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1.
Summary The simple cut criterion based on the accurate determination of the radii of the ions in alkali halides and previously introduced
by the authors for forecasting off-centre configuration of Li+ and F− has been extended to heavy ions (Ag+ and Cu+). It has been found that this criterion is valid for the Ag+ ion, whereas for Cu+ gives a less precise forecast because of the lack in knowledge of the effective partial charge on Cu+ ion. It has been evidenced that the critical value of the ratior
+
*
/r
+ between impurity and host ion radius which allows off-centre configuration is dependent on the impurity ion mass.
Work jointly supported by the Ministero della Pubblica Istruzione and by Consiglio Nazionale delle Ricerche, Gruppo Nazionale
di Struttura della Materia. 相似文献
2.
Using the pseudopotential method, theoretical investigation has been made on the firstorder Korteweg-deVries ion-acoustic
solitons in a multicomponent plasma consisting of warm positive ions, negative ions and isothermal electrons. The effects
of electron-inertia and drift motion of the ions on the amplitudes and widths of the solitons have been studied in a plasma
having (H+, Cl−), (H+, O−), (He+, H−) and (He+, O−) ions. Ion-acoustic double-layers have also been investigated for such plasmas. It has been found that drift velocity and
electron-inertia have significant contribution on the formation of double-layers in multicomponent plasma 相似文献
3.
Summary With the aid of the Sanderson model for nonmolecular structures a simple criterion has been derived for forecasting off-centre
configuration of monovalent impurity ions in alkali halide crystals based on the effect that the Sanderson partial charges
on atoms have on their radii.
Work jointly supported by Ministero della Pubblica Istruzione and by Consiglio Nazionale delle Ricerche, Gruppo Nazionale
di Struttura della Materia. 相似文献
4.
C. E. Bottani G. Caglioti A. Novelli P. M. Ossi 《Applied physics. B, Lasers and optics》1979,18(1):63-66
We present a method to measure the thermal diffusivity of metals. A homogeneous small heat source is fed into a cyclindrical
sample of titanium by thermoelastic compression. This heating process is followed by a thermal relaxation controlled by the
thermal diffusivity. The resulting temperature variation is detected by a miniature temperature sensor mounted on the lateral
surface of the sample. The value so obtained for the thermal diffusivity of titanium is (6.6±0.2)·10−6 m2/s.
Gruppo Nazionale Struttura della Materia del Consiglio Nazionale delle Ricerche 相似文献
5.
Summary By nonlinear mixing of IR and visible radiation,i.e. coherent Raman scattering by polaritons driven by a CO2 laser, it has been possible to get high-resolution spectra for theF-modes of a NaClO3 crystal in the region (907÷957) cm−1, where several isotopic modes are present. The obtained independent measurement of the refractive index and absorbance allows
an accurate determination of the polariton dispersion curve and its width inq-space. The experimental data confirm the existence of a localized isotopic mode at 931 cm−1 and a strongly damped isotopic mode near 960 cm−1. Finally, an accurate measurement of the dispersion of the second-order nonlinear polarizability in the same energy region
has been obtained for the first time.
This work was supported by the Italian Consiglio Nazionale delle Ricerche and Ministero della Pubblica Istruzione. 相似文献
6.
Comparative studies of the emission of quasi-thermal atomic and cluster ions from V, Nb, Ta, Au, and In targets bombarded
by cluster ions Au
m
−(m = 1–9), as well as from Si and Bi targets bombarded by cluster ions Au
m
−(m = 1–9) and Bi
m
−(m = 1–5), with energy E
0 ranging from 6 to 21 keV are carried out. In the case of bombardment by heavy cluster ions, the fraction of the quasi-thermal
component in the energy spectra of sputtered atomic ions reaches 50 (for V, In, and Au), 70 (Nb), or more than 90% (Ta). In
addition, quasi-thermal ions play a considerable part in the emission of small cluster ions Au2+, In2+, In3+, and Bi
n
+(n = 2–7). The results of the generalizing investigation favor the presence of thermal spike conditions at cluster bombardment
and their appreciable contribution to the emission of atomic and small cluster ions. 相似文献
7.
Yin-Zhe Ma Yan Gong Xuelei Chen 《The European Physical Journal C - Particles and Fields》2009,60(2):303-315
We investigate the observational signatures of the holographic dark-energy models, including both the original model and a
model with an interaction term between the dark energy and dark matter. We first delineate the dynamical behavior of such
models, especially considering whether they would have a “big rip” for different parameters; then we use several recent observations,
including 182 high-quality type Ia supernovae data observed with the Hubble Space Telescope, the SNLS and ESSENCE surveys,
42 latest Chandra X-ray cluster gas mass fraction, 27 high-redshift gamma-ray burst samples, the baryon acoustic oscillation
measurement from the Sloan Digital Sky Survey, and the CMB shift parameter from the WMAP three-year result to give more reliable
and tighter constraints on the holographic dark-energy models. The results of our constraints for the holographic dark-energy
model without interaction is c=0.748−0.009+0.108, Ω
m0=0.276−0.016+0.017, and for the model with interaction (c=0.692−0.107+0.135, Ω
m0=0.281−0.017+0.017, α=−0.006−0.024+0.021, where α is an interacting parameter). As these models have more parameters than the ΛCDM model, we use the Bayesian Evidence as a model-selection criterion to make comparisons. We found that the holographic
dark-energy models are mildly favored by the observations as compared to the ΛCDM model. 相似文献
8.
