Function Of Internal Energy Research Articles

Insight into the Influence of the Integrated Chitosan on the Adsorption Properties of Chitosan/Al-MCM-41 Composite for As (V) Metal Ions: Characterization and Advanced Equilibrium Studies

Ecofriendly chitosan/Al-MCM-48 (CH/Al-MCM) was synthesized from natural microcline and assessed as a potential adsorbent of As (V) ions with enhanced capacity. The As (V) adsorption properties of CH/Al-MCM were assessed in comparison with Al-MCM-41 as a single phase. The studied CH/Al-MCM exhibits 178.6 mg/g as As (V) adsorption capacity which is higher than Al-MCM-41 (124 mg/g). The adsorption properties were illustrated based on the pseudo-first-order kinetic, Langmuir isotherm, and monolayer model with one energy site. Based on the recognized steric parameters, CH/Al-MCM displays significant enhancement in the active sites density (Nm = 88.8 mg/g (20°C)) as compared to Al-MCM (Nm = 61.5 mg/g). This signifies the role of the chitosan integration process in enhancing the adsorption capacity by increasing the availability of the present active sites. The number of adsorbed arsenic ions (2.01 to 2.66) suggests the uptake of 2 or 3 ions per free site by a multi-ionic and physical mechanism considering the adsorption energy (−16.3 to −16.9 kJ/mol). The thermodynamic functions of entropy, internal energy, and free enthalpy reflect the spontaneous and exothermic properties of the studied As (V) adsorption system by CH/Al-MCM. Moreover, the composite displays significant As (V) adsorption capacity in the existence of other dissolved ions.

Differential Cross Sections for Pair-Correlated Rotational Energy Transfer in NO(A2Σ+) + N2, CO, and O2: Signatures of Quenching Dynamics.

A crossed molecular beam, velocity-map ion-imaging apparatus has been used to determine differential cross sections (DCSs), as a function of collider final internal energy, for rotationally inelastic scattering of NO(A2Σ+, v = 0, j = 0.5f1) with N2, CO, and O2, at average collision energies close to 800 cm-1. DCSs are strongly forward scattered for all three colliders for all observed NO(A) final rotational states, N'. For collisions with N2 and CO, the fraction of NO(A) that is scattered sideways and backward increases with increasing N', as does the internal rotational excitation of the colliders, with N2 having the highest internal excitation. In contrast, the DCSs for collisions with O2 are essentially only forward scattered, with little rotational excitation of the O2. The sideways and backward scattering expected from low-impact-parameter collisions, and the rotational excitation expected from the orientational dependence of published van der Waals potential energy surfaces (PESs), are absent in the observed NO(A) + O2 results. This is consistent with the removal of these short-range scattering trajectories via facile electronic quenching of NO(A) by O2, in agreement with the literature determination of the coupled NO-O2 PESs and the associated conical intersections. In contrast, collisions at high-impact parameter that predominately sample the attractive van der Waals minimum do not experience quenching and are inelastically forward scattered with low rotational excitation.

Inferring electrospray emission characteristics from molecular dynamics and simulated retarding potential analysis

In this work, we present coordinated molecular dynamics, ion cluster acceleration, and retarding potential analysis simulations to determine cluster fragmentation behavior in a realistic emitter geometry for electrosprays operating in the pure ionic regime. Molecular dynamics simulations are used to determine the fragmentation rates of ionic liquid clusters as a function of internal energy, electric field strength, and cluster size. A simplified model of electrospray cluster acceleration is developed from previous electrohydrodynamic emission models and used to simulate retarding potential analysis curves. Fragmentation rates and beam composition are inferred for experimental data based on the molecular dynamics and cluster acceleration simulations. We find that for these experimental data, temperatures of EMI-BF4 dimers likely range between 590 and 687 K while trimer temperatures are larger between 989 and 1092 K. The percentage of monomers, dimers, and trimers in the beam is approximately 45%, 30%–43%, and 13%–25%, respectively. Both ionic liquid cluster temperatures and beam composition agree with previous analysis of this experimental work, supporting the use of coordinated molecular dynamics and retarding potential analysis as a method of inferring electrospray beam parameters. Insights gained from this simulation process are discussed in the context of currently unexplained electrospray emitter behavior and experimental results including the presence of tetramers and trimers in the beam and fragmentation rates in high electric field regions.

Efficient radiative cooling of tetracene cations C18H12+: absolute recurrent fluorescence rates as a function of internal energy.

