共查询到20条相似文献,搜索用时 46 毫秒
1.
K. Ueda R. Püttner N. A. Cherepkov F. Gel’mukhanov M. Ehara 《The European physical journal. Special topics》2009,169(1):95-107
This paper summarizes recent developments for experimental and theoretical studies on core-level
photoelectron spectroscopy of N2. Analysis of experimental spectra reveals that the 1σg and
1σu core-hole states differ in energy by ~100meV and in equilibrium bond length by ~0.04pm,
in agreement with ab initio predictions. The ratio of the 1σg and 1σu photoionization cross sections
measured in the photon energy range up to 1 keV reveals oscillatory structure due to two-center interference, equivalent to
Young’s
double-slit experiment, as Cohen and Fano predicted. The experimental Auger rates for the transition to the dicationic ground
state
are found to be different by a factor of two for 1σg and 1σu hole states and are well reproduced by the
ab initio calculations. All these findings support the delocalized picture of the core hole. Discussion is given how many-body
processes involved and observations for these processes affect the observation of the localized and/or delocalized core hole. 相似文献
2.
F. Ellinghaus W.-D. Nowak A.V. Vinnikov Z. Ye 《The European Physical Journal C - Particles and Fields》2006,46(3):729-739
We investigate the possibility of acquiring information on the generalized parton distribution E and, through a model for
E, also on the u-quark total angular momentum Ju by studying deeply virtual Compton scattering and hard exclusive ρ0 electroproduction on a transversely polarized hydrogen target at HERMES. It is found that a change in Ju from zero to 0.4 corresponds to a 4σ (2σ) difference in the calculated transverse target-spin asymmetry in deeply virtual
Compton scattering (ρ0 electroproduction), where σ is the total experimental uncertainty.
PACS 12.38.Bx, 13.60.Le 相似文献
3.
Large-amplitude solitary waves are investigated in ion-beam plasma system. The Sagdeev’s pseudopotential is determined in
terms of the ion speedu. It is found that there exists a critical value ofu
0, the value ofu at (u′)2 = 0, beyond which the solitary waves cease to exist. The critical value also depends on σ (the ion temperature) or σb (the ion beam temperature).
One of the author (PC) is grateful to UGC, India for the financial support under SAP(No F.510/8/DRS/2004(SAP-1)). 相似文献
4.
S. R. Hanna 《Il Nuovo Cimento C》1990,13(6):889-894
Summary At downwind distances of 400 m or less, the angular standard deviation, σθc, of the lateral distribution of pollutants released from a point source over a given time period is shown to equal the standard
deviation, σθ, of the wind direction fluctuations observed over the same time period. Data taken during light wind, stable conditions at
two field sites (Idaho Falls, ID, and Oak Ridge, TN) are used in this analysis. This relation is most reliable if the pollutant
concentration distribution is observed on a circle at constant distance from the source (i.e., on a polar coordinate system).
Paper presented at the GNFAO/EURASAP Meeting, Turin, September 1989.
To speed up publication, proofs were not sent to the author and were supervised by the Scientific Committee. 相似文献
5.
The Young’s modulus and the internal friction of beryllium polycrystals (size grain from 6 to 60 μm) prepared by the powder
metallurgy method have been studied as functions of the amplitude and temperature in the range from 100 to 873 K. The measurements
have been performed using the composite piezoelectric vibrator method for longitudinal vibrations at frequencies about 100
kHz. Based on the acoustic measurements, the data have been obtained on the elastic and inelastic (microplastic) properties
as functions of vibration stress amplitudes within the limits from 0.2 to 30–60 MPa. The microplastic deformation diagram
is shown to become nonlinear at the amplitudes higher than 5 MPa. The beryllium mechanical characteristics (the yield strength
σ
0.2, the ultimate strength σ
u
, and the conventional microscopic yield strength σ
y
) obtained with various grain sizes are compared. At room temperature, all the parameters satisfactorily obey the Hall-Petch
relationship, although there is no complete similarity. The temperature dependences are quite different, namely: σ
0.2(T) and σ
u
(T) decrease monotonically during heating from room temperature to higher temperatures; however, σ
y
(T) behaves unusually, and it has a minimum near 400 K. The different levels of stresses and the absence of similarity indicate
that the scattering of the ultrasound energy and the formation of a level of the macroscopic flow stresses in beryllium occur
on dislocation motion obstacles of different origins. 相似文献
6.
