共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
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
3.
ESR investigations on exchange coupled pairs of Cu ions in single crystals of Cu(dtc)2, isomorphously diluted with the corresponding diamagnetic zinc salt, are reported. The spin Hamiltonian parameters for the
coupled species (S=1) are:g
‖=2.1025,g
+=2.031,A=75.1×10−4 cm−1,B=14.8×10−4,D=276.0×10−4 cm−1 andE=46.7×10−4 cm−1. While theg andA tensors show tetragonal symmetry, the zeor-field splitting tensor is rhombic and has principal axes different from those
of theg andA tensors. Intensity measurements made down to 4.2 K indicate that the exchange is ferromagnetic with |FFF| ∼ 10 cm−1. Direct dipole-dipole interaction appears to be the major contribution to the zero-field splitting. A calculation on the
distributed point dipole model shows that dipolar interaction is considerably modified by the high covalency of the Cu-S bond
and accounts for the rhombic nature of the tensor. The possible exchange mechanisms in Cu(dtc)2—direct exchange and superexchange through the bridging sulphurs—are discussed. 相似文献
4.
Lorenzo Iorio 《General Relativity and Gravitation》2011,43(6):1697-1706
The strategy followed so far in the performed or proposed tests of the general relativistic Lense-Thirring effect in the gravitational
field of the Earth with laser-ranged satellites of LAGEOS type relies upon the cancelation of the disturbing huge precessions
induced by the first even zonal harmonic coefficient J
2 of the multipolar expansion of the Newtonian part of the terrestrial gravitational potential by means of suitably designed
linear combinations of the nodes Ω of more than one spacecraft. Actually, such a removal does depend on the accuracy with
which the coefficients of the combinations adopted can be realistically known. Uncertainties of the order of 2 cm in the semimajor
axes a and 0.5 milliarcseconds in the inclinations I of LAGEOS and LAGEOS II, entering the expression of the coefficient c
1 of the combination of their nodes used so far, yield an uncertainty δc
1 = 1.30 × 10−8. It gives an imperfectly canceled J
2 signal of 10.8 milliarcseconds per year corresponding to 23% of the Lense-Thirring signature. Uncertainties of the order
of 10–30 microarcseconds in the inclinations yield δc
1 = 7.9 × 10−9 which corresponds to an uncanceled J
2 signature of 6.5 milliarcseconds per year, i.e. 14% of the Lense-Thirring signal. Concerning a future LAGEOS-LAGEOS II-LARES
combination with coefficients k
1 and k
2, the same uncertainties in a and the less accurate uncertainties in I as before yield δk
1 = 1.1 × 10−8, δk
2 = 2 × 10−9; they imply a residual J
2 combined precession of 14.7 milliarcseconds per year corresponding to 29% of the Lense-Thirring trend. Uncertainties in the
inclinations at ≈ 10 microarcseconds level give δk
1 = 5 × 10−9, δk
2 = 2 × 10−9; the uncanceled J
2 effect is 7.9 milliarcseconds per year, i.e. 16% of the relativistic effect. 相似文献
5.
The rate constant for spin exchange in a system consisting of a metastable helium atom and an alkali-metal atom is determined.
An experiment on optical orientation of atoms established that the rate constant for spin exchange in a collision of a metastable
23
S
1 helium atom with a cesium atom in the 62
S
1/2 ground state equals (2.8±0.8)×10−9 cm3 s−1. The rate constant for chemoionization of cesium atoms by metastable helium atoms was determined at the same time to be (1.0±0.3)×109 cm3s−1.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 145–148 (10 August 1997) 相似文献
6.
Encapsulation of iron nanoparticles in alginate biopolymer for trichloroethylene remediation 总被引:2,自引:0,他引:2
Achintya N. Bezbaruah Sai Sharanya Shanbhogue Senay Simsek Eakalak Khan 《Journal of nanoparticle research》2011,13(12):6673-6681
Nanoscale zero-valent iron (NZVI) particles (10–90 nm) were encapsulated in biodegradable calcium-alginate capsules for the
first time for application in environmental remediation. Encapsulation is expected to offers distinct advances over entrapment.
Trichloroethylene (TCE) degradation was 89–91% in 2 h, and the reaction followed pseudo first order kinetics for encapsulated
NZVI systems with an observed reaction rate constant (k
obs) of 1.92–3.23 × 10−2 min−1 and a surface normalized reaction rate constant (k
sa) of 1.02–1.72 × 10−3 L m−2 min−1. TCE degradation reaction rates for encapsulated and bare NZVI were similar indicating no adverse affects of encapsulation
on degradation kinetics. The shelf-life of encapsulated NZVI was found to be four months with little decrease in TCE removal
efficiency. 相似文献
7.
