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1.
A theoretical analysis is made of the flow of vibrationally excited hydrogen in a channel. It is shown that coverage of the
channel walls with adsorbed hydrogen atoms can substantially increase the concentration of vibrationally excited molecules
in the stream. The possibility of applying these results to bulk sources of negative H− hydrogen ions is discussed. It is shown that the rate of H− ion generation in the source may be enhanced appreciably under conditions where this generation is achieved by dissociative
attachment of thermal electrons to H2 molecules injected into the discharge chamber, whose vibrational distribution function has been pre-enriched in excited molecules
by suitably organizing the hydrogen flow in the channel.
Zh. Tekh. Fiz. 69, 15–21 (June 1999) 相似文献
2.
A. D. Bass J. H. Bredehöft E. Böhler L. Sanche P. Swiderek 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(2):53
Thermal desorption spectrometry (TDS) and electron stimulated desorption (ESD) are
employed to investigate mechanisms responsible for the formation of
C2H6 in electron irradiated multilayer films of acetonitrile
(CH3CN) at 30 K. Using a high sensitivity time-of-flight mass spectrometer,
we observe the ESD of anionic fragments H−,
CH2
−,
CH3
−
and CN−. Desorption occurs following dissociative electron attachment (DEA) via
several negative ion resonances in the 6 to 14 eV energy range and correlates well with a
“resonant” structure seen in the TDS yield of C2H6 (i.e., at mass
30 amu). It is proposed that C2H6 is formed by the reactions of
CH3 radicals generated following DEA to CH3CN which also yields
CN−. Between 2 and 5 eV, a second resonant feature is seen in the
C2H6 signal. While DEA is observed in the gas phase at these
energies, no anion desorption occurs since anionic fragments likely have insufficient
kinetic energy to desorb. Since the CH2
−
ion has not been observed in gas-phase measurements, we propose that it is formed, along
with HCN (that is detected in TDS) when dissociation into
CH3
−
and CN is hindered by adjacent molecules. 相似文献
3.
V. Vizcaino S. E. Huber P. Sulzer M. Probst S. Denifl P. Scheier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(1):27
A detailed study on dissociative electron attachment (DEA) to
2,3-dimethyl-2,3-dinitrobutane (DMNB) in the gas phase is presented. Ion yields as a
function of the incident electron energy from about 0 to 14 eV have been measured for the
most dominant fragments including anions such as NO2
−,
[M-NO2]− or N2O4
−. To help
identifying which anion and neutral fragments are formed upon electron attachment we
calculated the thermodynamic thresholds using the G4(MP2) method. 相似文献
4.
The unit cell of triglycine sulfate (TGS) contains the following glycine ions: dimers (GIISHBGIII)+ with a short hydrogen bond (SHB) and a monomer (SO4LHBGI)+ with a long hydrogen bond (LHB) to the SO4
2− anion. The spontaneous polarization results from a statistical charge distribution and the Coulomb interaction between SO4
2− and fast rotating –NH3
+ groups. In the lamellar model, chains of –SO4–(GIISHBGIII)–SO4–(GIISHBGIII)–SO4 lying along the polar b-axis are linked perpendicularly to this axis by SO4LHBGI+ units. Tilting the LHBGI+ ion around the axis in the mirror plane decides on the direction of the charge displacement from this symmetry plane. The
reversal of the spontaneous polarization, i.e., −P
S↔ +P
S, is related to the rotation of the NH3 group. If this rotation becomes slowed down at low temperature and/or under high pressure, the coercive field increases dramatically.
Application of an external electric field E
⊥ perpendicular to the b-axis leads to a hysteresis loop of the polarity P(E), and finally to its disappearance. This phenomenon comes from an ordering of protons in hydrogen bonds perpendicular to
the polar axis. This is the first study of the E
⊥ effect by nuclear magnetic resonance.
Authors' address: Jan Stankowski, Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, Poznań 60-179,
Poland 相似文献
5.
