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Papers by Yuri Dyakov

Russian Journal of Physical Chemistry B, Mar 1, 2020

The empirical approximations of atmospheric pressure-field oscillations were constructed based on... more The empirical approximations of atmospheric pressure-field oscillations were constructed based on observational data on atmospheric pressure variations at the land surface, which were obtained at the network of four microbarographs located in the Moscow region during the passage of an atmospheric front. The approximating functions were used as a lower boundary condition to numerically calculate the propagation of acoustic-gravity waves into the upper atmosphere from their source in the lower troposphere. The amplitude of upper atmosphere temperature disturbances caused by acoustic-gravity waves from the atmospheric front was estimated at about 170 K, while the amplitude of upper atmosphere temperature disturbances caused by background pressure variations at the land surface was estimated at 4-5 K.

Advances in Space Research, Nov 1, 2019

The main chemical reactions that lead to formation of the nonequilibrium two-temperature plasma a... more The main chemical reactions that lead to formation of the nonequilibrium two-temperature plasma and highly excited Rydberg complexes are considered. A special attention is given to l-mixing reaction responsible for the formation of quantum resonance properties for radio wave propagation medium. A detailed analysis of the influence of Rydberg states to the behavior of GPS signals in D and E layers of the ionosphere is presented. It is shown that the transition frequencies between the excited states of orbitally degenerate Rydberg complex are resonant with respect to the carrier frequencies of GPS. That is why these states are the main cause of the GPS signal distortion. The mechanism of GPS signal delay in D and E layers is also discussed.

arXiv (Cornell University), Jul 5, 2022

The notion of mean temperature is crucial for a number of fields including climate science, fluid... more The notion of mean temperature is crucial for a number of fields including climate science, fluid dynamics and biophysics. However, so far its correct thermodynamic foundation is lacking or even believed to be impossible. A physically correct definition should not be based on mathematical notions of the means (e.g. the mean geometric or mean arithmetic), because they ignore the peculiarities of the notion of temperature, and because they are not unique. We offer a thermodynamic definition of the mean temperature that is based upon the following two assumptions. First, as the correct definition should necessarily involve equilibration processes in the initially non-equilibrium system, the mean temperature is bounded from below and above via looking at (respectively) the reversible versus fully irreversible extremes of equilibration. Second, within the thermodynamic approach we assume that the mean temperature is determined mostly by energy and entropy. Together with the dimensional analysis, the two assumptions lead to a unique definition of the mean temperature. The mean temperature for ideal and (van der Waals) non-ideal gases with temperature-independent heat capacity is given by a general and compact formula that (besides the initial temperatures) only depends on the heat-capacities and concentration of gases.

Russian Journal of Physical Chemistry B, Sep 1, 2021

The increase in the concentration of methane in the atmosphere as a result of anthropogenic activ... more The increase in the concentration of methane in the atmosphere as a result of anthropogenic activity, melting of permafrost, and decomposition of gas hydrates on the seabed has attracted close attention of the scientific community in recent decades due to the potentially dangerous effect of methane on the ozone layer and the Earth's climate. According to various estimates, the greenhouse effect from methane is dozens of times stronger than the similar effect from carbon dioxide; therefore, the processes of methane transfer to the upper layers of the Earth's atmosphere, as well as its lifetime and interaction with other substances present in the stratosphere, mesosphere and ionosphere are of great scientific interest. In this study, we consider the chemical reactions occurring during collisions of methane molecules with methyl carbonyl oxide CH 3 CHOO in the upper atmosphere. It is shown that this process initiates the formation of the OH radical and starts a cascade of chemical reactions, the products of which are CH 3 , atomic hydrogen, acetone, acetaldehyde, propaldehyde, methyl alcohol, and water. These compounds are able to actively influence the composition of the atmosphere and its physicochemical properties.

Russian Journal of Physical Chemistry B, May 1, 2021

Criegee intermediates, or carbonyl oxides, are formed during the ozonolysis of alkenes, which are... more Criegee intermediates, or carbonyl oxides, are formed during the ozonolysis of alkenes, which are typical anthropogenic air pollutants. They play an important role in a variety of chemical reactions occurring both in the near-surface layer and in the upper layers of the Earth's atmosphere. In the lower troposphere, Criegee intermediates have time to lose their internal vibrational energy due to collisions with nitrogen molecules and interact with other components of the atmosphere in their original form. The products of such reactions are, for example, sulfuric and nitric acids. In the stratosphere and mesosphere, Criegee intermediates decompose into chemically active fragments that participate in a variety of secondary reactions. In this study, we consider the processes of decomposition of the methylcarbonyloxide isomer anti-CH 3 CHOO in the upper atmosphere. It is shown that the main decay products are atomic oxygen, methane, CO, CO 2 , and OH radicals. The formation of more complex chemically active fragments is also possible.

