The dissociative recombination coefficient of O2+ ions with electrons in the temperature range 180°–630°K

Smith, David; Goodall, C. V.

doi:10.1016/0032-0633(68)90129-3

Cited by 32 publications

(9 citation statements)

References 15 publications

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“…The temperature dependence of the O 2 + recombination (shown in Figure ) was determined to validate the technique since this recombination has been studied previously in detail. ,− , Measurements were made at a series of temperatures ranging from 80 to 500 K to establish the temperature dependence. Table lists the present and previous α e at 300 K and the power of the temperature dependence.…”

Section: Resultsmentioning

confidence: 99%

Flowing Afterglow Studies of the Temperature Dependencies for Dissociative Recombination of O₂⁺, CH₅⁺, C₂H₅⁺, and C₆H₇⁺ with Electrons

et al. 2004

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A temperature-variable flowing afterglow with an electrostatic Langmuir probe has been used to determine the rate coefficients,R e , for the recombination of a series of molecular ions with electrons. The R e for O 2 + , CH 5 + , C 2 H 5 + , and C 6 H 7 + have been determined at temperatures ranging from 80 to 600 K. Data for O 2 + over the temperature range of 100-500 K establish a single-power law dependence, which is consistent with previous data in this temperature range. The hydrocarbon data show that the R e are large at room temperature, being 1.1 × 10 -6 , 1.2 × 10 -6 , and 2.4 × 10 -6 cm 3 s -1 for CH 5 + , C 2 H 5 + , and C 6 H 7 + , respectively, and exhibit significant dependencies on temperature consistent with theoretical models based on the direct and indirect mechanisms. The change between these two dependencies occurs at a temperature of ∼300 K. The dissociative recombination of these ions is significant to molecular synthesis in interstellar clouds and the ionosphere of Titan, which is to be probed by the NASA Huygens-Cassini spacecraft that reaches the Saturnian system in July 2004. The relevance of the present data to these media is briefly discussed.

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Section: Resultsmentioning

confidence: 99%

Flowing Afterglow Studies of the Temperature Dependencies for Dissociative Recombination of O₂⁺, CH₅⁺, C₂H₅⁺, and C₆H₇⁺ with Electrons

et al. 2004

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“…For the Mariner 6 and 7 entry cases, the average peak dectron densities are 1.59 cm -a at 136.5 km and 1.73 cm -a at 137.5 km, respectively. The formal error limits (---3tr) [Smith and Goodall, 1968] implies that the altitude of peak production lies below the altitude of peak electron density, for a positive temperature gradient in this region. It is true that the altitude of peak production will be slightly below the level of unit optical depth if T increases with altitude [Rishbeth and Garriott, 1969], but the compensating effect of the temperature dependence of ao•., implies that we are at least half of one scale height above the level of unit optical depth at 150 km.…”

Section: With This Assumption a Curve Which Is To Properlymentioning

confidence: 99%

Radio Occultation Measurements of The Mars Atmosphere with Mariners 6 and 7

Hogan¹,

Stewart²,

Rasool³

1972

Radio Science

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An analysis of the Mariner 6 and 7 occultation data has been completed. Final profiles of temperature, pressure, and electron density have been obtained for the Mariner 6 and 7 entry and exit cases, and results are presented for both the lower atmosphere and the ionosphere. The results of a detailed analysis of the systematic and formal errors introduced at each stage of the data reduction process are also included. At all four occultation points, the lapse rate of temperature was subadiabatic up to altitudes in excess of 20 km. A pronounced temperature inversion was present above the surface at the Mariner 6 exit point. All four profiles exhibit a sharp, superadiabatic drop in temperature at high altitudes, with temperatures falling below the frost point of CO2. These results give a strong indication of frozen CO2 in the middle atmosphere of Mars. The analysis for the upper atmosphere indicates peak electron populations of 1.59±0.2×105 cm−3 near 137 km and 1.73±0.2×103 cm−3 near 138 km, at the Mariner 6 and 7 entry points, respectively. The plasma scale heights above these maxima were 43±6 and 47±4 km, corresponding to average topside temperatures of 388±54 and 424±35°K, for Mariner 6 and 7 entries, respectively.

