Fraction Of Available Energy Research Articles

Transverse spin asymmetries for inclusive $\rho^0$ production in SIDIS at COMPASS

The production of vector mesons in SIDIS is a particularly interesting channel to study the polarized fragmentation and related phenomena. Preliminary COMPASS results for the first measurement of inclusive \rho^0ρ0 Collins and Sivers transverse-spin asymmetries are presented here for the first time. The analysis is based on the data-set collected by COMPASS in 2010 using a 160 GeV/c \mu^+μ+ beam and a transversely polarized NH_3NH3 target. The asymmetries are extracted as function of Bjorken-x, of the total transverse momentum of the oppositely charged hadron pair and of the fraction of available energy z carried by the pair. Indications for positive Collins and Sivers asymmetries are obtained as expected from models.

An ecological explanation for hyperallometric scaling of reproduction

Abstract In wild populations, large individuals have disproportionately higher reproductive output than smaller individuals. Some theoretical models explain this pattern—termed reproductive hyperallometry—by individuals allocating a greater fraction of available energy towards reproductive effort as they grow. Here, we propose a simple ecological explanation for this observation: differences between individuals in rates of resource assimilation, where greater assimilation causes both increased reproduction and body size, resulting in reproductive hyperallometry at the level of the population. We illustrate this effect by determining the relationship between size and reproduction in wild and laboratory‐reared Trinidadian guppies. We show that (a) reproduction increased disproportionately with body size in the wild but not in the laboratory, where resource competition was eliminated; (b) in the wild, hyperallometry was greatest during the wet season, when resource competition is strongest; and (c) detection of hyperallometric scaling of reproduction at the population level was inevitable if individual differences in assimilation were ignored. We propose that ecologically driven variation in assimilation—caused by size‐dependent resource competition, niche expansion and chance—contributes substantially to observations of hyperallometric scaling of reproduction in natural populations. We recommend that models incorporate such ecologically caused variation when seeking to explain reproductive hyperallometry. Read the free Plain Language Summary for this article on the Journal blog.

Dynamics of Reaction CH3CHI + O2 Investigated via Infrared Emission of Products CO, CO2, and OH.

The reaction CH3CHI + O2 has been commonly employed in laboratories to produce a methyl-substituted Criegee intermediate CH3CHOO, but the detailed dynamics of this reaction remain unexplored. We carried out this reaction by irradiating a flowing mixture of CH3CHI2 (∼70 mTorr) and O2 (∼4 and 8 Torr) at 308 or 248 nm and observed infrared emission of the products with a step-scan Fourier-transform spectrometer. Upon irradiation at 248 nm with O2 ∼4 Torr, a Boltzmann distribution of CO (v ≤ 4, J ≤ 25) with average vibrational energy (12 ± 2) kJ mol-1 and of OH (v = 1, J ≤ 5.5) were observed and assigned to be produced from the decomposition of CH3C(O)OH* to form CO + CH3OH and OH + CH3CO, respectively. The observed broadband emission of CO2 was simulated with two vibrational distributions of average energies (42 ± 3) and (114 ± 6) kJ mol-1 and assigned to be produced from the decomposition of CH3C(O)OH* and (methyl dioxirane)*, respectively. The results upon irradiation of the sample at 308 nm are similar, likely indicating a small fraction of energy partition into these products and rapid thermalization of CH3CHI*. Compared with reaction CH2I + O2, the title reaction yielded products with much less internal excitation, consistent with the expectation that these observed products receive much less fraction of available energy upon fragmentation when an additional methyl moiety was present in the parent. The large-v component of CO observed in experiments of CH2I + O2 at 248 nm, produced from secondary reaction HCO + O2, was absent in this work because the corresponding secondary reaction CH3CO + O2 in decomposition of CH3CHOO* produces α-lactone + OH or H2CO + CO + OH.

An ab initio-based global potential energy surface for the SH3 system and full-dimensional state-to-state quantum dynamics study for the H2 + HS → H2 S + H reaction.

