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101.
G. Werth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):121-124
Spectroscopic experiments in static or dynamic ion traps have produced results of extremely high precision. They have been,
however, performed mainly on systems with simple electronic level schemes as available in singly charged ions of the earth-alkaline
elements. In this contribution the most complex system investigated so far, Eu+, is used as example to discuss the possibility of spectroscopy on superheavy elements in traps. 相似文献
102.
The thermo-luminescence (TL) of rare earth ions RE3+ (RE=Ln, excluding Pm, Eu and Lu) co-doped phosphors CaGa2S4:Eu2+, RE3+ was studied between room temperature and 300 °C, and 3D thermo-luminescence of the phosphors were measured from room temperature to 400 °C. The basic material CaGa2S4:Eu2+, showed at least two bands in the TL glow curve. Changing the auxiliary activator RE3+ (rare earth ion), intensities and the positions of the TL glow curve peaks were affected significantly. For the phosphors with long afterglow, auxiliary activator such as Ce3+, Pr3+, Gd3+, Tb3+, Ho3+, or Y3+ created some new defects in these compounds at lower trap levels and enhanced their TL intensities. The Nd3+ or Er3+ auxiliary activator only enhanced TL intensities to a low extent, so these two phosphors have short persistent luminescence at room temperature. TL intensities of La3+, Sm3+, Tm3+ or Yb3+ co-doped phosphors were suppressed greatly and no afterglow was shown. The relationship between auxiliary activators and corresponding thermo-luminescence curves of phosphors CaGa2S4:Eu2+, RE3+ are discussed in detail. According to our results, suitable activation energy and enough high corresponding trap density are necessary for the phosphor with long afterglow. 相似文献
103.
Photoluminescent phosphors CaGa2S4: Eu2+, RE3+ (RE3+ including all rare earth ions except for Sc3+, Pm3+, Eu3+ and Lu3+) were prepared by sintering at high temperature in a reductive atmosphere, and their luminescent properties were studied intensively. The influences of co-doping rare earth ions on their luminescent properties were also investigated. No remarkable differences were found from excitation spectra of co-doped phosphors CaGa2S4: Eu2+, RE3+ in contrast with that of phosphor CaGa2S4: Eu2+, but there were a few differences in emission spectra of Ce3+, Pr3+ or Ho3+ co-doped phosphors. Phosphors CaGa2S4: Eu2+, RE3+ (RE=Ce, Pr, Gd, Tb, Ho and Y) had persistent afterglow, and very short afterglow was shown for Nd3+ or Er3+ co-doped phosphors, but no long afterglow appeared when auxiliary activator was La3+, Sm3+, Dy3+, Tm3+ or Yb3+. Among the phosphors with long-lasting phosphorescence, in our experiments, CaGa2S4: Eu2+, Ho3+ had the longest and the highest brightness long yellow afterglow. Thermo-luminescence of all co-doped phosphors was measured to find the answer of different influences from different rare earth auxiliary activators. 相似文献
104.
H. R. Zeng K. Shimamura E. A. G. Villora S. Takekawa K. Kitamura G. R. Li Q. R. Yin 《固体物理学:研究快报》2008,2(3):123-125
The ferroelectric domain wall thickness of a fluoride BaMgF4 single crystal was investigated by piezoresponse force microscopy. It was found that the domain wall thickness shows a strong spatial variation in the as‐grown crystal and the polarization reversal process. The original wall thickness is greater (about two to seven times) than that switched by the tip fields of the atomic force microscope. A significantly narrower domain wall was obtained in the higher tip‐field. The trapped defects at the domain wall play an important role in the spatial variation of the polarization width of 180° domain wall in the BaMgF4 single crystal. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
105.
Reiter G 《The European physical journal. E, Soft matter》2002,8(2):251-255
I present some tentative ideas on the possibility of plastic deformation which might be relevant in ultra-thin polymer films
at temperatures close but below the glass transition temperature. Several possible sources for sufficiently strong forces
are discussed. The relevance of such forces in experiments aiming at determining thin-film properties like the glass transition
temperature, thermal expansion or surface morphology is discussed.
Received 19 September 2001 and Received in final form 5 December 2001 相似文献
106.
