Papers by Alexander G Maryasov
Journal of Magnetic Resonance, Series A, 1995
Echo-detected EPR spectra of the cholestane spin label in a macroscopically oriented lipid multib... more Echo-detected EPR spectra of the cholestane spin label in a macroscopically oriented lipid multibilayer have been obtained at temperatures between 50 and 210 K, The drastic temperature dependence which the spectra reveal was attributed to relaxation induced by the orientational oscillations of the spin-label molecule, The scheme of computer simulations of echo-detected spectra for the model of uniaxial orientational oscillations (librations) is described in detail, The simulated spectra show a remarkable dependence on the orientation of the motional axis in the molecular frame, The simulation and experimental results agree when the projection of this axis in the plane of the nitroxide fragment makes an angle of 70 degrees +/- 10 degrees with the direction of the NO bond, This was attributed to librational motion of the label about the long axis of the cholestane moiety.
Journal of Magnetic Resonance, Series A, 1995
ESR spectra of pairs of paramagnetic centers with anisotropic g tensors are considered. The cente... more ESR spectra of pairs of paramagnetic centers with anisotropic g tensors are considered. The centers are assumed to be point magnetic dipoles with effective spins 1/2. The dipole coupling Hamiltonian is discussed, Powder spectra are numerically calculated in the secular approximation for the dipole splitting. The temperature dependence of the spectral lineshape due to spin polarization is also studied, Special attention is paid to pairs containing an unobservable partner with g(perpendicular) =0.
Journal of Membrane Science, 1998
A model of pressure-driven membrane process of electrolyte separation is presented. The electric ... more A model of pressure-driven membrane process of electrolyte separation is presented. The electric ®eld potential assumed as being known, exact solution for permeate composition is readily obtained. All species are assumed to have the same convection velocity. Local electroneutrality condition is not used. The electric potential has been taken into account under high temperature approximation, thus reducing the problem to algebraic equation in exp(É), where É is dimensionless¯ow potential, and making it possible to calculate concentrations of ions in permeate. Negative retention is shown to be possible for one-component electrolyte solution. For electrolyte mixtures, concentration of ion with high charge is shown to``govern'' the membrane selectivity in respect to low-charge ions. Results obtained are in qualitative accordance with the earlier experimental data on membrane separation of reaction mixtures in homogeneous catalysis. # 1998 Elsevier Science B.V.
Journal of Magnetic Resonance, 2007
The off-resonant pump pulse used in double electron electron resonance (DEER) measurements produc... more The off-resonant pump pulse used in double electron electron resonance (DEER) measurements produces dynamic phase shifts that are explained here by simple analytic and vector descriptions of the full range of signal behaviors observed during DEER measurements, including: large phase shifts in the signal; changes in the position and shape of the detected echo; and changes in the signal intensity. The dynamic phase shifts depend on the width, amplitude and offset frequency of the pump pulse. Isolated radicals as well as pairs or clusters of dipolar-coupled radicals have the same dynamic phase shift that is independent of pump pulse delay in a typical measurement. A method of calibrating both the pump pulse offset frequency and the pump pulse field strength is outlined. A vector model is presented that explains the dynamic phase shifts in terms of precessing magnetization that is either spin locked or precessing about the effective pump field during the pump pulse. Implications of the dynamic phase shifts are discussed as they relate to setting up, calibrating and interpreting the results of DEER measurements.
Journal of Aerosol Science, 1993
Applied Magnetic Resonance, 1995
The emissive CIDNP was observed during photolysis of acetone solutions in solid cyclohexane-d~2. ... more The emissive CIDNP was observed during photolysis of acetone solutions in solid cyclohexane-d~2. The polarization is assumed to arise in contact triplet radical pairs asa result of their T -S, conversion and their recombination.
Applied Magnetic Resonance, 2002
The transverse electron spin magnetization of a paramagnetic center with effective spin S = 1/2 i... more The transverse electron spin magnetization of a paramagnetic center with effective spin S = 1/2 interacting with nonquadrupolar nuclei may be presented asa function of pairs of nuclei magnetization vectors which precess around the effective magnetic field directions. Each rector of the pair starts its precession perpendicular to both effective fields. The free induction deeay (FID) signal is proportional to the scalar product of the vectors for nuclear spin [ = 1/2. The electron spin echo (ESE) signal can be described with two pairs of magnetization vectors. The ESE shape is not equal to two back-to-back FID signals except in the absence of ESE envelope modulation. A recur-sion relation is obtained which allows calculation of ESE signals for larger nuclear spins in the absence of nuclear quadrupole interaction. This relation can be used to calculate the time course of the ESE signal for arbitrary nuclear spins asa function of the nuclear magnetization vectors. While this formalista allows quantitative calculation of modulation from nuclei, it also provides a qualita-tire means of visualizing the modulation based on simple magnetization vectors.
