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1.
The role of low density upflowing field-aligned electron beams (FEBs) on the growth rate of the electron cyclotron waves at
the frequencies ω
r < Ωe, propagating downward in the direction of the Earth’s magnetic field, has been analysed in the auroral region at ω
e/Ωe < 1 where ω
e is the plasma frequency and Ωe is the gyrofrequency. The FEBs with low to high energy (E
b) but with low temperature (T
‖b) have no effect on these waves. The FEBs with E
b < 1 keV and T
‖b (> 1.5 keV) have been found to have significant effect on the growth rate. Analysis has revealed that it is mainly the T
‖b which inhibits the growth rate (magnitude) and the range of frequency (bandwidth) of the instability mainly in the higher
frequency spectrum. The inhibition in the growth rate and bandwidth increases with increase in T
‖b. The FEBs with less E
b (giving drift velocity) reduce growth rate more than the beams with larger E
b. The inhibition of growth rate increases with the increase in the ratio ω
e/Ωe indicating that the beams are more effective at higher altitudes.
相似文献
2.
Three four-parameter potentials,U
I,U
II andU
III have been proposed and their accuracy has been demonstrated by finding the mean square deviation from the true RKR potential
curve for 15 electronic states of 12 diatomic molecules. Their percentage average mean square deviations from RKR curve have
been found to be 1.45, 1.86 and 2.89, respectively. These compare favourably with the value 2.67 for the recently suggested
four-parameter potential of Wei Hua which itself yields better results than the commonly employed three-parameter potentials.
The superiority of the new potentials (especially ofU
I andU
II has been further established by using these potentials to calculate the molecular constants αe and ωexe following Dunham’s method. The corresponding percentage average mean deviations, for αe, turn out to be 3.75, 5.13 and 15.43 and for ωexe 8.73, 17.23 and 27.49, respectively, against the respective values of 7.97 and 18.88 with Wei Hua’s four-parameter potential.
Also included are the values of dissociation energy determined with these potentials and these too corroborate the better
performance ofU
I andU
II. The relative worth of various potential functions has been further tested by carrying out numerical study of vibrational
partition function (evaluated by sum over states method), entropy and thermal capacity for the ground state of 7 molecules
and comparing these with the corresponding findings based on the RKR data. 相似文献
3.
Suresh Chandra 《Pramana》2005,65(6):1133-1137
Statement of Kaur and Mahajan [1] about the definition of Δ used by Chandra [2] is not correct. Even if we take Δ = μω
e
2
r
e
2
/2De, the relation between Δ and G(=8ωexe/Be) is obtained as Δ = 4.21452856G, provided the vibrational energy of a diatomic molecule is expressed in terms of limited
Dunham coefficients, Y10, Y20, Y01 and Y11. This relation is still different from that of Kaur and Mahajan [3] 相似文献
4.
We report the first observation of “quasi-Planck” spectra of capillary turbulence on the surface of liquid hydrogen in the
dissipation domain. Capillary waves have been driven by low-frequency random force. We have observed that the frequency spectrum
of surface elevation changes its dependence from power-like 〈|ηω2|〉 ∼ ω−2,8 at middle-frequency domain to “quasi-Planck” distribution ∼e
ω/ω
d
at higher frequencies. The frequency ω
d
is proportional to the boundary frequency between inertial interval and dissipation domain and it is scaled up with the increase
of driving force. 相似文献
5.
The value of adjustable parameterC in the four-parameter potentialU(r) =D
e [(1 - exp[-b(r -r
e)])/(1 -C exp[-b(r -r
e)])]2 has been expressed in terms of molecular parameters and its significance has been brought out. The potential so constructed,
withC derived from the molecular parameters, has been applied to ten electronic states in addition to the states studied by Wei
Hua. Average mean deviation for these 25 states has been found to be 3.47 as compared to 6.93, 6.95 and 9.72 obtained from
Levine, Varshni and Morse potentials, respectively. Also Dunham’s method has been used to express rotation-vibration interaction
constant (αe) and anharmonicity constant (ωexe) in terms ofC and other molecular constants. These relations have been employed to determine these quantities for 37 electronic states.
For αe, the average mean deviation is 7.2% compared to 19.7% for Lippincott’s potential which is known to be the best to predict
these values. Average mean deviation for (ωexe) turns out to be 17.4% which is almost the same as found from Lippincott’s potential function. 相似文献
6.