An accurate potential energy surface for the ground electronic state of SH3 system has been constructed with 41,882 high level ab initio energy points and the neural network fitting method. The time-dependent wave packet method has been used to calculate the first state-to-state differential cross sections for the title reaction up to 1.2 eV in full dimensions, based on the reactant-product decoupling scheme. It is found that the majority of H2 S are produced in the ground vibrational state, with a large fraction of available energy for the reaction ending up as product translational motion. The differential cross sections at the threshold energy are dominated by a very narrow peak in the backward direction. With the increase of collision energy, the width of the angular distribution increases considerably, which is a typical feature of a direct reaction via abstract mechanism, similar to the H2 + OH → H2 O + H reaction. © 2018 Wiley Periodicals, Inc.

Quasi-Classical Trajectory Dynamics Study of the Cl(2P) + C2H6 → HCl(v,j) + C2H5 Reaction. Comparison with Experiment.

To understand and simulate the dynamics behavior of the title reaction, QCT calculations were performed on a recently developed global analytical potential energy surface, PES-2017. These calculations combine the classical description of the dynamics with pseudoquantization in the reactants and products to perform a theoretical/experimental comparison on the same footing. Thus, in the products a series of constraints are included to analyze the HCl(v = 0,j) product, which is experimentally detected. At collision energies of 5.5 and 6.7 kcal mol-1 the largest fraction of available energy is deposited as translation, 67%, while the ethyl radical shows significant internal energy, 27%, and so it does not act as a spectator of the reaction, thus reproducing recent experimental evidence. The HCl(v=0, j) rotational distribution is cold, peaking at j = 2, only one unit hotter than experiment, which represents an error of 0.12 kcal mol-1. At a collision energy of 5.5 kcal mol-1 product translational distribution is slightly hotter than experiment, but at 6.7 kcal mol-1 agreement with recent experiments is practically quantitative, suggesting that the first experiments should be revised. In addition, we observe that the HCl(v=0, j) scattering distribution shifts from isotropic at low values of j to backward at high values of j, which is in agreement with experimental data. Finally, no evidence was found for the "chattering" mechanism suggested to explain the low translational energy of the HCl product in the backward scattering region. In sum, agreement with experiments of a series of sensible dynamic properties permits us to be optimistic on the quality and accuracy of the theoretical tools used in the present work, QCT and PES-2017.

Photodissociation of acetone from 266 to 312 nm: Dynamics of CH3 + CH3CO channels on the S0 and T1 states.

The photodissociation dynamics of acetone (CH3)2CO, cooled in a molecular beam, have been explored over the wavelength range 266-312 nm. Nascent CH3 fragments were detected by resonance-enhanced multiphoton ionization, followed by mass-selected ion imaging. For photolysis at λ = 306 nm, the image shows a sharp ring, which, when converted to a translational energy distribution, reveals a narrow Gaussian peak with a maximum at 90% of the available energy. As the photolysis energy is increased, the distribution slowly broadens and shifts to higher recoil translational energy. The fraction of available energy in translation energy decreases in favour of internal energy of the CH3CO fragment. These observations are consistent with a dynamical model in which the energy of the exit channel barrier on the T1 surface evolves mostly into relative translational energy. Energy in excess of the barrier is partitioned statistically into all degrees of freedom. No evidence was found for any other dynamical pathway producing CH3 fragments, including reaction on S0 or S1, for dissociation between 306 and 266 nm. For λ > 306 nm, a diffuse, slow recoil component to the image appears. The translational energy distribution for this component is fit well by a statistical prior distribution of energy. We attribute this component to dissociation on the S0, ground state surface; to our knowledge, this is the first direct observation of this channel. The appearance of S0 dynamics and the disappearance of the T1 component are consistent with previously inferred barrier height on T1 for the production of CH3CO + CH3. The possible atmospheric implications of our findings are discussed.

State-to-state differential cross sections for a four-atom reaction: H2 + OH → H2O + H in full dimensions.