APPLIED MAGNETIC RESONANCE, 2002
It is shown that under the action of a proper microwave pulse sequence the equilibrium polarizati... more It is shown that under the action of a proper microwave pulse sequence the equilibrium polarization of the electron spin may be transferred dynamically to the longitudinal nuclear magnetization which will oscillate due to the nuclear spin precession around the effective fields relating to different electron quantum number manifolds. These oscillations may be measured directly in the radio-frequency band. Analytical formulae are obtained for the case when all the nuclei coupled to an unpaired electron have spins of 1/2.
APPLIED MAGNETIC RESONANCE, 2001
The analytical expressions for the spectral density of the dead rime free electron spin echo enve... more The analytical expressions for the spectral density of the dead rime free electron spin echo envelope modulation (ESEEM) signal of disordered system are obtained for a paramagnetic center with nuclear spin 1/2 and weak axially symmetric hyperfine interaction. The spectral density is given by the Fourier transformation of the ESE signal averaged over all orientations. The order of the two linear operations may be changed. Fourier transformation of the nonaveraged ESE signal supplies us with the sum of the Dirac delta -functions. Averaging of such a spectrum is a rather trivial operation leading to the spectral densities in the final form.
Magnetic Resonance in Chemistry, 1994
Applications of EPR in Radiation Research, 2014
EPR methods to determine the nanometer-scale distribution of radiation
damage products in solids... more EPR methods to determine the nanometer-scale distribution of radiation
damage products in solids are reviewed. The emphasis is on pulsed EPR methods
that measure weak dipolar interactions between radiation-induced paramagnetic
centers. The dipolar interactions provide a convenient ruler for distance measurement
that is well-matched to the sizes of spurs and tracks created by photons and
particles. The properties of dipolar interactions between paramagnetic centers are
discussed with their effect on various EPR measurements. Electron spin echo measurements have determined the pair correlation function between geminate products produced by UV photolysis. Measurements on tracks of ionizing particles show that the paramagnetic centers resulting from the initial holes and electrons have quite different spatial distributions resulting from their different mobilities. Newer methods of EPR dipolar spectroscopy, particularly DEER, have considerable promise for obtaining detailed profiles of the structure of damage distributions in irradiated solids. The radius of the damage region and the number or density of paramagnetic centers created in it can be determined. Both quantities depend on LET of the radiation and can help characterize radiation for dosimetric applications and can aid in understanding the differential effects of irradiation from different sources.
The Journal of Physical Chemistry B, 2004
It is shown that HYSCORE spectra of paramagnetic centers having nuclei of spin I=1 with isotropic... more It is shown that HYSCORE spectra of paramagnetic centers having nuclei of spin I=1 with isotropic hfi and arbitrary NQI consist of ridges having zero width. A parametric presentation of these ridges is found which shows the range of possible frequencies in the HYSCORE spectrum and aids in spectral assignments and rapid estimation of spin Hamiltonian parameters. An alternative approach for the spectral density calculation is presented that is based on spectral decomposition of the Hamiltonian. Only the eigenvalues of the Hamiltonian are needed in this approach. An atlas of HYSCORE spectra is given in the Supporting Information. This approach is applied to the estimation of the spin Hamiltonian parameters of the oxovanadium-EDTA complex.
Russian Chemical Bulletin, 2011
A procedure was developed for the synthesis of the kinetically stable nitroxide 2 (N tert butyl N... more A procedure was developed for the synthesis of the kinetically stable nitroxide 2 (N tert butyl N hydroxyamino) 4,4,5,5 tetramethyl 4,5 dihydro 1H imidazole 3 oxide 1 oxyl con taining the sterically hindered hydroxylamino group. The crystal and molecular structure of this compound was determined. The isolation of this nitroxide hydroxylamine in the individual state enabled a new procedure for the preparation of its oxidation product, viz., the corresponding nitroxide biradical. The results of quantum chemical calculations of the electron exchange in the biradical molecule are in good agreement with the experimental data on the triplet ground state of the molecule in the crystal obtained earlier.
