Average Dipole Moment Research Articles

Nonlinearity in the Medium for Electromagnetic Wave Propagation Induced by Quantum Mechanical Interaction of the Field With Finite-State Atoms

We consider the interaction between a classical time-varying electric field and the atomic electrical dipole moment operator of a finite state atom and calculate approximately the mixed state evolution of the atom with such an interaction Hamiltonian up to quadratic orders in the external classical electric field using Schrodinger’s equation for mixed state evolution. From this approximate expression for the state evolution, we evaluate the average atomic electric dipole moment as a linear-quadratic function of the electric field. Later on, we also take into account Brownian motion bath noise that couples to the atomic dynamics, so that the Schrodinger equation dynamics gets modified to the Lindblad dynamics of an open quantum system, i.e., the master equation. From the average atomic dipole moment, we obtain an expression for the average polarization field of atoms constituting the medium through which the classical electromagnetic wave propagates. This average polarization is a linear-quadratic causal functional of the electric field. The resulting Maxwell equations for wave propagation, taking into account this polarization current density, thus acquire a quadratic nonlinearity which can be used to explain higher harmonic frequencies at the output of an optical fiber when the input is excited by the electric field coming from a monochromatic laser. We are then also able to calculate the mean square fluctuations in the polarization field using the evolving atomic state, and hence the electric field propagating through the medium of atoms acquires quantum fluctuations which can be used to explain time-varying random shifts in the spectral lines. As mentioned above, we include in this article an extension of this problem to the case when there is white Gaussian noise corrupting the state evolution dynamics of the atom and also the case when there is a pairwise interaction between the spin dipoles of atoms at two different locations. In the former case, we derive an approximate formula for the polarization field as well as its temporal statistical correlations, and we show how this computation can be extended to the latter case too. When there is a pairwise interaction between the atomic spins, we use a version of the approximate quantum Boltzmann equation to calculate the first and second order marginals of the atomic states, which is then used to compute the average polarization as well as its spatio-temporal correlations. Temporal correlations using second marginals of the atomic states cannot be computed using classical probabilistic methods owing to Heisenberg uncertainty, so we propose a sequential measurement-based strategy involving computation of the joint probabilities of the atomic spin components at two different times by first measuring one component of the spin, allowing for state collapse, and then following it up with nonlinear time evolution from the collapsed two-particle state using the quantum Boltzmann equation, followed further by measurement of another component of the spin at the second time.

Fingerprint of Dipole Moment Orientation of Water Molecules in Cu2+ Aqueous Solution Probed by X-ray Photoelectron Spectroscopy.

The electronic structure and geometrical organization of aqueous Cu2+ have been investigated by using X-ray photoelectron spectroscopy (XPS) at the Cu L-edge combined with state-of-the-art ab initio molecular dynamics and a quantum molecular approach designed to simulate the Cu 2p X-ray photoelectron spectrum. The calculations offer a comprehensive insight into the origin of the main peak and satellite features. It is illustrated how the energy drop of the Cu 3d levels (≈7 eV) following the creation of the Cu 2p core hole switches the nature of the highest singly occupied molecular orbitals (MOs) from the dominant metal to the dominant MO nature of water. It is particularly revealed how the repositioning of the Cu 3d levels induces the formation of new bonding (B) and antibonding (AB) orbitals, from which shakeup mechanisms toward the relaxed H-SOMO operate. As highlighted in this study, the appearance of the shoulder near the main peak corresponds to the characteristic signature of shakeup intraligand (1a1 → H-SOMO(1b1)) excitations in water, providing insights into the average dipole moment distribution (≈36°) of the first-shell water molecules surrounding the metal ion and its direct impact on the broadening of the satellite. It is also revealed that the main satellite at 8 eV from the main peak corresponds to (metal/1b2 → H-SOMO(1b1) of water) excitations due to a bonding/antibonding (B/AB) interaction of Cu 3d levels with the deepest valence O2p/H1s 1b2 orbitals of water. This finding underscores the sensitivity of XPS to the electronic structure and orientation of the nearest water molecules around the central ion.

