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1.
N. Yu. Svechnikov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(1):21-29
The 2D-photoemission image of the beam spot was obtained for the first time for the W5+ oxidation state on the preliminary irradiated WO3 − x
thin film surface, created by scanning of the SR beam over the film surface. The W5+ beam profile intensity was found to spread up to a distance of 3.2 μm for an amorphous film and 5.5 μm for a polycrystalline
film, it exceeds considerably the beam spot size. The image saturation dose was reached faster for a polycrystalline film.
Among the possible mechanisms explaining this phenomenon, for the case of an almost unchangeable O2s state under irradiation, a choice was made in favor of a photon-generated charge diffusion due to low-energy secondary electrons
from photoemission, which produce the “coloration” effect, e− + W6+ (W5+) W5+ → W5+(W4+). The O512-eV Auger peak was found to degrade at the distance of 1.5–2 mm outside the beam spot under long-time electron
beam irradiation, which is attributed to electron-stimulated oxygen desorption and outdiffusion. 相似文献
2.
The paper reports on a study of luminescence and excitation spectra of SrAlF5:Pr3+ (0.5 mol %) polycrystals performed at 10 and 300 K with synchrotron radiation in the range from 5 to 25 eV. The Pr3+ ions in SrAlF5 were shown to emit successively two photons in transitions from the 1 S 0 and 3 P 0 levels. The main energy characteristics of the compound, namely, the position of the 4f → 5d excitation band (5.95–8.0 eV), the energy separation between the 1 S 0, 4f and the lowest 5d levels (~0.15 eV), and the SrAlF5 band gap width (~12 eV), were determined. SrAlF5:Pr3+ was found to possess a number of features not found in other Pr3+-activated fluorides. 相似文献
3.
In this work, temporal evolution of two-photon laser optogalvanic signals of neon has been studied. Optogalvanic signals for four transitions from the metastable 2p53s[3/2]2 state to 2p54d′[3/2]1, 2p54d′[3/2]2, 2p54d′[5/2]3 and 2p54d′[5/2]2 states were recorded over a range of discharge currents (3.4–9 mA). It was found that the shape of the optogalvanic signal was strongly dependent on the discharge current so that its peak shifted to shorter times and its amplitude increased with the discharge current. The decay rates of the 4d states, calculated from the optogalvanic signals, were found to increase linearly with the discharge current in the range of 6.2–9 mA. However, for the range of 3.4–5.4 mA, the decay rates were observed to slightly decrease with the discharge current. 相似文献
4.
A combination of sheet resistance, stripping and Hall effect measurements have been made on phosphorus layers implanted into silicon at 40 and 100 keV with doses between 1 × 1015 and 5 × 1016 atoms/cm2. The implants were made at room temperature and 450°C. After annealing at 650°C, the profile of electrically active phosphorus following a high dose room temperature implant, was found to be flat topped with a concentration of approximately 5 × 1020/cm3. Very little diffusion occurred when annealing to 850°C where the free electron concentration increased to approximately 1.5 × 1021/cm3. Highly doped channeled tails were found when implanting at 450°C along the 〈110〉 direction and damage was being continuously annealed out preventing the formation of an amorphous phase. The rapid diffusion of the profile into the bulk found when annealing between 650°C and 850°C was speculated to be due to the presence of a dense dislocation entanglement in these layers following a hot implant. 相似文献
5.
Evaluation by empirically derived equations for the Substituent effect (α, β, γ, δ) on the 13C NMR chemical shifts for C-3, C-4. C-5 and halomethyl-substituent carbon (C-6) in isoxazoles 1-5 [where C-3 substituent (R1) = H, alkyl or phenyl, C-4 Substituent (R2) = H, alkyl, and C-5 substituent (R3) = di-or trihalomethyl, methyl and H], taking as reference the compound la, is reported. From the calculated values for the α, β, γ, δ effects for each substituent it was possible to estimate the chemical shift of each carbon of the compounds 1–5. The 13 C chemical shifts of the C-3, C-4, C-5, C-6 of these compounds, can be estimated with good precision: 94% of the calculated chemical shifts are found to be within ±1.0ppm, and 100% are found to be within ±1.5ppm. 相似文献
6.