We have measured recurrent fluorescence (RF) cooling rates of internally hot tetracene cations, C18H12+, as functions of their storage times and internal energies in two different electrostatic ion-beam storage rings - the cryogenic ring DESIREE with a circumference of 8.6 meters in Stockholm and the much smaller room temperature ring Mini-Ring in Lyon, which has a circumference of 0.71 meters. The RF rates were measured to be as high as 150 to 1000 s-1 for internal energies in the 7 to 9.4 eV energy range, where we have probed the time evolution of the internal energy distribution with nanosecond laser pulses with a 1 kHz repetition rate. These RF rates are found to be significantly higher than those of previously investigated smaller PAHs such as e.g. anthracene and naphthalene, for which the lowest non-forbidden electronic excited state, the D2 state, is populated with a smaller probability by inverse internal conversion. Furthermore, the D2-D0 transition rate is smaller for these smaller molecules than for tetracene. The complementary features of the two storage rings allow for RF rate measurements in a broader internal energy range than has been possible before. The smaller sampling period of about 6 μs in Mini-Ring is ideal to study the cooling dynamics of the hotter ions that decay fast, whereas DESIREE with a sampling period of about 60 μs is better suited to study the colder ions that decay on longer timescales ranging up to hundreds of milliseconds. The excellent agreement between the two series of measurements in the region where they overlap demonstrates the complementarity of the two electrostatic ion-beam storage rings.

Simplified Multiple-Well Approach for the Master Equation Modeling of Blackbody Infrared Radiative Dissociation of Hydrated Carbonate Radical Anions.

Blackbody infrared radiative dissociation (BIRD) in a collision-free environment is a powerful method for the experimental determination of bond dissociation energies. In this work, we investigate temperature-dependent BIRD of CO3·-(H2O)1,2 at 250-330 K to determine water binding energies and assess the influence of multiple isomers on the dissociation kinetics. The ions are trapped in a Fourier-transform ion cyclotron resonance mass spectrometer, mass selected, and their BIRD kinetics are recorded at varying temperatures. Experimental BIRD rates as a function of temperature are fitted with rates obtained from master equation modeling (MEM), using the water binding energy as a fit parameter. MEM accounts for the absorption and emission of photons from black-body radiation, described with harmonic frequencies and infrared intensities from quantum chemical calculations. The dissociation rates as a function of internal energy are calculated by Rice-Ramsperger-Kassel-Marcus theory. Both single-well and multiple-well MEM approaches are used. Dissociation energies derived in this way from the experimental data are 56 ± 6 and 45 ± 3 kJ/mol for the first and second water molecules, respectively. They agree within error limits with the ones predicted by ab initio calculations done at the CCSD(T)/aug-cc-pVQZ//CCSD/aug-cc-pVDZ level of theory. We show that the multiple-well MEM approach described here yields superior results in systems with several low-lying minima, which is the typical situation for hydrated ions.

Comprehensive survey of dissociative photoionization of quinoline by PEPICO experiments

Dissociative photoionization of quinoline induced by vacuum ultraviolet radiation is investigated using photoelectron-photoion coincidence spectroscopy. Branching ratios of all the detectable fragment ions are measured as a function of internal energy ranging from 2 to 30eV. A specific generation hierarchy is observed in the breakdown curves of a set of dissociation channels. Moreover, a careful comparison of the breakdown curves of fragments among the successive generations allowed to establish a decay sequence in the fragmentation of quinoline cation. This enabled us to revisit and refine the understanding of the first generation decay and reassign the origin of a few of the higher generation decay products of quinoline cation. With the help of the accompanying computational work (reported concurrently), we have demonstrated the dominance of two different HCN elimination pathways over previously interpreted mechanisms. For the first time, a specific pathway for acetylene elimination is identified in quinoline+ and the role of isomerization in both acetylene as well as hydrogen cyanide loss is also demonstrated. The experiment also established that the acetylene elimination exclusively occurs from the non-nitrogen containing rings of quinoline cation. The formation of a few astronomically important species is also discussed.

Radiative relaxation in isolated large carbon clusters: Vibrational emission versus recurrent fluorescence.

Recurrent fluorescence (RF) from isolated carbon clusters containing between 24 and 60 atoms is theoretically investigated as a function of internal energy, cluster size, and structural features. The vibrational relaxation kinetics and the associated IR emission spectra are determined by means of a Monte Carlo approach with vibrational density of states computed in the harmonic approximation. RF is generally found to be highly competitive with vibrational emission. The behaviors predicted for clusters of various sizes and archetypal structures indicate that the IR emission spectra are strongly influenced by RF, an energy gap law being obtained for the evolution of the RF rate constant depending on the electronic excitation state. The present results are relevant to the photophysics of the interstellar medium and could contribute to elucidating the carriers of the extended red emission bands and the continuum emission lying below the aromatic infrared bands believed to originate from mixed aromatic-aliphatic compounds.