Electrical conductivity, differential scanning calorimetry, and X-ray diffraction measurements were performed on a pentacesium trihydrogen tetrasulfate, Cs5H3(SO4)4, crystal. The transition entropy at a superionic phase transition and the activation energy of proton migrations in the superionic phase were determined to be 58.2 J K−1 mol−1 and 0.48 eV, respectively. The crystal structure of Cs5H3(SO4)4 at room temperature was refined. The electrical conduction in Cs5H3(SO4)4 was discussed with the refined structure. 相似文献
6.
The binding energy of a hydrogen molecule on metal atoms (Li, Be, Na, and Mg) attached to aromatic hydrocarbon molecules (benzene
and anthracene) was calculated using an ab initio molecular orbital method at the MP2(FC)/cc-pVTZ level with basis set superposition
error (BSSE) correction. The energy tended to become more negative as the metal atom had a more positive charge and a smaller
radius. The energies of Li2C6H6-H2, Li2C14H10-H2, Na2C14H10-H2, and MgC14H10-H2 were −2.7 to −2.2, −4.0 to −3.1, −2.8 to −0.3, and −1.3 kcal/mol, respectively. Most of these energies were more negative
than those on the hydrocarbons without metal atoms (ca. −1 kcal/mol). Analyzing the Lennard–Jones type potential with the
parameters determined by the MP2 calculations, it was found that these energies mainly consisted of the induction force caused
by the positive charge of the metal atom and the dispersion force from the nearest C6-ring. The energy of BeC14H10-H2 was more negative (−8.6 kcal/mol) than of the other complexes. The hydrogen molecule in this complex had a comparatively
longer H–H distance and a more positive H2 charge than the others. These data suggest that the hydrogen adsorption on this complex involves a charge transfer process
in addition to physisorption interactions. The hydrogen binding energies in some Li2C14H10-H2 systems (∼−4.0 kcal/mol) and BeC14H10-H2 are promising to operate hydrogen storage/release at ambient temperature with moderate pressure. 相似文献
7.
It is shown that high-accuracy contact-free measurements of the divergence and emittance of an accelerated H− ion beam at the exit from the source can in principle be performed by passive Doppler spectroscopy of a beam of excited hydrogen
atoms produced by neutralization of the ions with excitation on the residual gas in the source channel. The intensity of the
Hα-line radiation detected by the Doppler system is calculated, taking into account the principal processes leading to the excitation
and deexcitation of the 3s, 3p, and 3d levels of the hydrogen atoms in the beam, for residual gas densities of the order of 10−4–10−5 Torr in the source channel. The computed Hα-line intensity was confirmed experimentally, making it possible to perform photoelectronic detection of the spectral contour
of the line in the current mode rather than the photon-counting mode.
Zh. Tekh. Fiz. 68, 15–18 (June 1998) 相似文献
8.
Jií ejka Ray L. Frost Jií Sejkora Eloise C. Keeffe 《Journal of Raman spectroscopy : JRS》2009,40(11):1464-1468
Raman spectra of jáchymovite, (UO2)8(SO4)(OH)14·13H2O, were studied, complemented with infrared spectra, and compared with published Raman and infrared spectra of uranopilite, [(UO2)6(SO4)O2(OH)6(H2O)6]·6H2O. Bands related to the stretching and bending vibrations of (UO2)2+, (SO4)2−, (OH)− and water molecules were assigned. U O bond lengths in uranyl and O H· · ·O hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
9.
Water-soluble Mn2+-doped ZnS quantum dots (QDs) were prepared using mercaptoacetic acid as the stabilizer. The optical properties and structure
features were characterized by X-Ray, absorption spectrum, IR spectrum and fluorescence spectrum. In pH 7.8 Tris-HCl buffer,
the QDs emitted strong fluorescence peaked at 590 nm with excitation wavelength at 300 nm. The presence of sulfide anion resulted
in the quenching of fluorescence and the intensity decrease was proportional to the S2− concentration. The linear range was from 2.5 × 10−6 to 3.8 × 10−5 mol L−1 with detection limit as 1.5 × 10−7 mol L−1. Most anions such as F−, Cl−, Br−, I−, CH3CO2
−, ClO4
−, CO3
2−, NO2
−, NO3
−, S2O3
2−, SO3
2− and SO4
2− did not interfere with the determination. Thus a highly selective assay was proposed and applied to the determination of
S2− in discharged water with the recovery of ca. 103%. 相似文献
10.