Physical Chemistry Chemical Physics, 2010
The influence of liquid critical clusters temperature fluctuations caused by the radiation exchan... more The influence of liquid critical clusters temperature fluctuations caused by the radiation exchange (RTFs) on the nucleation process during a vapor to liquid phase transition is studied. This influence is significant when two conditions are met; (1) the RTFs amplitude is larger than the system overcooling thus allowing a reduction in the cluster temperature below the temperature of phase transition, and (2) RTFs correlation time is large enough to allow an extra emission of vapor molecules by the cluster of critical size thus making the cluster subcritical. The range of the system overcooling is found where RTFs may have a strong impact on the process of liquid phase formation.
Russian Chemical Reviews, 2008
The results of development of pulsed electron - electron double resonance (PELDOR) method and its... more The results of development of pulsed electron - electron double resonance (PELDOR) method and its applications in structural studies are generalised and described systematically. The foundations of the theory of the method are outlined, some methodological features and applications are considered, in particular, determination of the distances between spin labels in the nanometre range for iminoxyl biradicals, spin-labelled biomacromolecules, radical ion pairs and peptide ±membrane complexes. The attention is focussed on radical systems that form upon self-assembly of nanosized
complexes (in particular, peptide complexes), spatial effects, and radical pairs in photolysis and photosynthesis. The position of PELDOR among other structural EPR techniques is analysed. The bibliography includes 157 references.
Journal of Magnetic Resonance, 2006
The lineshapes of two-dimensional magnetic resonance spectra of disordered or partially ordered s... more The lineshapes of two-dimensional magnetic resonance spectra of disordered or partially ordered solids are dominated by ridges of singularities in the frequency plane. The positions of these ridges are described by a branch of mathematics known as catastrophe theory concerning the mapping of one 2D surface onto another. We systematically consider the characteristics of HYSCORE spectra for paramagnetic centers having electron spin S=1/2 and nuclear spin I=1 in terms of singularities using an exact solution of the nuclear spin Hamiltonian. The lineshape characteristics are considered for several general cases: zero nuclear quadrupole coupling; isotropic hyperfine but arbitrary nuclear quadrupole couplings; coincident principal axes for the nuclear hyperfine and quadrupole tensors; and the general case of arbitrary nuclear quadrupole and hyperfine tensors. The patterns of singularities in the HYSCORE spectra are described for each case.
Journal of Aerosol Science, 1994
The photochemical reactions in the gas phase are known to favour the formation of clusters [I]. E... more The photochemical reactions in the gas phase are known to favour the formation of clusters [I]. Earlier we have reported on the observation of the effects of chemical nuclear polarization (CIDNP) in the radical-ion reaction of the gas-phase photooxidation of triethylamine by naphthalene. The observation of CIDNP effects on the samples with a polar buffer gas (acetonitrile) has been related to the formation of clusters in the gas phase involving reagents and a buffer substance. The collision of an excited naphthalene molecule with electron molecule-donor (triethylamine) can cause electron transfer to naphthalene and give rise to a radical-ion pair (RIP). The ions in the gas phase can become the centers of condensation.
Combustion and Flame, 2004
The mechanism of Al 2 O 3 nanoparticles aggregation in air was studied under atmospheric pressure... more The mechanism of Al 2 O 3 nanoparticles aggregation in air was studied under atmospheric pressure conditions. Alumina nanoparticles were generated by combustion of a small sample of solid rocket propellant. Size and morphology of nanoparticles were studied by transmission electron microscopy. It was determined that alumina nanoparticles form aggregates of size about 1 µm composed of primary particles with a diameter of few tens of nm. The aggregates' coagulation was observed directly by a video system. In addition, the aggregate movement in the electric field was recorded by the video system. These observations showed that the majority of aggregates are charged. The typical aggregate charge is about 10 elementary units. Some aggregates are dipoles as indicated by the aggregate rotation when the electric field polarity is changed. The mechanism of aggregate formation has been proposed. The initial stage of alumina nanoparticle synthesis includes the formation of liquid oxide particles in the reaction zone located around the surface of burning Al droplet. When the particles pass to the relatively low-temperature region, solidification of particles occurs followed by clustering of solid spherical Al 2 O 3 particles. Later, an aggregation of clusters formed by different burning Al droplets occurs resulting in formation of final aggregates. Estimations of thermal emission of electrons by the burning Al droplets were carried out via solution of the Poisson-Boltzmann equation. These estimates showed that the negative volume charge in the reaction zone around the Al droplet is 10 8 -10 9 elementary charges per cm 3 .
