共查询到20条相似文献,搜索用时 31 毫秒
1.
K. R. Allakhverdiev M. Ö. Yetis T. K. Baykara S. M. T. Özbek E. Yu. Salaev 《Laser Physics》2011,21(3):598-600
Two methods of preparation of the devices for visualization of pulsed and continuous near-IR (near infrared) are described
and the results of conversion of pulsed and continuous IR (800–1360 nm) laser radiation into the visible range of spectra
(400–680 nm) by using a transparent substrate covered with the particles (including nanoparticles) of effective nonlinear
materials of GaSe
x
S1 − x
(0.2 ≤ x ≤ 0.8) are presented. Converted light can be detected in transmission or reflection geometry as a visible spot corresponding
to the real size of the incident laser beam. Developed device structures can be used for checking if the laser is working
or not, for optical adjustment, for visualization of distribution of laser radiation over the cross of the beam and for investigation
of the content of the laser radiation. Low energy (power density) limit for visualization of the IR laser pulses with 2–3
ps duration for these device structures are: between 4.6–2.1 μJ (3 × 10−4−1 × 10−4 W/cm2) at 1200 nm; between 8.4–2.6 μJ (4.7 × 10−4−1.5 × 10−4 W/cm2) at 1300 nm; between 14.4–8.1 μJ (8.2 × 10−4–4.6 × 10−4 W/cm2) at 1360 nm. Threshold damage density is more than 10 MW/cm2 at λ = 1060 nm, pulse duration τ = 35 ps. The results are compared with commercially existing laser light visualizators. 相似文献
2.
Chen Li-chuan A. Rabenau W. Weppner 《Applied Physics A: Materials Science & Processing》1978,17(3):233-237
The ionic and electronic conductivities of Ag2Tl6I10 single crystals have been studied as a function of crystallographic orientation and temperature from 20 to 135°C. EMF as
well as AC and DC techniques have been employed. The highly anisotropic material is predominantly an Ag+-ion conductor parallel toc-direction, with the Ag+ ions moving through linear channels that are not interconnected. The conductivity σ‖c
=1.6×10−7Ω−1cm−1 at 25°C, with an activation enthalpy for σ‖c
of 0.38 eV. The conduction perpendicular toc-direction has been found to be predominantly electronic with a value of σ⊥c
=3×10−9Ω−1cm−1 at 25°C and an activation enthalpy for σ⊥c
of 0.64 eV. This is the first observation of one-dimensional Ag+ conduction and this type of orientation-dependent change from ionic to electronic conduction.
On leave from Institute of Physics, Academia Sinica, Peking, China. 相似文献
3.
D. I. Stasel’ko S. A. Tikhomirov O. V. Buganov A. S. Shcheulin A. E. Angervaks A. I. Ryskin 《Optics and Spectroscopy》2011,110(1):33-41
The kinetics of photoinduced absorption spectra of CdF2 crystals with bistable indium and gallium centers under femtosecond pulsed excitation has been experimentally investigated.
Based on the example of indium ions, it is shown that the transmission band in the absorption spectrum of deep centers is
formed for 0.8–1 ps, which significantly exceeds the photon absorption time. This process is interpreted as a result of displacement
of indium ion from the initial interstitial position to a site of neighboring unit cell; the displacement velocity is estimated
to be 200–250 m/s, a value close to the thermal velocity of this ion at room temperature. The times characteristic of the
formation of free polarons as a result of the displacement of neighboring lattice ions have been experimentally estimated
for the first time at a level of 0.8–1.2 ps. The capture times of free polarons by trivalent gallium and indium ions are estimated
(5 and 10 ps, respectively), as well as the corresponding cross sections (2 × 10−16 and 8 × 10−16 cm2). 相似文献
4.
H. Zacharias R. Schmiedl K. H. Welge 《Applied Physics A: Materials Science & Processing》1980,21(2):127-133
State and isotope selective two-step photoionization of NO with mass spectroscopic ion detection has been demonstrated and
investigated. Using saturation condition the photoionization cross section for a single rotational level of the intermediate
state, No(A
2Σ+, ν′=0), has been measured: σi=(7.0±0.9) X 10−19 cm2. The charge transfer15NO++14NO→15NO+14NO+ has been observed and investigated, yielding a cross section of the order of 13×10−16 cm2, consistent with recent measurements at about 1 eV. 相似文献
5.
