Reaction product imaging: the h + d2 reaction

The differential cross section for the H + D(2) --> HD + D reaction has been measured using a technique called reaction product imaging. In this experiment, a photolytically produced beam of hydrogen (H) atoms crossed a beam of cold deuterium (D(2)) molecules. Product D atoms were ionized at the intersection of the two particle beams and accelerated toward a position-sensitive detector. The ion images appearing on the detector are two-dimensional projections of the three-dimensional velocity distribution of the D atom products. The reaction was studied at nominal center-of-mass collision energies of 0.54 and 1.29 electron volts. At the lower collision energy, the measured differential cross section for D atom production, summed over all final states of the HD(v,J) product, is in good agreement with recent quasi-classical trajectory calculations. At the higher collision energy, the agreement between the theoretical predictions and experimental results is less favorable.     

Partial control of an ion-molecule reaction by selection of the internal motion of the polyatomic reagent ion

The ion-molecule reaction NH(3)(+) + ND(3) has been studied at various collision energies (1 to 5 electron volts in the center of mass) with preparation of the NH(3)(+) reagent in two nearly isoenergetic vibrational states. One state corresponds to pure out-of-plane bending of the planar NH(3)(+) ion (0.60 electron volts), whereas the other state is a combination of in-plane and out-of-plane motion (0.63 electron volts). The product branching ratios differ markedly for these two vibrational-state preparations. The differences in reactivity suggest that the in-plane totally symmetric stretching mode is essentially inactive in controlling the branching ratio of this reaction.     

Breakdown of the Born-Oppenheimer approximation in the F+ o-D2 -> DF + D reaction

The reaction of F with H2 and its isotopomers is the paradigm for an exothermic triatomic abstraction reaction. In a crossed-beam scattering experiment, we determined relative integral and differential cross sections for reaction of the ground F(2P(3/2)) and excited F*(2P(1/2)) spin-orbit states with D2 for collision energies of 0.25 to 1.2 kilocalorie/mole. At the lowest collision energy, F* is approximately 1.6 times more reactive than F, although reaction of F* is forbidden within the Born-Oppenheimer (BO) approximation. As the collision energy increases, the BO-allowed reaction rapidly dominates. We found excellent agreement between multistate, quantum reactive scattering calculations and both the measured energy dependence of the F*/F reactivity ratio and the differential cross sections. This agreement confirms the fundamental understanding of the factors controlling electronic nonadiabaticity in abstraction reactions.     

香椿木干燥特性和干燥基准初探

本文以香椿木人工林木材为对象,采用百度试验法对其干燥特性进行了初步研究。结果表明：香椿木为较易干燥树种,其主要干燥缺陷为初期开裂和截面变形;香椿木的初期开裂、内部裂纹、截面变形、扭曲变形与干燥速度等级分别为3、1-2、3、2级和2级;根据干燥缺陷等级及相应的干燥条件初步拟定了其干燥基准。     

Images of Excited H3+ at the Foot of the lo Flux Tube in Jupiter's Atmosphere

The electrodynamic interaction between lo and the Jovian magnetosphere drives currents to and from the planet's ionosphere, where H(3)(+) emission is excited. Direct images of this phenomenon were obtained with the ProtoCAM infrared camera at the National Aeronautics and Space Administration's 3-m Infrared Telescope Facility. The emissions are localized to the instantaneous foot of the lo flux tube, approximately 8 degrees equatorward of the more intense auroral H(3)(+) emission associated with higher magnetic latitudes. The foot of the lo flux tube leads that of (undisturbed) model magnetic field lines passing through lo by 15 degrees to 20 degrees in longitude and is less visible in the northern hemisphere at longitudes where the surface magnetic field strength is greatest. These data favor the unipolar inductor model of the lo interaction and provide insight into the source location and generation of Jovian decameter radio emission.     

Acceleration of nitrogen ions to 7.4 gev in the princeton particle accelerator

Nitrogen ions in charge states N(5+) and N(6+) have been accelerated in the Princeton Particle Accelerator to 4 and 7.4 billion electron volts (Gev), respectively. An external N(5+) beam of 1 x 10(6) particles per second has been obtained and focused to a 6-millimeter-diameter spot. The N(6+) beam was about 2 x 10(5) particles per second. The total charge-changing collision cross section of N(5+) in water vapor was determined as a function of ion energy. The improvement in vacuum necessary to increase the N(5+) beam at least tenfold was calculated. The N(6+) total cross section is probably smaller than that of N(5+) at the higher energies.     