Synthesis and examination of alkoxycyanobiphenyl mesogens with a single fluorine atom at specific locations in the tail

ABSTRACT Selective fluorination is a well-established technique to tailor and improve many of the physical properties of liquid crystals. Cyanobiphenyls are among the best-known and understood thermotropic liquid crystals and have served admirably as a testbed for structural modifications that can eventually be extended to other classes of liquid crystals. As such, and expanding on our earlier work, in the present study of the alkoxycyanobiphenyl M series, the individual tail sites of both 4’-(butoxy)[1,1’-biphenyl]-4-carbonitrile (M12) and 4’-(pentyloxy)[1,1’-biphenyl]-4-carbonitrile (M15) were selectively monofluorinated in order to examine the influence on the phase behavior. These fluorinated compounds were synthesized using epoxidation, regioselective epoxide opening and deoxyfluorination chemistry. In all the fluorinated compounds in both series a monotropic nematic phase was found in the cooling cycle. It was observed that as the fluorine atom on the tail moves closer to the core, the compounds exhibited a metastable room temperature nematic mesophase, but recrystallization invariably occurred. Both enantiomers of 4’-(2-fluorobutoxy)[1,1’-biphenyl]-4-carbonitrile were synthesized in high enantiomeric purity by regioselective opening of chiral epoxide intermediates followed by deoxyfluorination, as established by chiral high-performance liquid chromatography, and their phase behaviors were determined. Moreover, the average dipole moments of the synthesized fluorine substituted derivatives were also calculated.

Effect of alternating electric field induced by cold atmospheric plasma on conformation and function of interleukin-6

Cold atmospheric plasma (CAP) is considered to be a very promising cancer treatment method due to its “selective” killing effect on cancer cells. The CAP can inhibit tumor inflammatory responses and activate the immune system by reducing the expression of the key inflammatory factor Interleukin-6 (IL-6). However, the influence of the strong alternating electric field induced by CAP on the conformation and function of IL-6 remains unclear. In this study molecular dynamics simulation is used to investigate the effects of alternating electric fields with different frequencies and intensities on the conformation of IL-6. We statistically analyze the root mean square fluctuations, root mean square deviation, secondary structural alterations, and dipole moment changes of IL-6 under different electric field parameters. Furthermore, molecular docking is utilized to assess the influence on the receptor-binding process. The results show that when the electric field frequency is below 30 MHz and the intensity exceeds 0.5 V/nm, the average dipole moment of IL-6 increases, leading to changes in the rigid regions at the C-terminus which maintain structural stability. Specifically, the salt bridges that stabilize the long helices rupture, and the number of α-helices decreases. The docking outcomes reveal that the distance between the key binding residues of the conformationally altered IL-6 and its receptor increases, thereby disrupting the normal binding process and potentially impairing its normal biological functionality. This study explains the internal interaction mechanism of CAP-induced electric fields affecting IL-6-related biological effects at the micro level, and provides important theoretical basis for optimizing parameters in the practical application of CAP in tumor inflammation treatment and the development of effective cancer therapy strategies.

Controlled dynamic variation of interfacial electronic and optical properties of lithium intercalated ZrO2/MoS2 vdW heterostructure

