, broadcasting scenarios, and finite Markov chains
PublicationOne of the classical results concerning quantum channels is the characterization of entanglementbreakingchannels [M. Horodecki et al., Rev. Math. Phys 15, 629 (2003)]. We address the questionwhether there exists a similar characterization on the level of quantum correlations which may gobeyond entanglement. The answer is fully affirmative in the case of breaking quantum correlationsdown to the, so called, QC (Quantum-Classical)...
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Grow first, gain fat in the meantime. Longitudinal study of anthropometric changes around menarche
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Social learning in cluster initiatives
PublicationPurpose – The purpose of the paper is to portray social learning in cluster initiatives (CIs), namely: 1) to explore, with the lens of the communities of practice (CoPs) theory, in what ways social learning occurs in CIs; 2) to discover how various CoPs emerge and evolve in CIs to facilitate a collective journey in their learning process. Subsequently, the authors address the research questions: In what ways does social learning...
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Estimators of covariance matrices in Msplit(q) estimation
PublicationThis paper proposes methods for the determination of covariance matrices of Msplit(q) estimators. The solutions presented here allow Msplit(q) estimation to be supplemented by the operations from the domain of accuracy analysis (especially that concerning estimators of parameters). Theoretical forms of covariance matrices of Msplit(q) estimators were established using the empirical influence functions and the equivalent covariance...
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High performance filtering for big datasets from Airborne Laser Scanning with CUDA technology
PublicationThere are many studies on the problems of processing big datasets provided by Airborne Laser Scanning (ALS). The processing of point clouds is often executed in stages or on the fragments of the measurement set. Therefore, solutions that enable the processing of the entire cloud at the same time in a simple, fast, efficient way are the subject of many researches. In this paper, authors propose to use General-Purpose computation...
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Electrodes criticality: the impact of CRMs in the leachate electrochemical oxidation
Publication. Landfill leachate possesses high concentrations of ammonia, micropollutants, and heavy metals, and are characterised for low biodegradability. For this reason, conventional treatment technologies may result ineffective for complete pollutant removal. Electrochemical oxidation allows most of the of recalcitrant pollutants to be oxidised effectively within an easy operational and acceptable retention time, without the need to provide...
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Entanglement of genuinely entangled subspaces and states: Exact, approximate, and numerical results
PublicationGenuinely entangled subspaces (GESs) are those subspaces of multipartite Hilbert spaces that consist only of genuinely multiparty entangled pure states. They are natural generalizations of the well-known notion of completely entangled subspaces, which by definition are void of fully product vectors. Entangled subspaces are an important tool of quantum information theory as they directly lead to constructions of entangled states,...
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Experimentally feasible semi-device-independent certification of four-outcome positive-operator-valued measurements
PublicationRecently the quantum information science community devoted a lot of attention to the theoretical and practical aspects of generalized measurements, the formalism of all possible quantum operations leading to acquisition of classical information. On the other hand, due to imperfections present in quantum devices, and limited thrust to them, a trend of formulating quantum information tasks in a semi-device-independent manner emerged....
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The lethal effect of hydrotechnical concrete on freshwater Bivalvia
PublicationMost hydrotechnical buildings under construction demand the concrete mixture to be set directly under water. The main reason for such a procedure is to limit the washing away of the the concrete binding mixture and to increase the efficiency of organisation of work so as to ensure continuity in concreting. The impact on the aquatic environment of recent developments in concrete technology and the use of new components has not yet...
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Elastic scattering of electrons from chloroform
PublicationWe present experimental and theoretical cross sections for elastic electron scattering from CHCl3. This is an important target because of its relevance to environmental chemistry and the plasma etching industry as a source of chlorine radicals. The experimental results were obtained at incident electron energies ranging from 0.5 to 800 eV in the 10deg-130deg scattering angle range. Theoretically, the scattering cross sections in...
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Low-energy positron scattering from gas-phase pyrimidine: A quantum treatment of the dynamics and a comparison with experiments
PublicationWe are reporting detailed quantum scattering calculations that describe the diffusion of a beam of low-energy positrons interacting with the pyrimidine target as a gas-phase partner. The calculations have employed an essentially ab initio model for the short-range correlation interaction and for the electrostatic interaction of an impinging positron and the electron+nuclear structure of the target molecule at its equilibrium geometry.
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Positron scattering on molecular hydrogen: Analysis of experimental and theoretical uncertainties
PublicationExperiments performed in recent years on positron scattering from molecular hydrogen indicated a rise of the total cross section in the limit of zero energy, but essentially disagree on the amplitude of this rise. Mitroy and collaborators [J.-Y. Zhang et al., Phys. Rev. Lett. 103, 223202 (2009)] predicted a scattering length somewhat different from values deduced experimentally. Using a Markov chain Monte Carlo modified effective...
