Fission product energies and anisotropies following complete fusion of16O+238U

Radioactive recoil techniques have been developed for measuring angular distributions and range distributions of individual fission products following heavy ion induced fission. From these measurements, values can be extracted for the recoil velocity of the fissioning nucleus, the velocity imparted by fission, and the fission anisotropy. These techniques were applied to reactions of 101 MeV¹⁶O on²³⁸U, and confirmed that the reaction mechanism is essentially entirely complete fusion-fission. Accepting this, the data determine the kinetic energy release in forming the various products to a precision of 1%; while the overall magnitude of the energy is in good agreement with previous results, the data suggest a systematic correlation between kinetic energy and the position of a product on the nuclear charge dispersion curve, not previously reported, which is similar to but significantly larger in magnitude than the effect expected from simple Coulomb repulsion. Significant variations in anisotropy are also observed between products, which appear to be partially correlated with the variations in kinetic energy.     

Measurement of the ratios of branching fractions and

We report an observation of the decay B(O)(S) --> D(-)(s)pi(+) in pp collisions at radical S = 1.96 TeV using 115 pb(-1) of data collected by the CDF II detector at the Fermilab Tevatron. We observe 83 +/- 11(stat) B(O)(s) --> D(-)(s)pi(+) candidates, representing a large increase in statistics over previous measurements and the first observation of this decay at a pp collider. We present the first measurement of the relative branching fraction Beta(B(O)(s) --> D(-)(s)pi(+))/Beta(B(0) --> D(-)(pi)(+)) = 1.32 +/- 0.18(stat) +/- 0.38(syst). We also measure Beta(B(+) --> D(0)pi(+))/Beta(B(0) -->D(-)pi(+)) = 1.97 +/- 0.10(stat) +/- 0.21(syst), which is consistent with previous measurements.     

Control of branching ratio in the photofragmentation of DCl+ ions: Effect of initial vibrational state

Photofragmentation of DCl⁺ ions alternatively leads to the formation of D⁺ + Cl or Cl⁺ + D in competing reaction channels. The branching ratio of the product yields D⁺/Cl⁺ has been investigated theoretically by numerically solving coupled time dependent Schrödinger equations and experimentally by femtosecond (fs) dissociative ionization of DCl. The theoretical analysis shows that this branching ratio increases step-like at intensities, which characteristically depend on the initial vibrational state for nonresonant multiphoton excitation. In general the threshold decreases with increasing initial vibrational quantum number. Experimental studies exhibit a similar step-like behavior of the D⁺/Cl⁺ branching ratio. Here the intensity at which the step occurs characteristically depends on the chirp of the fs-laser pulses, suggesting that different chirp may lead to intermediate DCl⁺ ions differing in the effective vibrational quantum number.     

离子速度影像装置及其在CCl3Br光解动力学研究中的应用

建立了一套高分辨的离子速度影像装置。在这套装置中,离了透镜的设计是利用Simion7．0应用程序对电场中离子的空间分布进行模拟“聚焦”得到的,达到了将离了源空间分布中速度相同而位置不同的离子聚焦在同一点上的效果。利用这套装置研究了CCl3Br在267nm附近的光解反应产物Br(^2P3.2)和Br^*(^2P1.2)的速度和角度的分布,得到了β(Br)=-0．48,β(Br^*)=1．44。     

H+H2O reaction dynamics: state distribution for the OH product

A method has been developed to study the dynamics of high barrier reactions by combining hot-atom production by laser photolysis and fast-product detection by laser induced fluorescence. The nascent OH rotational, vibrational and fine structure state distributions produced in the endothermic reaction have been measured with hot hydrogen atoms from the photodissociation of HBr at 193 nm. OH rotational excitation is low and corresponds to a partitioning of only around 3% of the total reaction energy to OH rotation. OH could only be observed in the vibrational ground state, i.e.(v=1)/(v=0)0.1. The OH spin doublets are produced statistically, but the partitioning in the -doublets is very non-statistical with a strong preference for the ⁺-component ((⁺)/(^–)=3.2±1.0) demonstrating the exit channel of the reaction to be preferentially planar. By measuring reactant and product densities at short times, an absolute total cross-section of 0.24±0.1[Ų] has been obtained.     

Higgs production at the LHC: an update on cross sections and branching ratios

New theoretical and experimental information motivates a re-examination of the Standard Model Higgs production rates at the LHC pp collider. We present calculations of the relevant cross sections and branching ratios, including recently calculated QCD next-to-leading order corrections, new parton distributions fitted to recent HERA structure function data, and new values for electroweak input parameters, in particular for the top quark mass. Cross sections are calculated at two collider energies, √s = 10 TeV and 14 TeV.     

Signatures in the angular power spectrum of the cosmic microwave background anisotropies: Topological defect scenarios versus inflationary models

Acoustic peaks in the angular power spectrum of the cosmic microwave background anisotropies may allow us to distinguish among the two classes of models—topological defect scenarios and inflationary models—which attempt to explain the origin of structure formation in the universe. I briefly sketch the main differences between these two classes of models and illustrate the relevant analysis of induced density perturbations, in a model where density perturbations are generated by global scalar fields, within a universe dominated by cold dark matter.     

