共查询到20条相似文献,搜索用时 35 毫秒
1.
R. Kadono R. F. Kiefl J. H. Brewer G. M. Luke T. Pfiz T. M. Riseman B. J. Sternlieb 《Hyperfine Interactions》1991,64(1-4):635-640
The diffusion rate of muonium in the III–V compound semiconductor GaAs has been determined from measurements of muon spinT
1 relaxation induced by motion in the presence of nuclear hyperfine interactions. It is shown for the first time in a semiconductor
that (a) there is a crossover of the transport mechanism at about 90 K from stochastic to zero-phonon hopping, as evidenced
by a steep rise in the hop rate at lower temperatures, and that (b) the muonium diffuses at the hop rate of 1010 s−1 (corresponding diffusion constantD≈10−6 cm2s−1) at lower temperatures as well as at room temperature. 相似文献
2.
Masayoshi Senba Alicia C. Gonzalez James R. Kempton Donald J. Arseneau James J. Pan Alexandra Tempelmann Donald G. Fleming 《Hyperfine Interactions》1991,65(1-4):979-986
The addition reaction Mu+NO+M→MuNO+M and the spin exchange reaction Mu(↑) +MO(↓)→Mu(↓)+NO(↑) have been measured by longitudinal
field μSR at room temperature in the presence of up to 58 atm of N2 as inert collider. The pressure dependence of the longitudinal relaxation rate due to the addition reaction (λc) demostrates that the system is still in the low pressure regime in this pressure range. The corresponding termolecular rate
constant has been determined ask
0,Mu
=(1.10±0.25)×10−32 cm6 molecules−2 s−1, almost 4 times smaller than the corresponding H atom reactionk
0,H=3.90×10−32 cm6 molecules−2 s−1 [I.M. Campbell et al., J. Chem. Soc. Faraday Trans. 1.71 (1975) 2097]. The average value of the spin exchange rate constants
in the 2.5–58 atm pressure range,k
SE=(3.16±0.06)×10−10 cm3 molecule−1 s−1, is in good agreement with previous values obtained by transverse field μSR [D.G. Fleming et al., J. Chem. Phys. 73 (1980)
2751]. 相似文献
3.
T. Kondow A. Matsushita K. Kuchitsu K. Nishiyama Y. Morozumi K. Nagamine 《Hyperfine Interactions》1986,32(1-4):807-812
Surface muons produced in UT-MSL were introduced into argon gas of 4.0±0.2 atm with NO2 (0–30 ppm), and muonium signals were detected in the presence of a transverse (1.7–3.4 G) and a longitudinal magnetic field
(0–3.5 kG) at 295±1 K. The cross section for the transverse relaxation was (11.0±1.0)×10−16 cm2. The relaxation rates in different longitudinal magnetic fields show that the rate does not follow the conventional equation
which assumes that the relaxation occurs mainly by spin-exchange interaction. Similar measurements were performed for the
Mu+O2 system. These findings indicate that chemical reactions contribute to these relaxation rates. 相似文献
4.
Jean Y. C. Ganti R. L. Cheng K. L. Venkateswaran K. Walker D. C. 《Hyperfine Interactions》1986,32(1-4):813-817
The bimolecular rate constants for muonium addition to ethene (CH2=CH2) in hydrocarbon liquids were found to be ∼2×1010 M−1s−1. These rate constants change with temperature in accordance with the Arrhenius equation; but the energy barrier to reaction
(Ea) in 2-methylbutane is much less than that for viscous flow. This suggests either non-classical interaction rates stemming
from the quantum character for muonium, or non-Stokes-Einstein behavior. 相似文献
5.
S. R. Kreitzman T. Pfiz S. Sun-Mack T. M. Riseman J. H. Brewer D. Ll. Williams T. L. Estle 《Hyperfine Interactions》1991,64(1-4):561-566
The ionization of muonium centers in Si and GaAs have been studied using radio frequency (RF) resonant techniques. In Si all
three muonic centers are detectable by RF. No evidence was found for delayed Mu and Mu* states at any temperature. However, our results on the diamagnetic final state (μ
f
+
) show that it is composed of prompt fractions (as seen by conventional μSR) and delayed fractions arising from the ionization
of Mu* and Mu. We observe a full μ
f
+
fraction at 317 K when the Mu relaxation rate is above 10 μs−1. GaAs differs from the situation in Si in that we observed only a partial conversion of Mu* and Mu to a μ+ final state up to 310 K in spite of the fact that the transverse field relaxation rates become very high at 150 and 250 K
respectively. 相似文献
6.
