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1.
Y.?C.?Zhong K.?S.?Wong A.?B.?Djuri?i? Y.?F.?Hsu 《Applied physics. B, Lasers and optics》2009,97(1):125-128
Two-photon excited photoluminescence (PL) measurements have been carried out on an individual ZnO tetrapod at low temperature
(8 K) using femtosecond laser pulses in the wavelength range of 714–850 nm. Simultaneously PL and second-harmonic generation
were observed. The integrated PL intensity excitation spectrum at different two-photon excitation frequencies has eight peaks,
which are in good correspondence to the exciton-phonon complexes L1b
, L1a
, and the free exciton lines B
n=3, A
n=3, B
n=2, A
n=2, B
n=1, and A
n=1 seen in ZnO film. This technique can be used to measure the optical transitions in individual nanostructures, which is very
difficult to achieve using the traditional transmission/reflection method. 相似文献
2.
Kinetic, spectral, intensity, angular, and polarization of resonant two-photon absorption (TPA) in β-CdP2 has been investigated. Resonant TPA was observed for which the total energy of the two photons was 2.60 eV. It is shown that
resonant TPA takes place via a real intermediate level d
3 in the band gap at the depth E
c-0.86 eV. The electron transverse relaxation time for resonant TPA, the cross section for absorption of laser photons in d
3→C transitions, the equilibrium population of d
3 centers in a doped n-type sample, and the resonant TPA constant were determined as 4.3×10−14 s, 1.25×10−17 cm2, 0.95, and 0.028 cm/MW, respectively.
Fiz. Tverd. Tela (St. Petersburg) 40, 1252–1256 (July 1998) 相似文献
3.
Studying the ω<Emphasis Type="Italic">N</Emphasis> elastic and inelastic cross section with nucleons
Ye.S. Golubeva W. Cassing L.A. Kondratyuk A. Sibirtsev M. Büscher 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):271-277
We explore the possibility to measure the elastic and inelastic ωN cross section in p+d→d+ω+p
sp and p+A reactions. Our studies indicate that the elastic scattering cross sections can be determined for ω momenta above 1 GeV/c
in p+d reactions by gating on high proton spectator momenta whereas the ωN absorption cross section down to low relative ω momenta is most effectively studied in p+A reactions at beam energies 2.0–2.7 GeV.
Received: 15 October 1999 相似文献
4.
5 s; the polarizing field was varied from 10 V/cm to 10 kV/cm, and the temperature between -190 °C and 25 °C.
The results confirm that the depolarization current in TGS follows the formula Id∼[(ωpt)n+(ωpt)m]-1, where n<1 and m>1. The values of the parameters n and m depend on both the electric field strength and the polarization
time as well as on the temperature of the experiment. The loss peak frequency ωp exhibits activation character: ωp∼exp(-E/kBT) with E=0.34 eV at temperatures directly below room temperature and E=0.013 eV in the range of liquid nitrogen temperatures.
Received: 1 April 1997/Accepted: 7 April 1997 相似文献
5.
K. P. Meletov A. A. Maksimov I. I. Tartakovskii 《Journal of Experimental and Theoretical Physics》1997,84(1):144-150
Measurements have been made of the Raman, optical absorption, and luminescence spectra of single crystals and pellets of the
fullerite C70 at T=300 K and at pressures up to 12 GPa. The baric shift dω/dP and the Grüneisen parameters of the Raman-active intramolecular phonon modes have been determined. It has been established
that the d
ω/dP value for certain phonon modes abruptly changes at pressures of P
1≈2 GPa and P
2≈5.5 GPa, as do the half-widths of the Raman lines. These features in the Raman spectrum are associated with phase transitions
at high pressure. The baric shifts of the absorption and luminescence edges of C70 crystals have been determined and are −0.12 eV/GPa and −0.11 eV/GPa, respectively, for absorption and luminescence. The baric
shift of the absorption edge decreases significantly with increasing pressure and is −0.03 eV/GPa at 10 GPa. These data have
been used to determine the deformation potential of the fullerite C70, which is about 2.1±0.1 eV.
Zh. éksp. Teor. Fiz. 111, 262–273 (January 1997) 相似文献
6.
Nonreciprocal birefringence due to magnetically induced spatial dispersion was observed in the T
d-class cubic semiconductors ZnTe, CdTe, and GaAs near the fundamental absorption edge. The dispersion of the parameters A and g, describing the contributions from terms of the type B
ikj to the diagonal and off-diagonal components of the permittivity tensor ε
ij(ω,B,k), is determined for ZnTe and CdTe. Analysis of the dispersion and anisotropy of the nonreciprocal birefringence shows that
in ZnTe, CdTe, and GaAs, in contrast to magnetic semiconductors of the type Cd1−x
MnxTe, it is due excitonic mechanisms.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 7, 514–519 (10 April 1999) 相似文献
7.
An analytic expression for the transmission coefficient as a function of the foil thickness d describing penetration of intense femtosecond laser pulses through ultra-thin foils with a thickness of the order of 30–100
nm is derived using the Vlasov-Boltzmann equation. It is found that the transmission of laser radiation stops at the skin
depth c/ω
p
, but sharp and narrow resonances occur for the foil thickness d > c/ω
p
with the transmission coefficient T = 1.