B. P. Lavrov 《Russian Journal of Physical Chemistry B, Focus on Physics》2012,6(2):239-248
A statistical analysis of all the available data on the wave numbers of spectral lines related to triplet-triplet electronic-vibrational-rotational
(rovibronic) radiation transitions into the H2 molecule (1sσ2sσ) a
3Σ
g
+ electronic state was performed for the first time. This allowed us to check and refine the controversial identification of
several spectral lines. Optimum rovibronic term values were found for 15 electronic states, including the (4pσ)f
3Σ
u
+, (4pπ)k
3Π
u
+, and (4pπ)k
3Π
u
− states studied in this work. The ratios between the oscillator strengths of R- and P-branch lines with common upper levels (branching coefficients) for the f
3Σ
u
+ → a
3Σ
g
+ and k
3Π
u
+ → a
3Σ
g
+ systems of H2 molecule bands were measured for the first time. Substantial deviations of the measured branching coefficients from the corresponding
ratios between the Henl-London factors were observed. The deviations monotonically increased as the rotational quantum number
N grew, which, in combination with substantial Λ-doubling in the k
3Π
u
state, was evidence of an important role played by electronicrotational interaction in the 4pσ3Σ
u
+ and 4pπ3Π
u
+ adiabatic electronic states. A strong correlation was observed between the N dependences of branching coefficients for transitions from the mutually perturbed f
3Σ
u
+ and k
3Π
u
+ electronic states. The results of this work show that the measured branching coefficients are a much more sensitive and capacious
channel of information about perturbation effects than rovibronic term values. 相似文献
7.
The airborne transport of particles on a granular surface by the
saltation mechanism is studied through numerical simulation of
particles dragged by turbulent air flow. We calculate the
saturated flux qs and show that its dependence on the wind
strength u* is consistent with several empirical relations
obtained from experimental measurements. We propose and explain
a new relation for fluxes close to the threshold velocity ut,
namely, qs=a(u*-ut)α with α≈2. We
also obtain the distortion of the velocity profile of the wind due to the
drag of the particles and find a novel dynamical
scaling relation. We also obtain a new expression for the dependence of
the height of the saltation layer as function of the strength of the wind. 相似文献
8.
N. A. Silant’ev 《Journal of Experimental and Theoretical Physics》1997,85(4):712-723
An analysis is made of the relation between accurate formulas for the coefficients of turbulent diffusion D
T and the alpha effect α
T for a magnetic field in the Lagrange and Euler representations. It is shown that the quadratic term with respect to α
T in the diffusion coefficient derived by Moffatt and Kraichnan is incorrect and should be dropped. First, a numerical solution
of the nonlinear equation (DIA equation) for the Green function is presented, describing the transport of a magnetic field
for the case of incompressible, uniform, isotropic, steady-state turbulence possessing helicity. These solutions are used
to calculate the steady-state coefficients D
T and α
T for various values of the parameters ξ
0=u
0
σ
0/R
0, a=H
0/u
0
2
p
0, σ
0/σ
1, and R
0/R
1, where u
0, σ
0, and R
0 are the characteristic velocity, lifetime, and scale of the turbulent pulsations, and H
0, σ
1, and R
1 are similar values describing the helicity of the medium h(1,2)=〈u(1)· (∇×u(2))〉, and the parameter α characterizes the degree of helicity. The DIA values of D
T and α
T and the self-consistent values of these quantities calculated using the Green tensor in the diffusion approximation are in
qualitative agreement. It is shown that the coefficient of turbulent diffusion is always positive for all the types of turbulence
studied. Nonsteady-state values of D
T(t) and α
T(t) calculated by a self-consistent method are given.
Zh. éksp. Teor. Fiz. 112, 1312–1331 (October 1997) 相似文献
9.
Large-amplitude solitary waves are investigated in a relativistic plasma with finite ion-temperature. The mass of electron
is also considered. The Sagdeev’s pseudopotential is determined in terms ofu, the ion speed. It is found that there exists a critical value ofu
0, the value ofu at which (u′)2=0, beyond which the solitary waves cease to exist. The critical value also depends on the parameters likeν, the soliton velocity;μ, the electronion mass ratio orσ, the temperature ratio of ion to electron. This result reproduces our previous result [Czech. J. Phys., Vol. 54 (2004), No.