Russian Journal of Physical Chemistry B, Mar 1, 2020

Abstract The search for ways to predict earthquakes, including predicting the point in time when ... more Abstract The search for ways to predict earthquakes, including predicting the point in time when they will occur and their possible coordinates and energy, is a global scientific problem. Researchers have discovered a number of natural phenomena that can be considered their precursors. Changes that occur in Earth’s ionosphere due to the emissions of radioactive radon in the compression regions are also related to earthquakes. They lead to the creation of an additional glow of heavy dust particles in a wide range of wavelengths (including the microwave and infrared ranges). The physical origin of this phenomenon is that sufficiently fast alpha particles interact with neutral air molecules and cause their ionization. The resulting ions charge heavy dust particles in the air with sufficient electric field strength to ionize the air. At the same time, these processes are accompanied by the neutralization of charged dust particles by air ions due to the recombination process. The published experimental data on the size of the region in which heavy dust particles glow and the observed times of glowing make it possible to estimate the typical sizes of these particles.

Russian Chemical Bulletin, Jul 1, 1995

The structure and dynamics of the hydrated cationic complexes in Nafion type membrane pores has b... more The structure and dynamics of the hydrated cationic complexes in Nafion type membrane pores has been studied by the molecular dynamics approach. The mechanism of the cationic transport has been examined. The dependence of the cationic transport coefficients on temperature and the number of water molecules has been investigated.

The Journal of Chemical Physics, 1998

Smoluchowski equation with a sink term is widely used as a model of a rate process in a slowly re... more Smoluchowski equation with a sink term is widely used as a model of a rate process in a slowly relaxing environment. Two approximate solutions for the rate constant obtained for a steeply growing sink are tested numerically using an exponential sink. Both analytical solutions are in a good agreement with the numerical results over a wide range of the problem parameters (environment relaxation rate). They show how the rate constant Γ decreases when the viscosity η of the environment increases. If the dependence is approximated by the fractional power law, Γ∝η−α, the exponent α is always less than unity and depends on η. It tends to zero for fast relaxation of the environment (small η) and increases when the relaxation slows down (η grows).

Journal of the American Society for Mass Spectrometry, Apr 2, 2020

Two separate temperature-dependent experiments were performed to investigate the ionization mecha... more Two separate temperature-dependent experiments were performed to investigate the ionization mechanism of ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI) of matrix 2,5-dihydroxybenzoic acid (2,5-DHB). First, the angular resolved intensity and velocity distributions of neutrals desorbed from the 2,5-DHB solid sample through UV laser (355 nm) pulse irradiation were measured using a rotating quadrupole mass spectrometer. Second, the desorbed neutrals, at an angle normal to the surface, and the desorbed ions were simultaneously detected for each laser shot using the quadrupole mass spectrometer and a time-of-flight mass spectrometer, respectively. Both experiments were conducted at two initial temperatures: 100 and 300 K. The measurements from these two experiments were used to calculate the initial temperature dependence of the ion-to-neutral ratio. The results closely agreed with the predictions of the temperature-dependent ion-toneutral ratio using the thermal model, indicating that thermally induced proton transfer is the dominant reaction that generates initial ions of 2,5-DHB in UV-MALDI.

International Reviews in Physical Chemistry, Apr 1, 2012

Energy transfer of highly vibrationally excited molecules has been studied extensively under bulk... more Energy transfer of highly vibrationally excited molecules has been studied extensively under bulk conditions in the past 40 years. On the other hand, in 1973 Fisk and co-workers reported the first experimental results of collisional energy transfer of highly vibrationally excited KBr using cross-molecular beams. Surprisingly, it is the only crossed molecular beam experiment about the energy transfer of highly vibrationally excited molecules. No other similar crossed molecular beam experiments have been reported in the following four decades. Recently we have studied the energy transfer of highly vibrationally excited molecules using crossed molecular beams/time-of-flight mass spectrometer in combination with time-sliced velocity map ion imaging techniques. Energy transfer probability density functions were accurately obtained and details of energy transfer mechanisms were evidenced from the cross-molecular beam scatterings. This paper reviews our recent work of energy transfer of highly vibrationally excited molecules. The effects of long-lived complex, initial translational energy, initial rotational temperature, vibrational motions, alkylation, attractive potential and electronic state on the energy transfer and supercollisions were discussed, and comparisons to theoretical calculations and experiments conducted under bulk conditions were made.

