共查询到20条相似文献,搜索用时 31 毫秒
1.
G. Imbriani H. Costantini A. Formicola A. Vomiero C. Angulo D. Bemmerer R. Bonetti C. Broggini F. Confortola P. Corvisiero J. Cruz P. Descouvemont Z. Fülöp G. Gervino A. Guglielmetti C. Gustavino Gy. Gyürky A. P. Jesus M. Junker J. N. Klug A. Lemut R. Menegazzo P. Prati V. Roca C. Rolfs M. Romano C. Rossi-Alvarez F. Schümann D. Schürmann E. Somorjai O. Straniero F. Strieder F. Terrasi H. P. Trautvetter 《The European Physical Journal A - Hadrons and Nuclei》2005,25(3):455-466
The astrophysical S(E) factor of 14N(p,γ)15O has been measured for effective center-of-mass energies between E
eff = 119 and 367 keV at the LUNA facility using TiN solid targets and Ge detectors. The data are in good agreement with previous
and recent work at overlapping energies. R-matrix analysis reveals that due to the complex level structure of 15O the extrapolated S(0) value is model dependent and calls for additional experimental efforts to reduce the present uncertainty in S(0) to a level of a few percent as required by astrophysical calculations. 相似文献
2.
L. J. Kaufman 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):501-503
The HAPPEX Collaboration at Jefferson Lab has measured the transverse beam spin asymmetries (AT) for elastic electron scattering from proton and 4He targets. The experiment was conducted using a vertically polarized electron beam of energy ∼ 3 GeV, at a Q
2 ∼ 0.1 GeV^2 and a scattering angle θlab ∼ 6° . The preliminary results are reported here. The 4He measurement is the first measurement of AT from a nucleus. AT for 4He is non-negligible; therefore, it will be necessary to make measurements of AT for future parity-violating experiments using nuclear targets. 相似文献
3.
E. L. Shangina K. V. Smirnov D. V. Morozov V. V. Kovalyuk G. N. Gol’tsman A. A. Verevkin A. I. Toropov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(1):100-102
The concentration dependence of the intermediate frequency bandwidth of heterodyne AlGaAs/GaAs detectors with 2D electron
gas is measured using submillimeter spectroscopy with high time resolution at T= 4.2 K. The intermediate frequency bandwidth f3dBfalls from 245 to 145 MHz with increasing concentration of 2D electrons n
s
= (1.6-6.6) × 10[su11] cm-2. The dependence f3dB ≈ n
s
- 0.04±is observed in the studied concentration range; this dependence is determined by electron scattering by the deformation
potential of acoustic phonons and piezoelectric scattering. 相似文献
4.
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
5.
L. Gialanella D. Rogalla F. Strieder S. Theis G. Gyürki C. Agodi R. Alba M. Aliotta L. Campajola A. Del Zoppo A. D'Onofrio P. Figuera U. Greife G. Imbriani A. Ordine V. Roca C. Rolfs M. Romano C. Sabbarese P. Sapienza F. Schümann E. Somorjai F. Terrasi H.P. Trautvetter 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):357-370
An excitation function of the ground-state γ0-ray capture transition in 12C (α,γ)16O at θγ = 90° was obtained in far geometry using six Ge detectors, where the study of the reaction was initiated in inverse kinematics
involving a windowless gas target. The detectors observed predominantly the E1 capture amplitude. The data at E = 1.32 to 2.99 MeV lead to an extrapolated astrophysical S factor S
E1(E
0) = 90±15 keV b at E
0 = 0.3 MeV (for the case of constructive interference between the two lowest E1 sources), in good agreement with previous works. However, a novel Monte Carlo approach in the data extrapolation reveals
systematic differences between the various data sets such that a combined analysis of all available data sets could produce
a biased estimate of the S
E1(E
0) value. As a consequence, the case of destructive interference between the two lowest E1 sources with S
E1(E
0) = 8±3 keV b cannot be ruled out rigorously.