A Fock space coupled cluster based probing of the single- and double-ionization profiles for the poly-cyclic aromatic hydrocarbons and conjugated polyenes.

Sequential formation of a poly-cyclic aromatic hydrocarbon (PAH) dication in the H I regions of the interstellar medium (ISM) is proposed to be a function of internal energy of the doubly ionized PAHs, which, in turn, is dependent on the single- and double-ionization potentials of the system. This sets a limit on the single- and double-ionization energies of the system(s) that can further undergo sequential absorption of two photons, leading to a dication (PAH+2). Here, we report the single-ionization (I+1) and double-ionization (I+2) energies and the I+2/I+1 ratio for some selected PAHs and conjugated polyenes obtained using the Fock space coupled cluster technique, enabling simultaneous consideration of several electronic states of different characters. The I+2 to I+1 ratio bears a constant ratio, giving allowance to determine I+2 from the knowledge of single-ionization (I+1) and vice versa. Our observations are in good agreement with the established literature findings, confirming the reliability of our estimates. The measured single- and double-ionization energies further demonstrate that the sequential formation and fragmentation of a PAH dication in the H I regions of the ISM for systems such as benzene and conjugated polyenes such as ethylene and butadiene are quite unlikely because I+2-I+1 for such system(s) is higher than the available photon energy in the H I regions of the ISM. Present findings may be useful to understand the formation and underlying decay mechanisms of multiply charged ions from PAHs and related compounds that may accentuate the exploration of the phenomenon of high-temperature superconductivity.

Barrierless Free Charge Generation in the High‐Performance PM6:Y6 Bulk Heterojunction Non‐Fullerene Solar Cell

Organic solar cells are currently experiencing a second golden age thanks to the development of novel non-fullerene acceptors (NFAs). Surprisingly, some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein, free charge generation in the high-performance blend of the donor polymer PM6 with the NFA Y6 is thoroughly investigated as a function of internal field, temperature and excitation energy. Results show that photocurrent generation is essentially barrierless with near-unity efficiency, regardless of excitation energy. Efficient charge separation is maintained over a wide temperature range, down to 100 K, despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA, measurements of the energetic disorder, and theoretical modeling suggest that CT state dissociation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier.

Equation of state for indium in shock waves

A model of the equation of state in the form of pressure as a function of density and specific internal energy is used to describe the properties of indium. Thermodynamic characteristics of this metal at high pressures are calculated and compared with the available experimental data on shock compressibility.

Collisional Energy Transfer from Vibrationally Excited Hydrogen Isocyanide.

Collisional deactivation of vibrationally excited hydrogen isocyanide (HNC) by inert gas atoms was characterized using nanosecond time-resolved Fourier transform infrared emission spectroscopy. HNC, with an average nascent internal energy of 25.9 ± 1.4 kcal mol-1, was generated following the 193 nm photolysis of vinyl cyanide (CH2CHCN) and collisionally deactivated with the series of inert atomic gases: He, Ar, Kr, and Xe. Time-dependent IR emission allows simultaneous experimental observation of the ν1 NH and ν3 NC stretch emissions from vibrationally excited HNC. Subsequent spectral fit analysis enables direct determination of the average energy of HNC in each spectrum and therefore a measure of the average energy lost per collision, ⟨ΔE⟩, as a function of internal energy. Collisional deactivation of excited HNC is shown to be relatively efficient, exhibiting ⟨ΔE⟩ values more than an order of magnitude larger than comparably sized molecules at similar internal energies. Furthermore, the lighter inert gases are shown to be more efficient quenchers. Both observations can be qualitatively explained by the momentum gap law modeled through the repulsive force dominated vibration-to-translation energy transfer mechanism. The feasibility of efficient collisional deactivation as a contributing factor to the observed overabundance of astrophysical HNC is discussed.

Double Imaging Photoelectron Photoion Coincidence Sheds New Light on the Dissociation of State-Selected CH3F+ Ions.