Journal of Physical Chemistry A, Sep 8, 2005

The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the p... more The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the photodissociation mechanism of azulene at 6.4 eV (the laser wavelength of 193 nm) upon absorption of one UV photon followed by internal conversion into the ground electronic state. Reaction pathways leading to various decomposition products have been mapped out at the G3(MP2,CC)//B3LYP level and then the RRKM and microcanonical variational transition state theories have been applied to compute rate constants for individual reaction steps. Relative product yields (branching ratios) for the dissociation products have been calculated using the steady-state approach. The results show that photoexcited azulene can readily isomerize to naphthalene and the major dissociation channel is elimination of an H-atom from naphthalene. The branching ratio of this channel decreases with an increase of the photon energy. Acetylene elimination is the second probable reaction channel and its branching ratio rises as the photon energy increases. The main C8H6 fragments at 193 nm are phenylacetylene and pentalene and the yield of the latter grows fast with the increasing excitation energy.

Journal of Chemical Physics, Oct 1, 2005

Ab initio calculations employing the configuration interaction method including Davidson’s correc... more Ab initio calculations employing the configuration interaction method including Davidson’s corrections for quadruple excitations have been carried out to unravel the dissociation mechanism of acetylene dication in various electronic states and to elucidate ultrafast acetylene-vinylidene isomerization recently observed experimentally. Both in the ground triplet and the lowest singlet electronic states of C2H22+ the proton migration barrier is shown to remain high, in the range of 50kcal∕mol. On the other hand, the barrier in the excited 2A″3 and 1A′3 states decreases to about 15 and 34kcal∕mol, respectively, indicating that the ultrafast proton migration is possible in these states, especially, in 2A″3, even at relatively low available vibrational energies. Rice-Ramsperger-Kassel-Marcus calculations of individual reaction-rate constants and product branching ratios indicate that if C2H22+ dissociates from the ground triplet state, the major reaction products should be CCH+(Σ−3)+H+ followed by CH+(Π3)+CH+(Σ+1) and with a minor contribution (∼1%) of C2H+(A12)+C+(P2). In the lowest singlet state, C2H+(A12)+C+(P2) are the major dissociation products at low available energies when the other channels are closed, whereas at Eint>5eV, the CCH+(A′1)+H+ products have the largest branching ratio, up to 70% and higher, that of CH+(Σ+1)+CH+(Σ+1) is in the range of 25%–27%, and the yield of C2H++C+ is only 2%–3%. The calculated product branching ratios at Eint≈17eV are in qualitative agreement with the available experimental data. The appearance thresholds calculated for the CCH++H+, CH++CH+, and C2H++C+ products are 34.25, 35.12, and 34.55 eV. The results of calculations in the presence of strong electric field show that the field can make the vinylidene isomer unstable and the proton elimination spontaneous, but is unlikely to significantly reduce the barrier for the acetylene-vinylidene isomerization and to render the acetylene configuration unstable or metastable with respect to proton migration.

Journal of Chemical Physics, Dec 28, 2010

Photodissociation and photoionization of 2,5-dihydroxybenzoic acid (25DHBA), at 193 and 355 nm we... more Photodissociation and photoionization of 2,5-dihydroxybenzoic acid (25DHBA), at 193 and 355 nm were investigated separately in a molecular beam using multimass ion imaging techniques. Two channels competed after excitation by one 193 nm photon. One channel is dissociation from the repulsive excited state along O-H bond distance, resulting in H atom elimination from meta-OH functional group. The other channel is internal conversion to the ground state, followed by H 2 O elimination. Some of the fragments further proceeded to secondary dissociation. On the other hand, absorption of one 355 nm photon gave rise to H 2 O elimination channel on the ground state. Absorption of more than one 355 nm photon resulted in the three-body dissociation which also occurs on the ground state. Dissociation on the excited state does not play a role at 355 nm. The large concentration ratio (2×10 5), between neutral fragments and cations produced from 355 nm multiphoton excitation indicates that internal conversion followed by dissociation, is the major channel for 355 nm multiphoton excitation. Multiphoton ionization is a minor channel. Multiphoton ionization of 25DHBA clusters only produces 25DHBA cations. Neither anion nor protonated 25DHBA cation were observed. It is very different from the ions produced from solid matrix-assisted laser desorption/ionization (MALDI), experiments. This suggests that protonated 25DHBA and negatively charged 25DHBA generated in MALDI experiments does not simply result from the ionization following proton transfer reactions or charge transfer reactions of the clusters in the gas phase.