4, 489–496] when the ion temperature is neglected. 相似文献
10.
W. J. Kossler X. H. Yu A. Greer H. E. Schone C. E. Stronach M. Davis R. S. Cary J. E. Crow W. F. Lankford J. Oostens 《Hyperfine Interactions》1991,63(1-4):81-86
Transverse and zero-field μSR measurements were made on YBa2(Cu1−xNix)3O7−y withx=0.1 and 0.2, and YBa2(Cu1−x
Zn
x
)3O7−y
withx=0.03, 0.06, 0.1, and 0.16, wherey≈0.1. Since doping may lead to magnetic ordering this was searched for with both zero and transverse field μSR, but no evidence
was found over the temperature range studied: 10–100 K. However, depolarization rates as functions of temperature were obtained,
and the low temperature values of these are σ=3.2 μs−1.1.6μs−1, and 1 μs−1 forx=0.01, and 0.2 Ni, respectively, and σ=0.8 μs−1, 0.75 μs−1, 0.65 μs−1, and 0.4 μs−1 forx=0.03, 0.06, 0.1, and 0.16 Zn, respectively. Estimates for the effect of decreasing electron concentration for Zn are made,
but these alone do not account for the drop in σ. Estimates for the effect of scattering on λ and hence σ are made. The reduction
in σ for Ni dopant is in surprisingly good agreement with these estimates. For Zn the order of magnitude is correct, but the
relative lack of further change in σ after the effect of the first 0.03 addition seems to imply a saturation of the effect
of scattering. 相似文献
11.
A. Abdoulaye S. S. Soulayman G. Chabanis J. C. Giuntini J. V. Zanchetta I. Brach 《Ionics》1996,2(1):39-45
On the basis of experimental measurements of the electrical conductivity of the Nafaujasite zeolites (NaY), treated under
vacuum up to 673 K for 24 hours, we clearly demonstrate that the behavior of the measured conductivity σac of the dehydrated zeolite NaY, over an interval of high frequency change, may be described by a power-law function: σac=A▹s. The exponent s, in this case, should be considered as temperature and frequency dependent when the parameter A is a temperature
dependent function. On the other hand, when considering the measured conductivity as a sum of two terms (σac=σ0+σ′(▹)) resulting from the contributions of the dc and the ac components respectively, we find that one of them obeys the
Arrhenius law while the other can be expressed as A▹s. Parameter s is practically frequency independent when the frequency of the applied electrical field is higher than a characteristic
value ▹c A comparison with the measurements performed on NaY dehydrated at 435 K is also included.
Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995 相似文献
12.
We have measured the absorption cross sections of oxygen molecules in oxygen and in an oxygen-argon mixture heated by a shock
wave, in the wavelength range 190–250 nm at temperatures of 1500–7000 K, for thermal equilibrium conditions behind the shock
wave front. Analysis of the absorption cross sections obtained allowed us to select a data set that adequately describes the
absorption characteristics of the electronic transition X3Σ
g
−
→ B3Σ
u
−
for the oxygen molecule.
In order to approximate the temperature dependence of these cross sections at a temperature of 1500–4500 K, we chose the function
σ(λ, T) = σ0(λ)(1 − exp (−θ/T)) exp (− n*θ/T) where θ0 = 1.4·10−17, 1.4·10−17, 1.2·10− 17, and 1.3·10−17 cm2, n* = 3.1, 4.1, 5.6, and 7.47 for wavelengths 190, 210, 230, and 250 nm, respectively; θ = 2240 K is the characteristic temperature
of the O2 molecules. The approximation error was 19–25% and did not exceed the experimental error.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 13–17, January–February, 2006. 相似文献
13.
A calculation of the current-quark mass dependence of hadron masses can help in using observational data to place constraints
on the variation of nature’s fundamental parameters. A hadron’s σ-term is a measure of this dependence. The connection between
a hadron’s σ-term and the Feynman-Hellmann theorem is illustrated with an explicit calculation for the pion using a rainbow-ladder
truncation of the Dyson-Schwinger equations: in the vicinity of the chiral limit σπ = mπ/2. This truncation also provides a decent estimate of σρ because the two dominant self-energy corrections to the ρ-meson’s mass largely cancel in their contribution to σρ. The truncation is less accurate for the ω, however, because there is little to compete with an ω → ρπ self-energy contribution
that magnifies the value of σω by ≲25%. A Poincaré-covariant Faddeev equation, which describes baryons as composites of confined-quarks and -nonpointlike-diquarks,
is solved to obtain the current-quark mass dependence of the masses of the nucleon and Δ, and thereby σN and σΔ. This “quark-core” piece is augmented by the “pion cloud” contribution, which is positive. The analysis yields σN ≃ 60 MeV and σΔ ≃ 50 MeV. 相似文献
14.