Suresh Chandra 《Pramana》2004,62(5):1181-1185
Kaur and Mahajan [1] have claimed to derive a universal relation InG = 1.91578(±0.09727) + 0.97111(±0.03809) In Δ between the Sutherland parameter Δ(=ω
er
e
2
/2De) and the dimensionless parameterG(= 8ω
exe/Be) for the ground as well as excited electronic states of diatomic molecules. Validity of this relation is checked and we find
that the relation is not correct. Next, we checked the validity of the relation Δ = 2.2re for the alkali group diatomic molecules. This relation is also found not to be correct. 相似文献
7.
8.
The dispersion relation of electromagnetic waves in the presence of magnetic monopoles of electron mass in a uniform magnetic
field is obtained. The waves of the frequencyω in the range ωϱi<Ωi<ω<Ω
e
<ωϱa are analysed. It is shown that the monopole charges lead to observable effects. Finally, the results are applied to a typical
pulsar. 相似文献
9.
The dissociation energy of twelve diatomic molecules has been determined by fitting four-parameter potential functionU(r)=D
e[[1−exp{−b(r−r
e)}]/ [1−Cexp{−b(r−r
e)}]]2 to the true Rydberg-Klein-Rees (RKR) curves for their fifteen electronic states using the mean square deviation as the criterion
for the selection of the best fit. Average deviation ofD
e has been found to be 2.7% as compared to 20.5% obtained with Lippincott’s potential function for these molecules. In addition
the anharmonocity constantω
exe has also been calculated for the same electronic states yielding average mean deviation 8.9%. 相似文献
10.
X. G. Wu M. J. Wan C. Q. Song T. Gao 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(2):263-267
Electronic structure and spectroscopic properties B
e, ωe, ωe
x
e, αe, T
e
of ground state and the low-lying excited states of HF+ and HF- molecular ions were
investigated within scalar relativistic multireference configuration
interaction with single and double excitations framework using the GAMESS-US
program package. All potential energy curves (PECs) were calculated using
the relativistic complete active space self-consistent field/spin-orbit
multi-configuration quasi-degenerate perturbation theory (CASSCF/SO-MCQDPT).
The curves are all fitted to the analytical potential energy function
(APEF), from which accurate spectroscopic constants are derived. The
spin-orbit splitting was also been studied, the split value of X2P^{2}{\rm \Pi} state of HF+ is determined to be 288.38 cm-1. The calculated properties are in good agreement with the available experimental value.
Spectroscopic constants of the ground states of HF- that have never
been observed in experiment are obtained. These curves provide an
interpretation of the known experimental observations on this system and
suggest a number of further experiments which possible provide a critical
test of this data. 相似文献
11.
The return current induced in a plasma by a relativisitc electron beam generates a new electron-ion two-stream instability
(return current instability). Although the effect of these currents on the beam-plasma e-e instability is negligible, there
exists a range of wave numbers which is unstable only to return current (RC) instability and not to e-e instability. The electromagnetic
waves propagating along the direction of the external magnetic field, in which the plasma is immersed, are stabilized by these
currents but the e.m. waves with frequencies,ω
2≪Ω
e
2
≪ω
pe
2
(Ω
e andω
pe being cyclotron and plasma frequency for the electrons of the plasma respectively) propagating transverse to the magnetic
field get destabilized. Heuristic estimates of plasma heating, due to RC instability and due to decay of ion-acoustic turbulence
generated by the return current, are made. The fastest time scale on which the return current delivers energy to the plasma
due to the scattering of ion-sound waves by the electrons can be ∼ω
pi
−1
(ω
pi being the plasma frequency for the ions). 相似文献
12.
L. Bartosch P. Kopietz 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):29-36
We consider the effect of Coulomb interactions on the average density of states (DOS) of disordered low-dimensional metals
for temperatures T and frequencies ω smaller than the inverse elastic life-time 1/τ. Using the fact that long-range Coulomb interactions in two dimensions (2d) generate ln2-singularities in the DOS ν(ω) but only ln-singularities in the conductivity σ(ω), we can re-sum the most singular contributions
to the average DOS via a simple gauge-transformation. If σ(ω) > 0, then a metallic Coulomb gapν(ω) ∝ |ω|/e
4 appears in the DOS at T = 0 for frequencies below a certain crossover frequency Ω
2 which depends on the value of the DC conductivity σ(0). Here, - e is the charge of the electron. Naively adopting the same procedure to calculate the DOS in quasi 1d metals, we find ν(ω) ∝ (|ω|/Ω
1)1/2exp(- Ω
1/|ω|) at T = 0, where Ω
1 is some interaction-dependent frequency scale. However, we argue that in quasi 1d the above gauge-transformation method is on less firm grounds than in 2d. We also discuss the behavior of the DOS at finite temperatures and give numerical results for the expected tunneling conductance
that can be compared with experiments.
