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1.
Absolute cross sections σ−(E, N) of electron attachment to clusters (H2O)
N
, (N2O)
N
, and (N2)
N
for varying electron energy E and cluster size N are measured by using crossed electron and cluster beams in a vacuum. Continua of σ−(E) are found that correlate well with the functions of electron impact excitation of molecules’ internal degrees of freedom.
The electron is attached through its solvation in a cluster. In the formation of (H2O)
N
−
, (N2O)
N
−
, and (N2)
N
−
, the curves σ−(N) have a well-defined threshold because of a rise in the electron thermalization and solvation probability with N. For (H2O)900, (N2O)350, and (N2)260 clusters at E = 0.2 eV, the energy losses by the slow electron in the cluster are estimated as 3.0 × 107, 2.7 × 107, and 6.0 × 105 eV/m, respectively. It is found that the growth of σ− with N is the fastest for (H2O)
N
and (N2)
N
clusters at E → 0 as a result of polarization capture of the s-electron. Specifically, at E = 0.1 eV and N = 260, σ− = 3.0 × 10−13 cm2 for H2O clusters, 8.0 × 10−14 cm2 for N2O clusters, and 1.4 × 10−15 cm2 for N2 clusters; at E = 11 eV, σ− = 9.0 × 10−16 cm2 for (H2O)200 clusters, 2.4 × 10−14 cm2 for (N2O)350 clusters, and 5.0 × 10−17 cm2 for (N2)260 clusters; finally, at E = 30 eV, σ− = 3.6 × 10−17 cm2 for (N2O)10 clusters and 3.0 × 10−17 cm2 for (N2)125 clusters.
Original Russian Text ? A.A. Vostrikov, D.Yu. Dubov, 2006, published in Zhurnal Tekhnicheskoĭ Fiziki, 2006, Vol. 76, No. 12,
pp. 1–15. 相似文献
2.
N. Nishida S. Okuma H. Miyatake S. Shiratake Y. Hidaka T. Murakami Y. Ueda K. Kosuge S. Kambe H. Yasuoka H. Takagi S. Uchida K. Nishiyama K. Nagamine Y. Kuno T. Yamazaki 《Hyperfine Interactions》1991,65(1-4):1027-1034
The negative muon spin rotation method (μ− SR) has been applied to studies of electronic states at oxygen sites of oxide superconductors YBa2Cu3O7, Nd2−x
Ce
x
CuO4−δ (x=0.15, oxygen reduced), LiTi2O4 and related oxide-insulators La2CuO4−δ, CuO, Cu2O. The paramagnetic shifts of μ− trapped at oxygen nuclei in these polycrystalline powder samples have been measured at 300 K. All the measured shifts are
positive. In copper-oxides the paramagnetic shifts are of the order 10−3, while in LiTi2O4 is very small (8.4±3.34×10−5). In YBa2Cu3O7, a fast μ− spin relaxation timeT
2
* (∼ 200 ns) has been observed; the reason for this is unknown and further studies are now in progress. 相似文献
3.
4.
The field dependence of the nuclear spin-lattice relaxation (SLR) of cold implanted 82Br (T ≤ 25 mK) in α-Fe single crystals was investigated with nuclear magnetic resonance of oriented nuclei (NMR/ON) at low temperatures
as experimental technique. The SLR at the lattice sites with the hyperfine fields found by earlier NMR/ON experiments was
measured as a function of the applied external magnetic field B
ext parallel to the three principle axes [100], [110] and [111] of the iron single crystal. The data were evaluated with the
full relaxation formalism in the single impurity limit and for comparison also with the often employed model of a single exponential function with an effective relaxation time
T
1′. With a phenomenological model the high field values of the relaxation rates r
∞, [100]′ = 6.6(2) · 10−15 T2sK−1, r
∞, [110] = 5.4(2) · 10−15 T2sK−1 and r
∞, [111] = 5.2(1) · 10−15 T2sK−1 were obtained. 相似文献
5.
