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1.
The angular variations of the five-fold differential cross section obtained by using different wave functions of helium are
compared with experimental data. It is found that in the coplanar geometry two kinematical arrangements, (i) equal energy
sharing between the two ejected electrons with one of them ejected along the momentum transfer direction and the other along
varying direction and (ii) the Bethe ridge condition with fixed sum of ejected electron energies and varying angle between
them, are very sensitive to e-e correlations contained in the target wave function. This comparison has been used to show
that open-shell class of wave functions better incorporate e-e correlations than the closed-shell class. 相似文献
2.
C.M. Andrei J.C. Walmsley H.W. Brinks R. Holmestad S.S. Srinivasan C.M. Jensen B.C. Hauback 《Applied Physics A: Materials Science & Processing》2005,80(4):709-715
NaAlH4 is a promising candidate material for hydrogen storage. Ti additives are effective in reducing the reaction temperatures and improving kinetics. In this work, the microstructure of NaAlH4 with 2% TiF3 has been studied in different conditions using a combination of transmission electron microscopy and scanning electron microscopy, both with energy-dispersive spectroscopic X-ray analysis. The effect of the additive on particle and grain size was examined after the initial ball-milling process and after 15 cycles. The additive has an uneven distribution in the sample after ball milling. Selected-area diffraction and high-resolution imaging confirmed the presence of TiF3. This phase accounts for most of the Ti in the material at this stage and showed limited mixing with the alanate. The grain size within particles for TiF3 is larger than for the alanate particles. Diffraction from the latter was dominated by metallic aluminium. After cycling, the TiF3 has decomposed and energy-dispersive spectroscopic X-ray analysis maps showed some combination of Ti with the alanate phase. There is no significant change in the measurable grain size of the Al-containing alanate particles between the ball-milled and the 15-cycled samples, but more cycles result in agglomeration of the material. PACS 61.14.-x; 68.37.LP; 68.37.Hk 相似文献
3.
Haselberg R Brinks V Hawe A de Jong GJ Somsen GW 《Analytical and bioanalytical chemistry》2011,400(1):295-303
In this work, the usefulness of capillary electrophoresis–electrospray ionization time-of-flight–mass spectrometry for the
analysis of biopharmaceuticals was studied. Noncovalently bound capillary coatings consisting of Polybrene-poly(vinyl sulfonic
acid) or Polybrene-dextran sulfate-Polybrene were used to minimize protein and peptide adsorption, and achieve good separation
efficiencies. The potential of the capillary electrophoresis-mass spectrometry (CE-MS) system to characterize degradation
products was investigated by analyzing samples of the drugs, recombinant human growth hormone (rhGH) and oxytocin, which had
been subjected to prolonged storage, heat exposure, and/or different pH values. Modifications could be assigned based on accurate
masses as obtained with time-of-flight–mass spectrometry (TOF-MS) and migration times with respect to the parent compound.
For heat-exposed rhGH, oxidations, sulfonate formation, and deamidations were observed. Oxytocin showed strong deamidation
(up to 40%) upon heat exposure at low pH, whereas at medium and high pH, mainly dimer (>10%) and trisulfide formation (6–7%)
occurred. Recombinant human interferon-β-1a (rhIFN-β) was used to evaluate the capability of the CE-MS method to assess glycan
heterogeneity of pharmaceutical proteins. Analysis of this N-glycosylated protein revealed a cluster of resolved peaks which appeared to be caused by at least ten glycoforms differing
merely in sialic acid and hexose N-acetylhexosamine composition. Based on the relative peak area (assuming an equimolar response per glycoform), a quantitative
profile could be derived with the disialytated biantennary glycoform as most abundant (52%). Such a profile may be useful
for in-process and quality control of rhIFN-β batches. It is concluded that the separation power provided by combined capillary
electrophoresis and TOF-MS allows discrimination of highly related protein species. 相似文献
4.