Efficient strategies for modifying the characteristics of van der Waals (vdW) layered materials in a precise and reversible mode remain challenging. Our suggested method for customization entails the implementation of layer-sliding and intercalation. In this work, a norm-conserving approach within the context of density functional theory has been used to examine the electronic and optical properties of two-dimensional (2D) van der Waals heterostructure (vdWHS), which is modeled by using 2D zirconium dioxide (1T-ZrO2) and molybdenum disulfide (1T-MoS2) monolayers of similar phase. Both contributing monolayers have similar lattice structures, with a minimum lattice mismatch of 0.83 %, and have corrugation on both sides that can successfully retain foreign species at the vdW-gap. In the next step, interfacial engineering through Li-intercalation and layer-sliding was employed to modify physical properties of the vdWHS. It is the worth mentioning that a narrow bandgap of 0.102 eV (0.22 eV) has been observed in the unintercalated ZrO2/MoS2 vdWHS when employing PW-LDA (hybrid-functional). Li-intercalation and sliding process significantly influenced the electronic properties of the studied vdWHS. Furthermore, un-slided and fully-slided Li-intercalated vdWHS exhibit an increase in the vdW-gap by 3.78 % and 27.14 %, respectively, as compared to unintercalated vdWHS. To further understand the electrical behaviour at the interface of contributing monolayers, a comparative study has also been made for the variation in the planar average charge density difference, charge transfer, and interface dipole moment for unintercalated and intercalated vdWHS. In the unintercalated vdWHS, the calculated values of ΔQ and μ(z) provide evidence of significant charge transfer from 1T-ZrO2 to 1T-MoS2 before sliding, whereas in the fully-slided vdWHS, there is 80.11 % more charge transfer from 1T-MoS2 to 1T-ZrO2. Li-intercalation increases the magnitude of ΔQ (by 90.27 %) near 1T-MoS2, indicating a sufficient quantity of charge transfer from the 1T-MoS2 monolayer. The results of the anisotropic analysis show that the calculated in-plane and out-of-plane components of the real and imaginary parts of the dielectric function differ significantly. The optical absorption and energy losses of Li-intercalated vdWHS experience a substantial decrease of about 90 % and 50 %, respectively, as compared to unintercalated vdWHS. Our employed method promotes the notion that interfacial engineering through simultaneous layer-sliding and intercalation approach can be used to regulate and modify the physical properties of 2D insulator/metal based vdWHS.

Palaeomagnetic field intensity measurements from the 2.6 Ga Yandinilling dyke swarm (Western Australia)

SUMMARY Precambrian palaeointensity measurements provide fundamental constraints on the evolution of the deep Earth. Core evolution models predict trends in dipole moment on billion-year timescales that can be tested by palaeomagnetic records. Here, we report new palaeointensity results from the recently identified ∼2.62 Ga Yandinilling dyke swarm of the Yilgarn Craton, Western Australia, and consider them alongside published measurements spanning 500 Myr across the late Archaean to earliest Proterozoic. Rock magnetic and scanning electron microscopy analysis confirm that the magnetic mineralogy is fine-grained magnetite, appearing mostly as exsolved lamellae with ilmenite. Six sites produced acceptable palaeointensity estimates from thermal and microwave IZZI protocol Thellier experiments and from double-heating technique Shaw experiments. These site mean values of 9–26 µT translate to virtual dipole moments of 11–44 ZAm2 that are considerably lower than today's dipole moment of ∼80 ZAm2 and the value predicted for this time period by some thermal evolution models. Their average (median = 41 ZAm2) is, however, similar to the long-term average during both of the intervals 2300–2800 Ma (median = 44 ZAm2; N = 103) and 10–500 Ma (median 41 ZAm2; N = 997). While there is little evidence for a substantial net change in average dipole moment between the late Archaean and Phanerozoic, there is preliminary evidence that its variance has increased between the two intervals. This lower variance more than two billion years ago supports the idea that the geodynamo, even while not producing a stronger magnetic field, was more stable on average at the Archaean–Proterozoic transition than it is today.

Electronic states, spectroscopic properties, electronic transitions, and bonding in ScH2+: A thermodynamic stable transition metal-hydrogen dication

Eight bound singlet and triplet electronic states of the diatomic dication ScH2+ are characterized theoretically at the SA-CASSCF/icMRCI/aug-cc-pV5Z level of theory by the construction of potential energy curves, and the evaluation of spectroscopic parameters. The states dissociating into the first channel are all thermodynamically stable. For the ground state, covalent bonding plays a relevant role in the stabilization of the molecule; for the other states, bonding results mainly from electrostatic charge-induced dipole interaction. Dipole moment (relative to the center of mass) functions and vibrationally averaged dipole moments quantify the polarity of the molecule. After evaluating transition moment functions, transition probabilities for spontaneous emission for selected pair of states are estimated by the Einstein Av´,v´´ coefficients and the stronger transitions identified; radiative lifetimes are also reported. Not yet known experimentally, this work is expected to motivate experimental investigations of transition metal-monohydrides diatomic dications.