L. S. Vorotilova L. V. Dmitrieva O. E. Kvyatkovskii B. F. Shchegolev 《Physics of the Solid State》1997,39(4):540-544
The NMR spectra of 27Al are measured in several disordered rare-earth aluminates CaREAlO4. A change in the shape of the resonance line of the transition 1/2↔−1/2 in the transverse orientation in the rare-earth series
RE=La, Pr, Eu, Y is observed, from a narrow (∼16 kHz), structureless line in the La compound to a wide (∼130 kHz), three-component
line in the Y compound. This is attributed to a nonuniform distribution of the electric field gradient tensor at the 27Al site. The electric field gradient tensor at the 27Al site in a cluster (AlO6)−9 is calculated by a nonempirical method (MO LCAO SCF) in the “deformable oxygen octahedron” model. The results are found to
be in satisfactory agreement with the experimental values of 〈V
zz〉 and can be used to obtain the experimental splitting of the resonance line in the Y compounds for reasonable values of the
parameters of the local deformations of the AlO6 octahedron. The nature of the strong axial correlations in the distribution of the Ca and Y atoms in CaYAlO4 is discussed.
Fiz. Tverd. Tela (St. Petersburg) 39, 618–623 (April 1997) 相似文献
6.
We have recorded and investigated the ESR spectrum of vanadium-doped α-RbTiOPO4 single crystals in the temperature interval 77–300 K. Two types of structurally distinct centers, V1 and V2, with a 4:1 ratio
of the peak intensities were observed. The angular dependences of the resonance magnetic fields are described by a spin Hamiltonian
corresponding to axial symmetry with the parameters g
∥1=1.9305, g
⊥1=1.9565, A
∥1=−168.2×10−4cm−1, and A
⊥1=−54.3×10−4cm−1 for V1 centers and g
∥2=1.9340, g
⊥2=1.9523, A
∥2=−169.0×10−4cm−1, and A
⊥2=−55.2×10−4cm−1 for V2 centers. A model of a paramagnetic center is proposed: The vanadium ions replace titanium ions in two structurally
distinct positions Ti1 and Ti2 (V1 and V2 centers, respectively). The possibility that a VO2+ ion forms when α-RbTiOPO4 crystals and crystals of the KTP group (KTiOPO4, NaTiOPO4, α-and β-LiTiOPO4), studied earlier, are doped with vanadium is discussed.
Fiz. Tverd. Tela (St. Petersburg) 40, 534–536 (March 1998) 相似文献
7.
The X-ray satellite spectra arising due to 2p
3/2
−13x
−1−3x
−13d
−1 (x ≡ s, p, d) transition array, in elements with Z = 40 to 48, have been calculated, using available Hartree-Fock-Slater (HFS) data on
1s
−1−2p
−1 3x
− and 2p
3/2
−1−3x
−1,3x
−1 Auger transition energies. The relative intensities of all the possible transitions have been estimated by considering cross
— sections for the Auger transitions simultaneous to a hole creation and then distributing statistically the total cross sections
for initial two hole states 2p
3/2
−1−3x
−1 amongst various allowed transitions from these initial states to 3x
−1 3d
−1 final states by Coster-Kronig (CK) and shake off processes. In both these processes initial single hole creation is the prime
phenomenon. Each transition has been assumed to give rise to a Gaussian line and the overall spectrum has been computed as
the sum of these Gaussian curves. The calculated spectra have been compared with the measured satellite energies in Lα1 spectra. Their intense peaks have been identified as the observed satellite lines. The peaks in the theoretical satellite
spectra were identified as the experimentally reported satellites α3, α4 and α5, which lie on the high-energy side of the Lα1 dipole line. 相似文献
8.
Total (elastic+inelastic) cross sections fore
−-O,e
−-O2 ande
−-O3 scattering have been calculated at sample energies between 100 and 1000eV. The basice
−-O atom scattering amplitudes are obtained from the partial wave analysis with a complex optical potential. Thee
−-O2 ande
−-O3 cross-sections are obtained through the independent atom model. Oure
−-O2 cross-sections reproduce the experimental data quite well. Adequate comparisons are made in all the three cases. 相似文献
9.
R. Yu. Abdulsabirov I. I. Antonova S. L. Korableva N. M. Nizamutdinov V. G. Stepanov N. M. Khasanova 《Physics of the Solid State》1997,39(3):423-425
The orientational dependences of the EPR spectra of Fe3+-doped LiCaAlF6 single crystals (space group P31c, Z=2), grown at the Laboratory of Magnetic Radio Spectroscopy at Kazan’ State University, have been investigated in detail.
