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1.
A C.W. multi-mode dye laser is used to obtain by optical pumping an orientation of the 2p5 3s3P0 (F = 3/2) state of 21Ne. A magnetic resonance experiment leads to the measurement of the g factor g (3P0) = 3.027 (8) × 10−4 to be compared with the theoretical prediction (3.025(6) × 10−4). One obtains also the metastability exchange cross section σ(3P0) = 18.4 ± 4 Å2 for collisions between metastable (3P0) Ne atoms and ground state Ne atoms. This result is compared with other measurements and theoretical evaluation.  相似文献   

2.
The betaspectra of 12B and 12N have been measured with a NaI crystal as spectrometer. Assuming a shape correction factor 1 + aW + bW2 and b = 1.106 × 10−4 MeV−2, b+ = −1.397 × 10−4 MeV−2, the spectra yield a = (+0.91 ± 0.11) × 10−2 MeV−1 and a+ = (−0.07 ± 0.09) × 10−2 MeV. the aa+ = (+0.98 ± 0.09) × 10−2 MeV−1 is in agreement with the weak magnetism prediction.  相似文献   

3.
An application of our developed silicon photodiode detector for radon progeny measurements is presented in this paper. It was determined the deposition velocity for free (3.6 ± 0.7) × 10−3 m s−1 and attached (1.0 ± 0.5) × 10−5 m s−1 fraction of short living radon progeny.  相似文献   

4.
P Fouquet  P.K Day  G Witte   《Surface science》1998,400(1-3):140-154
The scattering of metastable 23S He atoms (He*) from cleaved NiO(100) as well as from clean and CO-covered Cu(100) surfaces has been studied. For these varied surfaces, which were characterized in situ by ground state He atom scattering, only broad He* angular distributions without any diffraction peaks were observed. For metastable He atoms scattered from the clean Cu(100) surface a total survival probability of 1×10−6 was determined. For NiO(100) and the CO-covered Cu(100) surface values of about 1×10−5 were obtained. Time-of-flight spectra of the surviving He* atoms revealed a substantial energetic broadening which increases with the substrate temperature. This behaviour indicates a large well depth for the He*–surface interaction potential and is discussed in terms of an enhanced multiphonon excitation and/or trapping probability upon the scattering.  相似文献   

5.
Three kinds of peroxo-polytungstic acid (PPTA, C-PPTA and N-PPTA) were obtained by reacting hydrogen peroxide with metallic tungsten, tungsten carbide or tungsten nitride, respectively. Polytungstates, C-PPTA and N-PPTA, were found to contain oxalate and nitrate ligands. Their proton conductivities were compared using thin film specimens spin-coated from their water solution. Conductivity of each as-coated film was in the range from 10−3 to 10−4 S cm−1 under the relative humidity of 40% (25 °C). A sharp decrease in conductivity (to less than 10−7 S cm−1 at 25 °C) was observed for PPTA without acidic ligands after thermal treatment at 80 °C. However, the effect of thermal treatment on C-PPTA or N-PPTA was much milder. A 80 °C-treated C-PPTA film showed the conductivity of 1.0 × 10−5 S cm−1 (25 °C) with a very weak dependency on ambient humidity.  相似文献   

6.
The ionic conductivity of the bulk phase of bonded hydronium NASICON (HyceramTM) was measured at equilibrium with an H2O/N2 and then a D2O/N2 atmosphere, each at 100% relative humidity and 75% relative humidity over the temperature range 25°C to 50°C. At 100% relative humidity and 25°C, the protonic system had a bulk conductivity of 5.0×10−4 S/cm and an activation energy of 17.3kJ/mole; the same sample, when deuterated, had a bulk conductivity of 2.2×10−4 S/cm and an activation energy of 19.3kJ/mole. At 75% relative humidity and 25°C, the conductivity of the protonated system decreased to 1.4×10−4S/cm with an activation energy of 24.1 kJ/mole. The deuterated sample at 75% relative humidity had a bulk conductivity of 5.4×10−5 S/cm with an activation energy of 26.0 kJ/mole. The isotope effect suggested a proton hopping (Grotthus) mechanism as the means by which the protons pass through the lattice.  相似文献   

7.
Optical nonlinearities and photo-excited carrier lifetime in CdS at 532 nm   总被引:2,自引:0,他引:2  
Bound-electronic and free-carrier optical nonlinearities, and relaxation of photo-excited free carriers in CdS have been investigated by the use of a single-beam Z-scan technique at 532 nm. Under pulsed radiation of 35-ps duration with the input irradiances up to 4.8 GW/cm2, the two-photon absorption coefficient, the bound-electron nonlinear refractive index, the free-carrier absorption cross-section, and the change in the refractive index per unit carrier density are determined to be 5.4±0.8 cm/GW, −(5.3±0.8)×10−13 cm2/W, (3.0±0.5)×10−17 cm2 and −(0.8±0.1)×10−21 cm3, respectively. By using these values in the open-aperture Z-scans conducted with 7-ns laser pulses, the carrier recombination time is extracted to be 3.6±0.7 ns. The measured parameters are compared to theoretical calculations.  相似文献   