Journal of Physical Chemistry A, Sep 28, 2009

Multiphoton dissociation and ionization of 2,5-dihydroxyacetophenone (DHAP), an important matrix ... more Multiphoton dissociation and ionization of 2,5-dihydroxyacetophenone (DHAP), an important matrix compound in UV matrix-assisted laser desorption/ionization (MALDI), is studied in a molecular beam at 355 nm using multimass ion imaging mass spectrometer and time-of-flight mass spectrometry. For laser fluence larger than 130 mJ/cm 2 , nearly all of the irradiated molecules absorb at least one photon. The absorption cross section was found to be σ) 1.3((0.2) × 10-17 cm 2. Molecules excited by two photons quickly dissociate into fragments. The major channels are (1) C 6 H 3 (OH) 2 COCH 3 f C 6 H 3 (OH) 2 CO + CH 3 and (2) C 6 H 3 (OH) 2 COCH 3 f C 6 H 3 (OH) 2 + COCH 3. Molecules absorbing three or more photons become parent ions or crack into smaller ionic fragments. The concentration ratio of ions (parent ions and ionic fragments) to neutral fragments is about 10-6 :1. Changing the molecular beam carrier gas from He at 250 Torr to Ar at 300 Torr results in molecular beam clustering (dimers and trimers). Multiphoton ionization of clusters by a 355 nm laser beam produces only dimer cations, (C 6 H 3 (OH) 2 COCH 3) 2 +. Protonated clusters or negatively charged ions, observed from a solid sample of DHAP using 355 nm multiphoton ionization, were not found in the molecular beam. The experimental results indicate that the photoionization occurs in the gas phase after DHAP vaporizes from the solid phase may not play an important role in the MALDI process.

Atmosphere, 2021

Determination of the physical mechanisms of the energy transfer of tropospheric disturbances to t... more Determination of the physical mechanisms of the energy transfer of tropospheric disturbances to the ionosphere is one of the fundamental problems of atmospheric physics. This article presents the observational results of tropospheric and ionospheric disturbances during the passages of the solar terminator and solar eclipse. Lidar observations showed the occurrence of tropospheric regions with noticeably increased amplitudes of density, pressure, and temperature variations with periods corresponding to acoustic and internal gravity waves, which were generated in the troposphere during the development of these events. Simultaneous satellite measurements demonstrate the response of the ionosphere to these tropospheric disturbances. Based on the experimental data, we determine the typical periods and spatial scales of variations. It is shown that the response time of the ionosphere to tropospheric disturbances is 30–40 min.

International Conference on Atomic and Molecular Pulsed Lasers XII, 2015

The structure of intermetallic clusters Au12M (M=Hf, Ta, W, Re, Os) and features of their interac... more The structure of intermetallic clusters Au12M (M=Hf, Ta, W, Re, Os) and features of their interaction with electron donors and acceptor atoms, i.e. H and F, were investigated making use computer calculation based of density functional theory. In was found that metal clusters with effective electron number equal to 18 have more symmetrical shape then that with a number of electrons differing from 18. The interaction of gold nanoparticles with silica was modeled by attachment of SiO4H groups and the connection of the electronic structure with electronic transitions in spaser is discussed.

Russian Journal of Physical Chemistry B

Russian Journal of Physical Chemistry B

The Journal of Physical Chemistry A, 2009

The Journal of Physical Chemistry A, 2005

The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the p... more The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the photodissociation mechanism of azulene at 6.4 eV (the laser wavelength of 193 nm) upon absorption of one UV photon followed by internal conversion into the ground electronic state. Reaction pathways leading to various decomposition products have been mapped out at the G3(MP2,CC)//B3LYP level and then the RRKM and microcanonical variational transition state theories have been applied to compute rate constants for individual reaction steps. Relative product yields (branching ratios) for the dissociation products have been calculated using the steady-state approach. The results show that photoexcited azulene can readily isomerize to naphthalene and the major dissociation channel is elimination of an H-atom from naphthalene. The branching ratio of this channel decreases with an increase of the photon energy. Acetylene elimination is the second probable reaction channel and its branching ratio rises as the photon energy increases. The main C8H6 fragments at 193 nm are phenylacetylene and pentalene and the yield of the latter grows fast with the increasing excitation energy.