The vacuum ultraviolet (VUV) photoionization and dissociative photoionization of methyl fluoride (CH3F) in the 12.2-19.8 eV energy range were investigated by using synchrotron radiation coupled to a double imaging photoelectron photoion coincidence (i2PEPICO) spectrometer. The production of several fragment ions including CH2F+, CHF+, CH3+, and CH2+ as a function of state and internal energy of CH3F+ ions was identified and analyzed, with their individual appearance energies measured through threshold photoelectron spectroscopy. Dynamical information was inferred from electron and ion kinetic energy correlation diagrams measured at chosen fixed photon energies. The detailed mechanisms governing the dissociation of state-selected CH3F+ ions prepared in the X2E, A2A1, and B2E low-lying electronic states as well as outside the Franck-Condon region have been inferred based on the present experimental results and existing theoretical calculations. Both the CH2F+ and CH3+ primary fragment ions have three different channels of production from different electronic states of CH3F+. The spin-orbit splitting states of the F fragment, 2P3/2 and 2P1/2, in the CH3+ + F dissociation channels were assigned and adiabatically correlate to the X2E ground state and the A2A1 electronic state, respectively, with the aid of previous theoretical results. The CH3F+ ions in the high energy part of the X2E ground state are unstable and statistically dissociate to the CH2F+(11A1) and H(2S) fragments along the potential energy curve of the X2E state. The A2A1 electronic state is a repulsive state and exclusively dissociates to the CH3+(11A1') and F(2P1/2) fragments. In addition, the CH2F+, CHF+, CH3+, and CH2+ fragment ions are also produced in the B2E state and in the Franck-Condon gap by indirect processes, such as internal conversion or dissociative autoionization.

Application of the new IAPWS Guideline on the fast and accurate calculation of steam and water properties with the Spline-Based Table Look-Up Method (SBTL) in RELAP-7

Abstract The numerical simulation of thermalhydraulic processes in nuclear power plants requires very accurate and extremely fast algorithms for calculating the thermophysical properties of water and steam. In order to provide such algorithms, the International Association for the Properties of Water and Steam (IAPWS) has adopted the new “IAPWS Guideline on the Fast Calculation of Steam and Water Properties with the Spline-Based Table Look-Up Method (SBTL)”. In this article, the SBTL method is applied to property functions of specific volume and specific internal energy (v,e) based on the scientific formulation IAPWS-95 and the latest IAPWS formulations for transport properties. From the newly generated SBTL functions, thermodynamic and transport properties as well as their derivatives and inverse functions are calculable in the fluid range of state for pressures up to 100 MPa and for temperatures up to 1273 K, including the metastable liquid and the metastable vapor regions. The SBTL functions reproduce the underlying formulations with an accuracy of 10–100 ppm and significantly reduced computing times. The SBTL method has been implemented into the nuclear reactor system safety analysis code RELAP-7 [2] to consider the real fluid behavior of water and steam in a novel 7-equation two-phase flow model.

Self-averaging in the random two-dimensional Ising ferromagnet.

We study sample-to-sample fluctuations in a critical two-dimensional Ising model with quenched random ferromagnetic couplings. Using replica calculations in the renormalization group framework we derive explicit expressions for the probability distribution function of the critical internal energy and for the specific heat fluctuations. It is shown that the disorder distribution of internal energies is Gaussian, and the typical sample-to-sample fluctuations as well as the average value scale with the system size L like ∼Llnln(L). In contrast, the specific heat is shown to be self-averaging with a distribution function that tends to a δ peak in the thermodynamic limit L→∞. While previously a lack of self-averaging was found for the free energy, we here obtain results for quantities that are directly measurable in simulations, and implications for measurements in the actual lattice system are discussed.

On Constitutive Relations for Friction From Thermodynamics and Dynamics

Constitutive and dynamic relations for friction coefficient are presented. A first thrust combines the laws of thermodynamics to relate heat, energy, matter, entropy, and work of forces. The equation sums multiple terms—each with a differential of a variable multiplied by a coefficient—to zero. Thermodynamic considerations suggest that two variables, internal energy and entropy production, must depend on the others. Linear independence of differentials renders equations that yield thermodynamic quantities, properties, and forces as functions of internal energy and entropy production. When applied to a tribocontrol volume, constitutive laws for normal and friction forces, and coefficient of friction are derived and specialized for static and kinetic coefficients of friction. A second thrust formulates dynamics of sliding, with friction coefficient and slip velocity as state variables. Differential equations derived via Newton's laws for velocity and the degradation entropy generation (DEG) theorem for friction coefficient model changes to the sliding interface induced by friction dissipation. The solution suggests that the transition from static to kinetic coefficient of friction with respect to slip velocity for lubricant starved sliding is a property of the motion dynamics of sliding interacting with the dynamics of change of the surface morphology. Finally, sliding with stick-slip was simulated to compare this model to others.