8.
Cluster decay of 242Cm with emission of 34Si-particles was measured using track-recording phosphate glass detectors. The corresponding partial half-life is (1.4±0.3)×1023 s. The branching ratio relative to decay is 1.0×10−16 and relative to spontaneous fission 1.6×10−9.  相似文献   

9.
Phosphorescence characteristics of CdWO4 excited by one-photon (λ = 308 nm) and two-photon (λ = 570–590 nm) processes were measured. A Davydov splitting of 120 ± 20 cm−1 was obtained in the phosphorescence spectra, suggesting a diffusion coefficient of about 1.2 × 10−2 cm2 s−1, and a diffusion length of about 3.1 × 10−4 cm for the room temperature measured lifetime of 8μs. The phosphorescence quantum efficiency was less than 2% at low temperatures (only 0.25% at room temperature), indicating that the dominant decay mechanism was radiationless. The radiative lifetime was thus estimated as 1–2 ms. The two-photon phosphorescence excitation is characterized by an absorption cross-section of the order of 10−49cm4s.  相似文献   

10.
We report magnetic susceptibility and specific heat measurements on polycrystalline samples of the 30 K superconductor Ba0·6K0·4BiO3. Normal-state magnetization measurements indicate a Pauli-paramagnetic susceptibility of χpauli = 2.3 × 10−5 emu/mole, from which we infer a value for the density of states at the Fermi level of N(0) = 8.6 × 10 21ev−1cm.−3 Specific heat measurements performed between 1.6 K and 40 K indicate that considerable lattice softening occurs at low temperatures; the effective Debye temperature drops from 280 K at 35 K to 210 K at 4 K, implying that soft phonon modes are present in this compound. This result indicates that conventional phonon-mediated interactions may be responsible for the high transition temperature exhibited by Ba0·6K0·4BiO3.  相似文献   

11.
The emission of two photons above 25 MeV energy was observed in the capture of stopped pions by beryllium and carbon with a rate of (1.0 ± 0.1) × 10−5, respectively (1.4 ± 0.2) × 10−5 per capture. These rates are about two to four times greater than various free-nucleon estimates based on the π+→γγ annihilation mechanism alone.  相似文献   

12.
The diffusion process of copper through grain boundaries of 500 nm thick ion-plated Ag-12at%Sn films was studied in the temperature range 100–250°C. The method is based on the determination of the time of first appearance of Cu on the Ag---Sn surface using Auger electron spectroscopy for determining trace amounts of Cu. An activation energy of Ea = 0.53 eV and a diffusivity of Do = 1.3 × 10−7cm2s−1 was obtained. For comparison, diffusion studies of Cu through ion-plated pure Ag layers have been performed. In this case an activation energy of Ea = 0.68 eV and a diffusivity of Do = 2.3 × 10−5cm2s−1 have been found.  相似文献   

13.
D.-S. Choi  R. Gomer 《Surface science》1990,230(1-3):277-282
The diffusion of W on a (211) plane of a W field emitter has been re-examined by means of the fluctuation autocorrelation method. Diffusion along channels yielded E = 16.8 ± 0.5 kcal, D0 = (3 ± 1) × 10−5 cm2 s−1. For diffusion across channels E =6.6 kcal, D0 = 4 × 10−9cm2 s−1 at T < 752 K, and E = 24 kcal, D0 = 5 × 10−4 cm2 s−1 at T > 752 K. The results for diffusion along channels yield E and D0 values intermediate between recent results by Wang and Ehrlich [Surf. Sci. 206 (1988) 451] using field ion microscopy (E = 19 kcal, D0 = 7.7 × 10−3 cm2 s−1) and Tringides and Gomer [J. Chem. Phys. 84 (1986) 4049], using the same method as the present work but a larger slit (E = 13.3 kcal, D0 = 7 × 10−7 cm2 s−1). The results for cross channel diffus good agreement with those of Tringides and Gomer below 752 K, where these authors stopped. The new high temperature results suggest that the channel wall exchange mechanism postulated by Tringides and Gomer for cross channel diffusion at low T gives way to diffusion by climbing over the channel walls with higher E but also higher D0 above 752 K. Possible reasons for the discrepancies between these three sets of results and the absence of cross channel diffusion in the work of Wang and Ehrlich are briefly discussed.  相似文献   

14.
We have investigated the thermal and ionic conductivity properties of the elastomer poly(ethylene oxide-co-epichlorohydrin) filled with NaI and I2. The reason for using this composition is its potential application as electrolyte in photoelectrochemical cells. This copolymer was characterized as a function of NaI concentration, temperature and relative humidity. According to the data obtained, the Na+ ion interacts with the ethylene oxide repeating units by means of Lewis type acid–base interactions. The empirical Vogel–Tamman–Fulcher equation was used to model the conductivity and temperature relationships, indicating that the conduction occurs in the amorphous phase of the copolymer. The sample with 9.0% (w/w) of NaI presents a conductivity of 1.5×10−5 S cm−1 in a dry atmosphere (30°C, [H2O]<1 ppm) and 2.0×10−4 S cm−1 at 86% relative humidity (22°C).  相似文献   

