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1.
The temperature dependence of the binary recombination coefficient, α2, for the reaction NO++NO2? → products has been obtained over the range 185–530 K. It is found that the corresponding mean cross section is described by the power law , and that α2 ? B · T?0.4. Data has also been obtained for two cluster ion recombination reactions which indicate that their recombination cross sections are only about 40% larger than for the parent ions at a given temperature, the cross sections for these reactions also apparently increasing with decreasing temperature. In the light of this data and by considering the most probable positive and negative ions existing at various altitudes up to 90km in the atmosphere, the most appropriate ionic recombination coefficients in various altitude ranges are deduced. Thus, between 30 and 90 km, where the recombination process is two-body, the coefficient varies over the narrow range 5–9 × 10?8 cm3s?1, while below 30 km the process is predominantly three-body with an effective two-body rate increasing rapidly to a maximum value ≈3 × 10?6 cm3s?1 in the troposphere, these deductions being based on published laboratory determinations of three-body recombination coefficients. 相似文献
2.
Following our recently published measurements of the rate coefficients for mutual neutralization, α, of the ionospherically important reactions NO+ + NO2?(α1) and NO+ + NO3?(α2) carried out in ion-ion flowing afterglow plasmas at 300 K, we have determined the mutual neutralization rates for the water cluster ion H3O+ · (H2O)3 with a mixture of several negative ions which are known to exist in the D region. The α coefficients for these cluster ion reactions do not differ significantly from alpha;1 and α2, all of these reactions having α ?6 × 10?8 cm3/sec which is significantly smaller than values usually adopted in ionospheric calculations. Current information on the ionic composition of the D region and the implications of the present results to de-ionization rate calculations are discussed. 相似文献
3.
L.M.G. Poole 《Planetary and Space Science》1978,26(7):697-701
The emission of light arising from the dissociative recombination with electrons of meteoric ions that have been oxidized by ozone is discussed and it is shown that this radiation has the characteristics necessary to explain the main features of luminosity observed below ～95 km in the trains of meteors in the approximate magnitude range 0 to ?5, namely: (i) that most enduring luminosity is obtained from heights between ～85 and ～95 km, (ii) that in this region the luminosity decays with time t according to (1 + Kt)?2 (rather than in an exponential fashion) with a rate constant K varying from ～0.3 s?1 near 90km to ～3s?1 below 85km and (iii) that the spectrum contains mainly lines characteristic of neutral calcium, iron and magnesium. 相似文献
4.
While analyzing the archival data of the INTEGRAL observatory, we detected and localized a cosmic gamma-ray burst recorded on April 28, 2006, by the IBIS/ISGRI and SPI telescopes in their fields of view. Since the burst was not revealed by the INTEGRAL burst alert system (IBAS), information about its coordinates was not distributed in time and no search for its afterglow was conducted. The burst was recorded by the KONUS/WIND and RHES SI satellites. Its 20–200-keV fluence was 2.3 × 10?6 erg cm?2, the peak flux was 3.6 × 10?7 erg cm?2 s?1 (3.9 phot. cm?2 s?1). The burst had a complex multipeaked profile and stood out among typical bursts by an increase in its hardness with time. At the flux peak, the spectrum was characterized by a photon index α ? ?1.5 and a peak energy E p ? 95 keV. The burst lasted for ～12 s, after which its afterglow decaying as a power law with an index γ ～ ?4.5 was observed at energies 15–45 keV. The spectral hardness decreased noticeably during the afterglow. 相似文献
5.
Radio emission spectra of the J = 1?0 ground state transition of H12C14N has been detected in comet Kohoutek (1973f) before and after perihelion passage. The HCN gas production rate is about 1028 molecules sec?1 at a heliocentric distance of ～0.4 AU. Multiple Doppler shifts in the observed spectrum suggest jets with velocities ranging up to several km sec?1. 相似文献
6.
A.A. Viggiano F. Arnold D.W. Fahey F.C. Fehsenfeld E.E. Ferguson 《Planetary and Space Science》1982,30(5):499-506
The results of a rocket-borne mass spectrometer measurement indicate that large concentrations of negative ions exist above the bottom of the atmospheric atomic oxygen layer. A large majority of these ions have a mass greater than 100 amu. In addition, an ion at mass 76 was observed with concentrations too large to be CO4?. In order to explain these features, a number of reactions involving silicon oxide negative ions have been measured in a flowing afterglow system. The ion SiO3? is produced by reaction of O3?, and CO3?, with SiO. The SiO3? ion is extremely stable and does not react measurably with NO, NO2, CO, CO2, O3 or O. Since meteoroid ablation produces a large silicon input into the atmosphere, it appears possible that the ions observed at mass 76 may be SiO3?. Possible production mechanisms for this ion as well as the heavy ions are discussed. 相似文献
7.