Received 28 August 2001 / Received in final form 28 January 2002 Published online 9 July 2002 相似文献
13.
S. S. Murzin 《JETP Letters》2010,91(3):155-157
It has been shown that the observation of the transitions between the dielectric phase and the integer-quantum-Hall-effect
phases with the quantized Hall conductivity σ
xy
q ≥ 3e
2/h announced in a number of works is unjustified. In these works, the crossing points of the magnetic-field dependence of the
diagonal resistivity ρ
xx
at different temperatures T and ωcτ = 1 have been misidentified as the critical points of the phase transitions. In fact, these crossing points are due to the
sign change of the derivative dρ
xx
/dT owing to the quantum corrections to the conductivity. Here, ωc = eB/m is the cyclotron frequency, τ is the transport relaxation time, and m is the effective electron mass. 相似文献
14.
R. Mélin D. Feinberg 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):101-114
We derive a microscopic transport theory of multiterminal hybrid structures in which a superconductor is connected to several
spin-polarized electrodes. We discuss the non-perturbative physics of extended contacts, and show that such contacts can be
well represented by averaging out the phase of the electronic wave function. The intercontact Andreev reflection and elastic
cotunneling conductances are identical if the phase can be averaged out, namely in the presence of at least one extended contact.
The maximal conductance of a two-channel contact is proportional to (e
2/h)(a
0/D)2exp[-D/ξ(ω*)], where D is the distance between the contacts, a0 the lattice spacing, ξ(ω) is the superconducting coherence length, and ω* is the cross-over frequency between a perturbative regime ( ω < ω*) and a non perturbative regime ( ω* < ω < Δ).
Received 18 June 2001 and Received in final form 17 January 2002 相似文献
15.
The random matrix theory has been used for analyzing vibrational spectra of amorphous solids. The random dynamical matrix
M = AA
T
with nonnegative eigenvalues ɛ = ω2 has been investigated. The matrix A is an arbitrary square (N-by-N) real sparse random matrix with n nonzero elements in each row, mean values 〈A
ij
〉 = 0, and finite variance 〈A
ij
2〉 = V
2. It has been demonstrated that the density of vibrational states g(ω) of this matrix at N, n ≫ 1 is described by the Wigner quarter-circle law with the radius independent of N. For n ≪ N, this representation of the dynamical matrix M = AA
T
makes it possible in a number of cases to adequately describe the interaction of atoms in amorphous solids. The statistics
of levels (eigenfrequencies) of the matrix M is adequately described by the Wigner surmise formula and indicates the repulsion of vibrational terms. The participation
ratio of the vibrational modes is approximately equal to 0.2–0.3 almost over the entire range of frequencies. The conclusions
are in qualitative and, frequently, quantitative agreement with the results of numerical calculations performed by molecular
dynamics methods for real amorphous systems. 相似文献
16.
Rottereau M Gimel JC Nicolai T Durand D 《The European physical journal. E, Soft matter》2003,11(1):61-64
We present off-lattice Monte Carlo simulations of site-bond percolation of semi-penetrable spheres or, equivalently, of hard
spheres with a finite bond range. We will show that the crucial parameter is the effective volume fraction ( φe), i.e. the volume that is occupied or within the bond range of at least one particle. For the equivalent system of semi-penetrable
spheres 1 - φe is the porosity. The bond percolation threshold (p
b) can be described in terms of φe by a simple analytical expression: log(φe)/log(φec) + log(p
b)/log(p
bc) = 1, with p
bc = 0.12 independent of the bond range and φec a constant that decreases with increasing bond range.
Received: 10 March 2003 / Accepted: 23 April 2003 / Published online: 21 May 2003
RID="a"
ID="a"e-mail: jean-christophe.gimel@univ-lemans.fr 相似文献
17.