V. A. Pushkarchuk S. Ya. Kilin A. P. Nizovtsev V. E. Borisenko A. B. Filonov A. L. Pushkarchuk S. A. Kuten’ 《Optics and Spectroscopy》2010,108(2):247-253
The effect of the surface of diamond on atomic, electronic, and spin properties of diamond nanocrystals containing single
nitrogen-vacancy defects ([NV]− centers) is studied. The surface was modeled with clusters C33H30[NV]−, C66H72[NV]−, which were constructed based on bulk clusters C33H36[NV]− and C69H84[NV]−, respectively. In all cases, clusters in the triplet state S = 1 are considered with the cluster charge being −1. The geometric structure of clusters is optimized using the principle
of minimization of the total energy of the system; then, the electronic and spin characteristics of clusters are calculated
by the density functional theory. The isotropic and anisotropic hyperfine interaction constants of the electron spin of the
NV center with the nuclear spin of the nitrogen atom and 13C atoms located at different sites in the cluster are calculated. It is found that, in contrast to bulk clusters with [NV]-centers
in which the spin density is mainly localized at the three carbon atoms that are the nearest neighbors of the vacancy of the
center, upon arrangement of the NV center in the immediate proximity to the surface, the spin density is redistributed such
that it is mainly localized at the three carbon atoms that are the nearest neighbors of the nitrogen atom of the center and
at C atoms that form the first atomic layer of the (111) surface of the nanocrystal. 相似文献
11.
Ryosuke Nakahara Satomi Kashitani Kumi Hayakawa Yuuki Kitani Takako Yamaguchi Yoshikazu Fujita 《Journal of fluorescence》2009,19(5):769-775
A fluorophotometric method for the determination of hydrogen peroxide (H2O2) using fluorescin was developed. This method was based on the oxidative reaction of fluorescin, a colorless, non-fluorescent
lactoid fluorescein, by H2O2 to give highly fluorescein fluorescence emission. In the determination of H2O2, the calibration curve exhibited linearity over the H2O2 concentration range of 1.5–310 ng mL−1 at an emission wavelength of 525 nm with an excitation of 500 nm and with relative standard deviations (n = 6) of 2.51%, 2.48%, and 1.31% for 3.1 ng mL−1, 30.8 ng mL−1, and for 308 ng mL−1 of H2O2, respectively. The detection limit for H2O2 was 1.9 ng mL−1 six blank determinations was performed (ρ = 6). This proposed method was applied to detection of other reactive oxygen species and nitrogen species (ROS/RNS) such
as singlet oxygen (1O2), hydroxyl radical (•OH), peroxynitrite (ONOO−) etc., and it was possible to detect them with a high sensitivity. In addition, this proposed method was applied to the recovery
tests of H2O2 in calf serum, human saliva, rain water, and wheat noodles; the results were satisfactory. 相似文献
12.
The nonrelativistic and relativistic energy eigenvalues of the electron in the inhomogeneous magnetic fieldH
z
=Hr
−1,r=(x
2 +y
2)1/2 are derived in a form displaying the explicit spin dependence. The possibility of magnetic hydrogen atom formation and the
spontaneouse
+
e
− pair creation following from these eigenvalues is mentioned. The expressions for pressure, energy, particle number and magnetic
moment of an electron gas in this IMF are calculated in the degenerate limit. The possibility of spontaneous magnetisation,i.e., ferromagnetic behaviour, is established. Further, the pressure of the electron gas in the same type of fields is an order
of magnitude higher than those in a homogeneous magnetic field and crossed homogeneous electric and magnetic fields for comparable
field strengths. 相似文献
13.