The electron paramagnetic resonance (EPR) spectra of the trigonal prismatic complexes Tc(abt)3, Tc(bdt)3, Re(abt)3 and Re(bdt)3 (abt, O-aminobenzenethiol; bdt, benzene-1,2-dithiol) in dilute frozen solution are interpreted in terms of an axially symmetric spin
Hamiltonian, with g values close to two, principal hyperfine couplings of |A
Tc| ~ 5–12 × 10−4 cm−1, nuclear quadrupole couplings of |P
Tc| ~ 0.3–0.35 × 10−4 cm−1 and the unusual values 5 × 10−4 cm−1 ~ |A
zz
Re| < |P
Re| ~ |A
xx
Re| ~ |A
yy
Re| ~ 25 × 10−4 cm−1. Similar magnitudes of the parameters have been obtained by simulation of the previously published spectra of Re(pda)3, Re(tdt)3 and Re(pdt)3 (pda, O-phenylenediamine; tdt, toluene-3,4-dithiol; pdt, cis-1,2-diphenylethene-1,2-dithiol) by other authors. The unexpectedly large
value of P relative to A is a common feature of all the Re tris-dithiolato and related trigonal prismatic complexes studied by EPR and is attributed
to the high degree of delocalization of the unpaired electron onto the ligands and the distortion of the electron charge cloud.
These factors are less evident in the complexes Tc(abt)3 and Tc(bdt)3. Intermolecular dipolar interactions, narrowed by weak exchange, are responsible for some of the spectral features observed
in the solid state and concentrated (≫1 mM) frozen solutions, although there is no evidence for specific solute–solute interactions. 相似文献
8.
J. R. Kempton R. F. Marzke D. G. Fleming A. C. Gonzalez S. K. Leung J. J. Pan P. W. Percival M. Senba A. Tempelmann 《Hyperfine Interactions》1991,65(1-4):811-817
Results of the first μSR studies using Merck FO Optipur silica powder, which contains paramagnetic impurities at the ppb level
and has a surface area of 610±20 m2/g. are reported. Above 20 K, the transverse field muonium relaxation rate is roughly constant at 0.5 μs−1. Upon the addition of oxygen at ppm levels, the relaxation rate increases linearly with O2 concentration in the temperature range from 40–100 K yielding two-dimensional depolarization rate constants on the order
of 10−4 cm2 molecule−1 s−1. As the temperature is increased further, both oxygen and muonium desorb from the surface yielding a three-dimensional rate
constants at 300 K of 3.1(3)×10–10−10 cm3 molecule−1 s−1, in agreement with the gas phase value. Longitudinal field measurements suggest that MuO2 is formed and is able to spin exchange with other oxygen molecules. 相似文献
9.
Pramod Bhatt E. Carlegrim A. Kanciurzewska M. P. de Jong M. Fahlman 《Applied Physics A: Materials Science & Processing》2009,95(1):131-138
Thin film iron-tetracyanoethylene Fe(TCNE)
x
, x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed
physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron
spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE)
x
is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE− singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results.
The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge
transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE)
x
system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T
C
) seen for Fe(TCNE)
x
-type magnets. 相似文献
10.
M.?Silies H.?Witte S.?Linden J.?Kutzner I.?Uschmann E.?F?rster H.?Zacharias 《Applied Physics A: Materials Science & Processing》2009,96(1):59-67
The interaction of ultrashort laser pulses with solid state targets is studied concerning the production of short X-ray pulses
with photon energies up to about 10 keV. The influence of various parameters such as pulse energy, repetition rate of the
laser system, focusing conditions, the application of prepulses, and the chirp of the laser pulses on the efficiency of this
highly nonlinear process is examined. In order to increase the X-ray flux, the laser pulse energy is increased by a 2nd multipass
amplifier from 750 μJ to 5 mJ. By applying up to 4 mJ of the pulse energy a X-ray flux of 4×1010 Fe K
α
photons/s or 2.75×1010 Cu K
α
photons/s are generated. The energy conversion efficiency is therefore calculated to η
Fe≈1.4×10−5 and η
Cu≈1.0×10−5. The X-ray source size is determined to 15×25 μm2. By focusing the produced X-rays using a toroidally bent crystal a quasi-monochromatic X-ray point source with a diameter
of 56 μm×70μm is produced containing ≈104 Fe K
α1 photons/s which permits the investigation of lattice dynamics on a picosecond or even sub-picosecond time scale. The lattice
movement of a GaAs(111) crystal is shown as a typical application. 相似文献
11.