S. S. Novosad 《Technical Physics》1999,44(1):124-125
The effect of the conditions of preparation, temperature, and the action of x rays on the luminescence properties of calcium-iodide
scintillation crystals is investigated. On the basis of the results of a study of the spectral characteristics of CaI2 and CaI2:H2 crystals for optical and x-ray excitation in the temperature range 90–400 K, also taking into account the results of a study
of the luminescence properties of CaI2 crystals activated by Cl−, Br−, OH−, and Ca2+ impurities, it is suggested that the 236-nm band observed in the excitation spectra of crystals of calcium iodide may be
caused by an uncontrollable hydrogen impurity. The luminescence of these crystals with maximum at 395 nm is ascribed to radiative
recombination of excitons trapped at H− ions.
Zh. Tekh. Fiz. 69, 135–136 (January 1999) 相似文献
9.
An x-ray diffraction study of defect formation in silicon irradiated by Kr+ (210 MeV, 8×1012−3×1014 cm−2) and Xe+ (5.6 BeV, 5×1011−5×1013 cm−2) ions is reported. It has been established that irradiation produces a defect structure in the bulk of silicon, which consists
of ion tracks whose density of material is lower than that of the host. The specific features of defect formation are discussed
taking into account the channeling of part of the ions along the previously formed tracks and the dominant role of electron
losses suffered by the high-energy ions. It is shown that the efficiency of incorporation of stable defects by irradiation
with high-energy ions is lower than that reached by implanting medium-mass ions with energies of a few hundred keV.
Fiz. Tverd. Tela (St. Petersburg) 40, 1627–1630 (September 1998) 相似文献
10.
11.
The angular dependences of the electron spin resonance spectrum of 1% Ni2+ ions in a ZnSiF6·6H2O matrix are investigated experimentally at 36 GHz and 4.2 K. Besides the main spectrum of the isolated ion, we observed a
spectrum due to interacting pairs of Ni2+ ions, located in the first (nn) and second (2n) coordination spheres and coupled by, besides the magnetic dipole-dipole interaction, isotropic exchange: J
nn
= (−197±1)×10−4, J
2nα
= (−5±1)×10−4, and J
2nβ
= (3±2)×10−4 cm−1. Lines due to other isolated Ni2+ ions, which have a different initial splitting D, are also present in the spectrum with intensity comparable to the pair spectrum. Low-symmetry distortions of the crystal
field are observed, caused by a pair of impurity ions located close to one another. It is shown that the previously proposed
interpretation is incorrect.
Fiz. Tverd. Tela (St. Petersburg) 41, 1602–1608 (September 1999) 相似文献
12.
V. M. Andrianov 《Journal of Applied Spectroscopy》2007,74(1):1-12
A theoretical conformational analysis has been carried out for the side substituents of a fragment of the molecule for 2,6-carboxymethyl
cellulose (a water-soluble cellulose ether), and the frequencies and the potential energy distribution of the normal vibrations
have been calculated for the most stable conformers of the ether groups of this fragment in the approximation of the molecular
mechanics method. It has been shown that the most stable conformers are those that have the conformations gg, t, g−, g−, g−-for the groups of atoms on the bonds C5-C6, C6-O6, C13-O6, C10-C13, C10-O9 and the conformations g+g−, g+, g−, g−; g+g−, g−, g−, g−; g+g−, g−, g+, t for the groups of atoms on the bonds C2-O2, C11-O2, C7-C11, C7-O8. Comparative analysis of the calculated frequencies
and the potential energy distribution of the normal vibrations for 13 of the most stable conformers showed, as in the case
of the 2,6-hydroxyethyl cellulose molecule, that the frequencies and modes of the normal vibrations are highly sensitive to
conformational transitions in the analyzed spectral region (800–1500 cm−1). The characteristic patterns for the change in the frequencies and modes of the normal vibrations have been established
in connection with conformational transitions within both side substituents. The observed conformational lability of the bulky
substituents in the cellulose ether molecules and its manifestations in the vibrational spectrum provide a basis for hypothesizing
that one of the major mechanisms for the process of their thermal gelation in aqueous solutions is conformational transitions
within these substituents.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 5–15, January–February, 2007. 相似文献
13.
M. N. Drozdov Yu. N. Drozdov D. N. Lobanov A. V. Novikov D. V. Yurasov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(3):591-594
Ge
x
Si1 − x
layers are investigated by means of secondary ion mass spectrometry (SIMS). Experimental results obtained with the use of
a TOF-SIMS 5 instrument are presented. To surmount the so-called matrix effect, SIMS analysis is performed by using complex
secondary ions: Ge2−, CsGe+, and Cs2Ge+. 相似文献
14.