Machi I. Z. Connell S. H. Sellschop J. P. F. Bharuth-Ram K. 《Hyperfine Interactions》2001,136(3-8):723-726
A preliminary study of the diamagnetic (μd) and the paramagnetic (Mu
T
) states in a synthetic 13C diamond has been performed using the Transverse Field Muon Spin Rotation method. This system could be used to verify the
quantum diffusion behaviour observed before, however, with a more reliable extraction of the hopping rate. The results were
obtained in an applied magnetic field of 7.5 mT and at sample temperatures of 10 K, 100 K and 200 K. The prompt fraction,
f, of the μd state remains constant at 22(5)% in the range 10–200 K; that of the Mu
T
state increases from 53(10)% at 10 K to 78(10)% at 200 K. The fractions of the two states add to 100% at 200 K, suggesting
non-population of the bond-centred state, MuBC, which is often observed in other diamond samples. The μd state has a spin relaxation rate of 0.20(5) μs−1, in contrast to the zero value obtained in type II diamond samples. This indicates appreciable interaction of the μd state with the 13C atoms. The Mu
T
state has a large spin relaxation rate ranging from 3.0(5) μs−1 at 10 K to 7.0(5) μs−1 at 200 K, consistent with values obtained in diamond samples with defects. This work is part of ongoing studies of muon/muonium-defect
interactions in diamonds.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
7.
V. N. Gorelkin V. G. Grebinnik K. I. Gritsai V. N. Duginov V. A. Zhukov T. N. Mamedov V. G. Ol’shevski V. Yu. Pomyakushin A. V. Stoikov I. L. Chaplygin I. A. Krivosheev B. A. Nikol’skii A. N. Ponomarev 《JETP Letters》1996,63(7):566-571
The residual polarization of negative muons in n-type silicon with impurity density (1.6±0.2) · 1013 cm−3 is investigated as a function of temperature in the range 10–300 K. The measurements are performed in an external magnetic
field of 0.08 T oriented transversely to the spin of the muons. Relaxation of the muon spin and a shift of the precession
frequency are observed at temperatures below 30 K. The relaxation rate at 30 K equals 0.25±0.08 μs−1. The shift of the precession frequency at 20 K equals 7 · 10−3. Both the relaxation rate and the shift of the precession frequency increase as the temperature decreases. At temperatures
below 30 K the relaxation rate is described well by the relation Λ=bT
−q
, where q=2.8±0.2.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 7, 539–543 (10 April 1996) 相似文献
8.
A. Matsushita Y. Miyake Y. Murata K. Nishiyama K. Nagamine D. G. Fleming M. Morita T. Ohmi 《Hyperfine Interactions》1991,65(1-4):1071-1080
Evidence for the emission of slow muonium atoms from a 3.0-nm-thick SiO2 layer covered on an n-type Si is reported. Also, upon applying an rf-resonance technique at the muon frequency, a time-differential
observation of a delayed state-change from muonium to diamagnetic muon at room temperature was observed. Combining results
obtained by use of longitudinal field decoupling and transverse spin rotation methods, the conversion rate was estimated to
be 5 to 10 μs−1. Both of the above results, namely the observation of the emission and state-change of muonium, suggest a process in which
μ+ initially captures an electron from Si, then quickly converts to μ+ again during thermal diffusion in the Si towards the SiO2 layer. Within the oxide layer, muonium is again formed and subsequently is emitted from the SiO2 surface. 相似文献
9.
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
10.
Machi I. Z. Connell S. H. Sellschop J. P. F. Bharuth-Ram K. 《Hyperfine Interactions》2001,136(3-8):727-730
We report on transverse field muon spin rotation measurements on a nitrogen-rich type Ia diamond, both before and after the
conversion of some of the aggregated nitrogen centres to nitrogen-vacancy complexes known as H2/H3-centres. The prompt fractions
f and the spin relaxation rates λ were determined for the diamagnetic (μd) and the paramagnetic (MuT) states in the temperature range 10–300 K. The production of the nitrogen-vacancy complexes had little effect on the parameters
of the MuT state for which f and λ remained unchanged at approximately 30% and 4 μs−1, respectively. For the μd state, on the other hand, the formation of the H2/H3-centres resulted in an increase of the prompt fraction from 10(2)% to
20(3)%, and (for the first time) the spin relaxation rate showed a non-zero value of 0.020(3) μs−1. These results show evidence of strong μd interactions with the nitrogen-vacancy complexes in diamond, and suggest a more complex structure for this state than a bare
μ+.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
11.