Received: 6 June 2001 / Accepted: 26 July 2001 相似文献
6.
Experimental data on the spin-exchange rate constants for the He(23
S
1)-Na(32
S
1/2) system are reported for the first time. Measurements show that the spin-exchange rate constant is C
se
= (23 ± 11) × 10−10 cm3 s−1 and the chemical ionization rate constant is C
si
= (29 ± 14) × 10−10 cm3 s−1 at a temperature of 420 K. The results are compared with the data calculated from the rate constants. 相似文献
7.
T. Uesaka V. P. Ladygin L. S. Azhgirey Yu. V. Gurchin A. Yu. Isupov K. Itoh M. Janek J. -T. Karachuk T. Kawabata A. N. Khrenov A. S. Kiselev V. Kizka J. Kliman V. A. Krasnov A. N. Livanov Y. Maeda A. I. Malakhov V. Matoucek M. Morhac S. Nedev S. Rangelov S. G. Reznikov S. Sakaguchi H. Sakai Y. Sasamoto K. Sekiguchi K. Suda I. Turzo T. A. Vasiliev T. Wakui 《Physics of Particles and Nuclei Letters》2006,3(5):305-311
A new high-energy beam polarimeter is proposed for Nuclotron, which uses the Internal Target Station (ITS). This polarimeter
based on a measurement of asymmetry for the d–p elastic scattering will allow one to measure simultaneously both vector and tensor components of deuteron beam polarization.
For this purpose an analyzing powers measurement for the d–p elastic scattering at energies T
d = 0.88–2 GeV is proposed. The precise measurements of the deuteron analyzing powers over the energy range T
d = 300–2000 MeV can give an irreplaceable clue to the study of the spin dependence of three nucleon forces.
The text was submitted by the authors in English. 相似文献
8.
Absolute cross sections σ−(E, N) of electron attachment to clusters (H2O)
N
, (N2O)
N
, and (N2)
N
for varying electron energy E and cluster size N are measured by using crossed electron and cluster beams in a vacuum. Continua of σ−(E) are found that correlate well with the functions of electron impact excitation of molecules’ internal degrees of freedom.
The electron is attached through its solvation in a cluster. In the formation of (H2O)
N
−
, (N2O)
N
−
, and (N2)
N
−
, the curves σ−(N) have a well-defined threshold because of a rise in the electron thermalization and solvation probability with N. For (H2O)900, (N2O)350, and (N2)260 clusters at E = 0.2 eV, the energy losses by the slow electron in the cluster are estimated as 3.0 × 107, 2.7 × 107, and 6.0 × 105 eV/m, respectively. It is found that the growth of σ− with N is the fastest for (H2O)
N
and (N2)
N
clusters at E → 0 as a result of polarization capture of the s-electron. Specifically, at E = 0.1 eV and N = 260, σ− = 3.0 × 10−13 cm2 for H2O clusters, 8.0 × 10−14 cm2 for N2O clusters, and 1.4 × 10−15 cm2 for N2 clusters; at E = 11 eV, σ− = 9.0 × 10−16 cm2 for (H2O)200 clusters, 2.4 × 10−14 cm2 for (N2O)350 clusters, and 5.0 × 10−17 cm2 for (N2)260 clusters; finally, at E = 30 eV, σ− = 3.6 × 10−17 cm2 for (N2O)10 clusters and 3.0 × 10−17 cm2 for (N2)125 clusters.
Original Russian Text ? A.A. Vostrikov, D.Yu. Dubov, 2006, published in Zhurnal Tekhnicheskoĭ Fiziki, 2006, Vol. 76, No. 12,
pp. 1–15. 相似文献
9.
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
10.