Ramesh Narayan 《Pramana》1979,13(5):559-570
Ionic radii and compressibilities have been calculated for a number of monovalent and divalent ions and radicals on the basis
of the compressible ion theory. In this theory, the compression energy of an ion is given as a two-parameter function of its
radius,A exp (−r/p), the radius and compressibility of the ion being monotonically decreasing functions of the compressing force acting on it.
Choosing a standard force reflecting the average environment in the alkali halides, univalent radii and compressibilities
have been calculated. This is the first theory to estimate ionic compressibilities. The values show systematic trends among
groups of related ions. Anions are found to be significantly more compressible than cations (e.g., the compressibilities of
Ca++, K+, Cl− and S− − are respectively 0.8530, 1.342, 2.952 and 5.150 × 10−12 cm2/ dyne). Multivalent or ‘crystal’ radii and compressibilities have also been calculated by scaling the standard force by the
square of the ionic charge. The calculated ionic radii are closer to experimental values than the classical empirical radii. 相似文献
15.
G. K. Ivanov G. V. Golubkov S. V. Drygin I. E. Cherlina 《Journal of Experimental and Theoretical Physics》1997,84(5):888-892
Ionization and dissociation of diatomic molecules induced by a weak field (after preliminarily populating an intermediate
level) and by intense, linearly polarized monochromatic radiation have been studied. Field-induced mixing of rotational components
of various electronic-vibrational states of molecules (such as CO, NO, etc.) at field strength f∼10−4–10−5 atomic units can lead to migration among states with different angular momenta J. Therefore, ions with rotational momenta J
+ much higher than those prescribed by selection rules for three-photon absorption can be formed from molecules in the ground
state. The possibility of selective formation of ions with J
+≫1 and zero projection of the angular momentum on the polarization vector of the external electromagnetic radiation has been
investigated.
Zh. éksp. Teor. Fiz. 111, 1624–1632 (May 1997) 相似文献
16.
T. I. Arbuzova I. B. Smolyak S. V. Naumov A. A. Samokhvalov 《Physics of the Solid State》1998,40(10):1702-1705
The effect of doping with Li+, Zn2+, Ni2+, and Ga3+ ions on the magnetic susceptibility of the low-dimensional antiferromagnet CuO (T
N=230 K) has been studied within a broad temperature range of 77–600 K. The solubility of impurity ions in the CuO lattice
is low, ⩽3%. Impurity ions, similar to intrinsic defects, distort antiferromagnetic coupling and can shift the long-and short-range
magnetic-order regions toward lower T.
Fiz. Tverd. Tela (St. Petersburg) 40, 1876–1880 (October 1998) 相似文献
17.
18.
The surface distribution of elements is studied by scanning a 3-MeV proton beam along the surface of a bcc-Fe sample implanted
with aluminum ions in the dose interval (1–50) · 1016 cm−2. Ring-shaped regions, up to 30 μm in diameter, with a high density of aluminum, which appear at implantation doses (5–20) · 1016 cm−2, are observed. These regions appear as a result of radiation-stimulated segregation processes. A mechanism based on the existence
of a low density of dislocations in the initial crystal is proposed to explain the implanted impurity segregation processes.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 1, 86–89 (10 January 1997) 相似文献
19.
N. N. Loshkareva Yu. P. Sukhorukov B. A. Gizhevskii S. V. Naumov A. A. Samokhvalov A. S. Moskvin T. A. Belykh 《Physics of the Solid State》1998,40(3):383-388
Irradiation of various single-crystal CuO faces [ac,bc,(110)] with 4.6-MeV He+ ions has been found to result in reduction of CuO to Cu2O and Cu on the irradiated and unirradiated sides, lifting of forbiddenness from optical transitions in the [CuO4]7− electron center in the 0.7–0.95-eV energy range, a change in dichroism near the bands corresponding to transitions in the
hole centers, [CuO4]5−, and electron centers, [CuO4]7−, as well as in a resonant increase of absorption at 0.95–1.30 eV with an unusual polarization dependence. The results of
He+ irradiation of CuO single crystals are discussed in terms of a model of the nucleation of the phase of polar (electron and
hole) centers in copper-oxygen systems.
Fiz. Tverd. Tela (St. Petersburg) 40, 419–424 (March 1998) 相似文献
20.
The contact density |Ψ(0)|2 and the hyperfine splitting of positronium in naphthalene have been determined by means of a magnetic quenching experiment.
Results show that the perturbing effect of the medium on the hyperfine splitting is not interpretable as a change of the contact
density alone, since on passing from vacuum to the medium, the contact density and the splitting do not scale together. The
first is reduced by a factor of 0.25, the second by a factor of 0.067. A simple phenomenological model is presented.
This work was entirely supported by CISM (Centro Interuniversitario di Struttura della Materia) of the Ministero della Pubblica
Istruzione and by GNSM (Gruppo Nazionale di Struttura della Materia) of the Consiglio Nazionale delle Ricerche. 相似文献