Russian Journal of Physical Chemistry B, Mar 1, 2020

The empirical approximations of atmospheric pressure-field oscillations were constructed based on... more The empirical approximations of atmospheric pressure-field oscillations were constructed based on observational data on atmospheric pressure variations at the land surface, which were obtained at the network of four microbarographs located in the Moscow region during the passage of an atmospheric front. The approximating functions were used as a lower boundary condition to numerically calculate the propagation of acoustic-gravity waves into the upper atmosphere from their source in the lower troposphere. The amplitude of upper atmosphere temperature disturbances caused by acoustic-gravity waves from the atmospheric front was estimated at about 170 K, while the amplitude of upper atmosphere temperature disturbances caused by background pressure variations at the land surface was estimated at 4-5 K.

Advances in Space Research, Nov 1, 2019

The main chemical reactions that lead to formation of the nonequilibrium two-temperature plasma a... more The main chemical reactions that lead to formation of the nonequilibrium two-temperature plasma and highly excited Rydberg complexes are considered. A special attention is given to l-mixing reaction responsible for the formation of quantum resonance properties for radio wave propagation medium. A detailed analysis of the influence of Rydberg states to the behavior of GPS signals in D and E layers of the ionosphere is presented. It is shown that the transition frequencies between the excited states of orbitally degenerate Rydberg complex are resonant with respect to the carrier frequencies of GPS. That is why these states are the main cause of the GPS signal distortion. The mechanism of GPS signal delay in D and E layers is also discussed.

arXiv (Cornell University), Jul 5, 2022

The notion of mean temperature is crucial for a number of fields including climate science, fluid... more The notion of mean temperature is crucial for a number of fields including climate science, fluid dynamics and biophysics. However, so far its correct thermodynamic foundation is lacking or even believed to be impossible. A physically correct definition should not be based on mathematical notions of the means (e.g. the mean geometric or mean arithmetic), because they ignore the peculiarities of the notion of temperature, and because they are not unique. We offer a thermodynamic definition of the mean temperature that is based upon the following two assumptions. First, as the correct definition should necessarily involve equilibration processes in the initially non-equilibrium system, the mean temperature is bounded from below and above via looking at (respectively) the reversible versus fully irreversible extremes of equilibration. Second, within the thermodynamic approach we assume that the mean temperature is determined mostly by energy and entropy. Together with the dimensional analysis, the two assumptions lead to a unique definition of the mean temperature. The mean temperature for ideal and (van der Waals) non-ideal gases with temperature-independent heat capacity is given by a general and compact formula that (besides the initial temperatures) only depends on the heat-capacities and concentration of gases.

Russian Journal of Physical Chemistry B, Sep 1, 2021

The increase in the concentration of methane in the atmosphere as a result of anthropogenic activ... more The increase in the concentration of methane in the atmosphere as a result of anthropogenic activity, melting of permafrost, and decomposition of gas hydrates on the seabed has attracted close attention of the scientific community in recent decades due to the potentially dangerous effect of methane on the ozone layer and the Earth's climate. According to various estimates, the greenhouse effect from methane is dozens of times stronger than the similar effect from carbon dioxide; therefore, the processes of methane transfer to the upper layers of the Earth's atmosphere, as well as its lifetime and interaction with other substances present in the stratosphere, mesosphere and ionosphere are of great scientific interest. In this study, we consider the chemical reactions occurring during collisions of methane molecules with methyl carbonyl oxide CH 3 CHOO in the upper atmosphere. It is shown that this process initiates the formation of the OH radical and starts a cascade of chemical reactions, the products of which are CH 3 , atomic hydrogen, acetone, acetaldehyde, propaldehyde, methyl alcohol, and water. These compounds are able to actively influence the composition of the atmosphere and its physicochemical properties.

Russian Journal of Physical Chemistry B, May 1, 2021

Criegee intermediates, or carbonyl oxides, are formed during the ozonolysis of alkenes, which are... more Criegee intermediates, or carbonyl oxides, are formed during the ozonolysis of alkenes, which are typical anthropogenic air pollutants. They play an important role in a variety of chemical reactions occurring both in the near-surface layer and in the upper layers of the Earth's atmosphere. In the lower troposphere, Criegee intermediates have time to lose their internal vibrational energy due to collisions with nitrogen molecules and interact with other components of the atmosphere in their original form. The products of such reactions are, for example, sulfuric and nitric acids. In the stratosphere and mesosphere, Criegee intermediates decompose into chemically active fragments that participate in a variety of secondary reactions. In this study, we consider the processes of decomposition of the methylcarbonyloxide isomer anti-CH 3 CHOO in the upper atmosphere. It is shown that the main decay products are atomic oxygen, methane, CO, CO 2 , and OH radicals. The formation of more complex chemically active fragments is also possible.