The electron drift mobility in Γ conduction band of GaAs has been calculated before, but for the first time, we have made
attempts to estimate the electron mobilities in higher energy L and X minima. We have also calculated the value of mobility
of two-dimensional electron gas needed to predict hetero-structure device characteristics using GaAs. Best scattering parameters
have been derived by close comparison between experimental and theoretical mobilities. Room temperature electron mobilities
in Γ, L and X valleys are found to be nearly 9094, 945 and 247 cm2/V-s respectively. For the above valleys, the electron masses, deformation potentials and polar phonon temperatures have been
determined to be (0.067, 0.22, 0.39m
0), (8.5, 9.5, 6.5 eV), and (416, 382, 542 K) as best values, respectively. The 2-DEG electron mobility in Γ minimum increases
to 1.54 × 106 from 1.59 × 105 cm2/V-s (for impurity concentration of 1014 cm−3) at 10 K. Similarly, the 2-DEG electron mobility values in L and X minima are estimated to be 2.28 × 105 and 1.44 × 105 cm2/V-s at 10 K, which are about ∼4.5 and ∼3.9 times higher than normal value with impurity scattering present.
相似文献
11.
R Rajesh B Ramesh Kumar S K Varshney Manoj Kumar Chhaya Chavda Aruna Thakkar N C Patel Ajai Kumar Aditya Team 《Pramana》2000,55(5-6):733-740
Thomson scattering technique based on high power laser has already proved its superoirity in measuring the electron temperature
(T
e and density (n
e) in fusion plasma devices like tokamaks. The method is a direct and unambiguous one, widely used for the localised and simultaneous
measurements of the above parameters. In Thomson scattering experiment, the light scattered by the plasma electrons is used
for the measurements. The plasma electron temperature is measured from the Doppler shifted scattered spectrum and density
from the total scattered intensity. A single point Thomson scattering system involving a Q-switched ruby laser and PMTs as the detector is deployed in ADITYA tokamak to give the plasma electron parameters. The system
is capable of providing the parameters T
e from 30 eV to 1 keV and n
e from 5 × 1012cm−3−5 × 1013cm−3. The system is also able to give the parameter profile from the plasma center (Z=0 cm) to a vertical position of Z=+22 cm to Z=−14 cm, with a spatial resolution of 1 cm on shot to shot basis. This paper discusses the initial measurements of the plasma
temperature from ADITYA. 相似文献
12.
O. G. Ryazhskaya 《Il Nuovo Cimento C》1995,18(1):77-80
Summary The background produced by isolated neutrons in Cherenkov detectors studying the atmospheric neutrinos is discussed. The neutrons
are generated in nuclear showers initiated by muons in the rock surrounding the detectors. It is shown that, taking into account
the detection of π0 events from reactions of nA→π0X, which look likev
e detection, results in an observedI(v
μ)/I(v
e) ratio close to the expected one for the energy range 0.2–5 GeV. 相似文献
13.
A. Yu. Buki I. S. Timchenko N. G. Shevchenko 《The European Physical Journal A - Hadrons and Nuclei》2012,48(2):17
The Coulomb sums S
L(q) of the 6Li nucleus have been obtained from electron scattering measurements at 3-momentum transfers q = 1.125–1.625 fm−1. It is found that at q > 1.35 fm−1 the Coulomb sum of the nucleus becomes saturated: S
L(q) = 1 . 相似文献
14.
Results are presented from the first stage of studies on the passage of an electron beam with energy 100–500 eV in a magnetic
field of 300–700 Oe through the curvilinear solenoid of the KRéL unit, the latter being a prototype of the closing segment
of the Drakon stellarator system, in the plasma-beam discharge regime. The ion density at the end of the curvilinear part
of the chamber, n
i
≈8×108–1010 cm−3, the electron temperature T
e
≈4–15 eV, and the positions at which the beam hits the target for different distances from it to the electron source are determined
experimentally. The motion of the electron beam is computationally modeled with allowance for the space charge created by
the beam and the secondary plasma. From a comparison of the experimentally measured trajectories and trajectories calculated
for different values of the space charge, we have obtained an estimate for the unneutralized ion density of the order of 5×107 cm−3.