The coherent excitation of molecular vibrations in liquids via off-resonant stimulated Raman amplification is shown to consist of two parts with vastily different spectral and temporal properties. One component situated at the frequency difference
L
–e
S
of the driving fields follows almost instantaneously the system response function. The second part at the eigenfrequency e
0 carries information on the vibrational dephasing. Detecting both frequency components simultaneously by coherent anti-Stokes probe scattering a novel 2-channel method is demonstrated. The vibrational dephasing time of thev
3-mode of CH3I is directly measured to beT
2=2.6±0.15 ps. This result gives experimental support to the deconvolution techniques required in conventional spectroscopy. 相似文献
18.
Kotar M. Kijima 《Indian Journal of Physics》2011,85(1):201-204
The PHENIX experiment at RHIC has measured ω and ϕ meson production using di-electron decay mode over a psude-rapidity range of |η| ≤ 0.35 and a transverse momentum range of
0 < p
T
< 5 GeV/c in proton + proton collisions at $
\sqrt s
$
\sqrt s
= 200 GeV. The spectra of production cross section as a function of p
T
for ω and ϕ → e
+
e
− show good agreement with other hadornic decay channels ω → π
0
γ, ω
0
π
+
π
− and ϕ → K
+
K
−, respectively. 相似文献
19.
R. Hakalla R. Kępa W. Szajna M. Zachwieja 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(3):481-488
Three bands of the A1Π- X1Σ+ system
in the 12CH+ ion radical have been rephotographed under
high resolution as an emission spectra using a Geissler-type
discharge tube. The conventional technique of spectroscopy has
been implemented. Using the Th lines as a standards, as well as an
interferometric comparator equipped with a photoelectric scanning
device, the 0-0 , 0-1 and 2-1 bands have been
reanalyzed. By means of much longer bands (Jmax = 17 in the
Q(J) branch of the 0-0 band; Jmax = 16 in the R(J)
branch of the 0-1 band; Jmax = 14 in the P(J) and
Q(J) branches of the 2-1 band), than have been observed so
far, as well as the merged calculations, using another five bands
given by Carrington et al. [A. Carrington, D.A. Ramsay, Phys.
Scripta 25, 272 (1982)] additionally, more accurate molecular
constants for the X1Σ+ state, the improved reduced
band system origin Te = 24118.726 (14) cm-1 as well as for
the first time the equilibrium molecular constants with their one
standard deviation for the A1Π state in the CH+ molecule
have been computed: ωe'=1864.402(22),
ωexe'=115.832(14), ωeye'= 2.6301(24),
Be'=11.88677(72), αe'= 0.9163(18), γe'=
-2.29(12)×10-2, εe'= 4.95(20)×10-3,
De'=1.92960(31)×10-3, βe'=
1.0733(50)×10-4, δe'= -1.312(16)×10-5,
, αqe'=
-3.14(16)×10-3, and qDe'= -2.20(14)×10-5
cm-1. Only in our research the addition to the zero-point
energy Y'00=-1.9430 cm-1 and
cm-1
have been calculated. The equilibrium bond lengths of
r'e=1.235053(37) ? and
? for the
A1Π and X1Σ+ states, respectively have been
computed. Full quantum-mechanics characteristic of the A-X
bands system in the 12CH+ molecule, i.e. RKR turning
points, the Franck-Condon factors and r-centroids have been
obtained. Dissociation energies DeX1 Σ+=(38470±
3503) cm-1 and DeA1 Π= (14415 ±3509) cm-1
for the molecule under consideration have been estimated. 相似文献
20.
The microwave photoresistance of a double GaAs quantum well with two occupied size-quantization sub-bands E
1 and E
2 has been studied at the temperatures T = 1.6–4.2 K in the magnetic fields B < 0.5 T. The microwave photoresistance of such a system has been found to have a maximum amplitude when the maximum of the
magneto-intersubband oscillations with the number k = (E
2 − E
1)ℏωc coincides with the maximum or minimum of the ω/ωc oscillations, where ω is the microwave frequency and ωc is the cyclotron frequency. It has been shown that the resonance photoresistance that appears in the kth maximum of the magneto-intersubband oscillations is determined by the condition ℏω/(E
2 − E
1) = (j ± 0.2)/k, where k and j are positive integers. 相似文献