共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Lecointre D. S. Belic J. J. Jureta R. Janev P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,50(3):265-278
Absolute cross sections for electron-impact dissociative excitation and
ionization of CD+
4 leading to formation of ionic products (CD2+
4, CD+
3, CD+
2, CD+, C+, D+
3, D+
2, and D+) have been measured. The animated crossed-beams
method is applied in the energy range from the reaction threshold up to 2.5 keV. Around 100 eV, the maximum cross sections
are found to be (3.8±0.2) ×10-19 cm2,
cm2,
(7.1±0.8) ×10-17 cm2, (9.0±0.8) ×
10-17 cm2 and (3.7±0.4) ×10-17 cm2 for the
heavy carbonaceous ions CD2+
4, CD+
3, CD+
2, CD+ and C+ respectively. For the light fragments, D+
3, D+
2, and D+, the cross sections around the maximum are
found to be (5.0±0.6) ×10-19 cm2, (1.7±
0.2) ×10-17 cm2 and (10.6±1.0) ×10-17 cm2, respectively. The cross sections are presented in closed analytic
forms convenient for implementation in plasma simulation codes. The analysis
of ionic product velocity distributions allows determination of the kinetic
energy release distributions which are seen to extend from 0 to 9 eV for
heavy fragments, and up to 14 eV for light ones. The comparison of present
energy thresholds and kinetic energy release with available published data
gives information about states contributing to the observed processes.
Individual contributions for dissociative excitation and dissociative
ionization are determined for each detected product. A complete database
including cross sections and energies is compiled for use in fusion
application. 相似文献
2.
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
3.
A. Shumelyuk M. Wesner M. Imlau S. Odoulov 《Applied physics. B, Lasers and optics》2009,95(3):497-503
The intensity dependence of the photorefractive response of Sn2P2S6 is studied for the Kr+-laser wavelength of 647 nm and pump-beam intensities of up to 10 W/cm2. A considerable enhancement of the two-beam coupling gain factor with increasing intensity at a grating spacing of ≃1 μm
is attributed to a light-induced increase of the effective trap density. The large gain reached at high intensities is applied
for the build up of a double phase conjugate mirror with a sub-millisecond switch-on time. 相似文献
4.
We have studied photoluminescence and thermoluminescence (PL and TL) in CaGa2Se4:Eu crystals in the temperature range 77–400 K. We have established that broadband photoluminescence with maximum at 571 nm
is due to intracenter transitions 4f6 5d–4f7 (8S7/2) of the Eu2+ ions. From the temperature dependence of the intensity (log I–103/T), we determined the activation energy (E
a = 0.04 eV) for thermal quenching of photoluminescence. From the thermoluminescence spectra, we determined the trap depths:
0.31, 0.44, 0.53, 0.59 eV. The lifetime of the excited state 4f6 5d of the Eu2+ ions in the CaGa2Se4 crystal found from the luminescence decay kinetics is 3.8 μsec.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 112–116, January–February, 2009. 相似文献
5.
H. Cherkani-Hassani D. S. Belic J. J. Jureta J. Lecointre P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(1):85-94
Absolute cross-sections for electron-impact dissociative ionization of C2
H2+ and C2 D2+ to CH+, C+, C2+ , H+, CH2+
and C2D+ fragments are determined for electron energies ranging
from the corresponding threshold to 2.5 keV. Results obtained in a crossed
beams experiment are analyzed to estimate the contribution of dissociative
ionization to each fragment formation. The dissociative ionization cross
sections are seen to decrease for more than an order of magnitude, from
CH+ (5.37±0.10) × 10-17 cm2 over C+ (4.19±
0.16) × 10-17 cm2, C2D+ (3.94±0.38) ×
10-17 cm2, C2+ (3.82±0.15) × 10-17 cm2
and H+ (3.37±0.21) × 10-17 cm2 to CH2+
(2.66±0.14) × 10-18 cm2. Kinetic energy release
distributions of fragment ions are also determined from the analysis of the
product velocity distribution. Cross section values, threshold energies and
kinetic energies are compared with the data available from the literature.
