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1.
A. S. Zubkov V. I. Artyukhov L. A. Chernozatonskii O. S. Nedelina 《Russian Journal of Physical Chemistry B, Focus on Physics》2011,5(5):748-764
Electron transfer is an elementary chemical event involved in many biochemical reactions. Experiments have shown that some
oxyacids participating in electron transport are capable of dissociative capture of low-energy electrons, a process indicative
of the formation of a metastable anion. The present work reports the results of quantum-chemical simulations of the dissociative
electron attachment to a number of oxyacids (H3PO4, H2SO4−, HPO42−, H2SO4, HSO4−, B(OH)4−, HCOOH) with formation of a hydrogen atom in vacuum and in the aqueous medium. Phosphate is one of the most important building
units of biological molecules, whereas formic acid can serve as a model of the −COOH group in amino acids, carboxylic acids,
functional sites of enzymes, etc. The electron affinity of these oxyacids in the aquatic environment is positive and exceeds
the energy of hydrogen atom abstraction. The proton of the OH group captures the electron, while the aquatic environment stabilizes
it in the trapped state due to its polarizability. The data obtained provide a fresh look at the phenomenon of proton-assisted
electron transfer and at the use of oxyacid buffers. 相似文献
2.
M. A. Bolshov Y. A. Kuritsyn V. V. Liger V. R. Mironenko S. B. Leonov D. A. Yarantsev 《Applied physics. B, Lasers and optics》2010,100(2):397-407
A tunable diode laser absorption spectroscopy (TDLAS) technique and appropriate instrumentation was developed for the measurement
of temperature and water vapor concentrations in heated gases. The technique is based on the detection of the spectra of H2O absorption lines with different energies of low levels. The following absorption lines of H2O were used: 7189.344 cm−1 (E″=142 cm−1), 7189.541 cm−1 (E″=1255 cm−1), 7189.715 cm−1 (E″=2005 cm−1). Spectra were recorded using fast frequency scanning of a single distributed feedback (DFB) laser. A unique differential
scheme for the recording of the absorption spectra was developed. An optimal technique for fitting the experimental spectra
was developed. 相似文献
3.
A. E. Galashev O. R. Rakhmanova 《Russian Journal of Physical Chemistry B, Focus on Physics》2011,5(2):197-208
The molecular dynamics method is used to investigate the interaction of two, four, and six chloride ions with (H2O)50, clusters absorbing six ozone molecules. Chloride ions moving toward the cluster penetrate into it. The presence of ozone
increases the residence time of Cl− ions in the cluster. The duration of the perturbation increases with the number of Cl− ions surrounding the 6O3 + (H2O)50 system. The interaction with Cl− ions enhances the positional disorder of the molecules in the system and enhances the intensity of absorption and emission
of infrared radiation. These changes, however, are not monotonic function of the number of ions perturbing the system. As
a result of the interaction with Cl− ions, the integrated intensity of the Raman scattering on the (O3)6(H2O)50 cluster in the frequency range 0 ≤ ω ≤ 1100 cm−1 is significantly lower and the number of peaks in the spectrum is smaller. 相似文献
4.
A. E. Galashev O. R. Rakhmanova O. A. Novruzova 《Russian Journal of Physical Chemistry B, Focus on Physics》2011,5(3):450-460
The molecular dynamics method is used to study the interaction of the (Br−)
i
(H2O)50 − i
clusters in a medium of water vapor with ozone molecules. The clusters absorb O3 molecules and retain them, along with Br− ions, for a 25-ps-long calculation procedure. The presence of bromide ions results in significant increases in the values
of the real and imaginary parts of the relative permittivity. The addition of bromide ions causes a significant increase in
the integrated IR radiation absorption intensities and in the radiant power emitted by the clusters. The addition of Br− ions only slightly affects the intensity of the Raman spectra until the number of Br− reaches six, when a dramatic decrease of the integrated intensity of this spectrum occurs. Bromide ions absorbed by water
clusters produce a much more lasting impact on the ozone molecules trapped by the cluster than chlorine ions do, all other
things being equal. 相似文献
5.