Effective spatial and angular correlations in beams of any state of spatial coherence and an associated phase-space product

We study effective spatial and angular correlations in beams of any state of spatial coherence, and we introduce a phase-space product, Q , which takes these correlations into account. This phase-space product is shown to reduce to the conventional beam-quality factor M(2) when the beam is spatially fully coherent. We also determine the lower bound for the value of Q and demonstrate that it is attained for all Gaussian Schell-model beams.     

Investigation of 38Ar levels by 37Cl+p reactions: (I). Yield curves,excitation energies and branching ratios

Yield measurements have been performed on the reactions ³⁷Cl(p, p₀)³⁷Cl, ³⁷Cl(p, α₀)³⁴S (E_p = 1.17–1.70 MeV) and ³⁷Cl(p, n₀)³⁷Ar, ³⁷Cl(p.γ)³⁸Ar (E_p = 0.64–2.92 MeV); detailed investigations are restricted to resonances below E_p = 1.79 MeV. Resonance energies, strengths and (some) widths are reported for 12, 26 and 247 resonances in the reactions (p, p₀), (p, n₀) and (p, γ), respectively.Simultaneous (p, α₀) and (p, γ) yield measurements over selected E_p intervals in the E_p = 0.88–1.64 MeV range established the existence of 42 resonances decaying by both γ and α₀ emission. Analysis of the γ-ray spectra of 100 ³⁷Cl(p, γ)³⁸Ar resonances leads to precision excitation energies (ΔE_x = 0.1–2 keV) of 57 bound states (E_x < 8 MeV) and branching ratios of the resonances and of 50 bound states.     

Determination of angular momenta in the incomplete-fusion channels of the reactions Ta+22Ne and Ir+12C

By using the γ-ray-multiplicity technique, experiments were carried out to determine the input angular momenta lⁱⁿ corresponding to the heavy-ion induced incomplete-fusion reactions involving the emission of fast charged particles. The α-particle and Li-nuclei emission channels were investigated in the reaction ¹⁸¹Ta + ²²Ne at the average Ne-ion energy of 155 MeV and for the α-particle emission channel in the reaction ^natIr+¹²C at E = 100 MeV. The separation of the reaction channels was carried out using an X-ray spectrometer. The angular distributions of the fission fragments were measured in the reaction ¹⁸¹Ta(²²Ne, αf). The data obtained indicate that input angular momenta are equal to about 60 ? and 50 ? for the channels of Li emission and α-emission, respectively, being practically independent of the particle energy. For the α-emission channel the lⁱⁿ values are the same for both reactions within experimental errors. The lifetime of the system of interacting target and projectile nuclei, prior to the emission of an α-particle, has been estimated to be equal to 10^?20s.     

A study of angular correlations of projectile and target fragments in 1.4 A GeV Kr+Ag(Br) collisions

A sample of high multiplicity quasi-central Kr⁸⁴+Ag(Br) interactions has been'analysed in terms of angular correlations between projectile and target fragments. The azimuthal correlation of PFs and TFs suggests the presence of a weak collective (bounce-off) effect. Other observations like, target recoil velocity,F/B ratio of TFs with respect to direction of their source etc. are interpreted in terms of a simple two body quasi-elastic scattering and a modified Maxwell-Boltzmann distribution.     

Photoelectron branching ratios and asymmetry parameters of the two outermost molecular orbitals of methyl cyanide

Vibrationally resolved photoelectron branching ratios and asymmetry parameters have been determined for the two outermost molecular orbitals of methyl cyanide. The results are discussed briefly within the context of similar studies on cyanogen and hydrogen cyanide, and in relation to structures exhibited in the photoionization efficiency curve.     

Level lifetimes and branching ratios in the z3P0 term of neutral iron

The relative intensities of all significant transitions from each level of the z³P⁰ term in iron have been measured. The values are combined with absolute transition probabilities from the literature to determine the lifetime of each level.     

C+离子内壳激发共振态1s2s(3S)2p3的Auger能量和Auger分支率

利用精确的鞍点变分波函数和鞍点复数转动方法,计算了C+离子五电子原子系统内壳激发共振态1s2s(3S)2p3 2,4Po, 2,4Do 的俄歇能量和俄歇分支率,考察了俄歇跃迁的收敛性,对300-keV C+离子和CH4气体碰撞实验产生的高分辨率俄歇电子谱进行了标定,并指出这些类硼C+离子的内壳激发共振态对253-273eV范围的实验谱线有重要贡献. 本文计算结果与实验数据符合得很好.     

C~+离子内壳激发共振态1s2s(~3S)2p~3的Auger能量和Auger分支率(英文)

利用精确的鞍点变分波函数和鞍点复数转动方法,计算了C⁺离子五电子原子系统内壳激发共振态1s2s（³S）2p^32,4P°,^2,4D°的俄歇能量和俄歇分支率,考察了俄歇跃迁的收敛性,对300 keV C⁺离子和CH₄气体碰撞实验产生的高分辨率俄歇电子谱进行了标定,并指出这些类硼C⁺离子的内壳激发共振态对253～273 eV范围的实验谱线有重要贡献.本文计算结果与实验数据符合得很好.