The article is published in the original. 相似文献
8.
J. K. Baria 《Czechoslovak Journal of Physics》2004,54(4):469-485
A model pseudopotential depending on an effective core radius but otherwise parameter free is used to study the interatomic
interactions, phonon dispersion curves (inq and r-space analysis), phonon density of states, mode Grüneisen parameters, dynamical elastic constants (C
11,C
12 andC
44), bulk modulus (B), shear modulus (C′), deviation from Cauchy relation (C
12–C
44), Poisson’s ratio (σ), Young’s modulus (Y), behavior of phonon frequencies in the elastic limit independent of the direction (Y
1), limiting value in the [110] direction (Y
2), degree of elastic anisotropy (A), maximum frequencyω
max, mean frequency 〈ω〉, 〈ω
2〉1/2=(〈ω〉/〈ω
−1〉)1/2, fundamental frequency 〈ω
2〉, and propagation velocities of the elastic constants in Cu, Ag, Au, Ni, Pd, and Pt. The contribution of s-like electrons
is calculated in the second-order perturbation theory for the model potential while that of d-like electrons is taken into
account by introducing repulsive short-range Born-Mayer like term. Very recently proposed screening function due to Sarkar
et al. has been used to obtain the screened form factor. The theoretical results are compared with experimental findings wherever
possible. A good agreement between theoretical investigations and experimental findings has proved the ability of our model
potential for predicting a large number of physical properties of transition metals. 相似文献
9.
B. Lalevic N. Fuschillo B. Kuliyev W. Wang 《Applied Physics A: Materials Science & Processing》1974,5(2):127-132
Transport and dielectric properties of polycrystalline CoO films were studied as functions of the applied field, frequency
and temperature. TheI–V plots showed that the Poole-Frenkel field emission mechanism is responsible for conduction at fields>105 V/cm. The ac conductivity σ(ω), the imaginary part of the dielectric constantε
2, and tan δ plots as functions of frequency revealed three dispersion regions. The σ(ω) andε
2 frequency dependence indicates a non-adiabatic hopping of charge carriers at low frequencies and adiabatic hopping at high
frequencies. The activation energy of a dielectric oscillator is 0.15 eV.
Work supported by the Office of Naval Research. 相似文献
10.
A new mechanism of a “Coulomb explosion,” where ions are accelerated by the electric field separating charges at the magnetic
Debye radius r
B∼B/4πen
e, is proposed on the basis of a nonquasineutral model of electronic vortices in a magnetic field. It is shown by means of
numerical calculations that in the process of acceleration of the ions a collisionless shock wave, whose front has an effective
width of the order of δ∼r
B, determined by the breakdown of quasineutrality, is formed in a time of the order of ω
pi
−1
, where ωpi is the ion plasma frequency. The origin of such explosive dynamics is the formation of “holes” in the electron density at
characteristic times of the order of ω
pe
−1
(ωpe is the electronic plasma frequency) as a result of the generation of electronic vorticity by the Weibel instability of an
electromagnetic wave. Calculations for a laser pulse with intensity J∼6×1018 W/cm2 show that the ions expand in the radial direction with velocities up to 3.5×108 cm/s.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 10, 669–674 (25 November 1999) 相似文献
11.
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
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.
R.B. López-Martens T.W. Schmidt G. Roberts 《Applied physics. B, Lasers and optics》2002,74(6):577-581
The cycle-averaged ac Stark effect associated with the [
A
]2Σ+v′=2?[
X
]2Π1/2v′=0 two-photon absorption of NO at intensities between 7.7 and 15.2 TW cm-2 has been characterized in real time through a synergic combination of bichromatic laser experiments and quantum-dynamics
calculations. Measurements of the fluorescence emitted by the Rydberg [
A
]2Σ+v′=2 level as a function of time between Stark and probe components of a bichromatic field exhibit a characteristic evolution
in temporal peak structure with Stark-field intensity, which is interpreted in terms of a time-dependent Floquet analysis
of the laser–matter interaction. The experimental observations are consistent with a dynamic Stark shift of Δεs(ω1,ω2)≤0.23 eV of the optical transition at these intensities.
Received: 18 January 2002 / Revised version: 6 March 2002 / Published online: 24 April 2002 相似文献
14.
L. Gao X. P. Yu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):403-409
We derive expressions for the effective nonlinear susceptibility
tensors for both the second harmonic generation (SHG) and induced
third harmonic generation (THG) of nonlinear composite materials,
in which nondilute coated particles with radial dielectric
anisotropy are randomly embedded in the linear host. Two types of
coated particles are considered. The first is that the core
possesses a second order nonlinear susceptibility and the shell is
linear and radially anisotropic, while the second is that the
core is linear with radial anisotropy and the shell has a second
order nonlinear susceptibility. We observe greatly enhanced SHG
and THG susceptibilities at several surface plasmon resonant
frequencies. For the second model, due to the coating material
being metallic, there exists two fundamental resonant frequencies
ωc1 and ωc2, whose difference
ωc2-ωc1 is strongly dependent on the interfacial
parameter and the radial dielectric anisotropy. Furthermore, in
both systems, the adjustment of the dielectric anisotropy results
in larger enhancement of both SHG and induced THG susceptibilities
at surface plasmon resonant frequencies than the corresponding
isotropic systems. Therefore, both the core-shell structure and
the dielectric anisotropy play important roles in determining the
nonlinear enhancement and the surface resonant frequencies. 相似文献
15.