《International Journal of Infrared and Millimeter Waves》1997,18(9):1663-1679
The optical constants of crystal quartz in the far infrared (10 – 600 cm−1) are reported at room temperature and at 10 K, for both polarizations parallel and perpendicular to the c-axis, respectively
extraordinary and ordinary ray. These constants are obtained from the analysis of the transmissivity channeled spectra below
300 cm−1, and from the analysis of the reflectivity spectra between 300 – 600 cm−1, measured by using a grating infrared spectrometer. The extrapolated zero frequency refractive indices of quartz obtained
in the present work are: no(0) = 2.106 and ne(0) = 2.153 at 300 K; no(0) = 2.072 and ne(0) = 2.130 at 10 K. 相似文献
12.
Experimental performance parameters of Hg implanted Hg1−x
Cd
x
Te photovoltaic detectors are analyzed. At 77K, for 8–14 μm band, a comparison is made between performances and theoretical
ultimate diffusion limits in low frequency direct detection. Experimental features are well-explained by a model based on
the Auger band-to-band process for carrier recombination. Peak detectivities exceeding 1011 cm Hz1/2W−1, external quantum efficiencies as high as 90%, and zero-bias resistance-area products better than 1 Ω·cm2 have been achieved in devices with 12 μm cutoff wavelengths. In the 3–5 μm band performances are far from the diffusion limit.
Notwithstanding, at 77K zero-bias resistance-area products are better than 104Ω·cm2 and detectivities of the order of 1012 cm Hz1/2W−1 were observed at 5 μm.
Predominant generation-recombination contribution are present at room temperature in 1–1.3 μm photodiodes whose detectivities,
primarily limited by the Johnson noise, at 1.3 μm are higher than 1011 cm Hz1/2W−1 at 300 K.
The high frequency response of the photodiodes is also discussed. Response times as low as 0.5 ns are reached despite some
limitations arising from the implanted layer sheet resistance.
Work supported by CNR-CISE contract No. 73.01435. 相似文献
13.
B. Wyncke F. Bréhat H. Kharroubi 《International Journal of Infrared and Millimeter Waves》1997,18(2):475-489
Spectroscopic studies using far infrared reflectivity and transmissivity measurements between 10 and 600 cm−1, were performed on plane parallel quartz crystal plates, in the temperature range 10–300 K. The temperature dependence of
the optical mode parameters is reporeted for both polarizations parallel and perpendicular to the c-axis. The extraordinary
optical constants of quartz are determined at 10 and 300 K, from the A2 transmissivity channeled spectrum, between 10 and 300 cm−1. 相似文献
14.
The kinetics of the optical orientation of atoms in a helium-cesium gas-discharge plasma are considered, and kinetic equations
describing the optical orientation of atoms in the case of two simultaneously occurring processes, viz., an elastic process
(spin exchange) and an inelastic process (chemi-ionization), are derived. The rate constants of these processes are determined
experimentally: C
se=(2.8±0.8)×10−9 cm3s−1, C
ci=(1.0±0.3)×10−9 cm3s−1.
Zh. Tekh. Fiz. 69, 36–40 (September 1999) 相似文献
15.
Yu.?M.?Ba?kov 《Physics of the Solid State》2010,52(10):2044-2057
The self-diffusion coefficients of ions of the three chemical elements forming lithium hydroxide have been determined by the
crystal-crystal and crystal-gas isotope exchange method in the temperature range 500–720 K. Crystal samples with different
isotope compositions have been grown by the Bridgman method from melts. The melting temperature is 743 ± 2 K. Original methods
have been developed for high-precision measurements of the isotope ratios of all three elements, i.e., lithium (6Li/7Li), hydrogen (H/D), and oxygen (16O/18O), and their changes after diffusion annealings with the use of the same sample. The self-diffusion coefficients of lithium
and hydrogen ions differ but by a factor of no more than 3–5; however, their values exceed those for oxygen by several orders
of magnitude. In particular, at 670 K, they are equal to 6.0 × 10−9, 3.2 × 10−9, and 2.0 × 10−12 cm2 s−1 for hydrogen, lithium, and oxygen, respectively. In the range 680–720 K, the self-diffusion coefficients of hydrogen and
lithium increase sharply with increasing temperature to approximately 10−6 cm2 s−1. A probable mechanism of migration of protons and lithium ions in LiOH and the role played in this process by the oxygen
ions with a lower mobility have been discussed. 相似文献
16.
In the paper the dependence of the photorefraction (PhR) in LiNbO3 and LiNbO3−Fe (0.1 wt%, 0.3wt%) crystals on light intensity (within 1016–1023 quanta·cm−2·s−1 at wavelengths 496.5 nm and 600 nm) and temperature (in the region 100–500 K) is studied. For all the crystals the limiting
values of PhR are similar and atT=293 K Δn
sat
lim
≈3·10−3. In LiNbO3 the temperature dependence of PhR in the range 100–500 K requires to take into account at least two trapping centres. 相似文献
17.