The spectrum is described by a trigonal spin Hamiltonian with the following parameters: B
20=40.072×10−4 cm−1, B
40=−5.799×10−4 cm−1, B
43=−4.281×10−4 cm−1, A
s=24.33±1, A
p=6.13±1, g
∥=g
⊥=2.00217±0.0003. A theoretical calculation of the hyperfine structure parameters shows that they are described quite well
when allowance is made for the overlapping of the wave functions of the paramagnetic center and the ligands (F−).
Fiz. Tverd. Tela (St. Petersburg) 39, 488–490 (March 1997) 相似文献
10.
E. Yu. Loktionov A. V. Ovchinnikov Yu. Yu. Protasov D. S. Sitnikov 《Bulletin of the Lebedev Physics Institute》2010,37(3):82-84
Optical gas-dynamic processes occurring in polymeric targets ((CH2O)
n
, (C2F4)
n
) exposed to ultrashort laser pulses (τ
0.5 ∼ 45 − 70 fs; λ
I,II,III
= 266, 400, 800 nm; and E/S ∼ 0.1 − 40 J/cm2 at r
0 ∼ 20 μm) were studied under normal conditions and in vacuum (p ∼ 10−2 Pa). The dynamics of the mass flow from the target surface (m′ ∼ 10−5 − 10−4 g/J) was studied and the spectral-energy thresholds of laser ablation, the electron density distribution (n
e
∼ 1014 − 1018 cm−3), the mass-averaged velocity of the material flow from the target surface (∼ 103 m/s), and the chemical composition and average temperature in the near-surface plasma formation (T ∼ 5000 K) were determined using interference microscopy, emission spectroscopy, and shadowgraphy. 相似文献
11.
R. Cywinski S. H. Kilcoyne S. F. J. Cox C. A. Scott O. Schärpf 《Hyperfine Interactions》1991,64(1-4):427-433
Neutron polarisation analysis measurements reveal antiferromagnetic spin correlations persisting to temperatures of 120 K
in Pauli paramagnetic Y(Mn1−x
Fe
x
)2, 0.03≤x≤0.05. The mean moment at the Mn(Fe) site is found to be 0.2μ
B. Transverse field μSR is characterised by weak exponential damping with a rate of 0.02 μs−1 at 300 K increasing according to the power lawT
−0.75 to only 0.16μ
S
−1
at 12 K. It is suggested that these results are consistent with a slowing down of longitudinal spin fluctuations at the Mn
site as temperature decreases. 相似文献
12.
A large stack of lead-emulsion sandwich detector assembly was flown over Hyderabad, India. High energy gamma rays at the float
altitude were unambiguously identified from the cascades they induced, and their energies reliably determined by improved
methods. From an analysis of 163 gamma rays of energy ≳ 30 GeV, it is found that the differential energy spectrum is represented
by the power lawJ
r
(E)= 129·4E
−2·62±0·12 photons m−2 sr−1sec−1 GeV−1 at an effective atmospheric depth of 14·3 g cm−2; this is the first reliable balloon measurement of atmospheric gamma rays in the energy range 40–1000 GeV. After correcting
for the gamma rays radiated by the primary cosmic ray electrons, the production spectrum of gamma rays, resulting from the
collisions of cosmic ray nuclei with air nuclei, at the top of the atmosphere isP
r
(E, 0)=8·2 × 10−4 E2.60±0.09 photons g−1sr−1sec−1 GeV−1. The atmospheric propagation of the electromagnetic component due to the cascade process is also derived from the gamma ray
production spectrum. 相似文献
13.
We studied the spectral-luminescent characteristics of the luminescence of mixed-ligand polypyridine-phosphine complexes of
ruthenium(II) cis-[Ru(bpy)2(PPh3)X](BF4)
n
with ligands 2,2′-bipyridyl (bpy) and triphenylphosphine (PPh3) and X = Cl−, Br−, CN−, NO2−, NH3, MeCN, pyridine (py), 4-aminopyridine (pyNH2), and 4,4′-bipyridyl (4,4′-bpy) in a 4: 1 EtOH-MeOH alcoholic mixture at 77 K. The radiative and nonradiative deactivation
rate constants of the lowest electronically excited state of the complexes are determined. We find that triphenylphosphine
has a greater effect on the photophysical characteristics of ruthenium(II) complexes compared to π-acceptor strong-field ligands,
such as MeCN, CN−, and NO2−. At the same time, the characteristics of complexes cis-[Ru(bpy)2(PPh3)X]
n+ considerably depend on the nature of the second monodentate ligand X, which is coordinated to ruthenium(II), and correlate
with its position in the spectrochemical series of ligands. 相似文献
14.