A. I. Alekseev 《Journal of Experimental and Theoretical Physics》1997,84(1):35-50
The properties of the density matrix and the multipole moments arising in oriented and aligned atoms with zero nuclear spin
through the interaction with strong resonant ultrashort pulses with wave vector k
0 and circular or linear polarization have been found. Calculations have been made for the time-dependent light-induced magnetization
μ(t′) of a gas of pre-oriented and prealigned atoms following the passage of a weak resonant elliptically polarized pulse with
frequency ω and wave vector k collinear with k
0. It is shown that for oriented atoms, μ(t′) is an even function of the detuning from resonance, ω-ω
ba, and can be split into two terms whose directions are a consequence of symmetry and are determined by the vectors k
0 and k as well as by the direction of rotation of the electric fields corresponding to the pulses. For aligned atoms the vector
μ(t′) is collinear with k, and the first term is an even function of ω-ω
ba. However, the second term is an odd function of ω-ω
ba and reverses direction when the sign of ω-ω
ba changes, as well as when the orientation of the axes of the polarization ellipse is changed. It is shown that if a series
of weak linearly polarized pulses pass through the gas, the light-induced magnetization of the oriented and aligned gas atoms
can be decomposed into three factors: the first determines the direction and is a consequence of the symmetry; the second
(with the dimensions of magnetic moment) depends on the characteristics of the resonant transitions; and the third is a universal
function of t′ and ω-ω
ba that does not depend on the underlying characteristics of the resonant transition. These vector factors and the universal
functions are in principle different for oriented and aligned atoms.
Zh. éksp. Teor. Fiz. 111, 63–92 (January 1997) 相似文献
16.
We consider a magnetic Laplacian −Δ
A
= (id + A)* (id + A) on a non-compact hyperbolic surface M with finite area. A is a real one-form and the magnetic field dA is constant in each cusp. When the harmonic component of A satisfies some quantified condition, the spectrum of −Δ
A
is discrete. In this case, we prove that the counting function of the eigenvalues of −Δ
A
satisfies the classical Weyl formula, even when dA=0. 相似文献
17.
A. V. Derbin A. I. Egorov I. A. Mitropol’sky V. N. Muratova D. A. Semenov E. V. Unzhakov 《The European Physical Journal C - Particles and Fields》2009,62(4):755-760
A search for resonant absorption of 14.4 keV solar axions by a 57Fe target was performed. The Si(Li) detector placed inside the low-background setup was used to detect the γ-quanta appearing in the deexcitation of the 14.4 keV nuclear level: A+57Fe→57Fe*→57Fe+γ. The new upper limit for the hadronic axion mass has been obtained of m
A
≤159 eV (95% c.l.) (S=0.5, z=0.56). 相似文献
18.
19.
Kinetic, spectral, intensity, angular, and polarization studies of resonant two-photon absorption (RTPA) in β-CdP2 have been carried out. RTPA was observed with 2.60 eV total energy of the two quanta. It was found that RTPA occurs through
a real intermediated level which lies in the forbidden band at a depthE=0.86 eV. The transverse electron relaxation time during RTPA, the cross section for absorption of laser radiation quanta
ind
3→C transitions, the equilibrium population of thed centers forn type doped samples, and the RTPA constant were determined to be 4.3 · 1014 sec, 1.25 · 10−17 cm, 0.95, and 0.028 cm/MW respectively.
Ukrainian State Pedagogical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 1, pp.
21–26, January, 1999. 相似文献
20.
Influence of the reagent vibration on the stereo-dynamics of the reactions D- + H2 and H- + D2 下载免费PDF全文
Employing the quasi-classical trajectory method and the potential energy surface of Panda and Sathyamurhy [Panda A N and Sathyamurthy N 2004 J. Chem. Phys. 121 9343], the effect of the reagent vibration on vector correlation of the ion-molecule reactions D- + H2 and H- + D2 is studied at a collision energy of 35.7 kcal/mol. Four generalized polarization-dependent differential cross sections (2π/σ)(dσ00/dωt),(2π/σ)(dσ20/dωt),(2π/σ)(dσ22/dωt), and (2π/σ)(dσ20/dωt) are presented in the centre-of-mass reference frame, separately. At the same time, the effects on the product angular distributions P(θr), P(φr) and P(θr,φr) of the title reactions are also analysed. The calculated results show that the scattering tendencies of the product HD, the alignment and the orientation of j' sensitively depend on reagent molecule vibration. 相似文献