Dissociative recombination of electrons with NO⁺ ions     

J.N. Bardsley 《Planetary and Space Science》1983,31(6):667-670

Resonant scattering theory is applied to the calculation of the rate of dissociative recombination in e-NO⁺ collisions. For ground state ions at 300 K, the recombination rate is 4.3 × 10^?7 cm³ s^?1, in good agreement with the afterglow data. At higher electron temperatures, the calculated rate lies between the values measured in afterglow and trapped-ion experiments. A possible explanation of this discrepancy is offered. For vibrationally excited ions, the recombination coefficient is significantly lower than that of the ground state.  相似文献   

The dissociative recombination of N₂⁺ (v = 0, 1) as a source of metastable atoms in planetary atmospheres     

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 T_e = 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   

Flowing afterglow studies of temperature dependencies for electron dissociative recombination of HCNH, CH₃CNH and CH₃CH₂CNH and their symmetrical proton-bound dimers     

J.L. McLain 《Planetary and Space Science》2009,57(13):1642-39

A study has been made using a variable temperature flowing afterglow Langmuir probe technique (VT-FALP) to determine the equilibrium temperature dependencies of the dissociative electron-ion recombination of the protonated cyanide ions (RCNH⁺, where R=H, CH₃ and C₂H₅) and their symmetrical proton-bound dimers (RCNH⁺NCR). The power law temperature dependencies of the recombination coefficients, α_e, over the temperature range 180 to 600 K for the protonated ions are α_e(T)(cm³ s⁻¹)=3.5±0.5×10⁻⁷ (300/T)^1.38 for HCNH⁺, α_e(T)=3.4±0.5×10⁻⁷ (300/T)^1.03 for CH₃CNH⁺, and α_e(T)=4.6±0.7×10⁻⁷ (300/T)^0.81 for CH₃CH₂CNH⁺. The equivalent values for the proton-bound dimers are α_e(T)(cm³ s⁻¹)=2.4±0.4×10⁻⁶(300/T)^0.5 for (HCN)₂H⁺ to α_e(T)=2.8±0.4×10⁻⁶(300/T)^0.5 for (CH₃CN)₂H⁺, and α_e(T)=2.3±0.3×10⁻⁶(300/T)^0.5 for (CH₃CH₂CN)₂H⁺. The relevance of these data to molecular synthesis in the interstellar medium and the Titan ionosphere are discussed.  相似文献   

Quenching of O⁺(²D) by electrons in the thermosphere     

Marsha R. Torr  D.G. Torr  P. Richards 《Planetary and Space Science》1980,28(6):581-584

A major loss process for the metastable species, O⁺(²D), in the thermosphere is quenching by electrons .To date no laboratory measurement exists for the rate coefficient of this reaction. Thermospheric models involving this process have thus depended on a theoretically calculated value for the rate coefficient and its variation with electron temperature. Earlier studies of the O⁺(²D) ion based on the Atmosphere Explorer data gathered near solar minimum, could not quantify this process. However, Atmosphere Explorer measurements made during 1978 exhibit electron densities that are significantly enhanced over those occurring in 1974, due to the large increases that have occurred in the solar extreme ultraviolet flux. Under such conditions, for altitudes ? 280 km, the electron quenching process becomes the major loss mechanism for O⁺(²D), and the chemistry of the N⁺₂ ion, from which the O⁺(²D) density is deduced, simplifies to well determined processes. We are thus able to use the in situ satellite measurements made during 1978 to derive the electron quenching rate coefficient. The results confirm the absolute magnitude of the theoretical calculation of the rate coefficient, given by the analytical expression k(T_e) = 7.8 × 10^?8 (T_e/300)^?0.5cm³s^?1. There is an indication of a stronger temperature dependence, but the agreement is within the error of measurement.  相似文献   

Ion-ion recombination rates in the earth's atmosphere     

D. Smith  M.J. Church 《Planetary and Space Science》1977,25(5):433-439

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 $\text{σ}$ is described by the power law $\text{σ}\text{? A · T}{}^{\mathrm{?0.9}}$, 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   

The dissociative recombination of O₂⁺ in the ionosphere     

Marsha R. Torr  D.G. Torr 《Planetary and Space Science》1981,29(9):999-1010

Aeronomical determinations of the dissociative recombination reaction rate coefficient for O₂⁺, α, depend directly on a knowledge of the rate coefficient for the charge exchange of O⁺ with O₂, k. A re-evaluation of the aeronomical determination of α using Atmosphere Explorer satellite data is necessary in the light of a subsequent laboratory measurement of k. The results reported here are in reasonable agreement with laboratory determinations to within the uncertainty of the analysis for night-time conditions. However, for data obtained under sunlit conditions the aeronomical determination differs significantly from the laboratory measurements. The results imply that the state of the O₂⁺ molecule resulting from the major thermospheric processes requires further examination.  相似文献   