Conforming to the scheme used in the study of the dissociative excitation of
C2H2+
( C2 D2+ )\left( {\rm C}_2 {\rm D}_2^+ \right), the cross-sections are presented in
a format suitable for their implementation in plasma simulation codes. 相似文献
6.
S. Vatnik M. C. Pujol J. J. Carvajal X. Mateos M. Aguiló F. Díaz V. Petrov 《Applied physics. B, Lasers and optics》2009,95(4):653-656
The three thermo-optic coefficients of the biaxial laser host KLu(WO4)2 are measured at 633 nm by a deflection method. Their values at 300 K amount to ∂
n
g
/∂
T=−7.4×10−6 K−1; ∂
n
m
/∂
T=−1.6×10−6 K−1 and ∂
n
p
/∂
T=−10.8×10−6 K−1. Nearly athermal propagation directions are found for polarizations along the N
m
and N
p
dielectric axes. 相似文献
7.
S. S. Novosad I. M. Matviishin I. S. Novosad O. S. Novosad 《Journal of Applied Spectroscopy》2008,75(6):826-831
We have studied the effect of lead dopant on the optical absorption, photoluminescence, and x-ray luminescence spectra, and
the scintillation characteristics of CdI2 at room temperature. The crystals for the study were grown by the Stockbarger-Bridgman method. Activation of CdI2 from the melt by the compound PbI2 leads to the appearance in the absorption spectra in the near-edge region of an activator band at 395–405 nm, which is interpreted
as an A band connected with electronic transitions from the 1S0 state to the 3P1 levels in the Pb2+ ion. For x-ray excitation, CdI2:Pb2+ crystals with optimal dopant concentration (∼1.0 mol%) are characterized by a light yield with maximum in the 570–580 nm
region that is an order of magnitude higher than for CdI2 crystals in the 490–500 nm band. For α excitation, the radioluminescence kinetics for cadmium iodide is characterized by
a very short (∼0.3 nsec) rise time and fast decay of luminescence, with τ1 ≈ 4 nsec and τ2 = 10–76 nsec. Depending on the conditions under which the crystals were obtained, the fast component fraction is 95%–99%.
The crystal is characterized by a similar scintillation pulse in the case of excitation by x-ray pulses. The radioluminescence
pulse shape for CdI2:Pb in the decay stage is predominantly exponential, with luminescence decay time constants τ1 ≈ 10 nsec and τ2 = 200–250 nsec. This system is characterized by low afterglow, at the level for the Bi4G3O12 scintillator. We have demonstrated the feasibility of using CdI2:Pb as a scintillator for detecting α particles.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 825–830, November–December, 2008. 相似文献
8.
The complex impedance of the Ag2ZnP2O7 compound has been investigated in the temperature range 419–557 K and in the frequency range 200 Hz–5 MHz. The Z′ and Z′ versus frequency plots are well fitted to an equivalent circuit model. Dielectric data were analyzed using complex electrical
modulus M* for the sample at various temperatures. The modulus plot can be characterized by full width at half-height or in terms of
a non-exponential decay function
f( \textt ) = exp( - \textt/t )b \phi \left( {\text{t}} \right) = \exp {\left( { - {\text{t}}/\tau } \right)^\beta } . The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law:
s( w) = s\textdc + \textAwn \sigma \left( \omega \right) = {\sigma_{\text{dc}}} + {\text{A}}{\omega^n} . The conductivity σ
dc follows the Arrhenius relation. The near value of activation energies obtained from the analysis of M″, conductivity data, and equivalent circuit confirms that the transport is through ion hopping mechanism dominated by the
motion of the Ag+ ions in the structure of the investigated material. 相似文献
9.
Tingyin Ning Cong Chen Yueliang Zhou Heng Lu Dongxiang Zhang Hai Ming Guozhen Yang 《Applied Physics A: Materials Science & Processing》2009,94(3):567-570
CaCu3Ti4O12 (CCTO) thin films were successfully prepared on LaAlO3 substrates by pulsed laser deposition technique. We measured the nonlinear optical susceptibility of the thin films using
Z-scan method at a wavelength of 532 nm with pulse durations of 25 ps and 7 ns. The large values of the third-order nonlinear
optical susceptibility, χ
(3), of the CCTO film were obtained to be 2.79×10−8 esu and 3.30×10−6 esu in picosecond and nanosecond time regimes, respectively, which are among the best results of some representative nonlinear
optical materials. The origin of optical nonlinearity of CCTO films was discussed. The results indicate that the CCTO films
on LaAlO3 substrates are promising candidate materials for applications in nonlinear optical devices. 相似文献
10.
