Relative Kinetic Energy Research Articles

Temperature Dependence of Ion Mobility of Carbon Cluster Cations: Intermediate Region Connecting Low- and High-Field Conditions

Abstract Effective temperature (Teff) dependences of reduced mobilities and collision cross section of small carbon cluster cations, Cn+ (n = 6–25), were investigated by using a drift cell with temperatures of 170–300 K coupled with a reflectron time-of-flight mass spectrometer. We have measured ion mobility within E/N = 16–28 Td, values of which are slightly higher than the general experimental value at low-field conditions. Thus, our conditions should correspond to medium field strength between low- and high-field conditions. Under the present conditions, collision cross section was found to be proportional to Teff−0.1 − Teff−0.2. The power in the temperature dependence was slightly closer to zero than results obtained previously (A. A. Shvartsburg, G. C. Schatz, M. F. Jarrold, J. Chem. Phys., 1998, 108, 2416). This difference is probably due to E/N, resulting in the difference of relative kinetic energy between Cn+ and buffer gas atoms, in spite of the same Teff region. The result showed that the hard-sphere model is more applicable in the present conditions.

Nucleon-Nucleon Potential and Its Non-Locality in Lattice QCD

By the quenched lattice QCD simulation for two nucleons with finite scattering energy, validity of the delivative expansion of the general nucleon-nucleon potential U(r,r') = V(r, {\nabla}_r) \delta^3(r-r') is studied. The relative kinetic energy between two nucleons is introduced through the anti-periodic boundary condition in the spatial directions. On a hypercubic lattice with the lattice spacing a ~ 0.137 fm and the spatial extent L_s ~ 4.4 fm with the pion mass m_{\pi} ~ 530 MeV, the local potentials for two different energies (E ~ 0 MeV and 45 MeV) are compared and found to be identical within statistical errors, which validates the local approximation of U(r,r') up to E=45 MeV for the central and tensor potentials. Central potentials in the spin-singlet channel for different orbital angular momentums (l=0 and l=2) at E ~ 45 MeV are also found to be the same within the errors, which also supports the local approximation.

Decoupling of spurious deeply bound states with the similarity renormalization group

The Similarity Renormalization Group (SRG) is a continuous series of unitary transformations that can be implemented as a flow equation. When the relative kinetic energy ($\Trel$) is used in the SRG generator, nuclear structure calculations have shown greatly improved convergence with basis size because of the decoupling of high-energy and low-energy physics. However this generator can sometimes be problematic. A test case is provided by a study of initial interactions from chiral effective field theories with large cutoffs, which can lead to spurious deep bound states. We would like the SRG to decouple these from the physical shallow bound states. However, with $\Trel$ the high- and low-energy bound states are not decoupled in the usual sense. Replacing $\Trel$ by the momentum-space diagonal of the Hamiltonian ($H_d$) in the SRG generator does produce decoupling, such that the shallow states are in the low-momentum region and the deep bound states are at higher momentum. The flow toward universal low-momentum interactions is also restored.

Use of terrestrial laser scanning for engineering geological applications on volcanic rock slopes – an example from Madeira island (Portugal)

Abstract. This study focuses on the adoption of a modern, widely-used Terrestrial Laser Scanner (TLS) application to investigate volcanic rock slopes in Ribeira de João Gomes valley (Funchal, Madeira island). The TLS data acquisition in May and December 2008 provided information for a characterization of the volcanic environment, detailed structural analysis and detection of potentially unstable rock masses on a slope. Using this information, it was possible to determine specific parameters for numerical rockfall simulations such as average block size, shape or potential sources. By including additional data, such as surface roughness, the results from numerical rockfall simulations allowed us to classify different hazardous areas based on run-out distances, frequency of impacts and related kinetic energy. Afterwards, a monitoring of hazardous areas can be performed in order to establish a rockfall inventory.

