The role of ion-molecule reactions in the conversion of N₂O₅ to HNO₃ in the stratosphere     

H. Böhringer  D.W. Fahey  F.C. Fehsenfeld  E.E. Ferguson 《Planetary and Space Science》1983,31(2):185-191

We have investigated the role of several ion-molecule reactions in the conversion of N₂O₅ to HNO₃. In the proposed conversion, an N₂O₅ molecule would react with an H₂O molecule clustered to an inert ion to produce two HNO₃ molecules. Subsequent clustering of an H₂O molecule to the inert ion would make the reaction catalytic. If such an ion-catalysed conversion of N₂O₅ to HNO₃ occurs, it would probably play a role in the stratospheric chemistry at high latitudes in winter. In this paper we present reaction rate constant measurements made in a flowing afterglow apparatus for hydrated H₃O⁺, H⁺(CH₃CN)_m (m = 1, 2, 3), and several negative ions reacting with N₂O₅. Slow rate constants were found for these ions for hydration levels that are predominant in the stratosphere. With the known stratospheric ion density, these slow rate constants preclude significant N₂O₅ conversion by ion-molecule reactions.  相似文献   

Ion chemistry in the cometary atmosphere     

Mikio Shimizu 《Astrophysics and Space Science》1975,36(2):353-361

Dirty ice of a second kind (major components, H₂O, CO, and N₂; minor components less than several percents, NH₃, CH₄, and other organic substances such as HCN, CH₃CN etc.) is assumed for the composition of volatiles in the cometary nucleus. The consistency with the observations of molecular ions and daughter molecules in the cometary atmosphere is argued by taking into account various ion-molecular reactions and dissociative recombinations. There is a satisfactory agreement for the second kind of dirty-ice model, but the presence of large amounts of CH₄ and NH₃ is found to be rather in contradiction with observational evidence. A velocity of 8 km s^?1 for the hydrogen atoms, derived from analysis of the hydrogen Lyman-alpha corona around comets, is found from the dissociative recombination of H₃O⁺, the dominant constituent of cometary ionosphere, in accordance with H₃O⁺+e ^?→OH+H+H.  相似文献   

The lower ionosphere of Titan     

L.A. Capone  R.C. Whitten  J. Dubach  S.S. Prasad  W.T. Huntress 《Icarus》1976,28(3):367-378

Ionization of the atmosphere of Titan by galactic cosmic rays is a very significant process throughout the altitude range of 100 to 400 km. An approximate form of the Boltzmann equation for cosmic ray transport has been used to obtain local ionization rates. Models of both ion and neutral chemistry have been employed to compute electron and ion density profiles for three different values of the H₂/CH₄ abundance ratio. The peak electron density is of the order 10³ cm^?3. The most abundant positive ions are C₂H₉⁺ and C₃H₉⁺, while the predicted densities of the negative ions H^? and CH₃^? are very small (<10^?4 that of the positive ions). It is suggested that inclusion of the ion chemistry is important in the computation of the H and CH₃ density profiles in the lower ionosphere.  相似文献   

Magnesium ion chemistry in the stratosphere     

E.E. Ferguson  B.R. Rowe  D.W. Fahey  F.C. Fehsenfeld 《Planetary and Space Science》1981,29(4):479-481

Laboratory measurements of reaction rate constants of magnesium ions and magnesium containing ions with O₃, NO, HNO₃, and H₂O₂ have been carried out in a flowing afterglow experiment. Mg⁺ ions react with O₃ to produce MgO⁺ ions, which in turn react with O₃ to produce Mg⁺ ions. Mg⁺ ions react with HNO₃ and H₂O₂ to produce MgOH⁺ ions. MgOH⁺ ions react rapidly with HNO₃ to produce NO⁺₂ ions and Mg(HO)₂. One can therefore conclude that Mg⁺, MgO⁺, or MgOH⁺ ions could not have significant concentrations in the stratosphere if gas phase magnesium compounds were present. The failure to observe these ions therefore cannot be used as evidence that the stratospheric magnesium, resulting from meteor ablation at higher altitudes, is in condensed phases. This is in contrast to the case for sodium where the ion chemistry is such that the failure to observe hydrated Na⁺ ions proves that gas phase sodium compounds are not present in the stratosphere.  相似文献   

Radial distribution of production rates, loss rates and densities corresponding to ion masses ?40 amu in the inner coma of Comet Halley: Composition and chemistry     