15.
The third-order nonlinear optical response of a triphenylmethane dye (Acid blue 7) was studied using the Z-scan technique with a continuous-wave He–Ne laser radiation at 633 nm. The magnitude and sign of the third-order nonlinear refractive index n2 of aqueous solution of Acid blue 7 dye were determined; the negative sign indicates a self-defocusing optical nonlinearity in the sample studied. The negative nonlinear refractive index n2 and nonlinear absorption coefficient β were estimated to be −1.88 × 10−7 cm2/W and −3.08 × 10−3 cm/W, respectively, corresponding to Re(χ(3)) = −8.35 × 10−6 esu, and Im(χ(3)) = −6.88 × 10−7 esu. The experimental results show that Acid blue 7 dye have potential applications in nonlinear optics.  相似文献   

16.
The lifetimes of the Cd+ 52P3/2 and 52P1/2 states have been measured by the Hanle effect. The Cd+ ions are produced in a d.c. discharge in cadmium vapor, with helium as buffer gas. The results are: τ(52P3/2) = (2.60±0.20) ×10−9sec, and τ(52P1/2) = (3.05 ± 0.13) × 10−9sec.

We measured also the cross sections for the destruction of the orientation in the 52P1/2Cd+ state (<5Å2), of the orientation (18±10Å2) and of the alignment (46±10Å2) in the 52P3/2 state due to collisions with the helium atoms.  相似文献   


17.
β-γ(CP) correlation measurements have been carried out on the sequence in the decay of the ground state of 49Ca to the (presumed) anti-analogue state at 3.105 MeV excitation in 49Sc. An asymmetry parameter of A = −0.132 ± 0.017 was obtained, making any spin-parity assignment other than very unlikely for the 3.105 MeV state. The deduced Fermi matrix element for the decay is |Mv| = |1.4 ± 9.7| × 10−3, which leads to an isospin impurity ( ) corresponding to the mixing of the analogue state (at 11.6 MeV) and the 3.105 MeV state of ||2 1.6 × 10−5. This leads in turn to an effective Coulomb matrix element of |Hc| = |3.9 ± 27.4| keV, a low value compared to the value of 100 keV obtained from a theoretical estimate based on simple shell-model wave functions for the single-particle states involved.  相似文献   

18.
In this work we studied the ionic conductivity for three copolymers of the title co-monomers as a function of LiClO4 content, temperature and ambient relative humidity. We also investigated the interactions between the salt and the co-monomer blocks in the copolymers and its effect on the morphology and thermal properties of the copolymer/salt complexes. Our data indicate that the Li+ ion predominantly interacts with the ethylene oxide repeating units of the copolymers. The copolymer with the highest ionic conductivity was obtained with an ethylene oxide/epichlorohydrin ratio of 84/16 containing 5.5% (w/w) of LiClO4. It showed a conductivity of 4.1×10−5 S cm−1 (30°C, humidity< 1 ppm) and 2.6×10−4 S cm−1 at 84% relative humidity (24°C). The potential stability window of the copolymer/salt complex is 4.0 V, as measured by cyclic voltammetry. For comparison, we also prepared a blend of the corresponding homopolymers containing LiClO4; it showed higher crystallinity and lower ionic conductivity.  相似文献   

19.
By undertaking AC electrochemical impedance experiments on yttria stabilised zirconia electrolytes with polished Y1Ba2Cu3O7−x electrodes, the activation energy for oxygen ion transport within the bulk of Y1Ba2Cu3O7−x, in air, over the temperature range 823 K–1043 K, was determined to be 1.50 ± 0.05 eV. At 1000 K the oxygen ionic conductivity was calculated to be around one order of magnitude lower than that in yttria stabilised zirconia. Typical calculated values were σ=5×10−5 (ω cm)−1 and 6×10−3 (ω cm)−1 at the respective temperatures 823 K and 1043 K. By employing a similar cell but with Y1Ba2Cu3O7−x paste electrodes, oxygen transfer between the Y1Ba2Cu3O7−x and the electrolyte was found to occur via a surface diffusional processes. Over the temperature range 873 K–1098 K, in air, the activation energy for in-diffusion at the surface was found to be 1.4±0.1 eV and that for out-diffusion at the surface to be 1.76±0.05 eV.  相似文献   

20.
Theoretical results are presented for nuclear excitation of low-lying isometric states of 197Au, 189Os and 237Np by a near-resonant electronic deexcitation process known as NEET. A detailed comparison is made between current and previous theoretical results in order to clarify a number of anomalies. For 197Au, the only case in which the current experimental precision appears to be sufficient to provide a stringent test of theory, the theoretical result for the NEET probability is PNEET=3.6×10−8. This is a factor of three lower than previous theoretical results and reduces the difference between theory and the recent experimental result, PNEET=(5.0±0.6)×10−8, to a level of approximately 2σ.  相似文献   

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