A. V. Anan’ev Yu. I. Zhdanov A. P. Gerashchenko K. N. Mikhalev S. V. Verkhovskii E. Yu. Medvedev K. A. Okulova N. I. Chebotaev V. N. Goshchitskii 《JETP Letters》1998,67(3):182-188
The spin-spin relaxation rate 63
T
2
−1
of 63Cu nuclei in CuO2 layers is measured in the normal and superconducting states of the compound YBa2Cu3O6.9 (T
c
onset
=94 K) subjected to radiation-induced disordering by a fast-neutron flux Φ to T
c
onset
=68 K (Φ=7×1018 cm−2) and T
c
onset
<4 K (Φ=12×1018 cm−2). It is found that as the structural disorder increases, the contribution of the indirect spin-spin interaction 63
T
2G
−1
, which is related to the value of the spin susceptibility at the boundary of the Brillouin zone of the copper planes χs(q={π/a; π/a}), decreases slightly at the transition to the superconducting state for the initial sample and remains unchanged for the
weakly disordered sample. This behavior of the short-wavelength contribution to the spin susceptibility attests to the stability
of the x
2−y
2 symmetry of the energy gap against structural disorder, in accordance with proposed theoretical models of Cooper pairing
for high-T
c cuprates.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 3, 172–177 (10 February 1998) 相似文献
15.
A. A. Samokhvalov T. I. Arbuzova N. A. Viglin V. V. Osipov N. I. Solin S. V. Naumov V. G. Bamburov N. I. Lobachevskaya O. G. Reznitskikh 《Physics of the Solid State》1999,41(2):262-264
Mg1−x
CuxO solid solutions having an NaCl structure with 0⩽x⩽0.20 are synthesized and Cu-Mg1−x
CuxO structures are prepared for superconductivity studies. The magnetic susceptibility χ, electron paramagnetic resonance (EPR), and electrical conductivity of the solid solutions are studied at temperatures of
5–550 K. It is shown that χ
−1(T) obeys the Curie-Weiss law with a paramagnetic Curie temperature Θ close to zero and an effective magnetic moment μ
eff=1.9 μ
B, close to the 1.73 μ
B of a Cu2+ ion with spin S=1/2. The width ΔH of the EPR line depends weakly on temperature and increases as x is raised. The volume narrowing of the EPR linewidth ΔH is used to estimate the exchange interaction parameter, 3×10−4 eV. The g-factor is close to 2 and is temperature independent. The electrical conductivity of Mg1−x
CuxO at T=300 K is ≈10−11–10−12 Ω−1 cm−1 for x=0 and increases to 10−5–10−6 Ω−1 cm−1 for x=0.15–0.20. The conductivity is p-type. Magnetic shielding is observed in Cu-Mg1−x
CuxO structures with x=0.15 and 0.20. The possible connection of this phenomenon with interference superconductivity in the contact layer of the
structure is discussed.
Fiz. Tverd. Tela (St. Petersburg) 41, 293–296 (February 1999) 相似文献
16.
The separation betweenT=0 andT=1 centroids of the empirical effective interaction is fairly large for the (d
3
2/−1
f
7/2)JT particle-hole interaction as compared to nearby (f
7/2)2
JT and (d
5/2)2
JT particle-particle interactions. This interesting feature of the empirical effective interaction is shown to arise as a consequence
of renormalization of the effective interaction as one truncates the configuration space from (s−d)−1(f−p)1 to (d
3
2/−1
f
7/2) and from (f−p)2 and (s−d)2 configurations to (f
7/2)2 and (d
5/2)2 respectively. 相似文献
17.