G. Gerasimov B. Krylov A. Loginov G. Zvereva R. Hallin A. Arnesen F. Heijkenskjöld 《Applied physics. B, Lasers and optics》1998,66(1):81-90
u , 0u
+ and the weakly bound ground state 0g
+. A semiempirical method was suggested and applied to describe the experimental spectra and to estimate the temperature of
the radiating plasma volume. Electron impact, transferring dimers from the ground state to the excited states, is shown to
be an efficient excitation mechanism in the 100–850 hPa and the 10–50 mA pressure and discharge current ranges. The spectra
obtained as well as the results of calculations corroborate the high rate of this mechanism.
Received: 31 July 1996/Revised version: 17 March 1997 相似文献
15.
K. Divakara Rao S. Anantha Ramakrishna P.K. Gupta 《Applied physics. B, Lasers and optics》2001,72(2):215-219
We report the results of our studies on the nonlinear optical response of thin films of tetraphenyl porphyrin doped in boric
acid glass for picosecond-duration pulses. The fluence-dependent transmission measurements show that the sample exhibits reverse
saturation behavior at 532 nm and saturable absorber action at 683 nm. By fitting the nonlinear transmission data at these
wavelengths to a rate equation model, values for σS
e and σL the excited singlet and ground state cross sections were obtained. The large value (≈8) for σS
e/σL makes it a potential material for optical limiting at 532 nm, whereas at 683 nm the ratio σL/σS
e≈4.3. Intensity dependence of degenerate forward four-wave mixing at 683 nm was also investigated to establish the order and
magnitude of the nonlinearity. The forward four-wave mixing signal at 683 nm showed a cubic dependence on the input intensity,
establishing the third-order nonlinearity. A value of 4×10-12 esu for the third-order susceptibility |χ(3)| was estimated from the measured efficiency. The time response of the nonlinearity was measured by the pump-probe transmission
experiment, resulting in a decay constant of about 1.8 ns for the repopulation of the ground singlet state at 683 nm.
Received: 13 April 2000 / Published online: 20 September 2000 相似文献
16.
In this paper we develop the ergodic theory for a horseshoe map f which is uniformly hyperbolic, except at one parabolic fixed point ω and possibly also on W
s
(ω). We call f a parabolic horseshoe map. In order to analyze dynamical and geometric properties of such horseshoes, by making use of induced
maps, we establish, in the context of σ-finite measures, an appropriate version of the variational principle for continuous potentials with mild distortion defined
on subshifts of finite type. Staying in this setting, we propose a concept of σ-finite equilibrium states (each classical probability equilibrium state is a σ-finite equilibrium state). We then study the unstable pressure function , the corresponding finite and σ-finite equilibrium states and their associated conditional measures. The main idea is to relate the pressure function to
the pressure of an embedded parabolic iterated function system and to apply the developed theory of the symbolic σ-finite thermodynamic formalism. We prove, in particular, an appropriate form of the Bowen-Ruelle-Manning-McCluskey formula,
the existence of exactly two σ-finite ergodic conservative equilibrium states for the potential –t
u
log |Df|E
u
| (where t
u
denotes the unstable dimension), one of which is the Dirac δ-measure supported at the parabolic fixed point and the other being non-atomic. We also show that the conditional measures
of this non-atomic equilibrium state on unstable manifolds, are equivalent to (finite and positive) packing measures, whereas
the Hausdorff measures vanish. As an application of our results we obtain a classification for the existence of a generalized
physical measure, as well as a criteria implying the non-existence of an ergodic measure of maximal dimension.
The research of the first author was supported in part by the NSF Grant DMS 0400481.
The research of the second author was supported in part by the National Science Foundation under Grant No. EPS-0236913 and
matching support from the State of Kansas through Kansas Technology Enterprise Corporation. 相似文献
17.
