Dissociative Recombination Of Electrons Research Articles

Dissociative recombination of electrons andD2+to yieldD(2p)

Cross sections have been measured as a function of electron energy (1.4 to 7.5 eV) for production of ${L}_{\ensuremath{\alpha}}$ photons from the dissociative recombination of electrons and ${\mathrm{D}}_{2}^{+}$. Ions made in a low-pressure ion source by electron bombardment and formed into a beam are reacted at right angles with a magnetically confined electron beam. Recombination was observed by detecting ${L}_{\ensuremath{\alpha}}$ photons from resultant excited atoms. It was demonstrated that a large fraction of the observed light arises from cascade to the $2p$ state from levels of higher principal quantum number. The measured cross section is thus presented as an upper limit for formation of $\mathrm{D}(2p)$ in the dissociative recombination process. The results, represented approximately by the expression $\ensuremath{\sigma}(2p)<(7.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}){E}^{\ensuremath{-}1.25}$ ${\mathrm{cm}}^{2}$, indicate that recombinations leading to formation of a $\mathrm{D}(2p)$ are a small fraction of the total recombination measured by Peart and Dolder.

Kinetics of dissociative recombination of free electrons with hydronium ions in premixed flames

The rate coefficient for the gas phase recombination of H3O+ ions and free electrons in H3O++ e–→ neutral products has been measured in atomospheric pressure flames of H2+ O2+ N2 over the temperature range 2025–2445 K. Concentrations of ions were arrived at by sampling each flame into a mass spectrometer. The recombination coefficient was not found to vary significantly with temperature, being 4.1 ± 1.0 × 10–7 ion–1 cm3 s–1 over this temperature range. This corresponds to a cross-section (πσ2) for the process of about 1.5 × 10–18 m2.

Ion-Molecular Reactions in Plasma Containment Devices

We investigate ion-molecule charge exchange followed by dissociative electron recombination with molecular ions due to the presence of common impurities in a plasma-containment device. For a ${\mathrm{He}}^{+}$ plasma with ${\mathrm{N}}_{2}$ impurity, the ionic constituency of plasmas is changed from ${\mathrm{He}}^{+}$ to nitrogen ions with a time constant ${\ensuremath{\tau}}^{*}$ given by ${\ensuremath{\tau}}^{*}P({\mathrm{N}}_{2})\ensuremath{\simeq}24$ msec $\ensuremath{\mu}$ Torr. However, those ion-molecular recombination processes are not responsible for the enhanced plasma loss in the Princeton spherator at the best vacuum condition.

Photodissociative excitation of O(1D) atoms in the day airglow

Photodissociative excitation of atomic oxygen dayglow emission, considering electron impact and dissociative recombination

Ionospheric Si+and SiO+

Summary. Narcisi's observation of Si+ and SiO+ ions in a thin layer at 110 km during a Leonid meteor shower implies an interconversion of these ions. It is proposed that the process involved is an ‘equilibrium’ Si+ + O2 ⇄ SiO+ + O. This process requires an elevated O2 vibrational temperature, from 500° to 1500°K, depending on uncertainties in the SiO+ bond strength. Since SiO+ presumably has a large electron dissociative recombination, the observed Si++SiO+ abundance implies a relatively large atmospheric silicon abundance as compared with other meteor species.

Measurement of O2/plus/ plus e/minus/ dissociative recombination in expanding oxygen flows

Oxygen cation electron dissociative recombination rate coefficient measurement during expanding oxygen flow in nozzle

Interferometric Study of Dissociative Recombination Radiation in Neon and Argon Afterglows

A photoelectric recording, pressure-tuned Fabry-Perot interferometer of high resolution is used to determine the spectral line profiles of 22 neon and 5 argon ($2{p}_{n}\ensuremath{\rightarrow}1{s}_{m}$) lines emitted from a microwave discharge and during the ensuing afterglow. All afterglow line profiles are broader than the corresponding discharge lines, and in most cases the afterglow line shapes are consistent with a dissociative origin of the excited atoms, indicating that the $2{p}_{n}$ excited states of neon and argon are produced by dissociative recombination of electrons with ${\mathrm{Ne}}_{2}^{+}$ and ${\mathrm{Ar}}_{2}^{+}$ ions, respectively. Detailed examination of the line profiles in neon indicates a "multishouldered" structure corresponding to several different dissociation kinetic energies, suggesting that different initial states of the ${\mathrm{Ne}}_{2}^{+}$ ion are involved in the dissociative recombination process. From the deduced molecular ion energy levels it appears that, in addition to the ${\mathrm{Ne}}_{2}^{+}$ ion state with a dissociation energy $D=1.35$ eV reported by Connor and Biondi, there may be a more weakly bound state with $D\ensuremath{\sim}0.5$ eV which contributes to the recombination.