Measurements of positive ion conversion and removal reactions relating to the Jovian ionosphere     

Rainer Johnsen  Manfred A. Biondi 《Icarus》1974,23(2):139-143

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   

The excitation of O₂(b¹Σ_g⁺) in the nightglow     

R.G.H. Greer  E.J. Llewellyn  B.H. Solheim  G. Witt 《Planetary and Space Science》1981,29(4):383-389

It is proposed that the available measurements of the O₂(b¹Σ_g⁺ ?X³Σ_g^?) atmospheric bands both in the nightglow and in the laboratory indicate that the excitation mechanism is a two-step process rather than the direct three body recombination of atomic oxygen. It is shown that such a two-step mechanism can explain observations of the atmospheric bands both in altitude and intensity.  相似文献   

Altitude profile of H in the atmosphere of Venus from Lyman α observations of Venera 11 and Venera 12 and origin of the hot exospheric component     

J.L. Bertaux  V.M. Lepine  V.G. Kurt  A.S. Smirnov 《Icarus》1982,52(2):221-244

Two extreme ultraviolet (EUV) spectrophotometers flown in December 1978 on Venera 11 and Venera 12 measured the hydrogen Lyman α emission resonantly scattered in the atmosphere of Venus. Measurements were obtained across the dayside of the disk, and in the exosphere up to 50,000 km. They were analyzed with spherically symmetric models for which the radiative transfer equation was solved. The H content of the Venus atmosphere varies from optically thin to moderately thick regions. A shape fit at the bright limb allows one to determine the exospheric temperature T_c and the number density n_c independently of the calibration of the instrument or the exact value of the solar flux. The dayside exospheric temperature was measured for the first time in the polar regions, with T_c = 300 ± 25°K for Venera 11 (79°S) and T_c = 275 ± 25°K (59°S) for Venera 12. At the same place, the density is n_c = 4_?2⁺³ × 10⁴ atom.cm^?3, and the integrated number density N_t from 250 to 110 km (the level of CO₂ absorption) is 2.1 × 10¹² atom.cm^?2, a factor of 3 to 6 lower than that predicted in aeronomical models. This probably indicates that the models should be revised in the content of H-bearing molecules and should include the effect of dynamics. Across the disk the value of N_t decreases smoothly with a total variation of two from the morning side to the afternoon side. Alternately it could be a latitude effect, with less hydrogen in the polar regions. The nonthermal component if clearly seen up to 40,000 km of altitude. It is twice as abundant as at the time of Mariner 10 (solar minimum). Its radial distribution above 4000 km can be simulated by an exospheric distribution with T = 10³⁰K and n = 10³ atom.cm^?3 at the exobase level. However, there are less hot atoms between 2000 and 4000 km than predicted by an ionospheric source. A by-product of the analysis is a determination of a very high solar Lyman α flux of 7.6 × 10¹¹ photons (cm² sec Å)^?1 at line center (1 AU) in December 1978.  相似文献   

Evidence for excited states of CO₃⁻¹ and NO₃⁻¹ from collisional dissociation processes     

Richard L.C. Wu  Thomas O. Tiernan 《Planetary and Space Science》1981,29(7):735-739

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   

Frank-Condon factors for H₂O⁺ molecular bands     

N.N. Shefov 《Planetary and Space Science》1983,31(11):1371-1372

Frank-Condon factors for H₂O⁺ bands have been calculated. They are used to estimate the photon scattering coefficient g_8.0 for the (8,0) band at 6158 Å.  相似文献   

Stratospheric in situ measurements of H₂SO₄ and HSO₃ vapors during a volcanically active period     

S. Qiu  F. Arnold 《Planetary and Space Science》1984,32(1):87-95

In situ measurements of stratospheric H₂SO₄ and HSO₃vapors using passive chemical ionization mass spectrometry were made in October 1982 after the eruption of volcano El Chichon. Data were obtained between about 20 and 41 km showing [H₂SO₄ + HSO₃] sum concentrations between about 10⁴ and 2 × 10⁵ cm^?3 below 29 km and a steep rise above this altitude. Maximum [H₂SO₄ + HSO₃] values of about 3 × 10⁶ cm^?3 are reached above 35 km.Partial [HSO₃] concentrations increase above 34 km reaching about $\text{4 × 10}{}^5\text{cm}{}^{\mathrm{?3}}$ around 40 km. From the measurements it is concluded that H₂SO₄ and probably HSO₃photolysis have an important influence above 34 km leading to the observed increase of [HSO₃] and a depletion of H₂SO₄vapor.It also seems that the data support the view of heterogeneous HSO₃ removal. If correct, this would imply that stratospheric aerosols are formed primarily from HSO₃ rather than H₂SO₄vapor.  相似文献   