The absorption, reflection, emission, and luminescence spectra of polycrystalline cadmium sulfide films have been studied at 77 deg K at 4500–5500 A. The films were prepared by sublimination of the powder in argon, hydrogen sulfide, or vacuum, followed by crystallization on a heated or unheated substrate.Specimens deposited on substrates below 350 deg C had simple absorption and emission spectra no matter which medium was used, but ones coated on substrates above 350 deg C had absorption, reflection, luminescence, and emission spectra with fine structure, which was due to transitions between the 5s21S0 ground state and 5s5p3P1, 5s5p3P2, and 5s5p3P0 excited states of atomic excess cadmium.Four maxima were found in the excitation spectrum of the blue luminescence (4545, 4605, 4670, and4740 A). The spectrum of the luminescence is independent of exciting wavelength in the range 2200–4900 A.This structure was observed only for films with hexagonal lattice symmetry. 相似文献
7.
8.
D. Yu. Podorozhkin Cheng Tien E.V. Charnaya M.K. Lee L.J. Chang D. Michel J. Haase Yu. A. Kumzerov 《Physica B: Condensed Matter》2012,407(12):2063-2067
NMR studies were carried out on three isotopes, 71Ga, 69Ga, and 115In, in liquid gallium-indium (Ga–In) alloy embedded into porous glasses with 200 and 5 nm pore sizes at two magnetic fields, 9.4 and 17.6 T. Spin-lattice relaxation and the Knight shift were found to depend on pore size. For porous glass with 5 nm pores the relaxation rate was field-dependent which evidenced that the extreme narrowing limit was no longer valid. Magnetization recovery data were used to evaluate the correlation times of atomic mobility and the quadrupole constants under nanoconfinement. 相似文献
9.
The impact broadening of strontium 5sns 1 S 0, 5snd 1 D 2 and 5snd 3 D 2 levels by He and Xe have been studied by measuring the collisional half-widths of Doppler-free two-photon absorption lines from the 5s 2 1 S 0 ground state in a thermionic diode. Large inelastic contributions to the broadening rates of the levels have been found where the moduli of the quantum defects of different level series are close to each other. A similar but continuousn-mixing behaviour along the series has also been found in our recent investigation on the broadening of Rb levels by noble gases. The broadening rates of the very high levels in Sr were found to be independent on the principal quantum number and the angular momentum of the levels and in good agreement with our recent broadening data of the Rb-He and Rb-Xe systems and the data for Na-He and Na-Xe found by the Columbia group. 相似文献
10.
From the velocity distribution of excited sputtered particles detailed information on the excitation process can be obtained. In the present paper the first direct measurement of velocity distribution of excited atoms sputtered from a metal target is presented. The irradiation of the Fe-target was performed with 10keV Ar+-ions. The sputtered atoms were detected using pulsed laser induced fluorescence (LIF). The sputtered Fe atoms in the metastable statea
5
F
5 at 0.86 eV shows a much broader distribution, than found for the ground-state atoms, but no energy threshold, implied in the statistical excitation models, was found. 相似文献
11.
W. M. Zuk W. F. Davidson M. R. Najam M. A. Awal 《Zeitschrift für Physik A Hadrons and Nuclei》1971,242(2):93-101
The low intensity β+/E.C. branches in the decay of45Ti to excited states of45Sc have been reinvestigated in order to resolve discrepancies in reported branching ratios. A new branch to the 974 keV level, having an intensity of 9.9±1.2×10?5/decay has been found. A previously reported branch to the 1237 keV level was found to be in error. The intensities for decay to the levels at 720, 1408 and 1661 keV levels were determined to be 154±12, 90.2±9.7 and 52.5±5.6, respectively, in units of 10?5 per decay. 相似文献
12.
A. O. Lindahl P. Andersson C. Diehl O. Forstner P. Klason D. Hanstorp 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(2):219-222
The electron affinity of tungsten has been measured using laser photodetachment threshold spectroscopy in a collinear geometry.
The electron affinity was determined to 6583.6(6) cm-1 by observing the onset of the process when W- ions in the 5d56s25d^56s^2
6S5/2 ground state are photodetached producing neutral W atoms in the 5d46s25d^46s^2
5D0 ground state. The measured value is in agreement with previous measurements and improves the accuracy by almost two orders
of magnitude. Further, a photodetachment signal below the ground state photodetachment threshold was found, which indicates
the existence of a bound excited state in W-. 相似文献
13.