Thin-walled (∼200 μm) tubular membranes intended for the catalytic partial oxidation of natural gas have been manufactured
from La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) powders using viscous plastic processing technology. The perovskite-type powders were synthesised using various conventional
and novel techniques. The tubes have been characterised using a custom-built gas analysis rig with on-line mass spectrometry.
Porosity levels of the membranes were found to be very low (<0.5%) as calculated using a mass spectrometry leakage test. This
was confirmed by microstructural analysis of polished cross-sections using SEM. The spontaneous oxygen flux across the tubular
membranes was determined as a function of temperature. Oxygen permeation rates were found to range from 0.1 to 0.3 μmol cm−2s−1 at 1273 K.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献
18.
V. V. Lemanov A. V. Sotnikov E. P. Smirnova M. Weihnacht 《Physics of the Solid State》2002,44(11):2039-2049
Ceramic samples of (1−x)SrTiO3-xSrMg1/3Nb2/3O3 and (1−x)SrTiO3-xSrSc1/2Ta1/2O3 were prepared, and their dielectric properties were studied at x=0.005–0.15 and 0.01–0.1, respectively, at frequencies 10 Hz–1 MHz and at temperatures 4.2–350 K. A giant dielectric relaxation
was observed in the temperature range 150–300 K, and not so strong but well-developed relaxation was found in the temperature
range 20–90 K. The activation energy U and the relaxation time τ0 were determined to be 0.21–0.3 eV and from 10−11 to 10−12 s for the high-temperature relaxation and 0.01–0.02 eV and 10−8–10−10 s for the low-temperature relaxation, respectively. The additional local charge compensation of the heterovalent impurities
Mg2+ and Nb5+ (or Sc3+ and Ta5+) by free charge carriers or the host ion vacancies is suggested to be the underlying physical mechanism of the relaxation
phenomena. On the basis of this mechanism, the Maxwell-Wagner model and the model of reorienting dipole centers Mg2+ (or Sc3+) associated with the oxygen vacancy are proposed to explain the high-temperature relaxation with some arguments in favor
of the latter model. The polaron-like model with the Nb5+-Ti3+ center is suggested as the origin of the low-temperature relaxation. The reasons for the absence of ferroelectric phase transitions
in the solid solutions under study are also discussed.
From Fizika Tverdogo Tela, Vol. 44, No. 11, 2002, pp. 1948–1957.
Original English Text Copyright ? 2002 by Lemanov, Sotnikov, Smirnova, Weihnacht.
This article was submitted by the authors in English. 相似文献
19.
A small fraction of implanted muons exists as a paramagnetic state (presumably MuBC
0, muonium at the Si—Si bond center) in heavily Sb‐doped Si (n-type, [Sb]\ \simeq 1018\ cm–3). The paramagnetic state is susceptible to illumination both at 10–20 K and 290 K, providing evidence that holes (minority
carriers) play an important role in determining the dynamical properties of muonium centers, where change may occur via a
process MuBC
0+ h+\to MuBC
+ followed by charge exchange reaction (or transition Mu+
BC+ e−→ Mu0
T).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
W. J. Kossler X. H. Yu A. Greer H. E. Schone C. E. Stronach M. Davis R. S. Cary J. E. Crow W. F. Lankford J. Oostens 《Hyperfine Interactions》1991,63(1-4):81-86
Transverse and zero-field μSR measurements were made on YBa2(Cu1−xNix)3O7−y withx=0.1 and 0.2, and YBa2(Cu1−x
Zn
x
)3O7−y
withx=0.03, 0.06, 0.1, and 0.16, wherey≈0.1. Since doping may lead to magnetic ordering this was searched for with both zero and transverse field μSR, but no evidence
was found over the temperature range studied: 10–100 K. However, depolarization rates as functions of temperature were obtained,
and the low temperature values of these are σ=3.2 μs−1.1.6μs−1, and 1 μs−1 forx=0.01, and 0.2 Ni, respectively, and σ=0.8 μs−1, 0.75 μs−1, 0.65 μs−1, and 0.4 μs−1 forx=0.03, 0.06, 0.1, and 0.16 Zn, respectively. Estimates for the effect of decreasing electron concentration for Zn are made,
but these alone do not account for the drop in σ. Estimates for the effect of scattering on λ and hence σ are made. The reduction
in σ for Ni dopant is in surprisingly good agreement with these estimates. For Zn the order of magnitude is correct, but the
relative lack of further change in σ after the effect of the first 0.03 addition seems to imply a saturation of the effect
of scattering. 相似文献