Penetration Factor for Nuclear Fusion Reaction in Nonthermal Astrophysical Plasmas

The nonthermal effects on the nuclear fusion reaction process are investigated in Lorentzian astrophysical plasmas. The closed expression of the classical turning point in Lorentzian plasmas is obtained by the Lambert $W$-function. Using the WKB analysis with the effective screening length, the closed expressions of the fusion penetration factor and the cross section for the nuclear fusion reaction in Lorentzian plasmas are obtained as functions of the spectral index, relative kinetic energy, and plasma parameters. It is shown that the nonthermal character of the Lorentzian plasma enhances the fusion penetration factor. In addition, the nonthermal effect on the penetration factor is found to be more significant in plasmas with higher densities. It would be expected that the fusion reaction rates of the $p$–$p$ chain and the CNO cycle in nonthermal plasmas are always greater than those in thermal Maxwellian plasmas.

Dynamics Analysis and Modeling of Ship-mounted Boom Crane

The dynamic model of a kind of boom crane mounted on ships is established.The relative kinetic energy is calculated in the non-inertial coordinate frame fixed on the crane ship.Introducing the inertial force,the Lagrange's equations successfully depict the movement of the system consisting of the boom and payload,which is impacted not only by the control forces:the luffing and slewing moments of the boom and the rope's strain,but also the 6 degrees of the crane ship's movement mainly caused by ocean wave.The structure of the obtained model is suitable for the dynamics analysis and controller design for the system.Some kinematic features are demonstrated by the provided simulation results.

Assessing an Impulsive Model for Rotational Energy Partitioning to Acetyl Radicals from the Photodissociation of Acetyl Chloride at 235 nm

This work uses the photodissociation of acetyl chloride to assess the utility of a recently proposed impulsive model when the dissociation occurs on an excited electronic state that is not repulsive in the Franck-Condon region. The impulsive model explicitly includes an average over the vibrational quantum states of acetyl chloride when it calculates an impact parameter for fission of the C-Cl bond, as well as the distribution of thermal energy in the photolytic precursor. The experimentally determined stability of the resulting acetyl radical to subsequent dissociation is the key observable that allows us to test the model's ability to predict the partitioning of energy between rotation and vibration of the radical. We compare the model's predictions for three different assumed geometries at which the impulsive force might act, generating the relative kinetic energy and the concomitant rotational energy in the acetyl radical. Assuming that the impulsive force acts at the transition state for C-Cl fission on the S(1) excited state gives a poor prediction; the model predicts far more energy in rotation of the acetyl radical than is consistent with the measured velocity map imaging spectrum of the stable radicals. The best prediction results from using a geometry derived from the classical trajectory calculations on the excited state potential energy surface. We discuss the insight gained into the excited state dissociation dynamics of acetyl chloride and, more generally, the utility of using the impulsive model in conjunction with excited state trajectory calculations to predict the partitioning of internal energy between rotation and vibration for radicals produced from the photolysis of halogenated precursors.

Experimental studies of the dissociative recombination of CD3CDOD+and CH3CH2OH$_{2}^+$Unknown node mtable found in MathML fragment.

Aims. We determine branching fractions, cross sections and thermal rate constants for the dissociative recombination of CD3CDOD + and CH3CH2OH + at the low relative kinetic energies encountered in the interstellar medium. Methods. The experiments were carried out by merging an ion and electron beam at the heavy ion storage ring CRYRING, Stockholm, Sweden. Results. Break-up of the CCO structure into three heavy fragments is not found for either of the ions. Instead the CCO structure is retained in 23 ± 3% of the DR reactions of CD3CDOD + and 7 ± 3% in the DR of CH3CH2OH + , whereas rupture into two heavy fragments occurs in 77 ± 3% and 93 ± 3% of the DR events of the respective ions. The measured cross sections were fitted between 1–200 meV yielding the following thermal rate constants and cross-section dependencies on the relative kinetic energy: σ(Ecm[eV]) = 1.7 ± 0.3 × 10 −15 (Ecm[eV]) −1.23±0.02 cm 2 and k(T) = 1.9 ± 0.4 × 10 −6 (T/300) −0.73±0.02 cm 3 s −1 for CH3CH2OH + as well as k(T) = 1.1 ± 0.4 × 10 −6 (T/300) −0.74±0.05 cm 3 s −1 and σ(Ecm[eV]) = 9.2 ± 4 × 10 −16 (Ecm[eV]) −1.24±0.05 cm 2 for CD3CDOD +

Breakup excitation function at backward angles from α-spectra in the 6Li + 144Sm system

Breakup cross sections were obtained for the 6Li + 144Sm system at energies above and below the Coulomb barrier from a detailed analysis of the data recorded at backward angles. These cross sections are compared with inelastic target excitations previously reported revealing a similar behavior as a function of the bombarding energy but a large absolute difference between them. Using kinematical considerations we have analyzed possible contributions from different breakup channels and we have extracted information on magnitudes such as the relative kinetic energies of the corresponding breakup fragments.

