Figure 1 - uploaded by Maxim Golubkov
Content may be subject to copyright.
States participating in dissociative recombination from lower vibrational states of the H + 2 ion (Guberman 1983). The energy is measured from the ground (v = 0) state X 1 + g of the H 2 molecule.
Source publication
The reaction of dissociative recombination is investigated taking into account the electron and rotation - vibrational coupling. Basic equations are formulated within the framework of the multichannel quantum-defect theory for the collision T-matrix. Combining the rigorous account of nonadiabatic coupling in the closed channels with respect to smal...
Contexts in source publication
Context 1
... reaction e − + H + 2 following through the stage of the intermediate complex H * * 2 is not well enough studied even for transitions into the low-lying 1 + g dissociative state (see figure 1), because coupling between the scattering and reaction channels is not yet clear. Moreover, information about contributions of the s-, p-and d-orbitals to this reaction needs additional revising. ...
Context 2
... 1983, Hazi et al 1983, Shimamura et al 1990, Schneider et al 1991, 1992, 1994, Takagi 1993a, and the multitude of references cited therein). The potential curve of this state (see figure 1) crosses the ionic term U i (R) near point R * c = 2.65 au placed in the vicinity of the right-hand classical turning point of the first excited vibrational level v = 1. Therefore, the cross section of the reaction ...
Context 3
... small for v i = 0 and rises appreciably as v i increases. Using the pattern of potential curves displayed in figure 1 we can determine the relation between the scattering channels and channels of reaction (44). On account of weak mixing of s-, p-, and d-orbitals, strictly definitive configurations of the intermediate complex H * * 2 should correspond to partial llwaves of incident electrons in the adiabatic representation (Takagi and Nakamura 1983). ...
Similar publications
The complex eigenenergy surfaces of quasistationary states for the hydrogenic Stark problem as a function of complex field strength have been calculated. It is shown that the location of `hidden crossings' of energy surfaces connected with different states can be obtained from a semiclassical quantization of `top of the barrier' motion. A numerical...
A new optical pH sensor based on fibre Bragg grating (FBG) is demonstrated. The sensor consists of a FBG coated with pH sensitive hydrogel. The sensing was performed through the detection of wavelength shifts resulting from the induced strain on the FBG due to mechanical expansion of the hydrogel. An elastomeric coating was applied before the hydro...
![Figure 1. Multidimensional Nature of Computational Physics [1]](publication/347971594/figure/fig1/AS:1011764946808841@1618234969740/Multidimensional-Nature-of-Computational-Physics-1_Q320.jpg)
Particle image velocimetry (PIV) is a measurement technique which is well adapted to the study of the structure of turbulent flows, as it allows us to obtain quantitative information on the spatial structure of the velocity field. This contribution presents an experimental approach to characterize the measurement noise of a PIV system and the spati...
Citations
... This operator describes the interaction of the electron with the ion core in an isolated Rydberg configuration e À þ XY þ . Electron parts of matrix elements of the t operator in the mixed basis (14) are diagonal with respect to q and K and are expressed via R-de- ...
... Because the adiabatic basis jJMlKvi is related to channel basis (14) through the unitary transformation [14] as ...
... Because the adiabatic basis jJMlKvi is related to channel basis (14) through the unitary transformation [14] as ...
The endothermic reaction of associative ionization of nitrogen and oxygen atoms was studied in the case of slow atom collisions in the framework of multichannel quantum defect theory. The diabatic potential energy curves of the NO molecule excited states were calculated using multireference configuration interaction methods implemented in MOLPRO package. It was shown that cross section dependence on the energy of the colliding atoms is in a good agreement with the experiment. The rate coefficient of the reaction was defined at the temperature 100K≤T≤1000K range. The obtained data may be used for calculating the tiered kinetics of highly excited Rydberg state population in low-temperature plasma.
... On this basis, the states of a two-atomic molecule are classified by the values of J and L; i.e., the electronic angular momentum l is generally not conserved. The basis functions in the Rydberg states (taking into account the vibrational and rotational motions) are [74] JMrLv; AE j i¼ X l a J l rL JMlLv; AE j i ; ...
... Because the diabatic (1.80) and channel (1.76) bases are related by the unitary transformation, the following relationship is true for the elements t J lNv; l 0 N 00 v 0 inducing vibrational-rotational transitions in XY þ [74]: ...
Uncontrollable sporadic distortions of global positioning system (GPS) satellite signals, caused by phase and group delays in the propagation of electromagnetic radiation through a medium, take place during periods of high solar activity and formation of geomagnetic disturbances in the Earth’s ionosphere. Determining ways of ensuring sustainability of GPS systems is a fundamental scientific and technical challenge.