Nano-sized Al3+-doped V2O5 cathode materials, Al0.2V2O5.3−δ
, were prepared by an oxalic acid assisted sol–gel method at 350 °C (sample A) and 400 °C (sample B). X-ray diffraction confirmed
that samples A and B were pure phase Al0.2V2O5.3−δ
with an orthorhombic structure close to that of V2O5. Scanning electron microscopy showed that sample A was in nanoscale with a mean particle size about 50 nm. Cyclic voltammetry
showed the good electrochemical and structural reversibility of the Al0.2V2O5.3−δ
nanoparticles during the Li+ insertion/extraction process. The Al0.2V2O5.3−δ
nanoparticles exhibited excellent charge–discharge cycling performance and rate capability compared to that of bulky V2O5 electrodes. For instance, the materials delivered a reversible specific capacity about 180 mAh g−1 (sample A) and 150 mAh g−1 (sample B), in the potential window of 4.0–2.0 V at the current density of 150 mA g−1. The Al0.2V2O5.3−δ
nanoparticles in particular showed almost no capacity fading for at least 50 cycles. 相似文献
18.
Variation of interface trap level charge density within the bandgap of 4H-SiC with varying oxide thickness 总被引:1,自引:0,他引:1
Interfacial characteristics of metal oxide-silicon carbide (MOSiC) structure with different thickness of SiO2, thermally grown in steam ambient on Si-face of 4H-SiC (0 0 0 1) substrate were investigated. Variations in interface trapped
level density (D
it) was systematically studied employing high-low (H-L) frequency C–V method. It was found that the distribution of D
it within the bandgap of 4H-SiC varied with oxide thickness. The calculated D
it value near the midgap of 4H-SiC remained almost stable for all oxide thicknesses in the range of 109–1010 cm−2 eV−1. The D
it near the conduction band edge had been found to be of the order of 1011 cm−2 eV−1 for thicker oxides and for thinner oxides D
it was found to be the range of 1010 cm−2 eV−1. The process had direct relevance in the fabrication of MOS-based device structures. 相似文献
19.
355 nm UV laser was obtained with a pulse width of less than 5 ns and a peak power at megawatt level by adopting the 808 nm
pulse laser diode (LD) side-pumped ceramic Nd:YAG and BBO crystal electrooptical Q-switched. The single-pulse energy was measured
to be 24.3 mJ with 4.86 ns pulse width and 5.11 MW peak power at a repetition rate of 1Hz under a 120 A pump current. Using
a volume of beam splitting mirrors, wavelength outputs at 1064, 532, and 355 nm pulse laser was obtained simultaneously with
a respective average output power of 656.6, 357.1, and 260.5 mW, the beam quality factor M
2 are (M
x − 10642 = 5.83, M
y − 10642 = 5.61), (M
x − 5322 = 4.25, M
y − 5322 = 4.08) and (M
x − 3552 = 6.32, M
y − 3552 = 6.15), corresponding to a conversion efficiency at 11% from 1064 to 355 nm. 相似文献
20.
E. Z. Utyanskaya B. V. Lidskii M. G. Neigauz A. E. Shilov 《Russian Journal of Physical Chemistry B, Focus on Physics》2009,3(6):884-895
It was shown earlier that the hydrolysis of the (CuATP2−)2 dimeric complex to CuADP− and inorganic phosphate P
i
was an irreversible reaction. The main intermediate hydrolysis product, the formation of which should be taken into account
at comparatively early hydrolysis stages, was the IntK pentacovalent intermediate. It was formed in parallel with hydrolysis
to CuADP− and P
i
through the common intermediate product (CuATP2−)2OH− — DOH−. We studied the influence of the addition of various concentrations of Mg2+ ions to the reaction mixture at pH 7.1–7.2, a range for which the kinetics of hydrolysis is sensitive to the rate constants
of deactivation of DOH− active centers (conjugated with CuADP− formation and occurring via the formation of IntK). The conversion of ATP above which stationary hydrolysis regime was observed
decreased as the concentration of Mg2+ grew. The DOH−
$
\underset{{OH^ - }}{\overset{{OH^ - }}{\longleftrightarrow}}$
\underset{{OH^ - }}{\overset{{OH^ - }}{\longleftrightarrow}}
IntK equilibrium according to the conversion of ATP was established more rapidly, and it was to a greater extent shifted toward
IntK. It was assumed that hydrated Mg2+ linked as a second metal ion with ATP β and γ phosphate groups hydrated IntK much stronger than DOH−. The Cu · OH2 · AMP complex played the role of a common acid catalyst and hydrated DOH− better than Mg2+ · OH2. The selective hydration of DOH− by the CuOH2 · AMP complex at early hydrolysis stages directed the process toward the formation of IntK, which caused the appearance of
an induction period in the formation of CuADP−. 相似文献