Extended Fluid–Dynamics and Collective Motion of Two Trapped Fermion Species with Pairing Interactions

We extend our earlier fluid–dynamical description of fermion superfluids incorporating the particle energy flow together with the equation of motion for the internal kinetic energy of the pairs. The formal scheme combines a set of equations similar to those of classical hydrodynamics with the equations of motion for the anomalous density and for its related momentum density and kinetic energy density. This dynamical frame represents a second order truncation of an infinite hierarchy of equations of motion isomorphic to the full time dependent Hartree–Fock–Bogoliubov equations in coordinate representation. We analyze the equilibrium solutions and fluctuations for a homogeneous, unpolarized fermion system of two species, and show that the collective spectrum presents the well-known Anderson–Bogoliubov low energy mode of homogeneous superfluids and a pairing vibration near the gap energy.

Primary photodissociation pathways of epichlorohydrin and analysis of the C–C bond fission channels from an O(P3)+allyl radical intermediate

This study initially characterizes the primary photodissociation processes of epichlorohydrin, c-(H(2)COCH)CH(2)Cl. The three dominant photoproduct channels analyzed are c-(H(2)COCH)CH(2)+Cl, c-(H(2)COCH)+CH(2)Cl, and C(3)H(4)O+HCl. In the second channel, the c-(H(2)COCH) photofission product is a higher energy intermediate on C(2)H(3)O global potential energy surface and has a small isomerization barrier to vinoxy. The resulting highly vibrationally excited vinoxy radicals likely dissociate to give the observed signal at the mass corresponding to ketene, H(2)CCO. The final primary photodissociation pathway HCl+C(3)H(4)O evidences a recoil kinetic energy distribution similar to that of four-center HCl elimination in chlorinated alkenes, so is assigned to production of c-(H(2)COC)=CH(2); the epoxide product is formed with enough vibrational energy to isomerize to acrolein and dissociate. The paper then analyzes the dynamics of the C(3)H(5)O radical produced from C-Cl bond photofission. When the epoxide radical photoproduct undergoes facile ring opening, it is the radical intermediate formed in the O((3)P)+allyl bimolecular reaction when the O atom adds to an end C atom. We focus on the HCO+C(2)H(4) and H(2)CO+C(2)H(3) product channels from this radical intermediate in this report. Analysis of the velocity distribution of the momentum-matched signals from the HCO+C(2)H(4) products at m/e=29 and 28 shows that the dissociation of the radical intermediate imparts a high relative kinetic energy, peaking near 20 kcal/mol, between the products. Similarly, the energy imparted to relative kinetic energy in the H(2)CO+C(2)H(3) product channel of the O((3)P)+allyl radical intermediate also peaks at high-recoil kinetic energies, near 18 kcal/mol. The strongly forward-backward peaked angular distributions and the high kinetic energy release result from tangential recoil during the dissociation of highly rotationally excited nascent radicals formed photolytically in this experiment. The data also reveal substantial branching to an HCCH+H(3)CO product channel. We present a detailed statistical prediction for the dissociation of the radical intermediate on the C(3)H(5)O potential energy surface calculated with coupled cluster theory, accounting for the rotational and vibrational energy imparted to the radical intermediate and the resulting competition between the H+acrolein, HCO+C(2)H(4), and H(2)CO+C(2)H(3) product channels. We compare the results of the theoretical prediction with our measured branching ratios. We also report photoionization efficiency (PIE) curves extending from 9.25 to 12.75 eV for the signal from the HCO+C(2)H(4) and H(2)CO+C(2)H(3) product channels. Using the C(2)H(4) bandwidth-averaged absolute photoionization cross section at 11.27 eV and our measured relative photoion signals of C(2)H(4) and HCO yields a value of 11.6+1/-3 Mb for the photoionization cross section of HCO at 11.27 eV. This determination puts the PIE curve of HCO measured here on an absolute scale, allowing us to report the absolute photoionization efficiency of HCO over the entire range of photoionization energies.