S.A. Haider 《Icarus》2005,177(1):196-216

In this paper we have studied the chemistry of C, H, N, O, and S compounds corresponding to ions of masses ?40 amu in the inner coma of the Comet 1P/Halley. The production rates, loss rates, and ion mass densities are calculated using the Analytical Yield Spectrum approach and solving coupled continuity equation controlled by the steady state photochemical equilibrium condition. The primary ionization sources in the model are solar EUV photons, photoelectrons, and auroral electrons of the solar wind origin. The chemical model couples ion-neutral, electron-neutral, photon-neutral and electron-ion reactions among ions, neutrals, electrons, and photons through over 600 chemical reactions. Of the 46 ions considered in the model the chemistry of 24 important ions (viz., CH₃OH⁺₂, H₃CO⁺, NH⁺₄, H₃S⁺, H₂CN⁺, H₂O⁺, NH⁺₃, CO⁺, C₃H⁺₃, OH⁺, H₃O⁺, CH₃OH⁺, C₃H⁺₄, C₂H⁺₂, C₂H⁺, HCO⁺, S⁺, CH⁺₃, H₂S⁺, O⁺, C⁺, CH⁺₄, C⁺₂, and O⁺₂) are discussed in this paper. At radial distances <1000 km, the electron density is mainly controlled by 6 ions, viz., NH⁺₄, H₃O⁺, CH₃OH⁺₂, H₃S⁺, H₂CN⁺, and H₂O⁺, in the decreasing order of their relative contribution. However, at distances >1000 km, the 6 major ions are H₃O⁺, CH₃OH⁺₂, H₂O⁺, H₃CO⁺, C₂H⁺₂, and NH⁺₄; along with ions CO⁺, OH⁺, and HCO⁺, whose importance increases with further increase in the radial distance. It is found that at radial distances greater than ∼1000 km (±500 km) the major chemical processes that govern the production and loss of several of the important ions in the inner coma are different from those that dominate at distances below this value. The importance of photoelectron impact ionization, and the relative contributions of solar EUV, and auroral and photoelectron ionization sources in the inner coma are clearly revealed by the present study. The calculated ion mass densities are compared with the Giotto Ion Mass Spectrometer (IMS) and Neutral Mass Spectrometer (NMS) data at radial distances 1500, 3500, and 6000 km. There is a reasonable agreement between the model calculation and the Giotto measurements. The nine major peaks in the IMS spectra between masses 10 and 40 amu are reproduced fairly well by the model within a factor of two inside the ionopause. We have presented simple formulae for calculating densities of the nine major ions, which contribute to the nine major peaks in the IMS spectra, throughout the inner coma that will be useful in estimating their densities without running the complex chemical models.  相似文献   

Ion composition and chemistry in the coma of Comet 1P/Halley—A comparison between Giotto's Ion Mass Spectrometer and our ion-chemical network     

Martin Rubin  Kenneth C. Hansen  Michael R. Combi  Hans Balsiger 《Icarus》2009,199(2):505-519

In order to understand the cometary plasma environment it is important to track the closely linked chemical reactions that dominate ion evolution. We used a coupled MHD ion-chemistry model to analyze previously unpublished Giotto High Intensity Ion Mass Spectrometer (HIS-IMS) data. In this way we study the major species, but we also try to match some minor species like the CH_x and the NH_x groups. Crucial for this match is the model used for the electrons since they are important for ion-electron recombination. To further improve our results we included an enhanced density of supersonic electrons in the ion pile-up region which increases the local electron impact ionization. In this paper we discuss the results for the following important ions: C⁺, CH⁺, CH⁺₂, CH⁺₃, N⁺, NH⁺, NH⁺₂, NH⁺₃, NH⁺₄, O⁺, OH⁺, H₂O⁺, H₃O⁺, CO⁺, HCO⁺, H₃CO⁺, and CH₃OH⁺₂. We also address the inner shock which is very distinctive in our MHD model as well as in the IMS data. It is located just inside the contact surface at approximately 4550 km. Comparisons of the ion bulk flow directions and velocities from our MHD model with the data measured by the HIS-IMS give indication for a solar wind magnetic field direction different from the standard Parker angle at Halley's position. Our ion-chemical network model results are in a good agreement with the experimental data. In order to achieve the presented results we included an additional short lived inner source for the C⁺, CH⁺, and CH⁺₂ ions. Furthermore we performed our simulations with two different production rates to better match the measurements which is an indication for a change and/or an asymmetric pattern (e.g. jets) in the production rate during Giotto's fly-by at Halley's comet.  相似文献   

Collisional vibrational quenching of O2+(v) and other molecular ions in planetary atmospheres     

H. Böhringer  M. Durup-Ferguson  E.E. Ferguson  D.W. Fahey 《Planetary and Space Science》1983,31(4):483-487

New experimental techniques have yielded several thermal energy vibrational quenching rate constants for O₂⁺(v). Rates for quenching of O₂⁺(v = 1) by O₂, N₂, Ar, CO₂, H₂, and CH₄ are 3(?10), 2(?12), 1(?12), 1(?10), 2.5(?12), and 6(?10) cm³s^?1 at 300 K. The quenching is somewhat faster for O₂⁺(v = 2). The triatomic ions CO₂⁺, NO₂⁺, N₂O⁺, SO₂⁺, and H₂O⁺ are all vibrationally deexcited with an efficiency greater than 10^?3 in Ar or Ne collisions. A theoretical rationalization of the experimental results leads to the prediction that vibrational quenching in planetary atmospheres will generally be efficient, k > 1(?12) cm³s^?1 for almost all ion and neutral gas pairs.  相似文献   