Zh. Tekh. Fiz. 69, 22–26 (February 1999) 相似文献
15.
V. N. Bolotov G. I. Britvich I. P. Gouz A. I. Makarov A. P. Ostankov 《Physics of Atomic Nuclei》2010,73(12):2097-2102
The projected KLOD facility is intended for finding and investigating the ultrarare decay K
L
0 → π0ν$
\bar \nu
$
\bar \nu
; its branching ratio predicted by the Standard Model is Br = (3.0 ± 0.6) × 10−11. Designing and testing the prototype of the decay-volume veto system and beam veto calorimeter, which are the most important
detectors of the facility, are considered. It is shown that the proposed beam veto calorimeter is able to detect γ rays with a high efficiency at the neutron flux of 300 MHz. 相似文献
16.
We report the development of a method for recording the low-temperature (T=6 K) near-IR inelastic light scattering spectra and the observation of electronic scattering on the transitions 1s
3/2(Γ8) → 2s
3/2(Γ8) between the ground and excited states of different shallow acceptor centers in a n-type semi-insulating crystal si-GaAs (n=1.0 × 108 cm−3) and in a doped p-InP crystal (p=3.6×1017 cm−3). Moreover, a new line, associated with the transition 1s
3/2(Γ 8) → 2p
3/2(Γ8) and due to a dielectric local mode, recorded for the first time in the spectra of narrow-gap semiconductors, was found in
the residual-frequency band in the p-InP spectrum between TO(Γ) and LO (Γ) phonons.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 334–339 (10 March 1998) 相似文献
17.
S. G. Karshenboim V. G. Ivanov U. D. Jentschura G. Soff 《Journal of Experimental and Theoretical Physics》1998,86(2):226-236
We examine the properties of an atomic system consisting of a muon and antimuon. Expressions are derived for the probability
of decay and the hyperfine splitting of the lower levels with allowance for the leading radiative corrections, which are of
relative order α. The results for the lifetimes and the ground-state energy are τ(13
S
1)=1.7907(8)×10−12 s, τ(11
S
0)=0.59547(33)×10−12 s, and E
hfs (1s)=4.23284(35)×107 MHz. The relative probabilities for the various decay channels are calculated; in particular, for the 1 3
S
1 level it is found that Γ (μμ→eeγ)/Γ(μμ→ee)≈15%. Finally, possible applications are discussed.
Zh. éksp. Teor. Fiz. 113, 409–431 (February 1998) 相似文献
18.
K.S. Kim Myung Ki Cheoun Yeungun Chung Hyung Joo Nam 《The European Physical Journal A - Hadrons and Nuclei》2001,11(2):147-154
New results for the double beta decay of 76
Ge are presented. They are extracted from data obtained with the HEIDELBERG-MOSCOW experiment, which operates five enriched
76
Ge detectors in an extreme low-level environment in the Gran Sasso underground laboratory. The two-neutrino-accompanied double
beta decay is evaluated for the first time for all five detectors with a statistical significance of 47.7 kg y resulting in
a half-life of T
1/2
2ν = [1.55±0.01(stat)+0.19
-0.15(syst)]×1021 y. The lower limit on the half-life of the 0νββ decay obtained with pulse shape analysis is T
1/2
0ν > 1.9×1025(3.1×1025) y with 90% C.L. (68% C.L.) (with 35.5 kg y). This results in an upper limit of the effective Majorana-neutrino mass of 0.35
eV (0.27 eV) using the matrix elements of A. Staudt et al.'s work (Europhys. Lett. 13, 31 (1990)). This is the most stringent limit at present from double beta decay. No evidence for a majoron-emitting decay
mode is observed.
Received: 22 August 2001 / Accepted: 18 October 2001 相似文献
19.
