排序方式: 共有30条查询结果,搜索用时 15 毫秒
1.
K. Jungmann P. E. G. Baird J. R. M. Barr C. Bressler P. F. Curley R. Dixson G. H. Eaton A. I. Ferguson H. Geerds V. W. Hughes J. Kenntner S. N. Lea F. Maas M. A. Persaud G. zu Putlitz P. G. H. Sandars W. Schwarz W. T. Toner M. Towrie G. Woodman L. Zhang Z. Zhang 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,21(3):241-243
The 12 S 1/2(F=1)?22 S 1/2(F=1) energy interval in muonium has been investigated by Doppler-free two-photon laser spectroscopy. The transition was observed by uniquely identifying and counting the muons released after the photoionization of the 2S state by the same laser field. The measured transition frequency of 2455 528016(58)(43) MHz is in good agreement with QED calculations. The experiment can be interpreted as a test of the Lamb shift contributions at the 1% level. The method is also well suited for a precise determination of the mass of the positive muon in a muoniumhydrogen isotope shift measurement. 相似文献
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The efficient, high-yield synthesis of the important retinoic acid synthon ethyl trans-3-formyl-2-butenoate by Wadsworth-Emmons methodology is described. 相似文献
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Recent experiments suggest that the Ising pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7 display qualitative properties of the nearest-neighbor "spin ice" model. We discuss the dipolar energy scale present in both these materials and discuss how spin-ice behavior can occur despite the presence of long-range dipolar interactions. We present results of numerical simulations and a mean field analysis of Ising pyrochlore systems. Based on our quantitative theory, we suggest that the spin-ice behavior in these systems is due to long-range dipolar interactions, and that the nearest-neighbor exchange in Dy2Ti2O7 is antiferromagnetic. 相似文献
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Application of a femtosecond self-sustaining mode-locked Ti:sapphire laser to the field of laser scanning confocal microscopy 总被引:3,自引:0,他引:3
P. F. Curley A. I. Ferguson J. G. White W. B. Amos 《Optical and Quantum Electronics》1992,24(8):851-859
Developments in ultrafast Ti:sapphire laser technology can be applied in the investigation of nonlinear optical processes. We describe the application of a self-sustaining femtosecond Ti:sapphire laser as an illumination source in the field of confocal laser scanning fluorescence microscopy (LSM). We present spectra for various fluorescent stains under two-photon excitation and present LSM images of stained samples under mode-locked illumination. The potential for such a system as a non-destructive technique for studying live cells in biomedical research is discussed. 相似文献
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Griffin TP Diaz JA Arkin CR Soto C Curley CH Gomez O 《Journal of the American Society for Mass Spectrometry》2008,19(10):1411-1418
The visualization of hazardous gaseous emissions at volcanoes using in-situ mass spectrometry (MS) is a key step towards a
better comprehension of the geophysical phenomena surrounding eruptive activity. In-situ data consisting of helium, carbon
dioxide, sulfur dioxide, and other gas species, were acquired with a quadrupole based MS system. Global position systems (GPS)
and MS data were plotted on ground imagery, topography, and remote sensing data collected by a host of instruments during
the second Costa Rica Airborne Research and Technology Applications (CARTA) mission. This combination of gas and imaging data
allowed three-dimensional (3D) visualization of the volcanic plume and the mapping of gas concentration at several volcanic
structures and urban areas. This combined set of data has demonstrated a better tool to assess hazardous conditions by visualizing
and modeling of possible scenarios of volcanic activity. The MS system is used for in-situ measurement of 3D gas concentrations
at different volcanic locations with three different transportation platforms: aircraft, auto, and hand-carried. The demonstration
for urban contamination mapping is also presented as another possible use for the MS system. 相似文献
7.
Lynch WB Bechtel HA Steeves AH Curley JJ Field RW 《The Journal of chemical physics》2007,126(24):244307
The A1A" state of isocyanogen, CNCN, is observed using photofragment fluorescence excitation spectroscopy in a room temperature cell and in a molecular beam. The spectra are highly congested, but progressions that correspond to the Franck-Condon active C-N-C bending vibration in the excited state are evident. Linewidth measurements indicate that the excited state lifetime is <10 ps. These measurements are consistent with previous ab initio calculations, which predicted a bent excited state with a short lifetime due to predissociation. Although we do not believe that we have observed the origin band of the electronic transition, we place an upper limit of 42,523 cm(-1) on the energy of the excited state zero point level. 相似文献
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A. N. Danilewsky A. Crll J. Tonn M. Schweizer S. Lauer K. W. Benz T. Tuomi R. Rantamki P. McNally J. Curley 《Crystal Research and Technology》2009,44(10):1109-1114
The behaviour of dislocations in GaSb crystals grown in space both from a stoichiometric melt (floating zone method, FZ) and a Bi solution (floating solution zone, FSZ) respectively, is studied. Predominantly straight 60° dislocations with Burgers vectors of the type b = a/2 <110> in (111) glide planes are identified. In the 20 mm long FZ single crystal the linear growing out of the dislocations is observed which reduces the dislocation density in the centre of the crystal to values below 300 cm–2. The Bi incorporation in the FSZ crystal results in a misfit between seed and grown crystal and in a network of misfit dislocations at the interface. Thermocapillary convection during growth as well as the surface tension may be the reasons for the presence of curved dislocations and the higher dislocation density within a 1 – 2 mm border region at the edges of both of the crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
Abstract The long wavelength UV-induced photoisomerization of retinoic acid has been investigated in physiologic-like solutions. By high-performance liquid chromatographic analysis seven isomers of the parent molecule were observed at the photostationary state. The structures of these isomers have been determined using high-field nuclear magnetic resonance spectroscopy. While addition of a non-ionic detergent had no effect on the retinoic acid photoisomerization, a number of proteins, as well as a phospholipid, completely inhibited this process. Possible reasons for differences in observed isomer distribution relative to earlier studies, as well as for the effects of the photoprotectant compounds, are discussed. 相似文献