The time-dependent wave packet method has been employed to calculate state-to-state differential cross sections for the title reaction in full dimensions. It is found that the majority of H2O is produced in the first stretching excited states, with a large fraction of available energy for the reaction ending up as product internal motion. The differential cross sections for collision energy up to 0.4 eV are all peaked in the backward direction, but the width of the angular distribution increases considerably as the increase of collision energy. The isotope effect was also examined by comparing the scattering angular distribution for the title reaction with those for the HD + OH and D2 + OH reactions obtained in our previous work.

Crossed-beam DC slice imaging of fluorine atom reactions with linear alkanes.

We report the reaction dynamics of F atom with selected alkanes studied by crossed beam scattering with DC slice ion imaging. The target alkanes are propane, n-butane, and n-pentane. The product alkyl radicals are probed by 157 nm single photon ionization following reaction at a collision energy of ∼10 kcal mol(-1). The analyzed data are compared with the corresponding theoretical studies. Reduced translational energy distributions for each system show similar trends with little of the reaction exoergicity appearing in translation. However, the pentane reaction shows a somewhat smaller fraction of available energy in translation than the other two, suggesting greater energy channeled into pentyl internal degrees of freedom. The center-of-mass angular distributions all show backscattering as well as sharp forward scattering that decreases in relative intensity with the size of the molecule. Possible reasons for these trends are discussed.

COMPARISON OF ENERGY AVAILABLE FOR EVAPOTRANSPIRATION UNDER IN‐FIELD RAINWATER HARVESTING WITH WIDE AND NARROW RUNOFF STRIPS

ABSTRACTThe aim of the study was to quantify the energy balance components and to estimate evapotranspiration (ET) from maize crops under in‐field rainwater harvesting with wide and narrow runoff strip length (RSL) treatments. Based on micrometeorological measurements, energy balance components were compared for selected days under dry and wet conditions. Diurnal changes and daily evaporation flux peaks around midday were analysed. The average fraction of available energy was used to evaluate the efficiency of converting available energy to latent heat flux (LE). The results indicated that LE was higher in wide compared to narrow RSL during dry and wet conditions. However, sensible heat showed lower values on wide RSL during wet conditions due to the advective effect of the runoff area. The wide RSL with a higher basin leaf area ratio (BLAR) of 2.43 had more ET and used more energy on evaporating water compared to narrow runoff with a lower BLAR of 1.42. Wide runoff strips converted the higher available energy more efficiently into a higher biomass production than the narrow RSL. During wet days, the wide RSL used more than 70% of the available energy, while the narrow RSL response to the available energy (63%) was stronger during dry compared to wet days. Copyright © 2012 John Wiley & Sons, Ltd.

Time-dependent wave packet theory for state-to-state differential cross sections of four-atom reactions in full dimensions: Application to the HD + OH → H2O + D reaction

Time-dependent wave packet method has been developed to calculate differential cross section for four-atom reactions in full dimension, utilizing an improved version of reactant-product-decoupling scheme. Differential cross sections for the title reaction were calculated for collision energy up to 0.4 eV. It is found that the differential cross sections for the reaction are all peaked in the backward direction. The majority of H(2)O is produced in the first stretch excited state, with a large fraction of available energy for the reaction going into H(2)O internal motion. As compared in a previous report by Xiao et al. [Science 333, 440 (2011)], the differential cross section at E(c) = 0.3 eV and the differential cross section at the backward direction as a function of collision energy agree with experiment very well, indicating it is possible now to calculate complete dynamical information for some simple four-atom reactions, as have been done for three-atom reactions in the past decades.