J. Lecointre H. Cherkani-Hassani S. Cherkani-Hassani D. S. Belic J. J. Jureta P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(2):331-345
Absolute cross sections for electron-impact single ionization, dissociative
excitation and dissociative ionization of the ethynyl radical ion
(C2D+)^+) have been measured for electron energies ranging from the
corresponding reaction thresholds to 2.5 keV. The animated crossed
electron-ion beam experiment is used and results have been obtained for the
production of C2D2+, C2+, C2+_2^+ , CD+, C+ and
D+. The maximum of the cross section for single ionization is found to
be (2.01 ± 0.02) × 10-17 cm2, at the incident electron
energy of 105 eV. Absolute total cross sections for the various singly
charged fragments production are observed to decrease by a factor of almost
three, from the largest cross-section measured for C+, over C2+_2^+
and CD+ down to that of D+. The maxima of the cross sections are
obtained to be (14.5 ± 0.5) × 10-17 cm2 for C2+_2^+,
(12.1 ± 0.1) × 10-17 cm2 for CD+, (27.7 ±
0.2) × 10-17 cm2 for C+ and (11.1 ± 0.8) × 10-17 cm2 for D+.
The smallest cross section is measured to
be (1.50 ± 0.04) × 10-18 cm2 for the production of the
doubly charged ion C2+. Individual contributions for dissociative
excitation and dissociative ionization are determined for each
singly-charged product. The cross sections are presented in closed analytic
forms convenient for implementation in plasma simulation codes. Kinetic
energy release distributions of dissociation fragments are seen to extend
from 0 to 6 eV for the heaviest fragment C2+_2^+, up to 11.0 eV for
CD+, 14.2 eV for C+ and 11.2 eV for D+ products. 相似文献
11.
K.?Koyasu M.?Niemietz W.?Westh?user G.?Gantef?r 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):59-62
The decay path of an Ag8(O2)- cluster photoexcited by a 3.1 eV photon is elucidated using time-resolved photoelectron spectroscopy. Photoabsorption results
in the formation of an excited state giving rise to a peak in the photoelectron spectra with well-resolved vibrational finestructure.
With a lifetime of about 100 fs this bound state decays into an anti-bonding state which dissociates into O2 and Ag8- on a timescale of 10 ps. In the photoelectron spectra, this corresponds to a broad maximum shifting gradually towards higher
binding energy while the O2 and Ag8- separate. Finally, the spectrum of bare Ag8- appears. This process is unique to small clusters, because on metal surfaces excited state lifetimes are too short to allow
for direct dissociation. 相似文献
12.
S. Kar Y. K. Ho 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):1-8
We have investigated the ground state and the doubly excited 1,3P○ resonance states of plasma-embedded Li+ ion. The plasma effect is taken care of by using a screened Coulomb potential obtained from the Debye model. A correlated
wave function has been used to represent the correlation effect between the charged particles. The ground state of Li+ in plasmas for different screening parameters has been estimated in the framework of Rayleigh-Ritz variational principle.
In addition, a total of 18 resonances (9 each for 1P○ and 3P○ states) below the n=2 Li+ thresholds has been estimated by calculating the density of states using the stabilization method. For each spin state, this
includes four members in the 2snp+ (2≤n ≤5) series, three members in the 2snp- (3≤n ≤5) series, and two members in the 2pnd (n=3, 4) series. The resonance energies and widths for various Debye parameters
ranging from infinity to a small value for these 1,3P○ resonance states along with the ground state energies of Li+ and the Li2+ (1S), Li2+ (2S) threshold energies are reported. Furthermore, the wavelengths for the photo-absorption of lithium ion from its ground
state to such 1P○ resonance states for different Debye lengths are also reported. 相似文献
13.