J.L. Queffelec B.R. Rowe M. Morlais J.C. Gomet F. Vallee 《Planetary and Space Science》1985,33(3):263-270
The yield of metastable nitrogen atoms in dissociative recombination of N2+ (v = 0, 1)ions has been tudied for different experimental conditions. In a first experiment, the branching ratio for N(2D) production was directly measured as being higher than 1.85; for N2+ (v = 0) this implies that 2D + 2D is the main reaction channel; for N2+ (v = 1) a minor channel could be 2P + 2D, 2P being then quenched toward 2D by electrons. In a second experiment, at higher electron densities, the influence of superelastic collisions was studied; a steady state analysis yields the quenching rate coefficient k4, of 2D towards 4S equal to 2.4 × 10?10 cm3 s?1for Te = 3900 K and shows that 2D + 2D is always the major channel of the reaction for N2+ (v = 1), 2D + 2P being a minor channel. All these results are in good agreement with thermospheric models but imply that N2+ dissociative recombination is a less important source for nitrogen escape of Mars. 相似文献
8.
This paper reports results obtained on ionosphere formation in the Jovian upper atmosphere with special reference to some of the recently available reaction rates, and to recent models of the Jovian neutral atmosphere based on the possibility of a warmer mesopause. We find that the role of the hypothetical radiative association of H+ to H2 to form H3+, as brought to light in our earlier study, is still important, even with a reaction rate as low as 10?15 cm3sec?1. In the lower regions of the ionosphere three-body processes leading to the formation of H3+ and H5+ ions, which have very fast dissociative recombination rates, produce a dramatic reduction in the electron density. When no radiative association takes place, and the H+ ions are lost by radiative recombination alone, we confirm that the photochemical equilibrium profile is also the diffusive equilibrium profile. However, with collisional-radiative recombination, whose rate becomes altitude-dependent, diffusion tends to bring about some redistribution of the ionization. Inclusion of radiative association enhances the role of diffusion. In this case, diffusion brings about all the expected changes. In particular, the differences in the electron density profile, originated in the lower-middle ionosphere by radiative association, are propagated up to all higher altitudes by diffusion. The rate constant of radiative association is, however, unknown. It is hoped that the critical importance of this reaction for the Jovian ionosphere will be an incentive towards a careful laboratory determination of its rate coefficient. In the older models of the Jovian ionosphere the major ions were H+ which were lost only by pure radiative recombination. This led to high electron densities and practically no diurnal change. In contrast, our new models have relatively much smaller electron densities, especially in lower regions, and may be susceptible to significant diurnal variation. 相似文献
9.
Excitation functions for collision-induced dissociation reactions of CO 3? and NO3? to give O? and the corresponding neutral species have been studied using an in-line tandem mass spectrometer. When these ions were prepared from certain gaseous mixtures, larger cross-sections and lower thresholds were observed for the dissociation processes than those found for the same ions in their apparent ground states. These observations suggest the existence of long-lived excited states of CO3?1 and NO3?1. The heats of formation of these excited ionic states were determined to be ?4.8 ± 0.1 and ?0.3 ± 0.2 eV for CO3?1 and NO3?1, respectively. Possible implications of these findings with respect to the D -region negative ion reaction scheme are discussed. 相似文献
10.