Above-background incoherent ultra-high frequency (UHF) radiation is formed at altitudes of the E and D layers of the Earth’s ionosphere. Wavelengths of this radiation correspond to a range from 1 dm to 1 mm. This emission is caused by transitions between Rydberg states of atoms and molecules, which are excited by electrons in plasma and are surrounded by a neutral particle environment. Reliable information about UHF radiation flux power in this wavelength range is not currently available. The answer to this question depends entirely on the knowledge of impact and radiation quenching of Rydberg state dynamics and the kinetics of their location in a lower ionosphere, i.e., on the quantum optical properties of a perturbed environment. Analysis of existing experimental data has shown that UHF radiation is formed in the atmospheric layer located at altitudes of 60–110 km. A physical mechanism of satellite signal delay is caused by cascade resonance re-emissions of electromagnetic waves in the decimeter range while passing through this layer over a set of Rydberg states. The most promising approach to studies of medium optical quantum properties can be a simultaneous analysis of background additional noise and GPS signal propagation time delay, which determines a positioning error. Using standard methods of noise measurement, one cannot detect physical and chemical processes responsible for noise formation and errors affecting positioning. Therefore, the problem can be solved if the level of a background noise is considered as a noise of the measured GPS signal because propagation delays of the latter are caused by one of the most important atmospheric collisional process, i.e., the orbital degeneracy of highly excited states. For this purpose, it is advisable to use the S/N ratio where a signal corresponds to a level of a signal obtained by the GPS receiver and a noise corresponds to a GPS signal fluctuation.
In this chapter, a current state theory is examined, and manners of its further development are discussed. These are associated with the progress of theoretical methods for describing medium neutral particle impact effects on the dynamics of collision and radiation quenching focusing primarily on elementary processes involving molecules of nitrogen and oxygen. It has been shown that preliminary calculations of nonadiabatic transition dynamics between potential energy surfaces (PES) of Rydberg complexes, construction of appropriate electronic wave functions, calculations of allowed transition dipole moments, and determination of emission line shapes are necessary for the quantitative estimation of the influence of excited particles on a spectrum of incoherent UHF radiation of the atmosphere. These results should be included in the total kinetic scheme, which establishes the dependence of UHF radiation on temperature and density of the lower ionosphere. Then satellite-monitoring data of infrared (IR) radiation, which accompanies UHF radiation, can be directly used for the detection of Rydberg states and diagnostics of plasma parameters.
... These include protostellar outflows [8], envelopes of supernovae [9], and stellar atmospheres [10][11][12]. The inverse process of dissociative recombination of H 2 + is also known to be important in many astrophysical environments and, due to its technological importance, has been the subject of extensive theoretical [13][14][15][16][17][18][19][20][21][22] and experimental [23][24][25][26][27][28][29][30][31][32][33][34] investigations. Associative ionization between two metastable hydrogen atoms is less likely to occur naturally due to competition with other reactions. ...
Associative and Penning ionization cross sections are calculated for collisions between metastable hydrogen 2s atoms at thermal energies. Cross sections for deuterium 2s collisions are also reported. The associative ionization cross sections behave as E−1 for collision energy E, in agreement with an existing experiment. The Penning ionization cross sections dominate for all energies and are found to follow the E−2/3 behavior that was predicted in previous work for the total ionization cross section. The magnitudes of our theoretical associative ionization cross sections for H(2s)+H(2s) collisions are between two and four times larger than the experimental data.
Electron-molecule collisions are present in various astrophysical media such as interstellar molecular clouds, in planetary atmospheres, and in cold natural or manmade plasmas. Theoretical investigations are presented in this thesis for diatomic molecular cation and polyatomic molecules. Using an approach based on the multichannel quantum defect theory, the dissociative recombination and competitive processes are calculated for diatomic molecules. Different approaches of this theory are used to compute the cross-section and the corresponding rate coefficients for ArH+ molecular cation in a first case where a good agreement with merged beams measurement at low energy is shown. An extension of the theory is used to fully account the dissociative excitation and then computing all the processes cross-section of the HD+ molecular cation. In a second extension of the same theory, with more target states, results are presented for the N2+ molecular cation. The potential energy curves of the carbon dioxide negative ion is calculated and results are in good agreement with the previous calculation. Finally, the electron induces dissociation of HCO+ molecule is modeled in this thesis using an approach that combines the normal modes approximation for the vibrational states of the target molecule, the UK R-matrix code to obtain electron-molecule S-matrix for fixed geometries of the target and the vibrational frame transformation. The importance of the rate-coefficients in the collisional-radiative models of cold ionized media is outlined for all these species.
The main problems in the remote passive location of positions on the Earth’s surface are reviewed in detail. The central problem relates to the source of incoherent microwave radiation represented by a layer of two-temperature nonequilibrium ionospheric plasma at an altitude of ca. 80–110 km. This source is located below a low Earth-orbiting satellite and formed under the influence of solar activity. As a result, the satellite receives direct radiation from this layer and reflected radiation from the Earth’s surface. The next problem is the attenuation of the intensity of the incident radiation due to the scattering of radio waves by charged aerosol layers located below the luminous layer. Aerosol particles are affected by solar and cosmic radiation and electronic and ionic attacks, which become charged. Aerosol particles directly form a complete balance of atmospheric charges and are an effective catalyst for many physicochemical processes in neutral gaseous media. The processes related to the formation of aerosol particles, the kinetics of formation of their charge, and the processes of their interaction with incoherent microwave radiation are considered. The factors mentioned above give rise to the need to develop a fundamentally new scheme of passive location. Three possible versions of the arrangement of measurements are analyzed. The first version implements a complete set of measures when the receiving equipment is simultaneously installed on the Earth, an aircraft, and a low Earth-orbiting satellite. In the third version, only on one satellite. The separation of the contributions of direct and reflected incoherent radiation received by satellite can be achieved only using a particular mathematical approach to information processing (wavelet analysis), which has been under active development in recent years. We fully show its broad possibilities for solving geophysical problems and discuss the problems of the calibration of the measuring equipment. The latter is associated with the superposition of two types of radiation coming to a satellite and the temporal variation of the main parameters (concentration, flux density, and temperature of electrons) of the nonequilibrium two-temperature plasma.