Mariner 10 observations of hydrogen Lyman alpha emission from the venus exosphere: Evidence of complex structure     

P.Z. Takacs  A.L. Broadfoot  G.R. Smith  S. Kumar 《Planetary and Space Science》1980,28(7):687-701

The Ultraviolet Spectrometer Experiment on the MARINER 10 spacecraft measured the hydrogen Lyman α emmission resonantly scattered in the Venus exosphere at several viewing aspects during the encounter period. Venus encounter occurred at 17:01 GMT on 5 February 1974. Exospheric emissions above the planet's limb were measured and were analyzed with a spherically symmetric, single scattering, two-temperature model. On the sunlit hemisphere the emission profile was represented by an exospheric hydrogen atmosphere with T_c = 275±50 K and n_c = 1.5 × 10⁵ cm^?3 and a non-thermal contribution represented by T_H = 1250±100 K with n_H = 500±100 cm^?3. The observations of the dark limb showed that the spherically symmetric model used for the sunlit hemisphere was inappropriate for the analysis of the antisolar hemisphere. The density of the non-thermal component had increased at low altitudes, < 12,000 km, and decreased at high altitudes, > 20,000 km, by comparison. We conclude that the non-thermal source is on the sunward side of the planet. Analysis of the dark limb crossing suggests that the exospheric temperature on the dark side is <125 K if the exospheric density remains constant over the planet; upper limits are discussed. An additional source of Lyman α emission, 70 ± 15 R, was detected on the dark side of the planet and is believed to be a planetary albedo in contrast to multiple scattering from the sunlit side. Our analysis of the MARINER 10 data is consistent when applied to the MARINER 5 data.  相似文献   

Relative flow of H⁺ and O⁺ ions in the topside ionosphere at mid-latitudes     

G.I. Bailey  R.J. Moffett  J.A. Murphy 《Planetary and Space Science》1977,25(10):967-972

Theoretical results on the daily variation of O⁺ and H⁺ field-aligned velocities in the topside ionosphere are presented. The results are for an L = 3 magnetic field tube under sunspot minimum conditions at equinox. They come from calculations of time-dependent O⁺ and H⁺ continuity and momentum balance in a magnetic field tube which extends from the lower F2 region to the equatorial plane (Murphy et al., 1976).There are occasions when ion counterstreaming occurs, with the O⁺ velocity upward and H⁺ velocity downward. The conditions causing this counterstreaming are described: the H⁺ layer is descending whilst O⁺ is supplied from below either to increase the O⁺ concentration at fixed heights or to replace O⁺ ions lost by charge exchange with neutral H. It is suggested that the results of observations at Arecibo by Vickrey et al. (1976) of O⁺ and H⁺ concentrations and counterstreaming velocities are significantly affected by $\text{E}\text{×}\text{B}$ drift.  相似文献   

Mutual neutralization rates of ionospherically important ions     

D. Smith  N.G. Adams  M.J. Church 《Planetary and Space Science》1976,24(7):697-703

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   

A search for H₂O and Ch₄ in Comet Kohoutek     

W.A. Traub  N.P. Carleton 《Icarus》1974,23(4):585-589

A spectroscopic search for H₂O and CH₄ in Comet Kohoutek (1973f) was made using a Pepsios interferometer. No evidence was found for either molecule, allowing us to set an upper limit on their production rates (on about 21 January 1974) of Q(H₂O) < 6.2 × 10²⁸ sec^?1 and Q(CH₄) < 2.0 × 10³⁰ sec^?1. If the cometary surface is water-ice, this production rate leads to a product (1 ? A)·(πR₀²) < 2.2 km², where A is the Bond albedo, R₀ is the nuclear radius, and we assume that all the absorbed solar energy is used to evaporate H₂O.  相似文献   

On the structure of Mars' atmosphere at 120–220 km     

V.A. Krasnopolsky 《Icarus》1975,24(1):28-35

Altitude dependences of [CO₂] and [CO₂⁺] are deduced from Mariner 6 and 7 CO₂⁺ airglow measurements. CO₂ densities are also obtained from n_e radio occultation measurements. Both [CO₂] profiles are similar and correspond to the model atmosphere of Barth et al. (1972) at 120 km, but at higher altitudes they diverge and at 200–220 km the obtained [CO₂] values are three times less the model. Both the airglow and radio occultation observations show that a correction factor of 2.5 should be included into the values for solar ionization flux given by Hinteregger (1970). The ratio of [CO₂⁺]/n_e is 0.15–0.2 and, hence, [O]/[CO₂] is ～3% at 135 km. An atmospheric and ionospheric model is developed for 120–220 km. The calculated temperature profile is characterized by a value of T ≈ 370°K at h ? 220 km, a steep gradient (～2°/km) at 200-160 km, a bend in the profile at 160 km, a small gradient (～0.7°/km) below and a value of T ≈ 250°K at 120 km. The upper point agrees well with the results of the Lyman-α measurements; the steep gradient may be explained by molecular viscosity dissipation of gravity and acoustical waves (the corresponding energy flux is 4 × 10^?2 erg cm^?2sec^?1 at 180 km). The bend at 160 km may be caused by a sharp decrease of the eddy diffusion coefficient and defines K ≈ 2 × 10⁸cm²sec^?1; and the low gradient gives an estimate of the efficiency of the atmosphere heating by the solar radiation as ? ≈ 0.1.  相似文献   