Single crystals of gadolinium orthosilicate Gd2SiO5 containing 0.5 at% and 5 at% of Sm3+ were grown by the Czochralski method. Optical absorption spectra, luminescence spectra and luminescence decay curves were
recorded for these systems at 10 K and at room temperature. Comparison of optical spectra recorded in polarized light revealed
that the anisotropy of this optically biaxial host affects the intensity distribution within absorption and emission bands
related to transitions between multiplets rather than the overall band intensity. It has been found that among four bands
of luminescence related to the 4G5/2→6HJ (J=5/2–11/2) transitions of Sm3+ in the visible and near infrared region the 4G5/2 →6H7/2 one has the highest intensity with a peak emission cross section of 3.54×10−21 cm2 at 601 nm for light polarized parallel to the crystallographic axis c of the crystal. The luminescence decay curve recorded
for Gd2SiO5:0.5 at% Sm3+ follows a single exponential time dependence with a lifetime 1.74 ms, in good agreement with the 4G5/2 radiative lifetime τ
rad=1.78 ms calculated in the framework of Judd-Ofelt theory. Considerably faster and non-exponential luminescence decay recorded
for Gd2SiO5:5 at% Sm3+ sample was fitted to that predicted by the Inokuti-Hirayama theory yielding the microparameter of Sm3+–Sm3+ energy transfer C
da=1.264×10−52 cm6×s−1. 相似文献
14.
Vasily Lavrentiev Jiri Vacik Hiroshi Naramoto Kazumasa Narumi 《Applied Physics A: Materials Science & Processing》2009,95(3):867-873
The structure transformation occurring in fullerene film under bombardment by 50 keV C60+ cluster ions is reported. The Raman spectra of the irradiated C60 films reveal a new peak rising at 1458 cm−1 with an increase in the ion fluence. This feature of the Raman spectra suggests linear polymerization of solid C60 induced by the cluster ion impacts. The aligned C60 polymeric chains composing about 5–10 fullerene molecules have been distinguished on the film surface after the high-fluence
irradiation using atomic force microscopy (AFM). The surface profiling analysis of the irradiated films has revealed pronounced
sputtering during the treatment. The obtained results indicate that the C60 polymerization occurs in a deep layer situated more than 40 nm below the film surface. The deep location of the C60 polymeric phase indirectly confirms the dominant role of shock waves in the detected C60 phase transformation. 相似文献
15.
H. Cherkani-Hassani S. Cherkani-Hassani D. S. Belic J. J. Jureta J. Lecointre P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(1):75-83
Absolute cross-sections for electron-impact ionization and dissociation of
C2H2+ and C2D2+ have been measured for electron energies
ranging from the corresponding thresholds up to 2.5 keV. The animated
crossed beams experiment has been used. Light as well as heavy fragment ions
that are produced from the ionization and the dissociation of the target
have been detected for the first time. The maximum of the cross-section for
single ionization is found to be (5.56 ± 0.03)× 10-17 cm2 around 140 eV. Cross-sections for dissociation of C2
H2+ (C2D2+) to ionic products are seen to decrease for two orders
of magnitude, from C2D+ (12.6 ± 0.3) × 10-17 cm2 over CH+(9.55 ± 0.06) × 10-17 cm2,
C+ (6.66 ± 0.05) × 10-17 cm2, C2+ (5.36 ± 0.27) × 10-17 cm2, H+ (4.73 ±
0.29) × 10-17 cm2 and CH2+ (4.56 ± 0.27) × 10-18 cm2 to H2+ (5.68 ± 0.49) ×
10-19 cm2. Absolute
cross-sections and threshold energies have been compared with the scarce
data available in the literature. 相似文献
16.
This paper reports on the spectroscopic properties and energy transfer analysis of Tm3+-doped BaF2-Ga2O3-GeO2-La2O3 glasses with different Tm2O3 doping concentrations (0.2, 0.5, 2.0, 2.5, 3.0, 3.5, 3.5, 4.0 wt%). Mid-IR fluorescence intensities in the range of 1,300 nm−2,200 nm
have been measured when excited under an 808 nm LD for all the samples with the same pump power. Energy level structure and
Judd-Ofelt parameters have been calculated based on the absorption spectra of Tm3+, cross-relaxation rates and multi-phonon relaxation rates have been estimated with different Tm2O3 doping concentrations. The maximum fluorescence intensity at around 1.8 μm has been obtained in Tm2O3-3 wt% sample and the maximum value of calculated stimulated emission cross-section of Tm3+ in this sample is about 0.48 × 10−20 cm2 at 1,793 nm, and there is not any crystallization peak in the DSC curve of this sample, which indicate the potential utility
of Tm3+-doped BaF2-Ga2O3-GeO2- La2O3 glass for 2.0-μm optical fiber laser. 相似文献
17.