Activation of Dinitrogen by Solid and Liquid Aluminum Nanoclusters: A Combined Experimental and Theoretical Study

Cross sections for chemisorption of N2 onto Al44(+/-) cluster ions have been measured as a function of relative kinetic energy and the temperature of the metal cluster. There is a kinetic energy threshold for chemisorption, indicating that it is an activated process. The threshold energies are around 3.5 eV when the clusters are in their solid phase and drop to around 2.5 eV when the clusters melt, indicating that the liquid clusters are much more reactive than the solid. Below the melting temperature the threshold for Al44(-) is smaller than for Al44(+), but for the liquid clusters the anion and cation have similar thresholds. At high cluster temperatures and high collision energies the Al44N2(+/-) chemisorption product dissociates through several channels, including loss of Al, N2, and Al3N. Density functional calculations are employed to understand the thermodynamics and the dynamics of the reaction. The theoretical results suggest that the lowest energy pathway for activation of dinitrogen is not dynamically accessible under the experimental conditions, so that an explicit account of dynamical effects, via molecular dynamics simulations, is necessary in order to interpret the experimental measurements. The calculations reproduce all of the main features of the experimental results, including the kinetic energy thresholds of the anion and cation and the dissociation energies of the liquid Al44N2(+/-) product. The strong increase in reactivity on melting appears to be due to the volume change of melting and to atomic disorder.

TWO-COMPONENT JETS AND THE FANAROFF–RILEY DICHOTOMY

Transversely stratified jets are observed in many classes of astrophysical objects, ranging from young stellar objects, μ-quasars, to active galactic nuclei and even in gamma-ray bursts. Theoretical arguments support this transverse stratification of jets with two components induced by intrinsic features of the central engine (accretion disk + black hole). In fact, according to the observations and theoretical models, a typical jet has an inner fast low density jet, surrounded by a slower, denser, extended jet. We elaborate on this model and investigate for the first time this two-component jet evolution with very high resolution in 3D. We demonstrate that two-component jets with a high kinetic energy flux contribution from the inner jet are subject to the development of a relativistically enhanced, rotation-induced Rayleigh–Taylor type non-axisymmetric instability. This instability induces–strong mixing between both components, decelerating the inner jet and leading to overall jet decollimation. This novel scenario of sudden jet deceleration and decollimation can explain the radio source Fanaroff–Riley dichotomy as a consequence of the efficiency of the central engine in launching the inner jet component versus the outer jet component. We infer that the FRII/FRI transition, interpreted in our two-component jet scenario, occurs when the relative kinetic energy flux of the inner to the outer jet exceeds a critical ratio.

Quenching of internal rotations versus collisional cooling at ultralow energies for weakly interacting partners: Cs2(3Σu+)withHe3,4

Quantum-scattering calculations at ultralow (close to 10{sup -6} cm{sup -1}) collision energies are carried out for the Cs dimer in its spin-stretched triplet state, interacting with helium. An ab initio potential energy surface is computed and employed, while the target molecule is kept in its ground vibrational state and several excitated initial rotational states are considered in the quantum dynamics. The highly anisotropic interaction is seen to cause, in spite of its weakness, internal energy quenching rates comparable with the efficiency of the collisional cooling of relative kinetic energies. The rates of spin-flip processes are also analyzed and compared with pure rotational quenching events.

A New Method for Evaluating the Energy Characteristics of CHNO Energetic Compounds

AbstractFrom the law of conversation of energy, the release energy from the initiation to the Chapman–Jouguet point during the detonation of an energetic compound has been deduced as a function of initial density, detonation velocity, and detonation pressure. For CHNO energetic compounds the relative release energy per unit volume (Iv) approaches the relative specific wall kinetic energy (Ecyl/EHMX) at 19 mm wall displacement from the cylinder test with HMX as reference. A good linear relationship between Iv and Ecyl/EHMX has been regressed, implying that Ecyl/EHMX is also a function of initial density, detonation velocity, and detonation pressure. It has been concluded that Iv can reflect the driving force of detonation products of energetic compounds and is appropriate to be used for the evaluation of energy characteristics. The assessment of the energy for a series of synthesized and theoretically designed high‐energy compounds reveals that the future of CHNO energetic compounds is promising after CL‐20 and ONC.