The endothermic associative ionization reaction N(² D) + O(³ P) → NO∗∗ → NO(¹Σ⁺) +e⁻ in slow collisions of the atoms has been considered in terms of the multichannel quantum defect theory. The dependences of the partial and total cross sections of the reaction on the energy of the colliding atoms in the range of 0-0.3 eV have been calculated. It has been shown that the cross sections have a pronounced resonance structure, which is formed as a result of the multichannel interaction of autoionization states of the intermediate Rydberg complex NO∗∗ with dissociative states. The temperature dependence of the reaction rate constant is presented. The results are compared with those of other calculations and available experimental data.
This book is devoted to the modern theory and experimental investigations of the associative ionization (AI) reaction. The means of their further development are analyzed. Numerous applications in plasma chemistry, aeronomy, chemical physics of the upper atmosphere, and astrophysics have contributed to conducting this study. The threshold behavior of cross sections of the endothermic reaction AI is considered, and it is shown that the dependence of above-threshold energy E is a strictly linear in the quantum case, which differs substantially from the law E
3/2, resulting in a semiclassical theory. This result has a simple physical explanation because the matrix elements of scattering operator resulting from the tunneling effect are finite at E = 0. Comparison with the semiclassical theory has been made. A substantiation of the described possibility of elementary AI reaction dynamics in the diffusion approach is given. A detailed consideration of the applicability conditions of the “quantum chaos” theory for the spectrum of highly excited Rydberg molecules is carried out. A review of experimental studies of AI reaction under different conditions covering vapor cells, single effusive beams, two crossing beams, and cold matters (very briefly) is presented. The importance of accounting for specific distribution functions of atoms over a relative (colliding) velocity in AI rate constant evaluations is discussed, and a proper explanation of noticeable variations in experimental data is provided. Different types of colliding atomic/molecular pairs consisting of low-lying excited states (normal, metastable, and resonance) in inert and alkali gases are considered, and the corresponding futures of AI cross sections are analyzed. Experimental data on AI and Penning ionization processes involving the Rydberg states of hydrogen and alkali atoms are considered on the basis of a number of theoretical models. The relevance of diffusion motion of the optical electron through the Rydberg energy states toward the continuum resulting from appearance of the dynamics chaos regime in its evolution is demonstrated.
The low-temperature dissociative recombination reaction e- + O2+→O(1D) + O(3P) was studied; the reaction occurred in the field of monochromatic laser radiation in the frequency range 13000-22000 cm-1. The direct and resonance nonradiative transitions and bound-bound dipole-allowed transitions from Rydberg intermediate complex states to the Schumann-Runge continuum mixed with the 3pgπu(3∑u-) lower Rydberg state were considered. The analysis was performed within the framework of the theory of multichannel quantum defects with the use of the stationary formalism of the matrix of radiative collisions. The wave functions and the adiabatic terms of the system were considered to analyze the dependences of the reaction cross section on the energy of incident electrons and the frequency of an external electromagnetic field. The cross section of the reaction was shown to increase by three orders of magnitude in the specified frequency range compared with its value in the absence of a field.
Dissociative recombination (DR) of slow electrons and molecular ions is described within the MQD theory by a set of parameters deduced from the adiabatic characteristics of highly excited molecules. In this work we attract attention to the fact that under near-threshold conditions, negligibly small variations of some of these parameters (e.g., dependence of quantum defects on the interatomic distance) can entail significant changes in the cross sections and rate constants for DR reactions. Therefore we propose a special program for reconstructing parameters of the MQD theory from spectra of two-photon (1 + 1)-ionization of molecules induced by a weak field prepopulating an intermediate (working) level and by a strong monochromatic linearly polarized radiation. The form of the photoelectron spectra is analyzed as a function of variations of the parameters introduced in the theory and spectral ranges where these parameters can be assessed unambiguously and with a good accuracy are indicated.
The article examines the resonance structure of the differential and total cross sections for endothermic reaction and to the determination of temperature dependences of the corresponding rate constants. The necessity of its study is directly related to the problem of correct reconstruction of the parameters of the theory of multichannel quantum defects (MQD) from high resolution optical spectra because for the Rydberg states of molecules, this problem cannot be solved by methods of quantum chemistry. They are necessary for the quantum calculation of the level by level kinetics of population of highly excited Rydberg states in the photo ionization plasma formed in the upper atmosphere of the Earth under the action of a luminous flux coming from the solar flare.