Dynamics of Carbonium Ions Solvated by Molecular Hydrogen: CH5+(H2)n (n = 1, 2, 3)

The dynamics of the carbonium ion (CH(5)(+)), a highly reactive intermediate with no equilibrium structure, was studied by measuring the infrared spectra for internally cold CH(5)(+)(H(2))n(n = 1, 2, 3) stored in an ion trap. First-principle molecular dynamics methods were used to directly simulate the internal motion for these ionic complexes. The combined experimental and theoretical efforts substantiated the anticipated scrambling motion in the CH(5)(+) core and revealed the effect of the solvent molecular hydrogen in slowing down the scrambling. The results indicate the feasibility of using solvent molecules to stabilize the floppy CH(5)(+) ion in order to make it amenable to spectroscopic study.     

Escape of hydrogen from venus

Recombination of O(2)(+) represents a source of fast oxygen atoms in Venus' exosphere, and subsequent collisions of oxygen atoms with hydrogen atoms lead to escape of about 10(7) hydrogen atoms per square centimeter per second. Escape of deuterium atoms is negligible, and the ratio of deuterium to hydrogen should increase with time. It is suggested that the mass-2 ion observed by Pioneer Venus is D(+), which implies a ratio of deuterium to hydrogen in the contemporary atmosphere of about 10(-2), an initial ratio of 5 x 10(-5) and an original H(2)O abundance not less than 800 grams per square centimeter.     

田间枣树愈伤组织诱导及不定芽的发生

以‘星光'和‘月光'2个枣树品种为试材,比较了截干高度和截口粗度、覆盖方式、二甲基亚砜(DMSO)、TDZ(N-苯基-N'-1,2,3-噻二唑-5-基脲)、AgNO3和秋水仙素对田间枝干截面愈伤组织诱导和不定芽发生的影响.结果表明:高枝干截面愈伤发生快,愈伤生长旺盛,截口粗度对截面愈伤的发生有影响,差异显著.“塑料袋+...     

Ammonium ion concentration in the primitive ocean

If ion exchange on clay minerals regulated the cationts in the primitive ocean as it does in the present ocean, the pH would have been 8 and the K(+) concentration 0.01M. Since NH(4)(+) and K(+) are similar in their claymineral equilibria, the maximum NH(4) (+) concentration in the primitive ocean would also have been 0.01M. An estimate of the minimum NH(4)(+) concentratin is 1 x 10(-3)M, based on the reversible deamination of aspartic acid and the assumption that aspartic acid is necessary for the origin of life. The rate of this nonenzymic deamnination is rapid on the geological time scale.     

Experimental Studies and Theoretical Predictions for the H + D2 rarr > HD + D Reaction

The H + H(2) exchange reaction constitutes an excellent benchmark with which to test dynamical theories against experiments. The H + D(2) (vibrational quantum number v = 0, rotational quantum number j = 0) reaction has been studied in crossed molecular beams at a collision energy of 1.28 electron volts, with the use of the technique of Rydberg atom time-of-flight spectroscopy. The experimental resolution achieved permits the determination of fully rovibrational state-resolved differential cross sections. The high-resolution data allow a detailed assessment of the applicability and quality of quasi-classical trajectory (QCT) and quantum mechanical (QM) calculations. The experimental results are in excellent agreement with the QM results and in slightly worse agreement with the QCT results. This theoretical reproduction of the experimental data was achieved without explicit consideration of geometric phase effects.     

紫薇异倍体的杂交亲和性分析及子代倍性鉴定

以二倍体红薇(H,2n)、三倍体紫薇(Z,3n)、四倍体紫薇(Z,4n)及四倍体银薇(Y,4n)为试材,进行杂交试验,检测紫薇异倍体杂交的亲和性,并采用细胞学倍性鉴定法对杂交子代的倍性进行鉴定和比较。结果显示:不同杂交组合子代的结实特性以及种子的出苗率均存在差异,其中Z(4n)×H(2n)的单果重(0.22 g)、单果种子数(40.1)、千粒重(1.79 g)及出苗率(36.4%)均高于H(2n)×Y(4n),且差异达到显著水平,表明在二倍体与四倍体的杂交中,四倍体作为母本的亲和性更高;H(2n)×Z(3n)后代倍性主要为非整倍体,占80%以上,其次是2n,占11.8%;Y(4n)×H(2n)后代倍性主要为3n,占50%,其次是非整倍体,占40%;H(2n)×Z(3n)后代中,1株为3n,2株为非整倍体;Y(4n)×H(2n)后代中,6株为3n,3株为非整倍体;H(2n)×Y(4n)后代幼苗中,1株为2n,1株为3n;Z(4n)×Z(4n)后代中,1株为4n;在杂交组合H(2n)×Z(3n)、Y(4n)×H(2n)及H(2n)×Y(4n)后代中还出现三子叶变异的幼苗。     

He-H_2碰撞(E=0.2,1.2,2.2 eV)分波截面的理论研究

使用原子与双原子分子相互作用比较准确的Tang-Toennies势模型,通过密耦近似(Close-Coupling)方法计算了He原子与H2分子在不同碰撞能量(E=0.2,1.2,2.2 eV)时散射分波截面,首次对He-H2体系较高碰撞能量(大于2.0 eV)时的碰撞截面进行了研究,对计算结果进行了讨论,总结了该碰撞体系的分波散射截面在弹性散射00-00和非弹性散射00-04的变化规律.     