M. Bryushinin V. Golubev Y. Kumzerov D. Kurdyukov I. Sokolov 《Applied physics. B, Lasers and optics》2009,95(3):489-495
We report an experimental investigation of the non-steady-state photoelectromotive force in nanostructured GaN within porous
glass and polypyrrole within chrysotile asbestos. The samples are illuminated by an oscillating interference pattern created
by two coherent light beams and the alternating current is detected as a response of the material. Dependences of the signal
amplitude versus temporal and spatial frequencies, light intensity, and temperature are studied for two wavelengths λ=442 and 532 nm. The conductivity of the GaN composite is measured: σ=(1.1–1.6)×10−10 Ω−1 cm−1 (λ=442 nm, I
0=0.045–0.19 W/cm2, T=293 K) and σ=(3.5–4.6)×10−10 Ω−1 cm−1 (λ=532 nm, I
0=2.3 W/cm2, T=249–388 K). The diffusion length of photocarriers in polypyrrole nanowires is also estimated: L
D=0.18 μm. 相似文献
6.
L. Pintilie I. Pintilie D. Petre T. Botila M. Alexe 《Applied Physics A: Materials Science & Processing》1999,69(1):105-109
Thermally stimulated current (TSC) measurements performed in the 100 K–400 K temperature range on Bi4Ti3O12 (BiT) thin films annealed at 550 °C and 700 °C had revealed two trapping levels having activation energies of 0.55 eV and
0.6 eV. The total trap concentration was estimated at 1015 cm−3 for the samples annealed at 550 °C and 3×1015 cm−3 for a 700 °C annealing and the trap capture cross-section was estimated about 10−18 cm2. From the temperature dependence of the dark current in the temperature range 20 °C–120 °C the conduction mechanism activation
energy was found to be about 0.956–0.978 eV. The electrical conductivity depends not only on the sample annealing temperature
but also whether the measurement is performed in vacuum or air. The results on the dark conductivity are discussed considering
the influence of oxygen atoms and oxygen vacancies.
Received: 28 January 1998 / Accepted: 8 January 1999 / Published online: 5 May 1999 相似文献
7.
This paper reports on a study of the electron-stimulated desorption of negative oxygen ions from the O/Ru surface, which represents
an additional factor responsible for the destruction of the protective oxide layer of the mirrors used in ultraviolet lithography.
The cross section of degradation of the O/Ru layer due to the electron-stimulated desorption of the O+ and O− ions and the O atoms has been found to be 1.6 × 10−19 cm2. A comparison of the dependences of the electron-stimulated desorption yield of O+ and O− ions on the incident electron energy E with the ionization cross section of the adsorbate core level σ
O2s
(E) has revealed that the ionization of the O 2s level is the main channel of the electron-stimulated desorption of O− ions. 相似文献
8.
L. P. Avakyants V. S. Gorelik É. M. Temper S. M. Shcherbina 《Physics of the Solid State》1999,41(8):1369-1372
Structure in the Raman scattering spectra of near-surface n-GaAs layers (n=2×1018 cm−3) implanted with 100 keV B+ ions in the dose range 3.1×1011–1.2×1014 cm−2 is investigated. The qualitative and quantitative data on the carrier density and mobility and on the degree of amorphization
of the crystal lattice and the parameters of the nanocrystalline phase as a result of ion implantation are obtained using
a method proposed for analyzing room-temperature Raman spectra.
Fiz. Tverd. Tela (St. Petersburg) 41, 1495–1498 (August 1999) 相似文献
9.
The temperature dependence of the electrical conductivity, thermoelectric power and dielectric constant of the antiferromagnetic
CuWO4 have been studied in the temperature range 300–1000 K. The conductivity results can be summarised by the equations σI=6.31 × 10−3 exp (−0.29 eV/kT) ohm−1 cm−1 in the temperature range 300–600 K and σII=3.16 × 105 exp (−1.48 eV/kT) ohm−1 cm−1 between 600 K and 1000 K. The thermoelectric power can be expressed byθ=[− 1.25 (103/T) + 3.9] mV/K. Initially dielectric constant increases slowly but for high temperatures its increase is fast. 相似文献
10.
The trielectronic recombination of an In+ (4d
105s
2
1
S
0) ion in collisions with slow electrons, including the two-electron excitation of the 5s2 core of the ion with the simultaneous capture of the triply excited 5p
3 intermediate autoionizing state with its subsequent radiative stabilization 5p
3 → 5s5p
2 + hν has been detected and experimentally examined for the first time. The maximum effective cross section of trielectronic recombination
is 1.6 × 10−16 cm2, which is comparable to the effective cross sections for both dielectronic recombination and electron excitation of the In+ ion. 相似文献
11.