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“…Two nickel electrodes situated at the ends of the discharge vessel (figure 1) served both to define the plasma volume and to provide reference (or return) electrodes for Langmuir probe studies. Movable Langmuir probes of small collecting area were inserted into the plasma via Pyrex side-arms on the discharge vessel (Smith and Goodall 1968, Goodall and Smith 1968. This allowed electron temperatures, electron, positive-ion and negative-ion number densities, and electric fields to be determined at different afterglow times and at different points in the plasma.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Figure 3 shows a plot of the total positive-ion current to the orifice disc, when biased with a small negative potential with respect to the reference electrodes so as to collect net ion current, obtained in krypton/oxygen afterglow plasmas under recombination-controlled conditions. The electron number density in the centre of the vessel, as determined from the orbitallimited characteristics of the Langmuir probe (Smith andGoodall 1968, Smith and, is shown for comparison. The wall current is seen to approximately 'track' the electron number density over a limited range of ionization density, indicating that the spatial distribution of charge density outside the wall sheath boundary does not change significantly over such a range.…”

Section: 3 Obseruations In Recombination-controlled Afterglowsmentioning

confidence: 99%

An appraisal of the mass spectrometer diagnostic technique in the study of afterglow plasmas

Smith

Plumb

1973

J. Phys. D: Appl. Phys.

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An appraisal is presented of the mass spectrometer diagnostic technique as applied to the sampling of positive and negative ions diffusing towards an orifice probe located at the boundary of an afterglow plasma. The report is largely based on the results obtained from detailed studies over several years in these laboratories of time-resolved (or stationary) afterglow plasmas, together with reported observations of other workers. Several specific plasma situations are discussed and illustrated with data, including diffusion- and recombination-controlled positive-ion/electron plasmas and positive-ion/negative-ion plasmas. These examples emphasize the importance of spatial charge density distributions, space-charge sheaths and electric fields in both the vicinity of the sampling orifice and in the body of the plasma. Data are also presented which graphically illustrate the serious effects which can result from contamination of the sampling electrode in the region of the orifice. The problem of collisional break-up of weakly bound `cluster' ions in the sampling system is also briefly discussed. It is suggested that the serious discrepancies which exist between reported values of a large number of reaction rate coefficients obtained from afterglow studies are due at least in part to a lack of appreciation of some of these important physical phenomena. Throughout the paper, attempts are made to indicate the experimental conditions which must exist if valid data are to be obtained using the mass spectrometer sampling technique.

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The dissociative recombination coefficient of O2+ ions with electrons in the temperature range 180°–630°K

Cited by 32 publications

References 15 publications

Flowing Afterglow Studies of the Temperature Dependencies for Dissociative Recombination of O₂⁺, CH₅⁺, C₂H₅⁺, and C₆H₇⁺ with Electrons

Flowing Afterglow Studies of the Temperature Dependencies for Dissociative Recombination of O₂⁺, CH₅⁺, C₂H₅⁺, and C₆H₇⁺ with Electrons

Radio Occultation Measurements of The Mars Atmosphere with Mariners 6 and 7

An appraisal of the mass spectrometer diagnostic technique in the study of afterglow plasmas

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The dissociative recombination coefficient of O2+ ions with electrons in the temperature range 180°–630°K

Cited by 32 publications

References 15 publications

Flowing Afterglow Studies of the Temperature Dependencies for Dissociative Recombination of O2+, CH5+, C2H5+, and C6H7+ with Electrons

Flowing Afterglow Studies of the Temperature Dependencies for Dissociative Recombination of O2+, CH5+, C2H5+, and C6H7+ with Electrons

Radio Occultation Measurements of The Mars Atmosphere with Mariners 6 and 7

An appraisal of the mass spectrometer diagnostic technique in the study of afterglow plasmas

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Product

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Flowing Afterglow Studies of the Temperature Dependencies for Dissociative Recombination of O₂⁺, CH₅⁺, C₂H₅⁺, and C₆H₇⁺ with Electrons

Flowing Afterglow Studies of the Temperature Dependencies for Dissociative Recombination of O₂⁺, CH₅⁺, C₂H₅⁺, and C₆H₇⁺ with Electrons