Chemistry - A European Journal, 2014
Spin-labelled compounds are widely used in chemistry, physics, biology and the materials sciences... more Spin-labelled compounds are widely used in chemistry, physics, biology and the materials sciences but the synthesis of stable high-spin organic molecules is still a challenge. We succeeded in synthesising heteroatom analogues of the 1,1,2,3,3-pentamethylenepropane (PMP) diradicals with two nitronyl nitroxide (DR 1 ) and with two iminonitroxide (DR 2 ) fragments linked through the C(sp 2 ) atom of the nitrone group. According to magnetic susceptibility measurements, EPR data and ab initio calculations at the (8,6)CASSCF and (8,6)NEVPT2 levels, DR 1 and DR 2 have singlet ground states. The singlet-triplet energy splitting (2J) is low (J/k = À7.4 for DR 1 and À6.0 K for DR 2 ), which comes from the disjoint nature of these diradicals. The reaction of [Cu(hfac) 2 ] with DR 1 gives rise to different heterospin complexes in which the diradical acts as a rigid ligand, retaining its initial conformation. For the [{Cu(hfac) 2 } 2 (DR 1 )(H 2 O)] complex, sufficiently strong ferromagnetic interactions (J 1 /k = 42.7 and J 2 /k = 14.1 K) between two coordinating Cu II ions and DR 1 were revealed. In [{Cu(hfac) 2 } 2 (DR 1 )(H 2 O)][Cu(hfac) 2 -(H 2 O)], the very strong and antiferromagnetic (J/k = À416.1 K) exchange interaction between one of the coordinating Cu II ions and DR 1 is caused by the very short equatorial CuÀO bond length (1.962 ).
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Papers by Alexander G Maryasov
damage products in solids are reviewed. The emphasis is on pulsed EPR methods
that measure weak dipolar interactions between radiation-induced paramagnetic
centers. The dipolar interactions provide a convenient ruler for distance measurement
that is well-matched to the sizes of spurs and tracks created by photons and
particles. The properties of dipolar interactions between paramagnetic centers are
discussed with their effect on various EPR measurements. Electron spin echo measurements have determined the pair correlation function between geminate products produced by UV photolysis. Measurements on tracks of ionizing particles show that the paramagnetic centers resulting from the initial holes and electrons have quite different spatial distributions resulting from their different mobilities. Newer methods of EPR dipolar spectroscopy, particularly DEER, have considerable promise for obtaining detailed profiles of the structure of damage distributions in irradiated solids. The radius of the damage region and the number or density of paramagnetic centers created in it can be determined. Both quantities depend on LET of the radiation and can help characterize radiation for dosimetric applications and can aid in understanding the differential effects of irradiation from different sources.
complexes (in particular, peptide complexes), spatial effects, and radical pairs in photolysis and photosynthesis. The position of PELDOR among other structural EPR techniques is analysed. The bibliography includes 157 references.
damage products in solids are reviewed. The emphasis is on pulsed EPR methods
that measure weak dipolar interactions between radiation-induced paramagnetic
centers. The dipolar interactions provide a convenient ruler for distance measurement
that is well-matched to the sizes of spurs and tracks created by photons and
particles. The properties of dipolar interactions between paramagnetic centers are
discussed with their effect on various EPR measurements. Electron spin echo measurements have determined the pair correlation function between geminate products produced by UV photolysis. Measurements on tracks of ionizing particles show that the paramagnetic centers resulting from the initial holes and electrons have quite different spatial distributions resulting from their different mobilities. Newer methods of EPR dipolar spectroscopy, particularly DEER, have considerable promise for obtaining detailed profiles of the structure of damage distributions in irradiated solids. The radius of the damage region and the number or density of paramagnetic centers created in it can be determined. Both quantities depend on LET of the radiation and can help characterize radiation for dosimetric applications and can aid in understanding the differential effects of irradiation from different sources.
complexes (in particular, peptide complexes), spatial effects, and radical pairs in photolysis and photosynthesis. The position of PELDOR among other structural EPR techniques is analysed. The bibliography includes 157 references.