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91.
R. Schnabel M. Schultz-Johanning M. Kock 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):267-269
Radiative lifetimes of 19 selected W II levels with energies between 36 000 cm-1 and 55 000 cm-1 have been measured with the time-resolved laser-induced fluorescence technique. The ions are generated in a hollow cathode
discharge and stored in a linear Paul trap. Selected states are populated with tunable dye laser pulses and the subsequent
fluorescence is measured by means of a 5 Gigasample transient digitizer and a fast photodetector with a risetime of 700 ps.
By taking into account both the temporal profile of the laser pulses and the separately measured response function of the
system, the lifetime can be determined from the full decay curve. A refined evaluation procedure, taking into account saturation
effects in the signals, reduces the uncertainty in our data to around 1%.
Received: 30 July 1998 / Revised: 18 August 1998 相似文献
92.
半导体冰箱冷热端散热条件实验研究 总被引:11,自引:0,他引:11
半导体制冷器件是一种高热流密度元件,在红外测量、低温超导、生物医学、空间技术等领域有重要的应用,还可开发成专用制冷装置,适用于野外施工、勘探,考古以及郊游等户外活动食品饮料的保鲜,也可用于食品、饮料及医用疫苗等的冷藏。在给定工况下,通过改善半导体器件的冷热端散热条件,可使系统制冷量和制冷性能系数大幅提高。本文设计了实验装置,特别设计了8种实验工况对采用强迫对流换热和热端采用热管换热器散热的实际半导体制冷装置进行了实验分析,提出了改善半导体制冷元件散热条件的具体措施。 相似文献
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In a previous paper we discussed co-crystallization in a LDPE/HDPE blend using TREF and DSC. As part of that study it was observed that pure HDPE showed an unexpected fractionation behavior when quench crystallized in TREF. The overall peak broadened and two peaks appeared instead of the previously observed single peak for slow cooled HDPE.The development of two peaks was observed for all commercial HDPEs investigated, independent of their melting indices and densities. TREF and GPC were used in an attempt to evaluate the origin of the two HDPE components.The authors appreciate support from CAPES-BRAZIL (C.A.F.). Additional thanks go to Dr. G. W. Knight in Dow Chemical Company for kindly providing the polymer samples and performing the GPC analysis. 相似文献
95.
F. Pereira Dos Santos J. Léonard Junmin Wang C. J. Barrelet F. Perales E. Rasel C. S. Unnikrishnan M. Leduc C. Cohen-Tannoudji 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):103-109
We recently observed a Bose-Einstein condensate in a dilute gas of 4He in the 23S1 metastable state. In this article, we describe the successive experimental steps which led to the Bose-Einstein transition
at 4.7 μK: loading of a large number of atoms in a MOT, efficient transfer into a magnetic Ioffé-Pritchard trap, and optimization
of the evaporative cooling ramp. Quantitative measurements are also given for the rates of elastic and inelastic collisions,
both above and below the transition.
Received 15 October 2001 相似文献
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