R. Castro-Beltran G. Ramos-Ortiz C. K. W. Jim J. L. Maldonado M. H?u?ler D. Peralta-Dominguez M. A. Meneses-Nava O. Barbosa-Garcia B. Z. Tang 《Applied physics. B, Lasers and optics》2009,97(2):489-496
The nonlinear optical properties of a hyperbranched polyyne (hb-Polyyne) have been measured at infrared wavelengths by using femtosecond and nanosecond pulsed excitation. This hyperbranched
polyyne exhibited strong and intrinsic (simultaneous) two-photon absorption and upconverted blue fluorescent emission under
femtosecond excitation around 800 nm. The hb-Polyyne in chloroform solution is characterized by a large two-photon absorption cross section of 9068 GM (1GM=10−50 cm4 s) and a fluorescence quantum yield of 0.57. On the other hand, by third-harmonic generation (THG) spectroscopy with nanosecond
excitation, the measured third-order nonlinear susceptibility χ
(3) for solid films of hb-Polyyne ranged from 2.4×10−11 to 6.1×10−11 esu in the spectral range of 1100–1600 nm, with results comparable to the values exhibited by the well-known conjugated polymer
MEH:PPV, but with a much better transparency for visible wavelengths. 相似文献
12.
H. Kim A. Cepler C. Cetina D. Knies M. S. Osofsky R. C. Y. Auyeung A. Piqué 《Applied Physics A: Materials Science & Processing》2008,93(3):593-598
Present p-type ZnO films tend to exhibit high resistivity and low carrier concentration, and they revert to their natural n-type state
within days after deposition. One approach to grow higher quality p-type ZnO is by codoping the ZnO during growth. This article describes recent results from the growth and characterization
of Zr–N codoped p-type ZnO thin films by pulsed laser deposition (PLD) on (0001) sapphire substrates. For this work, both N-doped and Zr–N
codoped p-type ZnO films were grown for comparison purposes at substrate temperatures ranging between 400 to 700 °C and N2O background pressures between 10−5 to 10−2 Torr. The carrier type and conduction were found to be very sensitive to substrate temperature and N2O deposition pressure. P-type conduction was observed for films grown at pressures between 10−3 to 10−2 Torr. The Zr–N codoped ZnO films grown at 550 °C in 1×10−3 Torr of N2O show p-type conduction behavior with a very low resistivity of 0.89 Ω-cm, a carrier concentration of 5.0×1018 cm−3, and a Hall mobility of 1.4 cm2 V−1 s−1. The structure, morphology and optical properties were also evaluated for both N-doped and Zr–N codoped ZnO films. 相似文献
13.
This paper discusses the pulsed electron conductivity σ of KCl, KBr, and NaCl crystals when they are excited by an electron beam (0.2 MeV, 50 ps) with current densities in the interval
j=(30–104) A/cm2. It is shown that the lifetime of the electrons in the conduction band is τ≪100 ps. To explain the experimental σ(j) dependences, a model is proposed that includes electron capture by structural defects and stable radiation defects at low
excitation densities and electron capture predominantly by unstable radiation defects generated by the excitation pulse at
high excitation densities.
Fiz. Tverd. Tela (St. Petersburg) 41, 1200–1203 (July 1999) 相似文献
14.
The absorption spectra, fluorescence spectrum and fluorescence decay curve of Nd3+ ions in CaNb2O6 crystal were measured at room temperature. The peak absorption cross section was calculated to be 6.202×10−20 cm2 with a broad FWHM of 7 nm at 808 nm for E//a light polarization. The spectroscopic parameters of Nd3+ ions in CaNb2O6 crystal have been investigated based on Judd-Ofelt theory. The parameters of the line strengths Ω
t
are Ω
2=5.321×10−20 cm2,Ω
4=1.734×10−20 cm2,Ω
6=2.889×10−20 cm2. The radiative lifetime, the fluorescence lifetime and the quantum efficiency are 167 μs, 152 μs and 91%, respectively. The fluorescence branch ratios are calculated to be β
1=36.03%,β
2=52.29%,β
3=11.15%,β
4=0.533%. The emission cross section at 1062 nm is 9.87×10−20 cm2. 相似文献
15.
A. Benninghoven D. Jaspers W. Sichtermann 《Applied Physics A: Materials Science & Processing》1976,11(1):35-39
Secondary-ion mass spectroscopy (SIMS) is a hydrogen, isotope and compound sensitive analytical technique of extremely high
absolute sensitivity. Continuing earlier measurements for carboxylic acids, adsorbed alcohols etc., we have carried out a
systematical investigation of secondary-ion emission from metal-supported amino acids, containing various functional groups
(e.g., alanine, phenylalanine, cysteine, arginine). In order to avoid damage effects we applied extremely small primary-ion
current densities in the 10−9 A·cm−2 range.