Ganesh Prasad Yogesh Prasad G. S. Gusain Manjari Badoni J. M. S. Rana R. C. Ramola 《Indian Journal of Physics》2009,83(6):887-892
Radon was measured in soil-gas and groundwater in the Budhakedar area of Tehri Garhwal, India in summer and winter to obtain
the seasonal variation and its correlation with radon exhalation rate. The environmental surface gamma dose rate was also
measured in the same area. The radon exhalation rate in the soil sample collected from different geological unit of Budhakedar
area was measured using plastic track detector (LR-115 type II) technique. The variation in the radon concentration in soil-gas
was found to vary from 1098 to 31,776 Bq.m−3 with an average of 7456 Bq.m−3 in summer season and 3501 to 42883 Bq.m−3 with an average of 17148 Bq.m−3 in winter season. In groundwater, it was found to vary from 8 to 3047 Bq.l−1 with an average value 510 Bq.l−1 in summer and 26 to 2311 Bq.l−1 with an average value 433 Bq.L−1 in winter. Surface gamma dose rate in the study area varied from 32.4 to 83.6 μR.h−1 with an overall mean of 58.7 μ-R.h−1 in summer and 34.6 to 79.3 μR.h−1 with an average value 58.2 μR.h−1 in winter. Radon exhalation rate from collected soil samples was found to vary from 0.1 × 10−5 to 5.7 × 10−5 Bq.kg−1.h−1 with an average of 1.5 × 10−5 Bq.kg−1.h−1 in summer season and 1.7 × 10−5 to 9.6 × 10−5 Bq.kg−1.h−1 with an average of 5.5 × 10−5 Bq.kg−1.h−1. A weak negative correlation was observed between radon exhalation rate from soil and radon concentration in the soil. Radon
exhalation rate from the soil was also not found to be correlated with the gamma dose rate, while it shows a positive correlation
with radon concentration in water in summer season. Inter-correlations among various parameters are discussed in detail.
相似文献
14.
F. Bergsma J. Dorenbosch M. Jonker C. Nieuwenhuis J. V. Allaby U. Amaldi G. Barbiellini L. Barone A. Capone W. Flegel L. Lanceri M. Metcalf J. Panman R. Plunkett C. Santoni K. Winter I. Abt J. Aspiazu F. W. Büsser H. Daumann P. D. Gall T. Hebbeker F. Niebergall P. Schütt P. Stähelin V. Gemanov P. Gorbunov E. Grigoriev V. Kaftanov V. Khovansky A. Rosanov A. Baroncelli R. Biancastelli B. Borgia C. Bosio M. Diemoz U. Dore F. Ferroni E. Longo L. Luminari P. Monacelli F. de Notaristefani L. Tortora V. Valente CHARM Collaboration 《Zeitschrift fur Physik C Particles and Fields》1984,24(3):217-218
A search for fractionally chargedQ=1/3 (2/3) particles of different properties of interaction produced in (anti)neutrino-nucleus and in protonnucleus collisions was performed using the scintillator system of the CHARM neutrino detector at the CERN SPS. No events of the cases considered were found. In (anti)neutrino beams production was found to be less than a few times 10?5 per interaction of a beam particle. In a proton beam an upper limit on the production cross section of ~10?40 cm2 was obtained. 相似文献
15.
Laser ablation with fs laser pulses was performed in air on cobalt cemented tungsten carbide by means of a Ti : sapphire laser (800 nm, 100 fs). Small and moderate fluences (2, 5, 10 J/cm2) and up to 5×104 pulses per irradiated spot were used to drill holes with aspect ratios up to 10. Cross-section cuts from laser-irradiated samples were produced and they were analysed with optical microscopy and SEM. EDX analyses were carried out on selected zones. Quasi-cylindrical holes were found for 2 J/cm2, whereas for 5 and 10 J/cm2 irregular shapes (lobes, bottoms wider than hole entrances) were found to occur after a given number of incident pulses. Layers with modified structure were evidenced at pore walls. SEM revealed a denser structure, while EDX analyses showed uniform and almost similar contents of W, C, and Co in these layers. As a direct application, patterning of coated WC-Co was carried out with 2 J/cm2 and 100 pulses per pore. The resulted surfaces were tribologically tested and these tests revealed an improved friction and wear behaviour. PACS 42.65.Cs; 79.60.Ds 相似文献
16.