B. P. Barkov V. V. Vladimirskii V. K. Grigor’ev O. N. Erofeeva Yu. V. Katinov I. Ya. Korol’kov V. I. Lisin V. N. Luzin V. N. Nozdrachev V. V. Sokolovskii G. D. Tikhomirov S. A. Uzunyan Yu. P. Shkurenko I. A. Gridnev 《JETP Letters》1999,70(4):248-253
Data are presented which indicate the existence of a previously unknown narrow resonance near mass 1520 MeV, discovered while
analyzing the system K
S
K
S
. The data were obtained at ITEP using the 6-m magnetic spectrometer in a beam of 40-GeV negative particles. The resonance
is observed in π−
p and K
−
p interactions with a total statistical confidence of not less than 5 standard deviations. The width of this state is comparable
to the mass resolution of the spectrometer (∼5 MeV). The mass is 1521.5±2.5 MeV. Estimates of the product σ·BR (K
S
K
S
) give ∼5.0 nb in π−
p interactions and ∼250 nb in K
−
p interactions. From the fact that the production cross section of this resonance in the K
− beam is approximately 50 times greater than the production cross section in the π− beam, it can be concluded that this new state belongs to a system of mesons with hidden strangeness.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 242–246 (25 August 1999) 相似文献
20.
We have grown crystals Na0.4Y0.6F2.2:Ho3+ (NYF:Ho3+) by the Bridgman-Stockbarger method. The optical spectra and luminescence kinetics of NYF:Ho3+ crystals have been studied. Based on the analysis of low-temperature absorption spectra, we determine the structure of the
Stark splitting of holmium levels in NYF:Ho3+ crystals. From absorption spectra examined at T = 300 K, we calculate absorption cross-section spectra and oscillator strengths of transitions from the ground state of holmium
to excited multiplets. We show that the absorption spectra of NYF:Ho3+ crystals consist of broad bands that lie in the UV, visible, and near-IR ranges. The most intense bands are observed in the
visible range, they correspond to transitions 5
I
8 → (5
F
1, 5
G
6) and 5
I
8 → (5
F
4, 5
S
2), and their maximal absorption cross sections are σabsmax (λ = 450.3 nm) = 1.16 × 10−20 cm2 and σabsmax (λ = 535.1 nm) = 0.9 × 10−20 cm2. The intensity parameters Ω
t
have been calculated by the Judd-Ofelt method taking into account 10, 12, and 20 transitions from the 5
I
8 ground state to excited multiplets. We show that, with an increasing number of transitions taken into account in the calculation,
the parameters Ω
t
somewhat increase. For 20 transitions, we have obtained the following intensity parameters: Ω2 = 0.97 × 10−20, Ω4 = 1.74 × 10−20, and Ω6 = 1.15 × 10−20 cm2. With these parameters, we have calculated the probabilities of radiative transitions, the radiative lifetimes, and the branching
ratios. The rates of multiphoton nonradiative transitions have been estimated. The luminescence decay kinetics from excited
holmium levels 5
F
3 (5
F
4, 5
S
2) and 5
F
5 have been studied upon selective excitation in the range of 490 nm, and the lifetimes of these levels have been experimentally
determined. We find that the calculated and experimental rates of radiative and nonradiative relaxation from excited holmium
levels agree well with each other. We show that, upon pumping in the range of 490 nm, the multiplet (5
F
4, 5
S
2) is populated as a result of the radiative and nonradiative excitation relaxation from the 5
F
3 level, while the lower-lying 5
F
5 level is populated due to direct radiative transitions 5
F
3, 2 → 5
F
5, obviating the cascade scheme 5
F
3 → (5
F
4, 5
S
2) ↝ 5
F
5. We conclude that NYF:Ho3+ crystals are processable; admit doping by holmium in high concentrations (up to 100%); and, with respect to all their radiative
characteristics, can be considered as potential active media for solid-state continuously tunable lasers in the IR and visible
ranges. 相似文献