Thickness effects have been studied extensively, both numerically and analytically, only for the case where the intrinsic
absorber cross-section, σa, is an elemental
Lorentzian line having the natural Heisenberg width. Thickness effects with σa's corresponding to intrinsically (homogeneously or inhomogeneously) broadened lines have hardly not been studied. We report
a numerical study of the latter case in which the σa's are taken to be single Voigt lines of various Gaussian-width to Heisenberg-width ratios (O ≤ σ/Гo ≤ 10). We obtain “phase diagrams” showing effectively thin-absorber regions in the plane of intrinsic broadening (σ/Гo or FWHM of σa) versus total absorber thickness (O ≤ ta ≡ fanaσo ≤ 10). These diagrams are useful in evaluating when and to what extent spectral distortions from thickness effects need to
be taken into account in real situations. 相似文献
18.
Eugene Z. Xia 《Communications in Mathematical Physics》1999,203(3):531-549
Suppose X is a compact Riemann surface with genus g>1. Each class [σ] ∈ Hom(π1(X),PGL(2,ℝ))/PGL(2,ℝ) is associated with the first and second Stiefel–Whitney classes w
1([σ]) and w
2([σ]). The set of representation classes with a fixed w
1≠ 0 has two connected components. These two connected components are characterized by w
2 being 0 or 1. For each fixed w
1≠ 0, we prove that the component, characterized by w
2= 0, contains an open dense set diffeomorphic to the total space of a vector bundle of rank 2g−2 over a once punctured algebraic torus of dimension g−1. The other component, characterized by w
2= 1, contains an open dense set diffeomorphic to the total space of a vector bundle of rank 2g−2 over an algebraic torus of dimension g−1.
Received: 2 January 1997 / Accepted: 28 November 1998 相似文献
19.
V. V. Varlamov B. S. Ishkhanov V. N. Orlin S. Yu. Troshchiev 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):842-849
The results from experimental and theoretical studies of the total and partial cross sections of photoneutron reactions on
the 197Au isotope were analyzed. The cross sections for reactions σ(γ, nX) = σ(γ, n) + σ(γ, np) + … + σ(γ, 2nX) = σ(γ, 2n) + σ(γ, 2np) + … were evaluated in the energy range 7 ≤ E
γ ≤ 30 MeV using an approach free of the shortcomings of experimental photoneutron multiplicity sorting methods. The total
photoneutron reaction cross sections σexp(γ, xn) = σexp(γ, nX) + 2σexp(γ, 2nX) + … = σexp(γ, n) + σexp(γ, np) + 2σexp(γ, 2n) + 2σexp(γ, 2np) + … were used as the initial experimental data. The contributions from the cross sections σ(γ, nX) and σ(γ, 2nX) to the cross sections σexp(γ, xn) were separated using the multiplicity transition functions F
1
theor = σtheor(γ, 1nX)/σtheor(γ, xn) and F
2
theor = σtheor(γ, 2nX)/σtheor(γ, xn), calculated within an updated version of the pre-equilibrium model of photonuclear reactions. New evaluated data for both
partial reaction cross sections, i.e., σeval (γ, 1nX) = F
1
theorσexp(γ, xn) and σeval(γ, 2nX) = F
2
theorσexp(γ, xn), were obtained. The cross sections σeval(γ, nX) and σeval.(γ, 2nX) evaluated using the theoretically calculated functions F
1,2theor are consistent with the Livermore data, but substantially contradict the Saclay data. 相似文献
20.
Mahendra K. Verma 《Pramana》2003,61(3):577-594
Energy cascade rates and Kolmogorov’s constant for non-helical steady magnetohydrodynamic turbulence have been calculated
by solving the flux equations to the first order in perturbation. For zero cross helicity and space dimensiond = 3, magnetic energy cascades from large length-scales to small length-scales (forward cascade). In addition, there are energy
fluxes from large-scale magnetic field to small-scale velocity field, large-scale velocity field to small-scale magnetic field,
and large-scale velocity field to large-scale magnetic field. Kolmogorov’s constant for magnetohydrodynamics is approximately
equal to that for fluid turbulence (≈ 1.6) for Alfvén ratio 05 ≤r
A ≤ ∞. For higher space-dimensions, the energy fluxes are qualitatively similar, and Kolmogorov’s constant varies asd
1/3. For the normalized cross helicity σc →1, the cascade rates are proportional to (1 − σc)/(1 + σc , and the Kolmogorov’s constants vary significantly with σcc. 相似文献