Russian Journal of Physical Chemistry B, Mar 1, 2020

Abstract The search for ways to predict earthquakes, including predicting the point in time when ... more Abstract The search for ways to predict earthquakes, including predicting the point in time when they will occur and their possible coordinates and energy, is a global scientific problem. Researchers have discovered a number of natural phenomena that can be considered their precursors. Changes that occur in Earth’s ionosphere due to the emissions of radioactive radon in the compression regions are also related to earthquakes. They lead to the creation of an additional glow of heavy dust particles in a wide range of wavelengths (including the microwave and infrared ranges). The physical origin of this phenomenon is that sufficiently fast alpha particles interact with neutral air molecules and cause their ionization. The resulting ions charge heavy dust particles in the air with sufficient electric field strength to ionize the air. At the same time, these processes are accompanied by the neutralization of charged dust particles by air ions due to the recombination process. The published experimental data on the size of the region in which heavy dust particles glow and the observed times of glowing make it possible to estimate the typical sizes of these particles.

Russian Chemical Bulletin, Jul 1, 1995

The structure and dynamics of the hydrated cationic complexes in Nafion type membrane pores has b... more The structure and dynamics of the hydrated cationic complexes in Nafion type membrane pores has been studied by the molecular dynamics approach. The mechanism of the cationic transport has been examined. The dependence of the cationic transport coefficients on temperature and the number of water molecules has been investigated.

The Journal of Chemical Physics, 1998

Smoluchowski equation with a sink term is widely used as a model of a rate process in a slowly re... more Smoluchowski equation with a sink term is widely used as a model of a rate process in a slowly relaxing environment. Two approximate solutions for the rate constant obtained for a steeply growing sink are tested numerically using an exponential sink. Both analytical solutions are in a good agreement with the numerical results over a wide range of the problem parameters (environment relaxation rate). They show how the rate constant Γ decreases when the viscosity η of the environment increases. If the dependence is approximated by the fractional power law, Γ∝η−α, the exponent α is always less than unity and depends on η. It tends to zero for fast relaxation of the environment (small η) and increases when the relaxation slows down (η grows).

Journal of the American Society for Mass Spectrometry, Apr 2, 2020

Two separate temperature-dependent experiments were performed to investigate the ionization mecha... more Two separate temperature-dependent experiments were performed to investigate the ionization mechanism of ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI) of matrix 2,5-dihydroxybenzoic acid (2,5-DHB). First, the angular resolved intensity and velocity distributions of neutrals desorbed from the 2,5-DHB solid sample through UV laser (355 nm) pulse irradiation were measured using a rotating quadrupole mass spectrometer. Second, the desorbed neutrals, at an angle normal to the surface, and the desorbed ions were simultaneously detected for each laser shot using the quadrupole mass spectrometer and a time-of-flight mass spectrometer, respectively. Both experiments were conducted at two initial temperatures: 100 and 300 K. The measurements from these two experiments were used to calculate the initial temperature dependence of the ion-to-neutral ratio. The results closely agreed with the predictions of the temperature-dependent ion-toneutral ratio using the thermal model, indicating that thermally induced proton transfer is the dominant reaction that generates initial ions of 2,5-DHB in UV-MALDI.

International Reviews in Physical Chemistry, Apr 1, 2012

Energy transfer of highly vibrationally excited molecules has been studied extensively under bulk... more Energy transfer of highly vibrationally excited molecules has been studied extensively under bulk conditions in the past 40 years. On the other hand, in 1973 Fisk and co-workers reported the first experimental results of collisional energy transfer of highly vibrationally excited KBr using cross-molecular beams. Surprisingly, it is the only crossed molecular beam experiment about the energy transfer of highly vibrationally excited molecules. No other similar crossed molecular beam experiments have been reported in the following four decades. Recently we have studied the energy transfer of highly vibrationally excited molecules using crossed molecular beams/time-of-flight mass spectrometer in combination with time-sliced velocity map ion imaging techniques. Energy transfer probability density functions were accurately obtained and details of energy transfer mechanisms were evidenced from the cross-molecular beam scatterings. This paper reviews our recent work of energy transfer of highly vibrationally excited molecules. The effects of long-lived complex, initial translational energy, initial rotational temperature, vibrational motions, alkylation, attractive potential and electronic state on the energy transfer and supercollisions were discussed, and comparisons to theoretical calculations and experiments conducted under bulk conditions were made.