S. M. Pershin 《Physics of Wave Phenomena》2009,17(4):241-250
A mechanism is proposed for the previously observed [1] jump in erythrocyte fluidity through a microcapillary 1.3 μm in diameter
at a temperature of 36.6±0.3°C. Our interpretation is based on the experimental evidence both for existence of ortho and para
H2O isomers in water and on spin-selective interaction of proteins with para H2O isomers as hydration shells of biomolecules are being formed [2]. It is important that the formation of hydration shells
of proteins and DNA in aqueous solutions is accompanied by an increase in the Brillouin shift to 0.4 cm−1 (≃0.25 cm−1 in water), which points to the formation of icelike structures. We believe that the coincidence of the translational energy
kT of the Brownian motion and the energy of the rotational quanta for the 313–202 transition of para H2O isomers at the temperature 36.6°C increases the probability for excitation of para H2O isomers in collisions. Collisions mix quantum states of closely spaced levels in para H2O (313, 285.2 cm−1) and ortho H2O (330, 285.4 cm−1) and induce conversion of para isomers to ortho H2O. It is assumed that this conversion in the icelike hydration shell of hemoglobin (Hb) is accelerated under the catalyzing
effect of oxygen and iron present in Hb and triggers a chain reaction: release of ortho H2O isomers through the erythrocyte membrane→compaction of Hb molecules and increase in concentration of catalysts→acceleration
of conversion→structural gel-sol transition. It is the sequence of these processes that provides a jump in fluidity of erythrocytes
through a microcapillary and the anomalous increase in fluidity of the aqueous solution of hemoglobin by almost an order of
magnitude at temperatures close to 36.6°C and an increase in the solution concentration by a factor of 1.7. 相似文献
6.
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
7.
V. D. Maiorov G. I. Voloshenko N. B. Librovich 《Russian Journal of Physical Chemistry B, Focus on Physics》2011,5(2):271-277
The methanesulfonic acid (MSA)-diethylamine (DEA) binary liquid system is studied over the entire range of compositions at
30°C by using multiple frustrated total internal reflection IR spectroscopy. Solutions with acid: base equimolar ratio contain
only 1 : 1 ion pairs. Upon adding the acid, a MSA molecule abstracts an anion from the 1 : 1 complex to produce a protonated
DEA and an (H3C(O2)SO…H…OS(O2)CH3)− anion with a strong H bond: (C2H5)2(H)NH+ · OS(O2)CH3− + HOS(O2)CH3 ↔ (C2H5)2(H)NH+ + (H3C(O2)SO…H…OS(O2)CH3)−. This equilibrium is shifted to the left. The 1 : 1 complex is present in solutions even at an significant excess of the
acid. To protonate the complex, it is required at least two MSA molecules. Under conditions of an excess of the base, DEA
molecules do not solvate the 1 : 1 complex. The solution separates into two phases, composed of (C2H5)2(H)NH+ · OS(O2)CH3− complexes and pure DEA. 相似文献
8.
V. A. Kuz'mitskii 《Journal of Applied Spectroscopy》2005,72(3):360-370
The geometric structure of the chlorin molecule (H2Ch) has been calculated by the restricted and unrestricted Hartree-Fock (RHF and UHF) methods with an AM1 Hamiltonian. Transformations
of this molecule into excited electronic states have been calculated by the CNDO/S method. The RHF method without symmetry
restrictions gives a plane structure for the chlorin macrocycle with an alternation of the lengths of the bonds along the
18-member azacyclopolyene and a C1h symmetry for the molecule as a whole. The level of the first excited state Q1 of this structure is substantially shifted (δ
≅ +4000 cm−1) relative to the Qx level of porphin (H2P) toward shorter waves, which is in contradiction with the experimental data, according to which this shift is long-wave
and is equal to δ
= −400 to −550 cm−1. The optimization of the geometry of H2Ch by the UHF method has shown that it has a structure with an 18-member azacyclopolyene with bonds of equal lengths and a
D2h symmetry. For this geometry of H2Ch the calculated shift of the Qx level, equal to δ
= −70 cm−1, is bathochromic and the position of the Qy level is practically exactly coincident with the experimental one. For the geometry calculated by the RHF method with restrictions
on the D2h symmetry of the 18-member azacyclopolyene δ
= +180 cm−1, and for the geometry calculated with restrictions on the highest C2v symmetry of the H2Ch molecule δ
= +620 cm−1. The latter result shows that the “natural” requirement for the C2v symmetry of the H2Ch macrocycle, which is frequently used in various calculations, is inadequate to achieve a quantitative agreement between
the calculation and experimental data and, in this case, the lengths of the bonds along the 18-member azacyclopolyene are
not equal.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 339–347, May–June, 2005. 相似文献
9.
N. R. Troitsky L. E. Pirogov I. I. Zinchenko J. Yang 《Radiophysics and Quantum Electronics》2005,48(7):491-499
We present results of observations of 23 compact cores of molecular clouds associated with IRAS “ cold” infrared sources.