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Magnetizability of the relativistic hydrogenlike atom in an arbitrary discrete energy eigenstate: Application of the Sturmian expansion of the generalized Dirac-Coulomb Green function
PublicationThe Sturmian expansion of the generalized Dirac--Coulomb Green function [R.\/~Szmytkowski, J.\ Phys.\ B 30 (1997) 825; erratum 30 (1997) 2747] is exploited to derive a closed-form expression for the magnetizability of an arbitrary discrete state of the relativistic one-electron atom with a point-like, spinless and motionless nucleus of charge $Ze$. The result has the form of a double finite sum involving the generalized hypergeometric...
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Robust amplification of Santha-Vazirani sources with three devices
PublicationWe demonstrate that amplification of arbitrarily weak randomness is possible using quantum resources. We present a randomness amplification protocol that involves Bell experiments. We find a Bell inequality which can amplify arbitrarily weak randomness and give a detailed analysis of the protocol involving it. Our analysis includes finding a sufficient violation of Bell inequality as a function of the initial quality of randomness....
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Electron scattering from 2-methyl–1,3-butadiene,C5H8, molecules: Role of methylation
PublicationWe report cross-section results from experimental and theoretical investigations into electron collisions with the 2-methyl–1,3-butadiene [C5H8] molecule. The current results are compared with our previous results for the 1,3-butadiene [C4H6] molecule, a structural homologue of 2-methyl–1,3-butadiene, to investigate how the methylation (the substitution of hydrogen atom by a methyl group) affects the shape and/or magnitude of the...
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Information content of systems as a physical principle
PublicationTo explain the conceptual gap between classical and quantum and other, hypothetical descriptions of the world, several principles have been proposed. So far, all these principles have not explicitly included the uncertainty relation. Here we introduce an information content principle ( ICP ) which represents a constrained uncertainty principle. The principle, by taking into account the encoding and decoding properties of a single physical...
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Generic appearance of objective results in quantum measurements
PublicationMeasurement is of central interest in quantum mechanics as it provides the link between the quantum world and the world of everyday experience. One of the features of everyday experience is its robust, objective character, contrasting the delicate nature of quantum systems. Here we analyze in a completely model-independent way the celebrated von Neumann measurement process, using recent techniques of information flow, studied in...
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Redundant information encoding in QED during decoherence
PublicationBroadly understood decoherence processes in quantum electrodynamics, induced by neglecting either the radiation [L. Landau, Z. Phys. 45, 430 (1927)] or the charged matter [N. Bohr and L. Rosenfeld, K. Danske Vidensk. Selsk, Math.-Fys. Medd. XII, 8 (1933)], have been studied from the dawn of the theory. However, what happens in between, when a part of the radiation may be observed, as is the case in many real-life situations, has...
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Surfactants: a real threat to the aquatic geoecosystems of lobelia lakes
PublicationLobelia lakes are valuable elements of the natural environment. They are characterised by low trophy, mainly in-forest location and a high transparency of water. However, similarly to other surface waters, they are subjected to increasing anthropogenic pressures, a good indicator of which is the level of surfactants, also called surface-active agents (SAAs). The aim of the study was to evaluate the intensity of anthropogenic pressures...
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Reduction of measurement data before Digital Terrain Model generation vs. DTM generalisation
PublicationModern data acquisition technologies provide large datasets that are not always necessary in its entirety to properly accomplish the goal of the study. In addition, such datasets are often cumbersome for rational processing, and their processing is time and labour consuming. Therefore, methods that enable to reduce the size of the measurement dataset, such as the generalization of the Digital Terrain Model (DTM) or the reduction...
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Completely entangled subspaces of entanglement depth k
PublicationWe introduce a class of entangled subspaces: completely entangled subspaces of entanglement depth k (k-CESs). These are subspaces of multipartite Hilbert spaces containing only pure states with an entanglement depth of at least k. We present an efficient construction of k-CESs of any achievable dimensionality in any multipartite scenario. Further, we discuss the relation between these subspaces and unextendible product bases (UPBs)....
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The role of clusters as collective actors in the energy transformation: the case of Mazovia Cluster ICT
PublicationPurpose – In our paper we aim to show the possibilities of implementing the idea of sustainability in the context of energy transformation using the concept of an industrial cluster. The implementation of the idea of sustainability is of particular importance from the perspective of the functioning of the meta-organisations involved in the implementation and promotion of decarbonisation processes. Industrial clusters, as collective...