Characterizing electronic states in metal-rare gas diatomic dications: The cases of VAr2+ and VKr2+

Six low-lying bound quartet electronic states of the diatomic dications VAr2+ and VKr2+ are characterized theoretically at the SA-CASSCF/icMRCI/aug-cc-pV5Z level of theory by the construction of potential energy curves, and the evaluation of spectroscopic parameters. These molecules were found to be thermodynamically stable, where binding arises from purely electrostatic charge-induced dipole interaction; they are more strongly bound than the corresponding monocations. Their polarity is described by dipole moment functions and vibrationally averaged dipole moments. Transition probabilities for spontaneous emission for selected pair of states are estimated by the Einstein Av′v′′ coefficients and the stronger transitions identified; radiative lifetimes are also reported. Not yet known experimentally, this work is expected to motivate further experimental investigations of transition metal-rare-gas diatomic dications.

Charge Transfer and Level Lifetime in Molecular Photon-Absorption upon the Quantum Impedance Lorentz Oscillator.

On the strength of the new quantum impedance Lorentz oscillator (QILO) model, a charge-transfer method in molecular photon-absorption is proposed and imaged via the numerical simulations of 1- and 2-photon-absorption (1PA and 2PA) behaviors of the organic compounds LB3 and M4 in this paper. According to the frequencies at the peaks and the full width at half-maximums (FWHMs) of the linear absorptive spectra of the two compounds, we first calculate the effective quantum numbers before and after the electronic transitions. Thus, we obtain the molecular average dipole moments, i.e., 1.8728 × 10-29 C·m (5.6145 D) for LB3 and 1.9626 × 10-29 C·m (5.8838 D) for M4 in the ground state in the tetrahydrofuran (THF) solvent. Then, the molecular 2PA cross sections corresponding to wavelength are theoretically inferred and figured out by QILO. As a result, the theoretical cross sections turn out to be in good agreement with the experimental ones. Our results reveal such a charge-transfer image in 1PA near wavelength 425 nm, where an atomic electron of LB3 jumps from the ground-state ellipse orbit with the semimajor axis ai = 1.2492 × 10-10m = 1.2492 Å and semiminor axis bi = 0.4363 Å to the excited-state circle (aj = bj = 2.5399 Å). In addition, during its 2PA process, the same transitional electron in the ground state is excited to the elliptic orbit with aj = 2.5399 Å and bj =1.3808 Å, in which the molecular dipole moment reaches as high as 3.4109 × 10-29 C·m (10.2256 D). In addition, we obtain a level-lifetime formula with the microparticle collision idea of thermal motion, which indicates that the level lifetime is proportional (not inverse) to the damping coefficient or FWHM of an absorptive spectrum. The lifetimes of the two compounds at some excited states are calculated and presented. This formula may be used as an experimental method to verify 1PA and 2PA transition selection rules. The QILO model exhibits the advantage of simplifying the calculation complexity and reducing the high cost associated with the first principle in dealing with quantum properties of optoelectronic materials.

Electron Tunneling at Electrocatalytic Interfaces

It was recently proposed that tunneling current fluctuations in electrochemical scanning tunneling microscopy (EC-STM) can be used to map the electrocatalytic activity of surfaces with high spatial resolution. However, the relation between the increased noise in the electron tunneling signal and the local reactivity for such complex electrode/electrolyte interfaces is only explained qualitatively or hypothetically. Herein, we employ electron transport calculations to examine tunneling at Pt surfaces under the conditions of the oxygen reduction reaction as a case study. By computing current–voltage characteristics, we reveal that the tunneling barrier strongly depends on the chemical identity of the adsorbed reaction intermediate as well as on the orientation of the average dipole moment of water species mediating electron tunneling. Our theoretical results combined with EC-STM measurements suggest that detecting reaction intermediates at electrified interfaces in operando conditions is possible based on tunneling noise amplitudes. This study also aims to stimulate further explorations of tunneling-based electron-proton transfers to enable quantum electrocatalysis beyond conventional approaches.

Electric Dipole Moments from Stark Effect in Supersonic Expansion: n-Propanol, n-Butanol, and n-Butyl Cyanide.