The lower lonosphere of mars

A study is made of the ionization of the Martian atmosphere below 100 km in the context of recent data on the atmosphere and ionosphere of the planet. Suggested sources of ionization include: solar ultraviolet and X-radiation, cosmic rays, meteors, radioactive material within the atmosphere, and radioactivity of the surface, the solar wind, and protons originating from solar flares. Loss processes, including charge rearrangement, dissociative recombination of ions and electrons, and negative ion formation are detailed. Possible importance of the negative ion CO 4 − is discussed. Its distribution will depend on the O 2 content of the atmosphere as well as the distribution of O and CO. CO − and CO 3 − may also be present in the ionosphere. It is shown that combination of the solar photoionization rate with that due to cosmic radiation will lead to an ion density minimum. The magnitude of the ion density and location of the minimum will depend on the atmospheric model chosen, solar activity, and solar zenith angle as well as such factors as the presence of particulate matter and meteor ionization.

Dissociative recombination of electrons with molecular hydrogen ions

To a first approximation, the perturbation theory yields an explicit analytical expression for the cross section of the dissociative recombination of electrons with molecular hydrogen ions. The possible nonadiabatic transitions during the separation of the nuclei which lead to the appearance of H++H−, H(1s)+H(n=2), H(1s)+H(n=3) in finite reaction channels were considered. Numerical results are presented for the cross sections of direct and reverse reactions. The expression α=4. 2 · 10−8 T−1/2 cm3/sec2 was obtained for the recombination rate at low temperatures; this expression is in agreement with known results. Several general details of the calculation and their possible implications for the case of heavy molecular ions are discussed.

The visual dayglow

New observations of altitude profiles for dayglow emissions at λλ 3914(N 2+) 5200[N], 5577[O] and 6300[O] have been obtained with rocket borne photometers. These data are of adequate quality to justify an extensive theoretical discussion. The first portion of the paper constitutes a general review of dayglow excitations which may occur through five types of process: dissociative recombination of molecular ions; fluorescence (including resonance scattering) of sunlight; photodissociation of molecules; chemical reactions and collisions with energetic electrons. Only upper limits to yields of λλ 5577 and 6300 from photodissociation of O 2 can be deduced from measurements of total absorption coefficients, since a multiplicity of electronic transitions may contribute to the opacity. Also little detailed information is available on the production of excited states from dissociative recombination. A method for estimating some of the relevant rate coefficients is presented and applied to O( 1 D) and O( 1 S). Our analysis of the dayglow observations confirms laboratory measurements of the rate coefficients for N 2 + + O and N 2 + + O 2 reactions. We also obtain estimates of quenching rates for O( 1 D) and N( 2 D), in collisions with N 2 and O 2, respectively. An upper limit of 5R for λ5577 nightglow excited by photodissociation of O 2 by night-sky Lyman-α is obtained from an intercomparison of dayglow and nightglow data. The most important excitation processes are: resonance scattering for λ3914; dissociative recombination and ion-atom interchange for λ5200; three body association and photoelectron collisions for λ5577; and photodissociation, electron collisions and dissociative recombination for ϖ300. A summary of our results is presented in tabular form in Section 5.

Recombination Coefficient in the F-Regions: a Possible New Process of Ionization of Nitrogen Molecules

IT is now generally recognized1,2 that the high day-time rate of disappearance of electrons in the E- and F-regions of the ionosphere cannot be fully explained by the negative-ion formation theory of Bates and Massey3, which takes account of the electron loss mainly due to attachment. The high value of the recombination coefficient in the E-region and in the upper parts of the D-region has recently been explained by A. P. Mitra and Jones4 on the basis of dissociative recombination of electrons with O2 + and NO+ ions, which are believed to be the principal ionized constituents at the heights of these regions. It may therefore be inquired if the process of dissociative recombination may not also be operative in the high F-regions (F 1 and F 2) and be the determining factor for the disappearance of electrons.