C–Br bond fission dynamics in ultraviolet photodissociation of propargyl bromide

The photodissociation dynamics of propargyl bromide has been investigated at 234 and 267 nm using ion velocity imaging technique coupled with a [2+1] resonance-enhanced multiphoton ionization scheme. The translational energy and angular distributions of Br ( 2 p 3 / 2 ) and Br ∗ ( 2 p 1 / 2 ) fragments were obtained. The energy distributions for Br and Br ∗ fragments were found to consist of two Gaussian components, which corresponding to two reaction paths on the excited potential energy surface. The high kinetic energy component was produced via an electronic dissociation from the repulsive nσ ∗ state, while the low kinetic energy component stem from intersystem crossing from ππ ∗ state to πσ ∗ state. The average fraction of available energy imparted into product recoil for the high kinetic energy products was found to be nearly 0.46, in qualitative agreement with that predicted by a soft radical impulsive model. The angular distributions of Br and Br ∗ fragments show a mostly isotropic, which exhibited an admixture of π C C character with σ C – Br ∗ character in the Frank–Condon region upon electronic excitation.

C–Cl bond fission dynamics and angular momentum recoupling in the 235 nm photodissociation of allyl chloride

The photodissociation dynamics of allyl chloride at 235 nm producing atomic Cl((2)P(J);J=1/2,3/2) fragments is investigated using a two-dimensional photofragment velocity ion imaging technique. Detection of the Cl((2)P(1/2)) and Cl((2)P(3/2)) products by [2+1] resonance enhanced multiphoton ionization shows that primary C-Cl bond fission of allyl chloride generates 66.8% Cl((2)P(3/2)) and 33.2% Cl((2)P(1/2)). The Cl((2)P(3/2)) fragments evidenced a bimodal translational energy distribution with a relative weight of low kinetic energy Cl((2)P(3/2))/high kinetic energy Cl((2)P(3/2)) of 0.097/0.903. The minor dissociation channel for C-Cl bond fission, producing low kinetic energy chlorine atoms, formed only chlorine atoms in the Cl((2)P(3/2)) spin-orbit state. The dominant C-Cl bond fission channel, attributed to an electronic predissociation that results in high kinetic energy Cl atoms, produced both Cl((2)P(1/2)) and Cl((2)P(3/2)) atomic fragments. The relative branching for this dissociation channel is Cl((2)P(1/2))/[Cl((2)P(1/2))+Cl((2)P(3/2))]=35.5%. The average fraction of available energy imparted into product recoil for the high kinetic energy products was found to be 59%, in qualitative agreement with that predicted by a rigid radical impulsive model. Both the spin-orbit ground and excited chlorine atom angular distributions were close to isotropic. We compare the observed Cl((2)P(1/2))/[Cl((2)P(1/2))+Cl((2)P(3/2))] ratio produced in the electronic predissociation channel of allyl chloride with a prior study of the chlorine atom spin-orbit states produced from HCl photodissociation, concluding that angular momentum recoupling in the exit channel at long interatomic distance determines the chlorine atom spin-orbit branching.

Annual water balance and seasonality of evapotranspiration in a Bornean tropical rainforest

This study presents the results of 2 years combined field measurements of water vapor exchange with the atmosphere and simplified model calculations at Lambir Hills National Park, Sarawak, Malaysia (4°12′N, 114°02′E). The study site was located in a lowland mixed dipterocarp forest, a major type of Bornean tropical rainforest, where there is no clear seasonality in environmental factors such as radiation, temperature, vapor pressure deficits and precipitation; instead, unpredictable dry spells often occur throughout the year. Modified [Priestley, C.H.B., Taylor, R.J. (1972). On the assessment of surface heat flux and evaporation using large-scale parameters, Mon. Weather Rev. 100, pp. 81–92] and equilibrium evaporation expressions enabled us to understand further the environmental control of water vapor exchanges with the atmosphere and to produce a complete gap-filled data set of the hydrologic fluxes within this environment. The equilibrium evaporation from a well-watered surface sufficiently reproduced the transpiration rate ( T r ); any discrepancies between the equilibrium and actual evaporation rates were caused by unpredictable intra-annual dry spells, which reduced transpiration. There were some discrepancies during the study period because of exceptional dry sequences, but in normal years the annual transpiration rate can be obtained from the equilibrium evaporation expression. The estimated annual T r (1193.1 mm) and evapotranspiration (1545.0 mm) rates were nearly identical to the highest values reported for some humid tropical forests. Although, there were exceptional dry sequences during the study period, the annual average fraction of available energy dissipated by T r at this site (0.69) was almost the same as the medium value between the dry and wet seasons in Amazonian tropical forests. This implies that the annual dynamics of the latent heat flux for this tropical rainforest are under more humid conditions than those of other tropical rainforests.