The luminescence kinetics of the Cd II ion at a wavelength of 441.6 nm has been studied experi-mentally in a high-pressure
He-Cd mixture in the presence of Ar, Ne, Xe, and CCl4 impurities. Cadmium ions were excited through the bombardment of a cadmium foil heated up to 240°C by a pulsed electron beam
with an electron energy of 150 keV, a pulse duration of 3 ns, and a current of 500 A. The constants of collisional quenching
of the Cd II 5s
2
2
D
5/2 level by Ar, Ne, and Xe atoms and CCl4 molecules and the integral luminescence quenching constants of this level in the helium medium by these impurity gases have
been determined. The constants of collisional quenching appeared to be 8.1 × 10−12 (Ar), 1.2 × 10−12 (Xe), 1.5 × 10−13 (Ne), and 1.8 × 10−10 cm3/s (CCl4, for λ = 325 nm), while the integral constants were found to be, respectively, 4.1 × 10−11, 3.4 × 10−11, 9.5 × 10−12, 1.4 × 10−9 cm3/s for Ar, Ne, Xe, and CCl4 at a buffer gas pressure of 1 atm.
Original Russian Text ? A.I. Miskevich, Liu Tao, 2009, published in Optika i Spektroskopiya, 2009, Vol. 107, No. 1, pp. 45–49. 相似文献
12.
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
13.
J. P. Xu X. Zou C. X. Li P. T. Lai C. L. Chan 《Applied Physics A: Materials Science & Processing》2009,94(2):419-422
Reactive cosputtering is employed to prepare high-permittivity HfTiO gate dielectric on n-Ge substrate. Effects of Ge-surface
pretreatment on the interface and gate leakage properties of the dielectric are investigated. Excellent performances of Al/HfTiO/GeO
x
N
y
/n-Ge MOS capacitor with wet–NO surface pretreatment have been achieved with a interface-state density of 2.1×1011 eV−1 cm−2, equivalent oxide charge of −7.67×1011 cm−2 and gate leakage current density of 4.97×10−5 A/cm2 at V
g
=1 V. 相似文献
14.
A. V. Derbin A. S. Kayunov V. N. Muratova 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):805-810
A search for the axioelectric absorption of 5.5-MeV solar axions produced in the p + d → 3He + γ (5.5 MeV) reaction was performed with two BGO detectors placed inside a low-background setup. Constraints on the axion-electron
coupling constant were obtained for axions with masses in the (0.1–1.0)-MeV range: g
Ae ≤ (1.8–9.0) × 10−7. The solar positron flux from A → e− + e+ decay was determined for axions with masses m
A
> 2m
e. Using the existing experimental data on the interplanetary positron flux, a new constraint on the axion-electron coupling
constant for axions with masses in the (1.2–5.4)-MeV range was obtained: g
Ae ≤ (1–5) × 10−17. 相似文献
15.
The angular dependences of the electron spin resonance spectrum of 1% Ni2+ ions in a ZnSiF6·6H2O matrix are investigated experimentally at 36 GHz and 4.2 K. Besides the main spectrum of the isolated ion, we observed a
spectrum due to interacting pairs of Ni2+ ions, located in the first (nn) and second (2n) coordination spheres and coupled by, besides the magnetic dipole-dipole interaction, isotropic exchange: J
nn
= (−197±1)×10−4, J
2nα
= (−5±1)×10−4, and J
2nβ
= (3±2)×10−4 cm−1. Lines due to other isolated Ni2+ ions, which have a different initial splitting D, are also present in the spectrum with intensity comparable to the pair spectrum. Low-symmetry distortions of the crystal
field are observed, caused by a pair of impurity ions located close to one another. It is shown that the previously proposed
interpretation is incorrect.
Fiz. Tverd. Tela (St. Petersburg) 41, 1602–1608 (September 1999) 相似文献
16.
The binding of quercetin to lysozyme (LYSO) in aqueous solution was investigated by fluorescence spectroscopy, UV-vis absorption
spectroscopy and molecular simulation at pH 7.4. The fluorescence quenching of LYSO by addition of quercetin is due to static
quenching, the binding constants, K
a
, were 3.63 × 104, 3.31 × 104 and 2.85 × 104 L·mol−1 at 288, 298 and 308 K, respectively. The thermodynamic parameters, enthalpy change, ∆H, and entropy change, ∆S, were noted to be −7.56 kJ·mol−1 and 61.07 J·mol−1·K−1. The results indicated that hydrophobic interaction may play a major role in the binding process. The distance r between the donor (LYSO) and acceptor (quercetin) was determined as 3.34 nm by the fluorescence resonance energy transfer.