The orientation and magnitude of the molecular electric dipole moment are key properties relevant to topics ranging from the nature of intermolecular interactions to the quantitative analysis of complex gas-phase mixtures, such as chemistry in astrophysical environments. Stark effect measurements on rotational spectra have been the method of choice for isolated molecules but have become less common with the practical disappearance of Stark modulation spectrometers. Their role has been taken over by supersonic expansion measurements within a Fabry-Perot resonator cavity, which introduces specific technical problems that need to be overcome. Several of the adopted solutions are described and compared. Presently, we report precise electric dipole moment determinations for the two most stable conformers of the selected molecules of confirmed or potential astrophysical relevance: n-propanol, n-butanol, and n-butyl cyanide. All dipole moment components have been precisely determined at supersonic expansion conditions by employing specially designed Stark electrodes and a computer program for fitting the measured Stark shifts, inclusive of cases with resolved nuclear quadrupole hyperfine structure. The experimental values are compared with suitable quantum chemistry computations. It is found that, among the tested levels of computation, vibrationally averaged dipole moments are the closest to the observation and the molecular values are, as in the lighter molecules in the series, largely determined by the hydroxyl or nitrile groups.

Local intermolecular structure, hydrogen bonding and related dynamics in the liquid cis/trans N-methylformamide mixture: A density functional theory based Born-Oppenheimer molecular dynamics study

The local intermolecular structure and related dynamics in the liquid cis/trans N-methylformamide mixture at ambient temperature and density conditions have been systematically studied by employing Born-Oppenheimer molecular dynamics simulation techniques. Particular attention has been paid to the local structure around the cis- and trans- conformers and the formation and dynamics of hydrogen bonds with their closest neighbors. The calculated atom–atom radial distribution functions are in very good agreement with available experimental data and reveal the existence of different types of hydrogen bonding intermolecular interactions. The average number of hydrogen bonds formed by the cis- conformers is higher in comparison with the one corresponding to the trans- conformers. Moreover, the lifetimes of the hydrogen bonds formed in the liquid are longer when the cis- conformers participate in the bond formation, either as donors or acceptors. These findings clearly indicate that the local structural network around the cis- conformers in the liquid is more cohesive. The latter finding is also reflected in the slower reorientational dynamics of the cis- conformers and the low- and high-frequency region of the spectral densities of the atomic velocity time correlation functions. Finally, the calculated average dipole moments of the trans- and cis- conformers are significantly higher than their corresponding gas-phase values, signifying the importance of polarization effects in this particular polar liquid solvent.

Solvation of small gold clusters in supercritical water

Solvation in supercritical water features fascinating properties such as the selective dissolution or precipitation of non-polar versus polar species. This is known since long to open up astonishing possibilities in organic synthesis, catalysis, or engineering. Less known is the role that supercritical aqueous solutions play close to hydrothermal vents in the deep sea and in ore deposit formation in Earth’s crust. Within this realm, we explore here the solvation of small uncharged gold species, namely the gold dimer and tetramer, in supercritical water in terms of structural and electronic properties using ab initio molecular dynamics simulations. Our simulations reveal that a highly anisotropic first solvation shell is formed around these gold clusters which consists of less than two water molecules on average. Importantly, we find very significant charge transfer and polarization effects between these water molecules and the neutral gold particles, which cannot be captured when using non-polarizable force fields. These electronic many-body effects lead not only to enormous dipole moment fluctuations of the gold clusters themselves, but also to an unexpectedly strong increase of the average effective dipole moments in their first solvation shell. Thus, supercritical solutions of gold particles in water turn out to be surprisingly complex.

All-atom molecular dynamics simulations of the combined effects of different phospholipids and cholesterol content on electroporation.

The electroporation mechanism could be related to the composition of the plasma membrane, and the combined effect of different phospholipid molecules and cholesterol content on electroporation has rarely been studied nor conclusions drawn. In this paper, we applied all-atom molecular dynamics (MD) simulations to study the effects of phospholipids and cholesterol content on bilayer membrane electroporation. The palmitoyloleoylphosphatidylcholine (POPC) model, palmitoyloleoylphosphatidylethanolamine (POPE) model, and a 1 : 1 mixed model of POPC and POPE called PEPC, were the three basic models used. An electric field of 0.45 V nm−1 was applied to nine models, which were the three basic models, each with three different cholesterol content values of 0%, 24%, and 40%. The interfacial water molecules moved under the electric field and, once the first water bridge formed, the rest of the water molecules would dramatically flood into the membrane. The simulation showed that a rapid rise in the Z-component of the average dipole moment of the interfacial water molecules (Z-DM) indicated the occurrence of electroporation, and the same increment of Z-DM represented a similar change in the size of the water bridge. With the same cholesterol content, the formation of the first water bridge was the most rapid in the POPC model, regarding the average electroporation time (tep), and the average tep of the PEPC model was close to that of the POPE model. We speculate that the differences in membrane thickness and initial number of hydrogen bonds of the interfacial water molecules affect the average tep for different membrane compositions. Our results reveal the influence of membrane composition on the electroporation mechanism at the molecular level.