UV Photodissociation Dynamics of CD3SOCD3: Photofragment Translational and Internal Energy Distribution

The photodissociation of CD 3 SOCD 3 (DMSO-d 6 ) has been studied at four different wavelengths in the UV region (204-227 nm) using resonance enhanced multiphoton ionization (REMPI) and time-of-flight mass spectrometry (TOFMS) to measure TOF profiles and rotational and vibrational REMPI spectra of the CD 3 photoproduct. Three dissociation channels producing CD 3 fragments have been identified. The major primary channel proceeds via internal conversion to the ground state followed by unimolecular decomposition, and it is characterized by an isotropic statistical translational energy distribution. Internally hot CD 3 SO(X) fragments subsequently decompose over an exit barrier (45 ′ 2 kJ mol - 1 ) to produce CD 3 and SO. Another primary channel results from a fast dissociation (direct dissociation or predissociation) that yields anisotropic CD 3 and presumably electronically excited CD 3 SO(A) fragments with β = 0.30 ′ 0.05. In this last case, the fraction of available energy channeled into translation ((f t ) 10.62) is consistent with a soft impulsive model. The measured rotational spectra confirm the results obtained from the TOF profiles simulations.

Heating in current carrying molecular junctions

A framework for estimating heating and expected temperature rise in current carrying molecular junctions is described. Our approach is based on applying the Redfield approximation to a tight binding model for the molecular bridge supplemented by coupling to a phonon bath. This model, used previously to study thermal relaxation effects on electron transfer and conduction in molecular junctions, is extended and used to evaluate the fraction of available energy, i.e., of the potential drop, that is released as heat on the molecular bridge. Classical heat conduction theory is then applied to estimate the expected temperature rise. For a reasonable choice of molecular parameters and for junctions carrying currents in the nA range, we find the temperature rise to be a modest few degrees. It is argued, however, that using classical theory to describe heat transport away from the junction may underestimate the heating effect.

Velocity map imaging of ion-molecule reaction products: Co+(3F4)+isobutane

The velocity map imaging technique is applied to mass-selected CoC3H6++CH4 and CoC4H8++H2 elimination products from the Co+(3F4)+isobutane reaction studied under crossed-beam conditions at 0.21 eV collision energy. For both reactions we obtain the joint scattering probability distribution P(E,Θ), where E and Θ are the product translational energy and scattering angle. The fraction of available energy deposited into product translation is 0.4 for H2, compared with 0.1 for CH4. For the CH4 product, the angular distribution is forward-backwards symmetric and sharply peaked at Θ=0 and 180°. P(E,Θ) is not separable into the product of an energy and an angular function; rather, the angular distribution peaks more sharply at higher translational energy. Evidently, incipient CoC3H6++CH4 products equilibrate in the Co+(C3H6)(CH4) exit-channel well, from which they decay statistically. The product translational energy distribution P(E) is consistent with orbiting-transition state phase-space theory with no exit-channel barrier. In addition, the energy-integrated angular distribution T(Θ) is consistent with the predictions of the early statistical complex decay model of Miller and Herschbach for fragmentation from a transition state that is a prolate top. In sharp contrast, P(E) for the CoC4H8++H2 products exhibits a substantial hot, nonstatistical tail towards high energy. Perhaps the H2 channel has a late potential energy barrier some 0.5 eV above products, but we view this explanation as highly unlikely. Instead, we suggest that the potential energy from an earlier multicenter transition state is funneled efficiently, and highly nonstatistically, into product translation. This surprising conclusion may apply to H2 products for the entire family of reactions of the late-3D series transition metal cations Fe+, Co+, and Ni+ with alkanes.