土地整治项目灌溉渠道衬砌方案经济比选研究

灌溉渠道是农田重要的基础设施,而渠床渗漏是渠系水量损失的主要途径,渠道衬砌可减少渠床渗漏损失,提高灌溉效益。不同的衬砌方案效益各不相同,通过对相同流量、不同断面和不同衬砌方式的渠道进行单价分析,考察较适宜的衬砌方案。结果表明,3种断面中梯形断面渠道单价最低;矩形断面渠道单价次之,U型断面渠道单价最高。5种衬砌方式中,梯形断面边坡预制渠道单价最低,预制U型槽单价最高。     

土地整治项目中的输排水工程设计

输排水工程是土地整治项目中的重要内容。该文以南昌县向塘镇高田村土地整治项目为例,探讨了农田水利给排水工程方案的设计。通过对沟渠流量计算及纵横断面设计结果表明:设计灌水率是确定渠道设计流量的依据,排涝模数是确定排水沟设计流量的重要依据,而沟渠设计流量是确定纵横断面的主要依据。因此,在输排水工程中,合理确定设计灌水率及排涝模数尤为重要。     

Seemingly anomalous angular distributions in H + D₂ reactive scattering

When a hydrogen (H) atom approaches a deuterium (D(2)) molecule, the minimum-energy path is for the three nuclei to line up. Consequently, nearly collinear collisions cause HD reaction products to be backscattered with low rotational excitation, whereas more glancing collisions yield sideways-scattered HD products with higher rotational excitation. Here we report that measured cross sections for the H + D(2) → HD(v' = 4, j') + D reaction at a collision energy of 1.97 electron volts contradict this behavior. The anomalous angular distributions match closely fully quantum mechanical calculations, and for the most part quasiclassical trajectory calculations. As the energy available in product recoil is reduced, a rotational barrier to reaction cuts off contributions from glancing collisions, causing high-j' HD products to become backward scattered.     

The effect of magmatic activity on hydrothermal venting along the superfast-spreading East pacific rise

A survey of hydrothermal activity along the superfast-spreading (approximately 150 millimeters per year) East Pacific Rise shows that hydrothermal plumes overlay approximately 60 percent of the ridge crest between 13 degrees 50' and 18 degrees 40'S, a plume abundance nearly twice that known from any other rige portion of comparable length. Plumes were most abundant where the axial cross section is inflated and an axial magma chamber is present. Plumes with high ratios of volatile ((3)He, CH(4), and H(2)S) to nonvolatile (Mn and Fe) species marked where hydrothermal circulation has been perturbed by recent magmatic activity. The high proportion of volatile-rich plumes observed implies that such episodes are more frequent here than on slower spreading ridges.     

Interference of quantized transition-state pathways in the H + D2 -> D + HD chemical reaction

The collision-energy dependence of the state-resolved differential cross section at a specific backward-scattering angle for the reaction H + D2 --> D + HD is measured with the D-atom Rydberg "tagging" time-of-flight technique. The reaction was modeled theoretically with converged quantum scattering calculations that provided physical interpretation of the observations. Oscillations in the differential cross sections in the backward-scattering direction are clearly observed and are attributed to the transition-state structures that originate from the interferences of different quantized transition-state pathways.     

Infrared observations of the jovian system from voyager 1

The infrared spectroscopy and radiometry investigation has obtained spectra of Jupiter and its satellites between approximately 180 and 2500 cm(-1) with a spectral resolution of 4.3 cm(-1). The Jupiter spectra show clear evidence of H(2), CH(4) C(2)H(2), C(2)H(6), CH(3)D, NH(3), PH(3), H(2)O, and GeH(4). A helium concentration of 0.11 +/- 0.03 by volume is obtained. Meridional temperature cross sections show considerable structure. At high latitudes, the stratosphere is warmer in the north than in the south. The upper troposphere and lower stratosphere are locally cold over the Great Red Spot. Amalthea is warmer than expected. Considerable thermal structure is observed on Io, including a relatively hot region in the vicinity of a volcanic feature.     

Struvite and prebiotic phosphorylation

Struvite, MgNH(4)PO(4).6H(2)O, rather than apatite or amorphous calcium phosphate is precipitated when phosphate is added to seawater containing more than 0.01M NH(4)(+) ions. Struvite may have precipitated from evaporating seawater on the primitive earth, and may have been important for prebiotic phosphorylation.