Derivation of limiting ion mobility equation based on the application of solvation effect-incorporated Poisson-Boltzmann equation

Interaction potential energy between ion and solvent molecular dipole moments in solvation shell around ion was derived on basis of the application of the solution of linear SEI-PB (Solvation Effects-Incorporated Poisson-Boltzmann) equation. Based on application of the solution of linear SEI-PB equation, distribution of solvent molecules in solvation shell around ion in electrolyte solution at thermodynamic equilibrium was derived. In case approaching to limit of infinite dilution, analytical expression for evaluating limiting ion mobility is derived from the boundary condition that the average number of solvent molecules accompanying with translational motion of ion is equal to the mean solvation number of ion. The derived limiting ion mobility formula is different from the Stokes–Einstein relation and lies in relation to direct proportion with the cube of dynamic size of ion in solution, depending not only on the viscous coefficient, dielectric constant, the density and molecular weight of solvent but also on temperature.By virtue of the equation, it was possible to estimate dynamic sizes of ions in solution. It was found the estimated dynamic sizes of ions in aqueous solution to be compatible with the average ion–water distances, and to be always greater than crystallographic ionic radii in size.A new relation between the limiting ion mobility and the solvent molecular dipole moment in solvation shell was established based on the interaction potential energy between ion and solvent molecular dipole moments in solvation shell around ion. By virtue of the proposed relation, we could find out the average water molecular dipole moment in hydration shell to be different more or less in size from that in bulk solution according to ionic species in aqueous solution.

Characterizing electronic states and spectra in transition metal-rare gas diatomic cations: The cases of VAr+ and VKr+

Nine low-lying quintet electronic states of the cations VAr+ and VKr+ are characterized theoretically at the SA-CASSCF/icMRCI/aug-cc-pV5Z level of theory by the construction of potential energy curves and the determination of spectroscopic parameters. The polarity of the molecules is described by dipole moment functions and vibrationally averaged dipole moments. Transition probabilities for spontaneous emission for selected states are estimated by the Einstein Av´,v´´ coefficients and the stronger transitions identified; radiative lifetimes are also reported. For the photoabsorption process, the spectrum is modelled for the bands of the G 5Π – X 5Σ+ system of each species for which experimental photodissociation results are available in the literature. Not known experimentally, the intensity distribution is expected to help elucidate the assumed vibrational numbering of the upper state, and together with the overall electronic description and spectroscopic parameters motivate further experimental investigations of transition metal-rare-gas cations. Binding arises from purely electrostatic charge-induced dipole interaction.

Poly(butylene 2,4-furanoate), an Added Member to the Class of Smart Furan-Based Polyesters for Sustainable Packaging: Structural Isomerism as a Key to Tune the Final Properties.

High-molecular-weight poly(butylene 2,4-furanoate) (2,4-PBF), an isomer of well-known poly(butylene 2,5-furanoate) (2,5-PBF), was synthesized through an eco-friendly solvent-free polycondensation process and processed in the form of an amorphous film by compression molding. Molecular characterization was carried out by NMR spectroscopy and GPC analysis, confirming the chemical structure and high polymerization degree. Thermal analyses evidenced a reduction of both glass-to-rubber transition and melting temperatures, as well as a detriment of crystallization capability, for 2,4-PBF with respect to 2,5-PBF. Nevertheless, it was possible to induce crystal phase formation by annealing treatment. Wide-angle X-ray scattering revealed that the crystal lattices developed in the two isomers are distinct from each other. The different isomerism affects also the thermal stability, being 2,4-PBF more thermally inert than 2,5-PBF. Functional properties, such as wettability, mechanical response, and gas barrier capability, were tested on both amorphous and semicrystalline 2,4-PBF films and compared with those of 2,5-PBF. Reduced hydrophilicity was determined for 2,4-isomer, in line with its lower average dipole moment, suggesting better chemical resistance to hydrolysis. Stress–strain tests have evidenced the higher flexibility and toughness of 2,4-PBF with respect to those of 2,5-PBF and the possibility of improving its mechanical resistance by annealing. Finally, the different isomerism deeply affects the gas barrier performance, being the O2- and CO2-transmission rates of 2,4-PBF 50 and 110 times lower, respectively, than those of 2,5-PBF. The gas barrier properties turned out to be outstanding under a dry atmosphere as well as in humid conditions, suggesting the presence of interchain hydrogen bonds. The gas blocking capability decreases after annealing because of the presence of disclination associated with the formation of crystals.