W. Boujelben A. Cheikh-Rouhou J.C. Joubert 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(4):419-423
Deficiency effects in the A site upon the structural, magnetic and electrical properties in the lacunar perovskite manganite
oxides Pr0.7Sr0.3-x
xMnO3 ( 0 ?
x
? 0.3) and Pr0.7-x
xSr0.3MnO3 ( 0 ?
x
? 0.23) have been investigated. This study focuses on the different parameters which govern the magnetic and electrical properties
in such samples. The powder X-ray diffraction patterns for all samples could be indexed either with a rhombohedral perovskite
structure and R
c space group for x
? 0.2 in strontium deficient samples and for x
? 0.1 for praseodymium deficient ones. For other values of x the samples could be indexed in the orthorhombic structure with Pbnm space group. Magnetic and electrical investigations
show that praseodymium and strontium vacancies do not have similar effects on the lacunar compounds. Magnetization measurements
versus temperature show that all our samples exhibit a magnetic transition when the temperature decreases. All the praseodymium
deficient samples exhibit a paramagnetic-ferromagnetic transition when the temperature decreases while the strontium deficient
ones exhibit this transition only for low x values. The magnetic transition temperature shifts to lower values as the strontium deficiency increases (from 265 K for
x
= 0 to 90 K for x
= 0.3) and to higher values with the praseodymium deficiency increase (from 265 K for x
= 0 to 315 for x
= 0.23). Resistivity measurements as a function of temperature show a semiconducting-metallic transition for all x values in the praseodymium lacunar samples and only for low x values ( 0 ?
x
? 0.1) in the strontium lacunar ones when the temperature decreases.
Received 12 April 2000 and Received in final form 8 January 2001 相似文献
107.
M.-L. Almazor O. Dulieu F. Masnou-Seeuws R. Beuc G. Pichler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):355-363
We propose a new possibility to form ultracold molecules, via photoassociation of a pair of cold atoms into vibrational levels of the external well of an excited electronic state located
at intermediate interatomic distance ( ≈ 20 Bohr radii), and embedded in the dissociation continuum above its dissociation
limit. The existence of such a well is demonstrated by conventional free-free absorption spectroscopy at thermal energies.
Estimation for cold atom photoassociation and cold molecule formation rates are obtained within a perturbative approach [Drag
et al., IEEE J. Quant. Electr. 36, 1378 (2000)], and are found observable for usual conditions of photoassociation experiments.
Received 1st March 2001 相似文献
108.
Structural and optical properties of ZnO thin films prepared by sol-gel method with different thickness 总被引:1,自引:0,他引:1
In this work, ZnO thin films with different thickness were prepared by sol-gel method on glass substrates and the structural and optical properties of these films were studied by X-ray diffractometer, atomic force microscope, UV-visible spectrophotometer, ellipsometer and fluorophotometer, respectively. The structural analyses show that all the samples have a wurtzite structure and are preferentially oriented along the c-axis perpendicular to the substrate surface. The growth process of highly c-axis oriented ZnO thin films derived from sol-gel method is a self-template process. With the increase of film thickness, the structural disorder decreases and the crystalline quality of the films is gradually improved. A transition of crystal growth mode from vertical growth to lateral growth is observed and the transition point is found between 270 and 360 nm thickness. The optical analyses show that with the increase of film thickness, both the refractive index and ultraviolet emission intensity are improved. However, the transmittance in the visible range is hardly influenced by the film thickness, and the averages are all above 80%. 相似文献
109.
The surface of gloss fired porcelain with and without raw glaze coating was radiated by a CO2 laser working at 10.6 μm, a choice resulted from spectroscopic studies of suspensions made of China. The shine of the untreated sample was defined as the distribution of micro-droplets on the surface. The surface alterations due to laser heating were classified by the diameter of the completely melted surface, the ring of the surface at the threshold of melting, and the size of microscopic cracks. The diameter of the laser treated area was in the range of 3 mm, while the incident laser power and the duration of laser heating were varied between 1 and 10 W and 1-8 min, respectively. The different stages of surface modifications were attributed primarily to the irradiating laser power and proved to be rather insensitive to the duration of the treatment. We have found a range of parameters under which the white China surface coated with raw glaze and followed by laser induced melting exhibited very similar characteristics to the untreated porcelain. This technique seems prosperous for laser assisted reparation of small surface defects of unique China samples after the firing process. 相似文献
110.
Polystyrene supported TiCl4 (Ps‐TiCl4) and polystyrene supported FeCl3 (Ps‐FeCl3) were prepared by coordinating Lewis acids with polystyrene. The catalysts were characterized by TGA, BET, SEM, IR and pyridine‐adsorbed IR. The loading of Ps‐TiCl4 and Ps‐FeCl3 were 0.35 and 0.3 mmol·g?1 respectively. Both catalysts were found to be efficient for the tetrahydropyranylation and detetrahydropyranylation of various alcohols and phenols in different solvents. Two catalysts can be recovered and reused for five times with good activity. 相似文献