The synchronous fluorescence spectroscopy showed the polarity around the tryptophan residues increased and the hydrophobicity
decreased. Furthermore, the study of molecular simulation indicated that quercetin could bind to the active site (a pocket
made up of 24 amino-acid residues) of LYSO mainly via hydrophobic interactions and that there were hydrogen interactions between
the residues (Gln 57, Ile 98) of LYSO and quercetin. The accessible surface area (ASA) calculation verified the important
roles of tryptophan (Trp) residues during the binding process. 相似文献
17.
Wenwei Ge Hong Liu Xiangyong Zhao Xiaobing Li Xiaoming Pan Di Lin Haiqing Xu Xiangping Jiang Haosu Luo 《Applied Physics A: Materials Science & Processing》2009,95(3):761-767
In this paper, a single crystal of 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 with dimensions of Φ 30×10 mm was grown by the top-seeded-solution growth method. X-ray powder diffraction results show that the as-grown crystal
possesses the rhombohedral perovskite-type structure. The dielectric, piezoelectric and electrical conductivity properties
were systematically investigated with 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples. The room-temperature dielectric constants
for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples are found to be 650, 740 and 400 at 1 kHz. The (T
m, ε
m) values of the dielectric temperature spectra are almost independent of the crystal orientations; they are (306°C, 3718),
(305°C, 3613) and (307°C, 3600) at 1 kHz for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal. The optimum poling conditions were
obtained by investigating the piezoelectric constants d
33 as a function of poling temperature and poling electric field. For the 〈001〉 and 〈110〉 crystal samples, the maximum d
33 values of 146 and 117 pC/N are obtained when a poling electric field of 3.5 kV/mm and a poling temperature of 80°C were applied
during the poling process. The as-grown 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 crystal possesses a relatively large dc electrical conductivity, especially at higher temperature, having a value of 1.98×10−11 Ω−1⋅m−1 and 3.95×10−9 Ω−1⋅m−1 at 25°C and 150°C for the 〈001〉 oriented crystal sample. 相似文献
18.
R. Bernabei P. Belli F. Cappella R. Cerulli C. J. Dai A. d’Angelo H. L. He A. Incicchitti H. H. Kuang X. H. Ma F. Montecchia F. Nozzoli D. Prosperi X. D. Sheng Z. P. Ye 《The European Physical Journal C - Particles and Fields》2009,62(2):327-332
In this paper a new search for non-Paulian nuclear processes, i.e. processes normally forbidden by the Pauli Exclusion Principle
(PEP), is presented. It has been carried out at the Gran Sasso National Laboratory of the INFN by means of the highly radiopure
DAMA/LIBRA set-up (sensitive mass of about 250 kg highly radiopure NaI(Tl)). In particular, a new improved upper limit for
the spontaneous non-Paulian emission rate of protons with energy E
p
≥ 10 MeV in 23Na and 127I has been obtained: 1.63 × 10−33 s−1 (90% C.L.). The corresponding limit on the relative strength (δ
2) for the searched non-Paulian transition is δ
2≲(3–4)×10−55 (90% C.L.). Moreover, PEP-violating electron transitions in iodine atoms have also been investigated. Lifetimes shorter than
4.7×1030 s are excluded at 90% C.L.; this allows us to derive the limit δ
e
2<1.28×10−47 (90% C.L.). This latter limit can also be related to a possible finite size of the electron in composite models of quarks
and leptons providing superficial violation of the PEP; the obtained upper limit on the electron size is r
0<5.7×10−18 cm (energy scale of E≳3.5 TeV). 相似文献
19.
R. Yu. Abdulsabirov I. I. Antonova S. L. Korableva N. M. Nizamutdinov V. G. Stepanov N. M. Khasanova 《Physics of the Solid State》1997,39(3):423-425
The orientational dependences of the EPR spectra of Fe3+-doped LiCaAlF6 single crystals (space group P31c, Z=2), grown at the Laboratory of Magnetic Radio Spectroscopy at Kazan’ State University, have been investigated in detail.
The spectrum is described by a trigonal spin Hamiltonian with the following parameters: B
20=40.072×10−4 cm−1, B
40=−5.799×10−4 cm−1, B
43=−4.281×10−4 cm−1, A
s=24.33±1, A
p=6.13±1, g
∥=g
⊥=2.00217±0.0003. A theoretical calculation of the hyperfine structure parameters shows that they are described quite well
when allowance is made for the overlapping of the wave functions of the paramagnetic center and the ligands (F−).
Fiz. Tverd. Tela (St. Petersburg) 39, 488–490 (March 1997) 相似文献
20.
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