18.
L. Kovács M. Mazzera E. Beregi R. Capelletti 《Applied physics. B, Lasers and optics》2009,94(2):273-277
Several weak absorption bands have been observed in the optical absorption spectra of pure and rare-earth-doped YAl3(BO3)4 single crystals in the 3350– 3650 cm−1 wave number region. Two of them, peaking at about 3377 cm−1 and 3580 cm−1 in the 8 K spectra, appear in most of the samples. They are tentatively attributed to the stretching mode of OH− ions incorporated in the crystal during the growth. An additional absorption band at about 5250 cm−1 at 8 K has also been detected in almost all samples. The temperature and polarization dependences of these bands, and their
possible origin, are discussed. 相似文献
19.
V. P.S. Awana A. Vajpayee M. Mudgel V. Ganesan A. M. Awasthi G. L. Bhalla H. Kishan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):281-294
We report synthesis, structure/micro-structure, resistivity under magnetic
field [ρ(T)H], Raman spectra, thermoelectric power S(T), thermal conductivity
κ(T), and magnetization of ambient pressure argon annealed
polycrystalline bulk samples of MgB2, processed under identical
conditions. The compound crystallizes in hexagonal structure with space
group P6/mmm. Transmission electron microscopy (TEM) reveals electron micrographs
showing various types of defect features along with the presence of 3–4 nm
thick amorphous layers forming the grain boundaries of otherwise crystalline
MgB2. Raman spectra of the compound at room temperature exhibited
characteristic phonon peak at 600 cm-1. Superconductivity is observed
at 37.2 K by magnetic susceptibility χ(T), resistivity ρ(T), thermoelectric power
S(T), and thermal conductivity κ(T) measurements. The power law fitting
of ρ(T) give rise to Debye temperature (ΘD) at 1400 K which is
found consistent with the theoretical fitting of S(T), exhibiting Θ
D of 1410 K and carrier density of 3.81 × 1028/m3. Thermal
conductivity κ(T) shows a jump at 38 K, i.e., at Tc, which was
missing in some earlier reports. Critical current density (Jc) of up to
105 A/cm2 in 1–2 T (Tesla) fields at temperatures (T) of up to 10 K
is seen from magnetization measurements. The irreversibility field, defined
as the field related to merging of M(H) loops is found to be 78, 68 and 42 kOe
at 4, 10 and 20 K respectively. The superconducting performance parameters
viz. irreversibility field (Hirr) and critical current density
Jc(H) of the studied MgB2 are improved profoundly with addition of
nano-SiC and nano-diamond. The physical property parameters measured for
polycrystalline MgB2 are compared with earlier reports and a
consolidated insight of various physical properties is presented. 相似文献
20.
T. Rudolf Ch. Kant F. Mayr M. Schmidt V. Tsurkan J. Deisenhofer A. Loidl 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(2):153-160
We studied the optical properties of antiferromagnetic ZnCr2Se4 by infrared spectroscopy up to 28,000 cm-1 and for temperatures from 5 to 295 K. At the magnetic phase transition at 21 K, one of the four phonon modes reveals a clear
splitting of 3 cm-1 as a result of spin-phonon coupling, the other three optical eigenmodes only show shifts of the eigenfrequencies. The antiferromagnetic
ordering and the concomitant splitting of the phonon mode can be suppressed in a magnetic field of 7 T. At higher energies
we observed a broad excitation band which is dominated by a two-peak-structure at about 18,000 cm-1 and 22,000 cm-1, respectively. These energies are in good agreement with the expected spin-allowed crystal-field transitions of the Cr3+ ions. The unexpected strength of these transitions with d-d character is attributed to a considerable hybridization of the
selenium p with the chromium d orbitals. 相似文献