Infrared Chemiluminescence Study of the Reaction of Hydroxyl Radical with Acetaldehyde and the Secondary Reactions of Acetyl Radical with NO2, OH, and H

The hydrogen abstraction reactions from CH3CHO by OH and OD radicals were studied in a fast-flow reactor by observation of the infrared chemiluminescence from H2O and HOD. The fraction of available energy released as the vibrational energy of water was 〈fv〉 = 0.52 with ∼30% released as bending excitation and ∼65% released as stretching excitation of the newly formed OH bond. The pattern of energy disposal closely resembles that for OH + H2CO or (CH3)2S reactions, but differs from abstraction from secondary C−H bonds of hydrocarbons. Secondary reactions of CH3CO radical with NO2, OH, and H also were observed by infrared emission of products formed from the unimolecular decomposition of CH3C(O)ONO, CH3C(O)OH, and CH3C(O)H intermediate adducts. The CO2 vibrational distributions from the decomposition of CH3C(O)OH, CH3C(O)ONO, and HC(O)ONO are compared.

Laser-induced fluorescence studies of excited Sr reactions: II. Sr(3P1)+CH3F, C2H5F, C2H4F2

The vibrational and rotational energy distributions of ground state SrF(X 2Σ) formed in the reactions of electronically excited Sr(3P1) with methylfluoride, ethylfluoride, and 1,1-difluoroethane have been studied by laser-induced fluorescence. Although the reactions of ground state Sr with these reactants are exothermic, no SrF products are observed for those reactions in this study. The fraction of available energy disposed into the sum of rotational and vibrational energy of the SrF(X 2Σ) product is approximately the same for all three reactions, i.e., 40%. The reaction of Sr(3P1) with CH3F results in very low vibrational excitation in the SrF reaction product. The product vibration increases in going to C2H5F and C2H4F2. It is concluded that the alkyl group influences the energy disposal mechanism in these reactions, and some suggestions are given for a partial explanation of the observations.

Collisional excitation of CO 2(00 00) vibrationless state by the highly translationally excited HCN produced from the photodissociation of s-triazine

The collisional excitation of CO 2(00 00) state by quenching of highly translationally excited HCN has been studied with high-resolution diode laser absorption spectroscopy. The translationally hot HCN is produced from the photodissociation of s-triazine (1,3,5-triazine) at 266 nm. The average translational energy of HCN is measured to be 18±1 kcal/mol, which corresponds to 84% of available energy for the HCN fragment. The fraction of available energy partitioned into the rotational excitation is 15%. A little excitation in the HCN bending vibration is observed. The nascent rotational excitation in the 00 00 levels of CO 2, due to collisions with the translationally hot HCN (from s-triazine), is accompanied by a substantial enhancement in the translational energy. The excitation in the translational recoil velocities appears to increase with increasing J in 00 00 vibrational state.

Product state resolved stereodynamics of the reaction H(2S)+CO2OH(X2Π3/2; v = 0,N= 5) CO(1Σ+)

The detailed stereodynamics of the H+CO2 system have been studied using polarized Doppler resolved laser induced fluorescence to state selectively probe the OH product. The lambda-doublet specific differential cross-sections and translational energy distributions were measured, along with the scattering angle dependence of the rotational angular momentum polarization. The observed centre-of-mass differential cross-section has significant contributions in both the forward and backward hemispheres, with a small preference for backward scattering, and the measured fraction of available energy released as translational energy is greater than that predicted by statistical models. The rotational angular mometum vector of the OH product displays a polarized angular distribution, measured with respect to the reagent relative velocity vector k and the kk' scattering plane, with the π(A'') lambda-doublet component being significantly more strongly polarized than the π(A') level. In addition, those products scattered backwards are seen to have a different polarization from those scattered forwards. The unprecedented detail of the information obtained is explained in terms of rather stringent steric constraints in the entrance channel and the formation of short-lived collision complexes.