Hildner R Brinks D Stefani FD van Hulst NF 《Physical chemistry chemical physics : PCCP》2011,13(5):1888-1894
Employing femtosecond pulse-shaping techniques we investigate ultrafast, coherent and incoherent dynamics in single molecules at room temperature. In first experiments single molecules are excited into their purely electronic 0-0 transition by phase-locked double-pulse sequences with pulse durations of 75 fs and 20 nm spectral band width. Their femtosecond kinetics can then be understood in terms of a 2-level system and modelled with the optical Bloch equations. We find that we observe the coherence decay in single molecules, and the purely electronic dephasing times can be retrieved directly in the time domain. In addition, the Rabi-frequencies and thus the transition dipole moments of single molecules are determined from these data. Upon excitation of single molecules into a vibrational level of the electronically excited state also incoherent intra-molecular vibrational relaxation is recorded. Increasing the spectral band width of the excitation pulses to up to 120 nm (resulting in a transform-limited pulse width of 15 fs) coherent superpositions of excited state vibrational modes, i.e. vibrational wave packets, are excited. The wave-packet oscillations in the excited state potential energy surface are followed in time by a phase-controlled pump-probe scheme, which permits to record wave packet interference, and to determine the energies of vibrational modes and their coupling strengths to the electronic transition. 相似文献
5.
The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions.
The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential
and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated
sheath are made. 相似文献
6.
NaAlH(4) with TiCl(3) and Al were mixed by ball-milling and cycled three times. The hydrogen storage properties were monitored during cycling, and the products were characterized by synchrotron X-ray diffraction. Because of the previously described formation of Al(1)(-)(y)Ti(y) with y approximately 0.15 during cycling that traps Al beyond the amount associated with the formation of NaCl, some Na(3)AlH(6) has no free Al to react with to form NaAlH(4). This was counteracted in the present work by adding a stoichiometric amount of Al that increases the theoretical storage capacity. Due to limitations in metal diffusion small amounts of Na(3)AlH(6) were still detected. When approximately 7 mol % more Al than the stoichiometric amount was added, the observed storage capacity increased significantly, and the Na(3)AlH(6) content was negligible after prolonged rehydrogenation. Cycled NaAlH(4) + 10 mol % TiCl(3) were desorbed to two different levels, and the diffraction patterns were compared. There is no change in unit-cell dimensions during desorption, and there is no sign of changes in the bulk composition of the Al(1)(-)(y)Ti(y) phase during a cycle. Adding pure Ti to a NaH + Al mixture by ball-milling in argon or hydrogen results in formation of TiH(2) that is stable during at least one cycle. 相似文献
7.
The symmetric sinc-Galerkin method developed by Lund, when appliedto the second-order self-adjoint boundary value problem, givesrise to a symmetric coefficient matrix has a special structureso that it can be advantageously used in solving the discretesystem. In this paper, we employ the preconditioned conjugategradient method with banded matrices as preconditioners. Weprove that the condition number of the preconditioned matrixis uniformly bounded by a constant independent of the size ofthe matrix. In particular, we show that the solution of an n-by-ndiscrete symmetric sinc-Galerkin system can be obtained in O(nlog n) operations. We also extend our method to the self-adjointelliptic partial differential equation. Numerical results aregiven to illustrate the effectiveness of our fast iterativesolvers. 相似文献
8.
The angular distribution of the five-fold differential cross section for the electron impact double ionization of He (21
S) and He (23
S) has been studied. The kinematical conditions for maxima/minima in the angular distribution for the two cases have been compared.
The two-step process for the double ionization is found to contribute very little in the triplet case. 相似文献
9.
Andrei CM Walmsley JC Brinks HW Holmestad R Blanchard D Hauback BC Botton GA 《The journal of physical chemistry. B》2005,109(10):4350-4356
The microstructure of LiAlD(4) with TiCl(3).1/3(AlCl(3)) and VCl(3) additives has been studied during different steps of the decomposition process using electron energy loss spectroscopy and energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope. Energy filtered transmission electron microscopy was used to show elemental distributions in the samples. The spatial distribution of the additives and the main elements within the alanate particles was examined with a resolution of a few nanometers. The analysis of the electron energy loss spectra reveals the chemical state of Al, O, and the additives. Ti and V do not appear to mix chemically with Al to a significant degree. V was found in high concentration in just a few particles, while Ti is more uniformly distributed. All the samples showed evidence of oxidation despite procedures being adopted to avoid exposing the material to air. The additives are oxidized in all the samples, and Al(2)O(3) forms a thin layer at the surface of the particles. This paper gives a comparison between samples at different stages of the decomposition process using different additives. 相似文献
10.
MK Bhide RM Kadam MD Sastry Ajay Singh Shashwati Sen Manmeet Kaur DK Aswal SK Gupta VC Sahni 《Pramana》2002,58(5-6):799-802
Microwave absorption studies have been carried out on MgB2 superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for
polycrystalline (grain size ∼ 10 μm) samples suggested the absence of weak-link character. The field dependent direct microwave
absorption has been found to obey a ✓H dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime. 相似文献