Electrostatic Spacecraft Collision AvoidanceUsing Piecewise-Constant Charges

This paper develops a three-phase piecewise-constant spacecraft charge maneuver to achieve short-range collision avoidance with a symmetric relative trajectory. This symmetric trajectory guarantees collision avoidance, restores the original relative-motion direction, and keeps the relative kinetic energy level the same as the initial kinetic energy level. The paper first presents an analytical solution to calculate a unique symmetric trajectory when the middle phase is a circular trajectory. Next, a general symmetric-trajectory programming strategy is developed in which the middle phase can be any conic section. Four constraints are required to guarantee a symmetric collision-avoidance trajectory, and five independent variables are required to solve the problem. This leaves one degree of freedom that is used to optimize the trajectory subject to specific cost charge functions. There is a duality in the charge solution when solving for the open-loop trajectory, with one of the solutions being false. This is addressed by properly initializing and confining the region of the numerical search routine. Minimum charge criteria are determined to avoid a collision by analyzing the geometric properties of the two-body system and comparing the results from circular transitional trajectory calculations.

DISSOCIATIVE RECOMBINATION OF PROTONATED FORMIC ACID: IMPLICATIONS FOR MOLECULAR CLOUD AND COMETARY CHEMISTRY

At the heavy ion storage ring CRYRING in Stockholm, Sweden, we have investigated the dissociative recombination of DCOOD2+ at low relative kinetic energies, from similar to 1 meV to 1 eV. The therm ...

Dissociative recombination of the acetaldehyde cation, CH3CHO+

The dissociative recombination of the acetaldehyde cation, CH(3)CHO(+), has been investigated at the heavy ion storage ring CRYRING at the Manne Siegbahn Laboratory in Stockholm, Sweden. The dependence of the absolute cross section of the reaction on the relative kinetic energy has been determined and a thermal rate coefficient of k(T) = (1.5 ± 0.2) × 10(-6) (T/300)(-0.70±0.02) cm(3) s(-1) has been deduced, which is valid for electron temperatures between ∼10 and 1000 K. The branching fractions of the reaction were studied at ∼0 eV relative kinetic energy and we found that breaking one of the bonds between two of the heavy atoms occurs in 72 ± 2% of the reactions. In the remaining events the three heavy atoms stay in the same product fragment. While the branching fractions are fairly similar to the results from an earlier investigation into the dissociative recombination of the fully deuterated acetaldehyde cation, CD(3)CDO(+), the thermal rate coefficient is somewhat larger for CH(3)CHO(+). Astrochemical implications of the results are discussed.

Transport coefficients of dilute hydrogen gas, calculations and comparisons with experiments

The paper presents quantum mechanical ab initio calculations of transport coefficients of dilute H 2 gas, derived from an empirically corrected ab initio interaction potential used in so-called close-coupled channel calculations which provided scattering matrices and subsequently differential scattering cross sections of the elastic and inelastic rotational interactions, for grids of relative kinetic energies sufficient to obtain converged results of transport coefficients at temperatures up to 300 K. The formalism of the Waldmann–Snider theory of the Boltzmann equation has been used following previous work in this field. Results are presented for the pure para- and ortho-H 2 gas as well as for their mixtures. Excellent agreement has been found in comparisons with measured results of pure para-H 2 gas thus providing proof of the proper input used in the calculations. The comparison with measured normal H 2 transport coefficients was also successful for the calculated normal H 2 shear viscosity (±2%) and the calculated translational heat conductivity coefficient (±2%). Deviations from experiments of up to ≈10% have been found for the total normal H 2 heat conductivity in the temperature range between 75 and 225 K.

A time-dependent picture of the charge transfer process in the S3+ +H collision

In this work we observe for the first time the evolution of the electronic charge density in a collisional system. The model used is system S3+ + H over the range of relative ion kinetic energies from [1–10] eV. To this aim, ab initio potential energy surfaces and non-adiabatic couplings together with wavepacket propagations have been used.