When Ho3+:Yb3+:CaF2 crystalline powders prepared by combustion synthesis were exposed to near-infrared (λ ~ 975 nm) radiation, intense photon up-conversion (UC) was observed at the visible with emission bands peaked at ~ 545, ~650 and ~750 nm identified as 4f-4f transitions from higher levels (5F4, 5S2) and 5F5 to lower levels 5I8 and 5I7 of Ho3+. The emission bands at the green and red, in particular, have been demonstrated to be useful for temperature sensing based on luminescence intensity ratio technique. However, no model is available in literature to explain the change of the electronic populations of states (5F4, 5S2) and 5F5 with temperature. The UC phenomenon was studied from both theoretical and experimental points of view. A rate equation model with temperature dependent parameters for Ho3+ and Yb3+ electronic populations considering a high sensitization of Ho3+ ions by Yb3+ ions was used. High Yb3+ → Ho3+ energy transfer efficiency was found (~88% at room temperature). The change with temperature predicted by the model for the luminescence intensity ratio of the UC green and red emission lines agrees well with the experimental data. 相似文献
17.
M. Matoba M. Hyakutake J. Niidome K. Yagi Y. Aoki K. Sato 《Physics letters. [Part B]》1973,45(5):463-464
Strong L=5 transitions have been found in the (p, p′) reaction on 122,124,126,128,130Te. The possible 25-pole collective motion in Te nuclei is discussed. 相似文献
18.
Electron paramagnetic resonance studies were conducted on the photoinduced charge transfer and also hyperfine interaction
of U5+ stabilized in photorefractive matrix LiNbO3. This work deals with: (i) first observation of hyperfine structure due to233U (I=5/2) in its pentavalent state at octahedral sites and comparison with other possible site symmetries, (ii) photoinduced charge
transfer as observable by EPR and its relevance to photorefractive behaviour of LiNbO3. The effect of chemical bonding on the hyperfine interaction of 5f
1 configuration was also studied by converting the existing literature data on235U5+ to that of233U5+ by standard methods. This suggests that progressive substitution of oxygen by F−, in the series UO
6
7−
, (UO5F)6− and (UO4F2)5− drastically decreases the hyperfine coupling constantA
∥, along the local distortion axis. This trend is explained as being due to the absence of ligand ion along the distortion
axis at U5+ site in trigonal LiNbO3. The effects of illumination by copper vapor laser (CVL) on the intensity of the U5+ signal was studied in the 10–300K region. The kinetics of decay and restoration of U5+ was also studied between 10–100K range. The decay kinetics was found to obey double exponential. The reduction of concentration
of U5+ with CVL-illumination and its restoration in the absence of light show that pentavalent uranium takes part in the photorefractive
effects in LiNbO3. 相似文献
19.
The optimum calcination temperature for KLa(MoO4)2:Eu3+ phosphor was confirmed to be 1000 °C via checking the XRD patterns, SEM images and fluorescence spectra for the samples derived from solid state reaction. The energy transfer behavior between Eu3+ ions was studied. It was found that electric dipole–dipole interaction is responsible for the fluorescence quenching of 5D2 and 5D1 levels, but exchange interaction is in charge of 5D0 fluorescence quenching. It was also observed that color coordinates of the studied phosphor can be tuned when the doping concentration is relatively low. The fluorescence thermal quenching process was investigated. It was found the thermal quenching followed well crossover model. Judd–Ofelt parameters of Eu3+ in KLa(MoO4)2 were obtained, and the optical transition properties were further discussed. 相似文献
20.
《Applied Surface Science》1986,26(4):488-497
The photoreduction of polycrystalline samples of MoO3, WO3, Cu2O, CuO, PdO and PtO by UV irradiation was investigated by X-ray photoelectron spectroscopy (XPS). Photoreduction of these metal oxides was found upon irradiation with the emission lines from a mercury vapor lamp (2537 Å) at room temperature. Other oxides, like ZnO and V2O5, where not photoreduced. Mo6+ and W6+ were observed to partially photoreduce to Mo5+ and W5+. In the case of the copper oxides, both Cu2+ and Cu1+ were found to completely photoreduce to the metallic state. The photoreduction of PdO and PtO was observed to proceed slowly through the first few monolayers and was 75% completed within the XPS sampling depth ( ∼ 40 Å) after long irradiation times. All photoreduced species were observed to reoxidize upon exposure to the atmosphere. The oxidation of photoreduced metallic Pt and Pd at room temperature is unique since those metals usually do not oxidize in air. A model has been developed to explain and predict the extent of reduction of metal oxides surfaces by UV irradiation. It shows that depending on band gap and chemical stability, complete or partial reduction of many oxide surfaces can be achieved. 相似文献