Classical analytical description of negative hydrogen ions

Studies of negative hydrogen ions (NHI), such as, H– and D–, are important from both practical and fundamental points of view. One of the reasons for their practical importance has to do with heating tokamak plasmas by external beams of NHI. Another practical use is the injection of NHI in high-power proton accelerator facilities to enhance their performance. In addition, NHI are also important for studies of opacities of the atmospheres of the Sun and of A-type stars. We present a classical analytical description of NHI in the situation where the underlying hydrogen (or deuterium) atom constitutes a rapid subsystem while the outer electron represents a slow subsystem. We focus on the case where the inner electron is in a circular state, so that the subsystem “nucleus plus inner electron” does not have the average electric dipole moment — in distinction to previous studies where the presence of the average dipole moment was the crucial requirement. By using the separation of rapid and slow subsystems, we show analytically that there is a classical bound state in such system and studied its parameters. In particular, we calculate analytically the primary frequency of the radiation of such system. This could be used for its experimental detection. The states that we found for the above systems could be considered as classical counterparts of the double-excited states of NHI previously studied in the literature in frames of quantum mechanics. The existence of classical counterparts of the double-excited states of NHI is a counterintuitive result.

A theoretical contribution to the characterization of the electronic structure and spectroscopic properties of the low-lying states of strontium monoiodide, SrI

A high-level theoretical approach – SA-CASSCF/MRCI – is used to explore the electronic structure and spectroscopic properties of a manifold of low-lying electronic states of the radical strontium monoiodide, SrI. For both Λ + S and Ω representations, potential energy curves are constructed, and the associated spectroscopic parameters derived. Dipole moment functions and vibrationally averaged dipole moments allow one to quantify the polarity of the various states. With the transition dipole moment functions, Einstein Av'v’’ coefficients for spontaneous emission were computed for pairs of selected states and radiative lifetimes evaluated for the low-lying vibrational levels of the excited electronic states. Reliable results are also provided for the yet unknown states A’ 2Δ and E 2Σ+ which can guide spectroscopists to their experimental detection. Combined with recent theoretical work on SrF, SrCl, and SrBr one now can have a broad perspective of the trends in spectroscopic properties of this series of halides.

Crystal structure of 4-aminopyridinium 3-(4-aminopyridinium) succinate tetra hydrate: A new salt from 4-aminopyridine and maleic acid crystallization

A new salt, 4-aminopyridinium 3-(4-aminopyridinium) succinate tetra hydrate was synthesized from 4-aminopyridine and maleic acid in 2:1 stoichiometric ratio. The salt was characterised using single crystal X-ray diffraction, Raman scattering and DSC/DTA techniques. Intermolecular interactions in the salt investigated through Hirshfeld surfaces and 2D finger plots, showed that the C..H, N..H, O..H and H…H interactions were 15.4%, 2.2%,37.6% and 41.3% respectively. The water molecules occupy around 19.2% of the total volume of the unit cell and also contribute significantly to the stability of the crystal. As the salt crystallizes in a non-centerosymmetric space group, it can exhibit second order non-linear optical properties. MOPAC was used to calculate the hyperpolarizability, it was found to be 3.29378 10−30 esu. A database analysis to compare the bond parameters and the physical properties like hyperpolarizability etc. in 4-aminopyridine and its complexes was undertaken. It was found that, in general, complexation or salt formation leads to higher average polarizability, hyperpolarizability and dipole moment, and our salt also has higher hyperpolarizablilty than that of parent compound 4-aminopyridine.