An estimate of the PH₃, CH₃D,and GeH₄ Abundances on Jupiter from the Voyager IRIS data at 4.5 μm     

P. Drossart  T. Encrenaz  V. Kunde  R. Hanel  M. Combes 《Icarus》1982,49(3):416-426

The abundances of PH₃, CH₃D, and GeH₄ are derived from the 2100- to 2250-cm^?1 region of the Voyager 1 IRIS spectra. No evidence is seen for large-scale variations of the phosphine abundance over Jovian latitudes between ?30 and +30°. In the atmospheric regions corresponding to 170–200°K, the derived PH₃/H₂ value is (4.5 ± 1.5) × 10^?7 or 0.75 ± 0.25 times the solar value. This result, compared with other PH₃ determinations at 10 μm, suggests than the PH₃/H₂ ratio on Jupiter decreases with atmospheric pressure. In the 200–250°K region, we derive, within a factor of 2, CH₃D/H₂ and GeH₄/H₂ ratios of 2.0 × 10^?7 and 1.0 × 10^?9, respectively. Assuming a C/H value of 1.0 × 10^?3, as derived from Voyager, our CH₃D/H₂ ratio implies a D/H ratio of 1.8 × 10^?5, in reasonable agreement with the interstellar medium value.  相似文献   

Spectro-imaging observations of Jupiter's 2-μm auroral emission. I. H₃ distribution and temperature     

E. Raynaud  J.-P. Maillard  J.H. Waite Jr.  P. Drossart 《Icarus》2004,171(1):133-152

We report on spectro-imaging infrared observations of Jupiter's auroral zones, acquired in October 1999 and October 2000 with the FTS/BEAR instrument at the Canada-France-Hawaii Telescope. The use of narrow-band filters at 2.09 and 2.12 μm, combined with high spectral resolution (0.2 cm⁻¹), allowed us to map emission from the H₂S₁(1) quadrupole line and from several H₃⁺ lines. The H₂ and H₃⁺ emission appears to be morphologically different, especially in the north, where the latter notably exhibits a “hot spot” near 150°-170° System III longitude. This hot spot coincides in position with the region of increased and variable hydrocarbon, FUV and X-ray emission, but is not seen in the more uniform H₂S₁(1) emission. We also present the first images of the H₂ emission in the southern polar region. The spectra include a total of 14 H₃⁺ lines, including two hot lines from the 3ν₂-ν₂ band, detected on Jupiter for the first time. They can be used to determine H₃⁺ column densities, rotational (T_rot) and vibrational (T_vib) temperatures. We find the mean T_vib of the v₂=3 state to be lower (960±50 K) than the mean T_rot in v₂=2 (1170±75 K), indicating an underpopulation of the v₂=3 level with respect to local thermodynamical equilibrium. Rotational temperatures and associated column densities are generally higher and lower, respectively, than inferred previously from ν₂ observations. This is a likely consequence of a large positive temperature gradient in the sub-microbar auroral atmosphere. While the signal-to-noise is not sufficient to take full advantage of the 2-D capabilities of the observations, the search for correlations between line intensities, T_vib and column densities, indicates that variations in line intensities are mostly due to correlated variations in the H₃⁺ column densities. The thermostatic role played by H₃⁺ at ionospheric levels may provide an explanation. The exception is the northern “hot spot,” which exhibits a T_vib about 250 K higher than other regions. A partial explanation might invoke a homopause elevation in this region, but a fully consistent scenario is not yet available. The different distributions of the H₂ and H₃⁺ emission are equally difficult to explain.  相似文献   

The altitude dependence of the O₂(A³Σ_u⁺) vibrational distribution in the terrestrial nightglow     

I.C. McDade  E.J. Llewellyn  R.G.H. Greer  D.P. Murtagh 《Planetary and Space Science》1982,30(11):1133-1136

A simple vibrational relaxation model which reproduces the observed altitude integrated vibrational distribution of the Herzberg I bands in the nightglow is used to derive the altitude profiles of the individual vibrational levels at 1 km intervals in the 85–115 km height range. The possible errors associated with using rocket-borne photometer measurements of a limited number of bands in the O₂(A³Σ_u⁺?X³Σ_g^?) system to infer the total Herzberg I emission profile are assessed.  相似文献