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81.
A method to obtain well collimated beams of heavy ions on the basis of secundary ion emission is described. 相似文献
82.
Near-threshold photoionization of hydrogenlike uranium studied in ion-atom collisions via the time-reversed process 总被引:1,自引:0,他引:1
Stöhlker T Ma X Ludziejewski T Beyer HF Bosch F Brinzanescu O Dunford RW Eichler J Hagmann S Ichihara A Kozhuharov C Krämer A Liesen D Mokler PH Stachura Z Swiat P Warczak A 《Physical review letters》2001,86(6):983-986
Radiative electron capture, the time-reversed photoionization process occurring in ion-atom collisions, provides presently the only access to photoionization studies for very highly charged ions. By applying the deceleration mode of the ESR storage ring, we studied this process in low-energy collisions of bare uranium ions with low- Z target atoms. This technique allows us to extend the current information about photoionization to much lower energies than those accessible for neutral heavy elements in the direct reaction channel. The results prove that for high- Z systems, higher-order multipole contributions and magnetic corrections persist even at energies close to the threshold. 相似文献
83.
Benisty H. Lalanne PH. Olivier S. Rattier M. Weisbuch C. Smith C.J.M. Krauss T.F. Jouanin C. Cassagne D. 《Optical and Quantum Electronics》2002,34(1-3):205-215
We address the issue of out-of-plane losses in two-dimensional (2D) photonic crystals (PC) etched through a GaAs monomode waveguide clad with standard GaAlAs alloys. We correlate experimental transmission of PCs with two kinds of loss simulation results. The first kind is 2D and introduces an ad hoc imaginary index in the air holes to account for the losses [see (Benisty et al. Appl. Phys. Lett. 76, 532, 2000)]. The second kind is a novel exact three-dimensional calculation inspired by grating-Fourier analysis that provides quantitatively unprecedented agreement with experimental measurements taking into account hole depth as a limiting parameter. We conclude that, in revision to the conclusions of the above reference, the experimental losses are not the intrinsic ones, being larger by a factor of 5 to 10 due to insufficient hole depth. The transition occurs at a critical etch depth shown to be here around 700 nm. We thus predict, for holes deeper than 700 nm, much improved crystals with very low transmission losses and microresonators with ultra-high quality factors. 相似文献
84.
The impact-parameter dependence of 3dσ excitation has been derived from measurements of K- and L-shell excitation probabilities in very heavy, asymmetric collision systems (96?Z1+Z2?124). The first systematic evidence for the mechanism of the 3dσ-3dπ-3dδ rotational coupling has been found and is briefly discussed. 相似文献
85.
K. E. Stiebing H. Schmidt-Böcking W. Schadt K. Bethge R. Schuch P. H. Mokler F. Bosch D. Liesen S. Hagmann P. Vincent 《Zeitschrift für Physik A Hadrons and Nuclei》1984,319(3):239-251
The emission probabilities for quasimolecular K-x-radiation (K-MOR) have been measured in208Pb +208Pb collisions at 4.3 MeV/u and 4.8 MeV/u as a function of the scattering angle using the particle-photon-coincidence technique. The probabilities exhibit a superposition of two exponential slopes with different fall-off constants. We identify the sharp fall off at very small impact parameters (<60 fm) with the K-MOR contribution from the decay of 1sσ-vacancies. The flatter slope for impact parameters larger than 60 fm is attributed to the radiative decay of holes in 2p 1/2 σ molecular states. In this way, experimental “1sσ-MOR-emission probabilities” could be extracted and compared with theory. For 4.3 MeV/u the1sσ- and 2p 1/2 σ-excitation probabilities could also be determined and have been compared to coupled-channel calculations and to a scaling law for 1sσ excitation. 相似文献
86.
H. -H. Behncke D. Liesen S. Hagmann P. H. Mokler P. Armbruster 《Zeitschrift für Physik A Hadrons and Nuclei》1978,288(1):35-38
Using particle x-ray coincidence techniques, the probability to produceK-shell vacancies in 4.7 MeV/u Pb+Z2 (42≦Z 2≦92) collisions for impact parametersb<100 fm was measured. For these impact parameters, the 1sσ excitation probability is greater than 1 σ 10?2 and the 2p 1/2 σ excitation probability is greater than 1 σ 10?1. Binding energies of the 1sσ state derived from the measured probabilities agree well with theoretical calculations. 相似文献
87.
P. Armbruster H. -H. Behncke S. Hagmann D. Liesen F. Folkmann P. H. Mokler 《Zeitschrift für Physik A Hadrons and Nuclei》1978,288(3):277-281
From 90° line width analysis ofKα1 lines excited in very heavy ion-atom collisions (Z 1 +Z 2>137) mean impact parameters for the ionization probability are derived. The experimental mean impact parameters are shown to obey the Bang-Hansteen scaling rule¯bE(R)=C · ?v correlating the minimum momentum transferE(R)/v and the mean impact parameterb. Theoretical values of the constantC are (0.8±0.1) for 2p 1/2 σ excitation and (1.0±0.1) for 1sσ excitation in the rangeZ 1+Z 2=140–160. It is proposed to apply the scaling rule as a spectroscopic tool to study the 1sσ and 2p 1/2 σ levels in superheavy quasimolecules. The need of a sound theoretical base justifying the application of the scaling rule is emphasized. 相似文献
88.
马新文 T.Stohlker H.F.Beyer F.Bosch O.Brinzanescu C.Kozhuharov P.H.Mokler T.Ludziejewski Z.Stachura A.Warczak 《原子核物理评论》2002,19(2):131-135
分析了在重离子冷却储存环上测量的辐射电子俘获产生的X射线能谱,得出了K REC光子的相对微分角分布,通过与非相对论理论和全相对论理论的计算结果进行比较,从实验上证明了相对论重离子 原子碰撞中自旋翻转跃迁的存在,实验结果与全相对论理论计算结果一致.同时还证实,重离子体系本身的相对论性质对碰撞过程有重要影响. Radiative electron capture process occurring in high-Z ion-atom collisions studied on the heavy ion storage ring (ERS) is reviewed. The REC differential angular distributions are deduced from the X-ray spectra recorded at various observation angles for 310 and 88 MeV/u U 92+on N 2collisions, respectively. The experimental results are compared with non-relativistic and complete relativistic calculations. Deviations from sin 2θ lab are found in both cases. The contributions to near 0°observation... 相似文献
89.
Walied M. Alarif Khalid O. Al-Footy Muhammad Sulaiman Zubair Mohamed Halid PH Mohamed A. Ghandourah Salim A. Basaif 《Natural product research》2016,30(10):1150-1155
A new eudesmane sesquiterpenoid, eudesma-4(15),7-diene-5,11-diol (1) along with the known trinor-sesquiterene, teuhetenone (2), and a seco-eudesmane sesquiterpene, chabrolidione B (3), have been isolated from the Red Sea red alga Laurencia obtusa. The chemical structures were elucidated on the basis of extensive spectroscopic analysis. The antifungal and cytotoxic activities of the isolated metabolites were tested against several fungi, yeast and human mammary carcinoma cell line (MCF-7). Compounds 1 and 3 showed a much better activity [minimum inhibitory concentration (MIC): 2.9 μM] than that of amphotericin B (MIC: 4.6 μM). Interestingly, compound 2, the least active antifungal compound, retained the high anticancer activity against MCF-7 (22 μM) in comparison with cisplatin (59 μM), which was determined by employing lactate dehydrogenase assay. Compounds 1–3 are recorded here for the first time from algal flora. The chemotaxonomic importance of the isolated metabolites was discussed. 相似文献
90.