Journal of Physical Chemistry A, Sep 8, 2005

The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the p... more The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the photodissociation mechanism of azulene at 6.4 eV (the laser wavelength of 193 nm) upon absorption of one UV photon followed by internal conversion into the ground electronic state. Reaction pathways leading to various decomposition products have been mapped out at the G3(MP2,CC)//B3LYP level and then the RRKM and microcanonical variational transition state theories have been applied to compute rate constants for individual reaction steps. Relative product yields (branching ratios) for the dissociation products have been calculated using the steady-state approach. The results show that photoexcited azulene can readily isomerize to naphthalene and the major dissociation channel is elimination of an H-atom from naphthalene. The branching ratio of this channel decreases with an increase of the photon energy. Acetylene elimination is the second probable reaction channel and its branching ratio rises as the photon energy increases. The main C8H6 fragments at 193 nm are phenylacetylene and pentalene and the yield of the latter grows fast with the increasing excitation energy.

Journal of Chemical Physics, Oct 1, 2005

Ab initio calculations employing the configuration interaction method including Davidson’s correc... more Ab initio calculations employing the configuration interaction method including Davidson’s corrections for quadruple excitations have been carried out to unravel the dissociation mechanism of acetylene dication in various electronic states and to elucidate ultrafast acetylene-vinylidene isomerization recently observed experimentally. Both in the ground triplet and the lowest singlet electronic states of C2H22+ the proton migration barrier is shown to remain high, in the range of 50kcal∕mol. On the other hand, the barrier in the excited 2A″3 and 1A′3 states decreases to about 15 and 34kcal∕mol, respectively, indicating that the ultrafast proton migration is possible in these states, especially, in 2A″3, even at relatively low available vibrational energies. Rice-Ramsperger-Kassel-Marcus calculations of individual reaction-rate constants and product branching ratios indicate that if C2H22+ dissociates from the ground triplet state, the major reaction products should be CCH+(Σ−3)+H+ followed by CH+(Π3)+CH+(Σ+1) and with a minor contribution (∼1%) of C2H+(A12)+C+(P2). In the lowest singlet state, C2H+(A12)+C+(P2) are the major dissociation products at low available energies when the other channels are closed, whereas at Eint>5eV, the CCH+(A′1)+H+ products have the largest branching ratio, up to 70% and higher, that of CH+(Σ+1)+CH+(Σ+1) is in the range of 25%–27%, and the yield of C2H++C+ is only 2%–3%. The calculated product branching ratios at Eint≈17eV are in qualitative agreement with the available experimental data. The appearance thresholds calculated for the CCH++H+, CH++CH+, and C2H++C+ products are 34.25, 35.12, and 34.55 eV. The results of calculations in the presence of strong electric field show that the field can make the vinylidene isomer unstable and the proton elimination spontaneous, but is unlikely to significantly reduce the barrier for the acetylene-vinylidene isomerization and to render the acetylene configuration unstable or metastable with respect to proton migration.

Journal of Chemical Physics, Dec 28, 2010

Photodissociation and photoionization of 2,5-dihydroxybenzoic acid (25DHBA), at 193 and 355 nm we... more Photodissociation and photoionization of 2,5-dihydroxybenzoic acid (25DHBA), at 193 and 355 nm were investigated separately in a molecular beam using multimass ion imaging techniques. Two channels competed after excitation by one 193 nm photon. One channel is dissociation from the repulsive excited state along O-H bond distance, resulting in H atom elimination from meta-OH functional group. The other channel is internal conversion to the ground state, followed by H 2 O elimination. Some of the fragments further proceeded to secondary dissociation. On the other hand, absorption of one 355 nm photon gave rise to H 2 O elimination channel on the ground state. Absorption of more than one 355 nm photon resulted in the three-body dissociation which also occurs on the ground state. Dissociation on the excited state does not play a role at 355 nm. The large concentration ratio (2×10 5), between neutral fragments and cations produced from 355 nm multiphoton excitation indicates that internal conversion followed by dissociation, is the major channel for 355 nm multiphoton excitation. Multiphoton ionization is a minor channel. Multiphoton ionization of 25DHBA clusters only produces 25DHBA cations. Neither anion nor protonated 25DHBA cation were observed. It is very different from the ions produced from solid matrix-assisted laser desorption/ionization (MALDI), experiments. This suggests that protonated 25DHBA and negatively charged 25DHBA generated in MALDI experiments does not simply result from the ionization following proton transfer reactions or charge transfer reactions of the clusters in the gas phase.

