太阳风等离子体输出流量的全日面二维结构

本文根据1983年十个 Carrington 周(1733—1742)期间的 K-日冕亮度、行星际闪烁(IPS)观测和光球磁场观测,首次探讨了太阳风等离子体质量、动量和能量输出流量 F_M,F_P 和 F_E 的全日面二维平均结构及其与光球磁场结构的关系.     

Some symmetry-induced isotope effects in the kinetics of recombination reactions

Symmetry-induced isotope effects in recombination and collision-induced dissociation reactions are discussed. Progress on understanding the anomalous isotope effects in ozone is reviewed. Then, calculations are performed for the simpler reaction xNe+yNe+H<-->xNeyNe+H, where x and y label either identical or different isotopes. The atomic masses in the model are chosen so that symmetry is the only difference between the systems. Starting from a single potential energy surface, the properties of the bound, quasibound, and continuum states of the neon dimer are calculated. Then, the vibration rotation infinite order sudden approximation is used to calculate cross sections for all possible inelastic and dissociative processes. A rate constant matrix that exactly satisfies detailed balance is constructed. It allows recombination to occur both via direct three-body collisions and via tunneling into the quasibound states of the energy transfer mechanism. The eigenvalue rate coefficients are determined. Significant isotope effects are clearly found, and their behavior depends on the pressure, temperature, and mechanism of the reaction. Both spin statistics and symmetry breaking produce isotope effects. Under most conditions the breaking of symmetry enhances the rates, but a wide spectrum of effects is observed; they range from isotope effects with a normal mass dependence to huge, mass-independent isotope effects to cancellation and even to reversal of the isotope effects. This is the first calculation of symmetry-induced isotope effects in recombination rates from first principles. The relevance of the present effects to ozone recombination is discussed.     

CW diode pumping and FM mode locking of a Nd: KGW laser

We have demonstrated cw diode end pumping of Nd: KGW, a novel solid-state gain medium, with up to 30% conversion efficiency into near-TEM₀₀ (M² < 1.05) output at = 1.067 µm for a pump level of 2.7 W. The slope efficiency was limited by intracavity reflections to 36%; however, direct comparison to a similar Nd:YAG laser indicates the same intrinsic slope efficiency of 60%. FM mode locking of this laser at 200 MHz has produced 12 ps pulses (compared to 16 ps for Nd: YAG), although an intracavity etalon was required. Considerable reduction in pulse width is possible (the line width limit is 0.5 ps) but different techniques may be necessary. Spatial hole burning was evident in both the 120 GHz free-running spectrum and the etalon-limited mode-locked spectrum.     

Growth dynamics and intracluster reactions in Ni+(CO2)n complexes via infrared spectroscopy

Ni(+)(CO(2))(n), Ni(+)(CO(2))(n)Ar, Ni(+)(CO(2))(n)Ne, and Ni(+)(O(2))(CO(2))(n) complexes are generated by laser vaporization in a pulsed supersonic expansion. The complexes are mass-selected in a reflectron time-of-flight mass spectrometer and studied by infrared resonance-enhanced photodissociation (IR-REPD) spectroscopy. Photofragmentation proceeds exclusively through the loss of intact CO(2) molecules from Ni(+)(CO(2))(n) and Ni(+)(O(2))(CO(2))(n) complexes, and by elimination of the noble gas atom from Ni(+)(CO(2))(n)Ar and Ni(+)(CO(2))(n)Ne. Vibrational resonances are identified and assigned in the region of the asymmetric stretch of CO(2). Small complexes have resonances that are blueshifted from the asymmetric stretch of free CO(2), consistent with structures having linear Ni(+)-O=C=O configurations. Fragmentation of larger Ni(+)(CO(2))(n) clusters terminates at the size of n=4, and new vibrational bands assigned to external ligands are observed for n> or =5. These combined observations indicate that the coordination number for CO(2) molecules around Ni(+) is exactly four. Trends in the loss channels and spectra of Ni(+)(O(2))(CO(2))(n) clusters suggest that each oxygen atom occupies a different coordination site around a four-coordinate metal ion in these complexes. The spectra of larger Ni(+)(CO(2))(n) clusters provide evidence for an intracluster insertion reaction assisted by solvation, producing a metal oxide-carbonyl species as the reaction product.     

Relative reactivities of some dienes and acetylenes in copolymerization with sulfur dioxide

The reactivities of isoprene, piperylene,2,3-dimethylbutadiene, hex-1-yne, and phenylacetylene, at ?20°C, relative to that of cyclohexene, have been determined for the radical-initiated copolymerization with sulfur dioxide to form 1:1 polysulfones. The unsaturated hydrocarbons were copolymerized with sulfur dioxide in pairs and the composition of the terpolymers determined from the 100 MHz NMR spectra. The dienes react 11–15 times as fast as hex-1-ene, while hex-1-yne reacts 16 times more slowly. Phenylacetylene reacts 21 times as fast as hex-1-yne. The relative reactivities are interpreted mainly in terms of the effect of electron delocalization on the stability of the product radical.     

The synthesis of the potent anti-herpes virus agent, E-5(2-bromovinyl)-2′-deoxyuridine and related compounds

The synthesis of $\text{E}$-5(2-bromovinyl)-2′-deoxyuridine in good yield from deoxyuridine $\text{via}$ an intermediate organopalladium derivative is described. The corresponding chloro and iodo compounds have also been made as have the corresponding bromo and iodo 2′-deoxycytidines.     

Amide bond formation using an air-stable source of AlMe3

Synthesis of amides from coupling esters with a range of primary amines can be conveniently achieved in moderate to excellent yields (69-99%) using an air-stable adduct of trimethylaluminium (AlMe₃)₂·DABCO (DABCO is 1,4-diazobicyclo[2.2.2]octane), referred to as DABAL-Me₃. Reactions can be run without requiring the exclusion of atmospheric oxygen or the drying of solvents.     

Isomerization of 2,5-divinyltetrahydropyran and acid-catalyzed rearrangements of isomeric novel dihydropyrans

2,5-Divinyltetrahydropyran (1) can be isomerized using a ruthenium trichloride- triphenylphosphine catalyst to give 3,4-dihydro-3-vinyl-6-ethyl-2H-pyran (2) and 3,4-dihydro-3- ethylidene-6-ethyl-2H-pyran (3). These products give a variety of rearranged products on treatment with acid. The course of the reactions can be controlled by reaction conditions to give 4-ethyltoluene (5) or 3-hydroxymethyl-1-octen-6-one (4) from 2, and 3,4-dihydro-2-methyl-3-methylene-(6-ethyl-2H- pyran (7), 2,3,4-trimethyl-2-cyclohexen-1-one (8), or 3-hydroxymethyl-2-octen-6-one (6) from 3. All of these products (4–8) can be explained as arising by the initial opening of the dihydropyran to generate an unsaturated hydroxy ketone which then cyclizes to carbocyclic products.