The observations were performed in the J = 1−0 line of the C18O molecule on a 13.7-meter radio telescope of the Purple Mountain Observatory, China. The C18O (J = 1−0) line was detected in the emission of 21 objects. Column densities of the C18O and H2 molecules towards the maximum of integral intensity of the C18O emission were estimated in the approximation of local thermodynamic equilibrium and amounted to (2.5–10.4) · 1015cm−2 and (1.5–6.1) · 1022 cm−2, respectively. The kinetic temperatures determined for these maxima from the CO lines vary from 14 to 45 K. For six objects,
whose mapping has been almost completed, the dimensions of the C18O emission regions are estimated to range from 0.5 to 1.2 pc. The masses of these objects lie in the range of (390–1750) M⊙ and are close to the estimates following from the virial theorem. The range of average densities of the objects is (0.3–1.4)
· 104 cm−3.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 7, pp. 553–562, July 2005. 相似文献
10.
The chemical composition of ultrafine amorphous Fe−B powders prepared by a chemical reduction depends on the mixed molar ratio
of KBH4 to Fe ions. We propose the following reaction processes for the formation of ultrafine Fe−B powders: (1) 4Fe2++2BH4−+6OH−→2Fe2B+6H2O+H2 and (2) 4Fe2++2BH4−+7OH−→2Fe3B+Fe+BO2+5H2O+5/2H2. 相似文献
11.
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
12.
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
13.
Our previous theoretical work one
− − H2O scattering has been modified and extended to intermediate and high energiesE
i. Using the Bethe plot, we compare the present inelastic cross-sections with the experimental ionization cross sections. Total
cross-sections are analytically represented asQ
TOT(cm2)=a.(E
ieV)
−b
and the parameters ‘a’ and ‘b’ are discussed for molecules H2O, NH3 and CH4 in the rangeE
i=100–1000eV. 相似文献
14.
V. S. Pavlovich 《Journal of Applied Spectroscopy》2006,73(3):328-339
A detailed derivation is presented for relations making it possible to describe the effect of temperature on the halfwidth
of the P960 and P870 absorption bands and also on the electron transfer (ET) rate at reaction centers (RCs) of the purple
bacteria Rps. viridis and Rb. sphaeroides. Primary electron transfer is considered as a resonant nonradiative transition between
P* and P+B
L
−
states (where P is a special pair, BL is an additional bacteriochlorophyll in the L branch of the reaction center). It has been shown that the vibrational hα mode with frequency 130–150 cm−1 controls primary electron transfer. It has been found that the matrix element of the electronic transition between the states
P* and P+B
L
−
is equal to 12.7 ± 0.9 and 12.0 ± 1.2 cm−1 for Rps. viridis and Rb. sphaeroides respectively. The mechanism is discussed for electron transport from P* and BL and then to bacteriopheophytin HL.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 294–303, May–June, 2006. 相似文献
15.
Open circuit voltage (OCV) measurements in H2O/air concentration cells at T<580 K using Yb-doped SrCeO3 electrolyte indicate that under these conditions, protons are transported through the electrolyte as -ve ions, possibly as
hydroxyl (OH−) ions. The H+ ionic transport, which is generally reported, becomes the dominant mode for H2O/air concentration cells at temperatures greater than 750 K or when H2O/air electrodes are replaced by H2/Ar, and the anomalous OCV sign disappears. The combination of low temperature and the presence of hydrogen and oxygen as
provided by the H2O/air system appears to be necessary for the postulated hydroxyl ion electrode reactions to take place.
In addition to OCV measurements, results from impedance spectroscopy are used to provide evidence in support of the suggested
hydroxyl ion mode of protonic transport under the specified conditions. These findings are directly relevant in the development
of novel humidity sensors in the temperature range 450–580K and is reported in a separate paper in this conference.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996 相似文献
16.
Distinctive optical properties of single-wall carbon nanotubes (SWNT) are highly sensitive to variations in the environment.
Here, we have studied SWNT in aqueous suspensions at a low (less than 0.1 μg ml−1) concentration by four-wave mixing (FWM) spectroscopy in the spectral bands of 0.1 to 10 cm−1 (≈300 GHz) and 100 to 250 cm−1 (3 to 7.5 THz). We directly investigated the hydration layers around SWNT. A comparison of the FWM spectra of an SWNT aqueous
suspension and Milli-Q water shows a considerable increase in the intensity of low-frequency Raman modes, which are attributed
to the rotational transitions of H2O2 and H2O molecules. We explain the observed phenomenon by the hydrogen peroxide production and formation of a low-density depletion
layer at the water-nanotube interface. We have observed several SWNT radial breathing modes ω
RBM =118.5, 164.7, and 233.5 cm−1 in an SWNT aqueous suspension and estimated the corresponding SWNT diameters as ≈2.0, 1.5, and 1 nm. 相似文献
17.