The infrared spectra of tutton salts 1. A comparative study of (NH4)2 M″(SO4)2·6H2O (M″=Ni,Co or Mg)
The infrared spectra of (NH4)2M″(SO4)2.6H2O has been analysed in the region 4000–250 cm−1. The dynamics of each crystal has been discussed in terms of 234 phonon modes, including 3 acoustical ones, using the unit
cell approximation. The ambiguity in the assignments of the bands in the region 900–500 cm−1 has been removed by assigning the bands in this region to the libratory modes of H2O molecules. It has been concluded that the NH
4
+
and SO
4
2−
ions have a symmetry lower thanT
dand also the complex [M″(H2O)6]2+ has a symmetry lower than O
h
. The hydrogen bonding is the strongest in the Ni-salt and the weakest in the Mg-salt. 相似文献
14.
Hosseini M Ganjali MR Tavakoli M Norouzi P Faridbod F Goldooz H Badiei A 《Journal of fluorescence》2011,21(4):1509-1513
A novel and simple fluorescence enhancement method for selective pyrophosphate(PPi) sensing was proposed based on a 1:1 metal
complex formation between bis(8-hydroxy quinoline-5-solphonat) chloride aluminum(III) (Al(QS)2Cl), (L) and PPi in aqueous solution. The linear response range covers a concentration range of 1.6 × 10−7 to 1.0 × 10−5 mol/L of PPi and the detection limit of 2.3 × 10−8 mol/L. The association constant of L-PPi complex was calculated 2.6 × 105 L/mol. L was found to show selectively and sensitively fluorescence enhancement toward PPi over than I3-, NO3-, CN−, CO32−, Br−, Cl−, F−, H2PO4− and SO42−, which was attributed to higher stability of inorganic complex between pyrophosphate and L. 相似文献
15.
Fourier transform infrared spectroscopy studies have been conducted to investigate the interaction among components in a system
of high molecular weight polyvinylchloride (PVC)–lithium trifluoromethanesulfonate (LiCF3SO3) incorporated with different type of plasticizers, namely, ethylene carbonate (EC), propylene carbonate (PC), and dibutylphthalate
(DBP). Interaction between PVC and LiCF3SO3 was confirmed by C–H rocking mode at 1,255 cm−1 for PVC shift to 1,252 cm−1 in PVC–LiCF3SO3. The plasticizers’ carbonyl (C=O) oxygen atom which carries lone pair electrons interact with Li+ of LiCF3SO3 and methine hydrogen of PVC in LiCF3SO3–plasticizer system and PVC–plasticizer system, respectively. Changes in peaks assigned to 1,264 cm−1 (ν
as(SO3)), 1,033 cm−1 (ν
s(SO3)), 1,181 cm−1 (ν
as(CF3)), 1,230 cm−1 (ν
s(CF3)), 765 cm−1 (δ
s(CF3)), 644 cm−1 (δ
s(SO3)), 578 cm−1 (δ
as(CF3)), and 519 cm−1 (δ
as(SO3)) indicate the occurrence of complexation in the PVC–LiCF3SO3 system, LiCF3SO3–plasticizer system, and PVC–LiCF3SO3–plasticizer system. 相似文献
16.
E. V. Korolik R. G. Zhbankov A. A. Ivanov G. K. Il’ich N. I. Insarova V. G. Leshchenko 《Journal of Applied Spectroscopy》1998,65(6):906-910
Use of low-temperature IR spectroscopy in studies of compounds with a developed system of hydrogen bonds such as DL-serine
revealed a complete set of vibrational frequencies. The region of manifestation of stretching vibrations of OH groups involved
in the formation of strong hydrogen bonds was found. It is shown experimentally that in a crystal some of the molecules of
SL-serine exist in the nonionized form. On the basis of analysis of experimental data, frequency ranges of stretching deformation
and torsional vibrations of NH
3
+
, COO−, and OH groups were determined more accurately. It is found that in the crystals there exist molecules of DL-serine with
different spatial orientation of NH
3
+
COO−, and COH groups. It is shown that conformational diversity of molecular structures is also preserved at T=18 K.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 864–868, November–December, 1998. 相似文献
17.