Density-functional Monte-Carlo simulation of CuZn order-disorder transition

We perform a Wang-Landau Monte Carlo simulation of a Cu0.5Zn0.5 order-disorder transition using 250 atoms and pairwise atom swaps inside a 5 x 5 x 5 BCC supercell. Each time step uses energies calculated from density functional theory (DFT) via the all-electron Korringa-Kohn- Rostoker method and self-consistent potentials. Here we find CuZn undergoes a transition from a disordered A2 to an ordered B2 structure, as observed in experiment. Our calculated transition temperature is near 870 K, comparing favorably to the known experimental peak at 750 K. We also plot the entropy, temperature, specific-heat, and short-range order as a function of internal energy.

Equilibrium isotherm simulation of tetrachlorethylene on activated carbon using the double layer model with two energies: Steric and energetic interpretations

In this paper, the adsorption isotherms of tetrachlorethylene (PCE) on activated carbon at different temperature were simulated and interpreted using the double layer model with two energies. The formulation of this model was based on statistical physics formalism. Steric and energetic parameters related to the adsorption process were introduced in this model, such as the number of molecules per site (n), the receptor sites density NM and the concentrations at half saturation c1 and c2. These parameters were deduced by numerical simulation of the adsorption isotherms and interpreted at different temperatures. Thermodynamic functions of adsorption process, i.e., entropy, free enthalpy and internal energy were computed and their negative values indicate that the adsorption is exothermic and spontaneous.

Dissociation of doubly charged Coronene as a function of internal energy

SynopsisWe report on the dissociation of doubly charged Coronene (C24H122+) as a function of internal energy. The mass spectra were obtained for internal energy measured up to 50 eV using the CIDEC method in collisions with F+ and H+ at 3 keV. The dehydrogenation processes of the molecule were observed over this large range of energy as well as the other weaker channels, loss of C2Hn, 2C2Hn and ionization. The branching ratios for the fragments C24H12-n2+, C22H12-n2+, C20H12-n2+ and C24H12-n3+ (n=0-6) were measured.

Singlet and triplet states dissociation of doubly charged HDO, H2O and D2O as a function of internal energy

SynopsisThe fragmentation of HDO2+, H2O2+ and D2O2+ is reported as a function of the excitation energy. The doubly charged ions were prepared selectively to triplet or singlet excited states in collisions with F+ and H+ at 3 keV, respectively. For HDO2+ the isotopic ratio, ratio of probabilities for the two dissociation channels OD+ — H+ over OH+ — D+, was estimated to be 4.5 ± 0.8 using H+ and 3.8 ± 0.8 using F+ projectiles. Results are compared with recent calculations.

Numerical Analysis of the Hydrodynamic Behavior of Ion-beam-heated Uranium Targets for Equation-of-state Studies under Extreme Conditions

Abstract The equation of state (EOS) of fissile materials under extreme thermodynamic conditions is of great importance to assess the safety of nuclear energy systems related to extremely severe nuclear accidents and intentional nuclear terrorism. In this study, for a simple, safe, and precise measurement of these properties, we propose an experimental setup in which a small amount of fissile material sample is homogeneously heated by an intense short-pulsed heavy-ion beam, and subsequent hydrodynamic motion is examined. As an example, we investigated the response of a slab of uranium foam (density = 5% of solid density) to a pulsed 23 Na + beam with a duration of 2 ns and peak irradiation flux of 5 GW/mm 2 . The target thickness and incident beam energy were adjusted to 80 μm and 1.5 MeV/u, respectively, for the beam-energy deposition to occur almost at the top of the Bragg peak and inhomogeneity in the stopping power to be ±2.5%. The hydrodynamic motion of the target during and after irradiation was calculated with a one-dimensional radiation hydrodynamic code. To calculate beam-energy deposition in the target, we used density- and temperature-dependent projectile stopping data obtained with a finite-temperature Thomas-Fermi target atomic model and degeneracy-dependent dielectric response functions. The numerical results showed that the target was almost isometrically heated up to ≈ 10 5 K well before the rarefaction wave reached the center of the target, and fairly homogeneous temperature and density distributions were obtained at the end of the pulse duration. We discuss the feasibility of experimental EOS studies, such as the evaluation of pressures at off-Hugoniot conditions as a function of internal energy from the measurements of the target expansion velocity.