M. I. Abd-Elrahman 《Physics of Wave Phenomena》2011,19(1):13-17
Fundamental (lattice, rotational, and intermolecular) vibrations of the H2AsO4− anion in (C6H9N2)H2AsO4 crystal are calculated using the correlation theorem based on the group theory. The correlation between anionic site of symmetry
C
s and the factor group D
2h
of the crystal yields 12 modes for both lattice and rotational vibrations. The infrared and Raman spectra of these modes
do not coincide. Addition of two hydrogen atoms to AsO4− ion yields two As-OH bonds in the H2AsO4− anion. As a result, the molecular symmetry is reduced from T
d
to C
2υ
. The free H2AsO4− anion having C
2υ
symmetry gives in total 15 fundamental normal vibrations. Under the crystal field splitting effects, the number of intermolecular
vibrations for the anion in infrared and Raman spectra is calculated to be 56 active vibrations. The calculated fundamental
vibrationsmanifest themselves as the main features in an experimental infrared spectrum. 相似文献
18.
Summary The structure of water in bis(2-ethylhexyl)sodium sulfosuccinate (AOT) micelles has been studied as a function of the [H2O]/[AOT] ratio (W) by using the absorption IR due to O−H stretching modes in the 3800–3000 cm−1 range. Three systems have been studied: water/AOT/carbon tetrachloride, water/AOT/n-heptane and water/AOT iso-octane. Experimental spectra are presented and discussed for the O−H stretching region both of
H2O and isotopically diluted HDO molecules in D2O. We have restricted ourselves to the region of small amounts of water (0<W<20) where the properties of the systems change strongly with the water content. The results show that IR spectra can be expressed
as sum of contributions from interfacial and bulk-like water. The fraction of water in the two “regions” within the water
pool was evaluated as a function ofW. From the data a continuous variation appears in the water properties inside micellar cores rather than a two-steps hydration
mechanism. The solubilization of water is described in terms of hydration of the AOT head group and Na+ counterions. The maximum hydration number of AOT was found to be 3.5. The same behaviour has been observed in the three solvents
studied. 相似文献
19.
Fourier transform infrared spectroscopic and electrochemical complex impedance studies have been carried out on a series of
complexes containing poly(propylene glycol) of molecular weight 4,000 and silver triflate (AgCF3SO3) salt corresponding to the ether oxygen to metal cation ratios (O : M) in the range 16:1 to 12:1. The formation of ion pairs
and aggregates noticed in the case of specimens having high salt concentrations as well as the complete coordination of the
cation with the ether oxygen at low salt concentrations within the PPG4000-AgCF3SO3 polymer electrolyte system have been confirmed. The appearance of two weak triflate bands at 1,032 and 1,272 cm−1 in the absorption spectra in respect of low salt concentrations is indicative of the fact that triflate ions are free within
the polymer matrix. The room temperature (298 K) electrical conductivity is found to increase with increasing ether oxygen
content while exhibiting the maximum value of 7.1 × 10−5 Scm−1 possibly due to silver ionic transport in the case of the typical composition having an O : M ratio of 16:1. 相似文献
20.
The Raman spectra of the single crystal of K2Zn(SO4)2·6H2O belonging toC
2h
5
space group in the 40–1200 cm−1 region in different scattering geometries and their spectra ofthe microcrystalline salt in the 1500-50 cm−1 region have been reported. The dynamics of the crystal has been described in terms of 186 phonon modes under the unit cell
approximation. The weak bands in the region 400–900 cm−1 have been assigned to the libratory modes of H2O molecules in contradiction to the assignments reported by Ananthanarayanan. The ambiguities existing in the literature about
the assignments ofν
2
c
andν
5
c
modes of [Zn(H2O)6]2+ have also been removed. The translatory and libratory modes of different units of the crystal have been identified and assignments
are made using farir and Raman data on various isomorphous tutton salts.
It has been inferred that both SO
4
2−
tetrahedron and [Zn(H2O)6]2+ octahedron undergo linear as well as angular distortions from their free state symmetries in the crystal. 相似文献