《Icarus》1987,72(3):604-622
The electrical conductivity and electrical charge on the aerosols in atmosphere of Titan are computed for altitudes from 0 to 400 km. Ionization due to both galactic cosmic rays and electron precipitation from the Saturnian magnetosphere is considered. This ionization results in free electrons and the primary ions N2+ and N+ which are then rapidly converted into secondary ions such as H2CN+ and NH4+ which in turn form ion clusters such as H2CN+(HCN)n and NH4+(NH3)m. In contrast to the atmospheres of Venus and Earth, we find no species in the Titan atmosphere that lead to the formation of appreciable concentrations of negative ions. Consequently, the predicted conductivity is quite different in that a substantial concentration of electrons exists all the way to the surface of Titan. The ubiquitous aerosols observed in the Titan atmosphere also play an important role in determining the charge distribution in the atmosphere. At altitudes above 100 km and for aerosol concentrations above approximately 10/cc, the recombination of electrons and positive ions is controlled by the recombination on the surface of the aerosols rather than by the gas-kinetic recombination rate. For small aerosol concentrations, the ratio of the number of charges per particle to the radius of the particle is approximately 30, for radii in microns. This value is similar to that obtained by previous investigators for terrestrial noctilucent clouds. Because the aerosol particles are highly charged, coagulation is inhibited, particle sizes are smaller, and their settling rates are reduced. As a consequence, the optical depth of the atmosphere is much higher than it would be if the particles were uncharged. 相似文献
11.
It is argued that ozone measurements made by Weeks et al. (1972) can be interpreted in terms of the enhanced ionization present. The conversion of O2+ ions to oxonium, H3O+ · (H2O)n, ions plus the dissociative recombination of these ions provides for an increased OH and/or H formation rate. The resulting enhanced OH and HO2 concentrations reduce the ambient atomic oxygen and hence ozone populations. The net excess H + OH formation rate is found to lie between one and two times the ionization production rate at altitudes where oxonium ions are the dominant positive ion species. 相似文献
12.
Measured rates are presented for the reaction of He+ ions with H2 (and D2) molecules to form H+, H2+, and HeH+ ions, as well as for the subsequent reactions of H+ and HeH+ ions with H2 to form H3+. The neutralization of H3+ (and H5+) ions by dissociative recombination with electrons is shown to be fast. The reaction He+ + H2 is slow (k = 1.1 × 10?13 cm3/sec at300°K) and produces principally H+ by the dissociative charge transfer branch. It is concluded that there may be a serious bottleneck in the conversion of two of the primary ions of the upper Jovian ionosphere, H+ and He+ (which recombine slowly), to the rapidly recombining H3+ ion (α[H3+]?3.4 × 10?7 cm3/sec at 150°K). 相似文献
13.
E.E. Ferguson D.W. Fahey F.C. Fehsenfeld D.L. Albritton 《Planetary and Space Science》1981,29(3):307-312
Loss processes which remove Si+ ions selectively relative to other meteor-derived atomic ions in the E- and D-regions of the ionosphere have been identified and measured in the laboratory. The major Si+ loss in the E-region is the reaction Si+ + H2O → HSiO+ + H (1) with a rate constant 2.3 ± 0.9 × 10?10 cm3s?1 at 300 K. The corresponding reactions with Fe+, Mg+ and other metallic meteor ions are endothermic. Presumably (1) is followed by a fast dissociative-recombination with electrons to produce neutral SiO or Si. At lower altitudes Si+ ions associate in a three-body reaction with O2 with a much larger rate constant than the corresponding associations of Fe+ and Mg+ with O2. 相似文献
14.
For the first time, a model of the daytime disturbed D-region is presented which is consistent with experimental solar proton event (SPE) data, that of the 2–5 November, 1969 event in particular. Sunset electron concentration profiles also are shown to be quite compatible with the experimental results, but computed sunrise electron concentrations are found to rise faster with solar elevation than do the measurements. In the daytime, O2?, O?, CO4? and CO3? ions apparently do not retain electrons in contrast to NO2? and NO3? ions. Hydration of the latter two species is probably unimportant since photodetachment and/or photodissociation of these ions are insignificant processes even when they are unattached to water molecules. Difficulties at sunrise are thought to arise most likely from our omission of hydration processes for negative ions, the pre-sunrise negative ion populations undoubtedly having the highest diurnal hydration level. Sunset ozone computations using the latest chemistry are shown to match the data except for some problem at the highest altitude, near 70 km, for the earlier, more disturbed, of the two experimental profiles. 相似文献
15.
Following the recent mass spectrometric observations of the ambient stratospheric positive and negative ions we have carried out co-ordinated laboratory experiments using a selected ion flow tube apparatus and a flowing afterglow apparatus for the following purposes: (i) to consider whether CH3CN is a viable candidate molecule for the species X in the observed stratospheric ion series H+ (H2On (X)m and (ii) to determine the binary mutual neutralization rate coefficients αi for the reactions ofH+ (H2O4 and H+(H2O)(CH3CN)3 with several of the negative ion species observed in the stratosphere. We conclude from (i) that CH3CN is indeed a viable candidate for X and from (ii) that the αi for stratospheric ions are within the limited range (5–6) × 10?8 cm3 s?1. 相似文献
16.