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Negative result about the construction of genuinely entangled subspaces from unextendible product bases
PublicationUnextendible product bases (UPBs) provide a versatile tool with various applications across different areas of quantum information theory. Their comprehensive characterization is thus of great importance and has been a subject of vital interest for over two decades now. An open question asks about the existence of UPBs, which are genuinely unextendible, i.e., they are not extendible even with biproduct vectors. In other words,...
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Quantum strategies for rendezvous and domination tasks on graphs with mobile agents
PublicationThis paper explores the application of quantum nonlocality, a renowned and unique phenomenon acknowledged as a valuable resource. Focusing on an alternative application, we demonstrate its quantum advantage for mobile agents engaged in specific distributed tasks without communication. The research addresses the significant challenge of rendezvous on graphs and introduces a distributed task for mobile agents grounded in the graph...
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Complementarity between entanglement-assisted and quantum distributed random access code
PublicationCollaborative communication tasks such as random access codes (RACs) employing quantum resources have manifested great potential in enhancing information processing capabilities beyond the classical limitations. The two quantum variants of RACs, namely, quantum random access code (QRAC) and the entanglement-assisted random access code (EARAC), have demonstrated equal prowess for a number of tasks. However, there do exist specific...
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Selected anionic and cationic surface active agents: case study on the Kłodnica sediments
PublicationSurface active agents (surfactants) are a group of chemical compounds, which are used as ingredients of detergents, cleaning products, cosmetics and functional products. After use, wastes containing surfactants or their degradation products are discharged to wastewater treatment plants or directly into surface waters. Due to their specific properties of SAAs, compounds are able to migrate between different environmental compartments...
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Constructing genuinely entangled multipartite states with applications to local hidden variables and local hidden states models
PublicationBuilding upon the results of R. Augusiak et al. [Phys. Rev. Lett. 115, 030404 (2015)] we develop a general approach to the generation of genuinely entangled multipartite states of any number of parties from genuinely entangled states of a fixed number of parties, in particular, the bipartite entangled ones. In our approach, certain isometries whose output subspaces are either symmetric or genuinely entangled in some multipartite...
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Static magnetic multipole susceptibilities of the relativistic hydrogenlike atom in the ground state: Application of the Sturmian expansion of the generalized Dirac-Coulomb Green function
PublicationWe study far- and near-field magnetic and electric multipole moments induced in the ground state of the Dirac one-electron atom placed in a weak 2L-pole magnetostatic field. The analysis is carried out within the framework of the first-order Rayleigh-Schrödinger perturbation theory, with the use of the Sturmian expansion of the generalized Dirac-Coulomb Green function [Szmytkowski, J. Phys. B 30, 825 (1997);J. Phys. B 30, 2747(E)...
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Trade-offs in multiparty Bell-inequality violations in qubit networks
PublicationTwo overlapping bipartite binary input Bell inequalities cannot be simultaneously violated as this would contradict the usual no-signalling principle. This property is known as monogamy of Bell inequality violations and generally Bell monogamy relations refer to trade-offs between simultaneous violations of multiple inequalities. It turns out that multipartite Bell inequalities admit weaker forms of monogamies that allow for violations...
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System information propagation for composite structures
PublicationWe study in details decoherence process of a spin register, coupled to a spin environment. We use recently developed methods of information transfer study in open quantum systems to analyze information flow between the register and its environment. We show that there are regimes when not only the register decoheres effectively to a classical bit string, but this bit string is redundantly encoded in the environment, making it available...
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Second-order Stark effect and polarizability of a relativistic two-dimensional hydrogenlike atom in the ground state
PublicationThe second-order Stark effect for a planar Dirac one-electron atom in the ground state is analyzed within the framework of the Rayleigh-Schrödinger perturbation theory, with the use of the Sturmian series expansion of the generalized Dirac-Coulomb Green's function. A closed-form analytical expression for the static dipole polarizability of that system is found. The formula involves the generalized hypergeometric function ${}_{3}F_{2}$...
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Electron collisions with cyanoacetylene HC3N : Vibrational excitation and dissociative electron attachment
PublicationWe experimentally probe electron collisions with HC3N in the energy range from 0 to 10 eV with the focus on vibrational excitation and dissociative electron attachment. The vibrational excitation cross sections show a number of resonances which are mode specific: the two dominant π∗ resonances are visible in the excitation of all the vibrational modes; however, broad σ ∗ resonances are visible only in certain bond-stretching vibrational...