Journal of Physical Chemistry A, Sep 28, 2009

Multiphoton dissociation and ionization of 2,5-dihydroxyacetophenone (DHAP), an important matrix ... more Multiphoton dissociation and ionization of 2,5-dihydroxyacetophenone (DHAP), an important matrix compound in UV matrix-assisted laser desorption/ionization (MALDI), is studied in a molecular beam at 355 nm using multimass ion imaging mass spectrometer and time-of-flight mass spectrometry. For laser fluence larger than 130 mJ/cm 2 , nearly all of the irradiated molecules absorb at least one photon. The absorption cross section was found to be σ) 1.3((0.2) × 10-17 cm 2. Molecules excited by two photons quickly dissociate into fragments. The major channels are (1) C 6 H 3 (OH) 2 COCH 3 f C 6 H 3 (OH) 2 CO + CH 3 and (2) C 6 H 3 (OH) 2 COCH 3 f C 6 H 3 (OH) 2 + COCH 3. Molecules absorbing three or more photons become parent ions or crack into smaller ionic fragments. The concentration ratio of ions (parent ions and ionic fragments) to neutral fragments is about 10-6 :1. Changing the molecular beam carrier gas from He at 250 Torr to Ar at 300 Torr results in molecular beam clustering (dimers and trimers). Multiphoton ionization of clusters by a 355 nm laser beam produces only dimer cations, (C 6 H 3 (OH) 2 COCH 3) 2 +. Protonated clusters or negatively charged ions, observed from a solid sample of DHAP using 355 nm multiphoton ionization, were not found in the molecular beam. The experimental results indicate that the photoionization occurs in the gas phase after DHAP vaporizes from the solid phase may not play an important role in the MALDI process.

Atmosphere, 2021

Determination of the physical mechanisms of the energy transfer of tropospheric disturbances to t... more Determination of the physical mechanisms of the energy transfer of tropospheric disturbances to the ionosphere is one of the fundamental problems of atmospheric physics. This article presents the observational results of tropospheric and ionospheric disturbances during the passages of the solar terminator and solar eclipse. Lidar observations showed the occurrence of tropospheric regions with noticeably increased amplitudes of density, pressure, and temperature variations with periods corresponding to acoustic and internal gravity waves, which were generated in the troposphere during the development of these events. Simultaneous satellite measurements demonstrate the response of the ionosphere to these tropospheric disturbances. Based on the experimental data, we determine the typical periods and spatial scales of variations. It is shown that the response time of the ionosphere to tropospheric disturbances is 30–40 min.

International Conference on Atomic and Molecular Pulsed Lasers XII, 2015

The structure of intermetallic clusters Au12M (M=Hf, Ta, W, Re, Os) and features of their interac... more The structure of intermetallic clusters Au12M (M=Hf, Ta, W, Re, Os) and features of their interaction with electron donors and acceptor atoms, i.e. H and F, were investigated making use computer calculation based of density functional theory. In was found that metal clusters with effective electron number equal to 18 have more symmetrical shape then that with a number of electrons differing from 18. The interaction of gold nanoparticles with silica was modeled by attachment of SiO4H groups and the connection of the electronic structure with electronic transitions in spaser is discussed.

Russian Journal of Physical Chemistry B

Russian Journal of Physical Chemistry B

The Journal of Physical Chemistry A, 2009

The Journal of Physical Chemistry A, 2005

The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the p... more The ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) approach has been applied to investigate the photodissociation mechanism of azulene at 6.4 eV (the laser wavelength of 193 nm) upon absorption of one UV photon followed by internal conversion into the ground electronic state. Reaction pathways leading to various decomposition products have been mapped out at the G3(MP2,CC)//B3LYP level and then the RRKM and microcanonical variational transition state theories have been applied to compute rate constants for individual reaction steps. Relative product yields (branching ratios) for the dissociation products have been calculated using the steady-state approach. The results show that photoexcited azulene can readily isomerize to naphthalene and the major dissociation channel is elimination of an H-atom from naphthalene. The branching ratio of this channel decreases with an increase of the photon energy. Acetylene elimination is the second probable reaction channel and its branching ratio rises as the photon energy increases. The main C8H6 fragments at 193 nm are phenylacetylene and pentalene and the yield of the latter grows fast with the increasing excitation energy.