Jeffrey A. Macdonald Manfred A. Biondi Rainer Johnsen 《Planetary and Space Science》1984,32(5):651-654
The dissociative recombination coefficients α for capture of electrons by H3+ and H5+ ions have been determined as a function of electron temperature Te using a microwave afterglow-mass spectrometer apparatus. At ion and neutral temperatures Tu+ = Tn = 240 K, the coefficient α (H3+) is found to vary slowly with Te at first, decreasing from 1.6 × 10?7 cm3/s at Te = 240 K to 1.2 × 10?7 cm3/s at Te = 500 K, thereafter falling as Te?1 over the range 500 K ? Te, ? 3000 K. These results, which have a ± 20% uncertainty, agree satisfactorily over the common energy range (0.03–0.36 eV) with the recombination cross sections determined in merged beam measurements by Auerbach et al. At T+ = Tn = 128 K, the coefficient α(H5+) is found to be (1.8 ± 0.3) × 10?6 [Te(K)/300]?0.69 cm3/s over the range 128 K ? Te ? 3000 K, with a more rapid decrease, as Te?1, between 3000 K and 5500 K. The implications of these results for modelling planetary atmospheres and interstellar clouds are briefly touched on. 相似文献
18.
High resolution electric field and particle data, obtained by the S23L1 rocket crossing over a discrete prebreakup arc in January 1979, are studied in coordination with ground observations (Scandinavian Magnetometer Array—SMA, TV and all-sky cameras) in order to clarify the electrodynamics of the arc and its surroundings. Height-integrated conductivities have been calculated from the particle data, including the ionization effects of precipitating protons and assuming a steady state balance between ion production and recombination losses. High resolution optical information of arc location relative to the rocket permitted a check of the validity of this assumption for each flux tube passed by the rocket. Another check was provided by a comparison between calculated (equilibrium values) and observed electron densities along the rocket trajectory. A way to compensate for the finite precipitation time when calculating the electron densities is outlined. The height-integrated HalI-Pedersen conductivity ratio is typically 1.4 within the arc and about 1 at the arc edges, indicative of a relatively softer energy spectrum there. The height-integrated conductivities combined with the DC electric field measurements permitted calculation of the horizontal ionospheric current vectors (J⊥), Birkeland currents (from div J⊥) and energy dissipation through Joule heating (ΣpE2). An eastward current of typically 1 A m?1 was found to be concentrated mainly to the arc region and equatorward of it. A comparison has been made with the equivalent current system deduced from ground based magnetometer data (SMA) showing a generally good agreement with the rocket results. An intense Pedersen current peak (1.2 A m?1) was found at the southern arc edge. This edge constituted a division line between a very intense (> 10 μA m?1) and localized (~ 6 km) downward current sheet to the south, probably carried by upward flowing cold ionospheric electrons and a more extended upward current sheet (> 10 μA m?2) over the arc carried by measured precipitating electrons. Joule and particle heating across the arc were anticorrelated, consistent with the findings of Evans et al. (1977) with a total value of about 100mW m?2. 相似文献
19.
Juan C. López Vieyra Alexander V. Turbiner Nicolais L. Guevara 《Astrophysics and Space Science》2007,308(1-4):499-503
A first detailed study of the low-lying electronic states of the H 3 + molecular ion in linear configuration, parallel to a magnetic field, is carried out for B=0–4.414×1013 G in the Born-Oppenheimer approximation. The variational method is employed with a single, physically adequate trial function which includes, in particular, explicitly the electronic correlation term in the form exp?(γ r 12), where γ is a variational parameter. The state of the lowest total energy (ground state) depends on the magnetic field strength. It evolves from spin-singlet 1Σ g for small magnetic fields B?5×108 G to weakly-bound spin-triplet 3Σ u for intermediate fields and eventually to spin-triplet 3Π u state for B?5×1010 G. 相似文献
20.
The dipole moment of the A2Πu?x2Πg transition of O+2 is calculated as a function of internuclear distance using ab initio methods. The band absorption oscillator strengths and band transition probabilities of the second negative system are derived and the resulting lifetimes are compared with experimental data. The high-lying v″ levels of the ground state may decay into low-lying v′ levels of the excited state. The corresponding radiative lifetimes are calculated. 相似文献