In the present work, five systems of samples have been prepared by the solution casting technique. These are the plasticized
poly(methyl methacrylate) (PMMA-EC) system, the LiCF3SO3 salted-poly(methyl methacrylate) (PMMA-LiCF3SO3) system, the LiBF4 salted-poly(methyl methacrylate) (PMMA-LiBF4) system, the LiCF3SO3 salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiCF3SO3) system, and the LiBF4 salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiBF4) system. The conductivities of the films from each system are characterized by impedance spectroscopy. The room temperature
conductivity in the pure PMMA sample and (PMMA-EC) system is 8.57 × 10−13 and 2.71 × 10−11 S cm−1, respectively. The room conductivity for the highest conducting sample in the (PMMA-LiCF3SO3), (PMMA-LiBF4), ([PMMA-EC]-LiCF3SO3), and ([PMMA-EC]-LiBF4) systems is 3.97 × 10−6, 3.66 × 10−7, 3.40 × 10−5, and 4.07 × 10−7 S cm−1, respectively. The increase in conductivity is due to the increase in number of mobile ions, and decrease in conductivity
is attributed to ion association. The increase and decrease in the number of ions can be implied from the dielectric constant,
ɛr-frequency plots. The conductivity–temperature studies are carried out in the temperature range between 303 and 373 K. The
results show that the conductivity is increased when the temperature is increased and obeys Arrhenius rule. The plots of loss
tangent against temperature at a fixed frequency have showed a peak at 333 K for the ([PMMA-EC]-LiBF4) system and a peak at 363 K for the ([PMM-EC]-LiCF3SO3) system. This peak could be attributed to β-relaxation, as the measurements were not carried out up to glass transition temperature,
T
g. It may be inferred that the plasticizer EC has dissociated more LiCF3SO3 than LiBF4 and shifted the loss tangent peak to a higher temperature.
Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006 相似文献
18.
A new chemosensing ensemble that displays sensitive and selective fluorescent recognition of pyrophosphate in water at pH
7.4 has been developed. The ensemble is constructed by a copper complex (receptor) and eosin Y (indicator), the constructed
ensemble is capable of highly selectively discriminate pyrophosphate from other common existing anions such as CH3COO−, HSO4−, NO3−, H2PO4−, HPO42−, PO43−, NCS−, I−, Cl−, Br−, F−as well as some structurally similar carboxylates such as citrate, tartrate, oxalate, malonate, succinate and glutarate. 相似文献
19.
ABSTRACT Raman spectra of the uranyl-containing mineral coconinoite, Fe2Al2(UO2)2(PO4)4(SO4)(OH)2 · 20H2O, are presented and compared with the mineral's infrared spectra. Bands connected with (UO2)2+, (PO4)3?, (SO4)2?, (OH)?, and H2O stretching and bending vibrations are assigned. Approximate U?O bond lengths in uranyl, (UO2)2+, and O?H…O hydrogen bond lengths are calculated from the wavenumbers of the U?O stretching vibrations and (OH)? and H2O stretching vibrations, respectively, and compared with published data for similar natural and synthetic compounds. 相似文献
20.
Chunhua Zhu Mingcui Guo Xinbao Zhu Jiafu Chen Ji-Hu Su 《Applied magnetic resonance》2012,42(3):313-320
Paramagnetic centers of the solid superacid catalyst in the sulfated TiO2 are prone to the electron paramagnetic resonance (EPR) spectroscopy. The induction of the catalytic-active sites in TiO2 powder presubmerged in H2SO4 solution as a function of the calcinated temperature of 293–873 K is investigated by X-band in situ continuous-wave EPR measurements.
Sulfated-acid sites composed of the Ti3+ ion are formed upon calcination. The overall experimental results show that the population of these sites goes uphill with
the elevating temperature, reaches a maximum at ~623 K and decreases afterward to close zero. During the process, the decomposition
of the TiO2/SO4
2− leads to the formation of Ti3+ species and then to the increasing EPR signal amplitude, and the consecutive decomposition of the sulfur at higher temperature
(>650 K) to the diminishing signal. The X-ray diffraction indicates that the introduction of SO4
2− stabilizes the geometric structure in the anatase phase. 相似文献