The main results of our investigations can be summarized as follows:
相似文献
– | - All investigated amino acids produce high-intensity secondary-ion parent peaks (M+1)+ and (M−1)−. |
– | - In addition positive as well as negative fragment ions representative for the different functional groups are emitted with high yields. |
– | - For 2.5 keV Ar+-ions the absolute yields for the parent ions and the most important fragment ions are in the range of 0.1; the damage cross section is >10−14 cm2 for all investigated acids. The resulting absolute sensitivities are below 10−6 of one monomolecular layer or <10−12 g. |
16.
The total cross sections for positron impact on hydrocarbons have been calculated using the additivity rule in which the total
cross section for a molecule is the sum of the total cross section for the constituent atoms. The energy range considered
is from a few eV to several thousand eV. The total cross sections for positron impact on an atom are calculated by employing
a complex spherical potential which comprises of a static, polarization and an absorption potential. We have good agreement
with the experimental results for hydrocarbons for positron energy ⩾100 eV. Our results also agree with the available calculations
for CH4 and C2H2 which employed full molecular wavefunctions beyond 100 eV. Our absorption cross sections also agree with molecular wave-function
calculations for C2H2 and CH4 beyond 100 eV. We have shown the Bethe plots fore
+−C ande
+−H scattering systems and Bethe parameters have been extracted. We have fitted the cross section for positron impact on hydrocarbons
in the formσ
t(C
n
H
m
)=naE
−
b+mcE
−
d in the energy range 300–5000 eV wherea=195.0543,b=0.7986,c=371.1757 andd=1.1379 withE in eV andσ
t in 10−16 cm2. 相似文献
17.
In this paper we report on measurements of spin-flip-Raman gain inn-InSb as a function of the magnetic field. The measurements were carried out at temperatures of 1.8 K and 4.2 K and at a carrier
concentration of 1.35×1015 cm−3. The Raman cross sections obtained from these results, e.g. 1.25×10−20 cm2/sr at a magnetic field of 10 kG and a pump frequency of 1884.35 cm−1, agree very well with those theoretically predicted by Wherrett and Wolland.
Furthermore, these measurements yield line shapes and linewidths of the spontaneous scattering (100–1500 MHz) and allow the
determination of the effectiveg-value with an accuracy known from ESR-investigations. These results are discussed in terms of already published theoretical
investigations. 相似文献
18.
U. Heinzmann D. Schinkowski H. D. Zeman 《Applied Physics A: Materials Science & Processing》1977,12(1):113-113
The results of the measured absolute photoionization cross section from the 72
P excited states of cesium are reported. The following values have been obtained: (6.2±0.5)×10−18 cm2 and (8.8±1.6)×10−18 cm2 for the levels 72
P
1/2 and 72
P
3/2, respectively. 相似文献
19.
A. K. Dharmadhikari J. A. Dharmadhikari D. Mathur 《Applied physics. B, Lasers and optics》2009,94(2):259-263
Filamentation occurs within a 1.5 cm-long crystal of BaF2 during the propagation of intense, ultrashort (40 fs) pulses of 800 nm light; a systematic study as a function of incident
power enables us to extract quantitative information on laser intensity within the condensed medium, the electron density
and the six-photon absorption cross section. At low incident power, a single filament is formed within the crystal; two or
more filaments are observed along the direction transverse to laser propagation at higher incident powers. Further, due to
fluorescence from six-photon absorption (6PA), we are able to map the intensity variation in the focusing–refocusing cycles
along the direction of laser propagation. At still higher incident powers, we observe splitting of multiple filaments. By
measuring the radius (L
min ) of single filament inside BaF2, we obtain estimates of peak intensities (I
max ) and electron densities (ρ
max ) to be 3.26×1013 W cm−2 and 2.81×1019 cm−3, respectively. Use of these values enables us to deduce that the 6PA cross-section in BaF2 is 0.33×10−70 cm12 W−6 s−1. 相似文献
20.
S. I. Pesotskii R. B. Lyubovskii P. Behm W. Biberacher K. Andres M. V. Kartsovnik A. E. Kovalev T. G. Togonidze J. A. A. J. Perenboom N. D. Kushch R. N. Lyubovskaya E. I. Zhilyaeva 《Journal of Experimental and Theoretical Physics》1998,87(3):621-627
We study quantum (Shubnikov-de Haas and de Haas-van Alphen) oscillations and angular oscillations of the reluctance in the
organic quasi-two-dimensional metal (BO)2Clx(H2O)y. We show that the Fermi surface in this compound consists of a slightly corrugated cylinder with its axis perpendicular to
the conducting plane. The cross section of the cylinder in this plane is a perfect circle of radius k
F≃3×107 cm−1. The effective carrier mass associated with this cylinder is m*=(1.65–2.0) m
0 in the conducting plane, while the Dingle temperature is T
D=3–4 K.
Zh. éksp. Teor. Fiz. 114, 1137–1146 (September 1998) 相似文献