Mass spectrometric measurements of fractional ion abundances in the stratosphere—Positive ions     

F. Arnold  G. Henschen  E.E. Ferguson 《Planetary and Space Science》1981,29(2):185-193

Measured fractional abundances for stratospheric positive ions are reported for the first time. The measurements which were obtained from balloon-borne ion mass spectrometer experiments relied on recent simulation studies of electric field induced cluster ion dissociation conducted at our laboratory.The ion abundance data provide strong support for identifications of the observed ions as H⁺(H₂O)_n and Hx⁺x_L(H₂O)_m proposed previously. Moreover, it is found that x most likely cannot be identified as NaOH or MgOH which implies that gaseous metal compounds do not exist in the middle stratosphere in significant abundances.Implications of the present findings for the composition and chemistry of stratospheric ions as well as for stratospheric aerosols are discussed.  相似文献   

Electronic Sputtering Analysis of Astrophysical Ices     

L. S. Farenzena  P. Iza  R. Martinez  F. A. Fernandez-Lima  E. Seperuelo Duarte  G. S. Faraudo  C. R. Ponciano  M. G. P. Homem  A. Naves de Brito  K. Wien  E. F. da Silveira 《Earth, Moon, and Planets》2005,97(3-4):311-329

Experimental results on fast ion collision with icy surfaces having astrophysical interest are presented. ²⁵²Cf fission fragments projectiles were used to induce ejection of ionized material from H₂O, CO₂, CO, NH₃, N₂, O₂ and Ar ices; the secondary ions were identified by time-of-flight mass spectrometry. It is observed that all the bombarded frozen gas targets emit cluster ions which have the structure X_nR^±, where X is the neutral ice molecule and R^± is either an atomic or a molecular ion. The shape of the positive or negative ion mass spectra is characterized by a decreasing yield as the emitted ion mass increases and is generally described by the sum of two exponential functions. The positive ion water ice spectrum is dominated by the series (H₂O)_nH₃O⁺ and the negative ion spectrum by the series (H₂O)_nOH⁻ and (H₂O)_nO⁻. The positive ion CO₂ ice spectrum is characterized by R⁺ = C⁺, O⁺, CO⁺, O₂⁺ or CO₂⁺ and the negative one by R⁻ = CO₃⁻. The dominant series for ammonia ice correspond to R⁺ = NH₄⁺ and to R⁻ = NH₂⁻. The oxygen series are better described by (O₃)_nO_m⁺ secondary ions where m = 1, 2 or 3. Two positive ion series exist for N₂ ice: (N₂)_nN₂⁺ and (N₂)_nN⁺. For argon positive secondary ions, only the (Ar)_nAr⁺ series was observed. Most of the detected molecular ions were formed by one-step reactions. Ice temperature was varied from ∼20 K to complete sublimation.  相似文献   

Initial interpretation of Titan plasma interaction as observed by the Cassini plasma spectrometer: Comparisons with Voyager 1     

R.E. Hartle  E.C. Sittler  R.E. Johnson  F. Crary  D.T. Young  D. Simpson  D. Reisenfeld  J.J. Berthelier  J. Vilppola  N. Andre 《Planetary and Space Science》2006,54(12):1211-1224

The Cassini plasma spectrometer (CAPS) instrument made measurements of Titan's plasma environment when the Cassini Orbiter flew through the moon's plasma wake October 26, 2004 (flyby TA). Initial CAPS ion and electron measurements from this encounter will be compared with measurements made by the Voyager 1 plasma science instrument (PLS). The comparisons will be used to evaluate previous interpretations and predictions of the Titan plasma environment that have been made using PLS measurements. The plasma wake trajectories of flyby TA and Voyager 1 are similar because they occurred when Titan was near Saturn's local noon. These similarities make possible direct, meaningful comparisons between the various plasma wake measurements. They lead to the following: (A) The light and heavy ions, H⁺and N⁺/O⁺, were observed by PLS in Saturn's magnetosphere in the vicinity of Titan while the higher mass resolution of CAPS yielded H⁺ and H₂⁺as the light constituents and O⁺/CH₄⁺ as the heavy ions. (B) Finite gyroradius effects were apparent in PLS and CAPS measurements of ambient O⁺ ions as a result of their absorption by Titan's extended atmosphere. (C) The principal pickup ions inferred from both PLS and CAPS measurements are H⁺, H₂⁺, N⁺, CH₄⁺ and N₂⁺. (D) The inference that heavy pickup ions, observed by PLS, were in narrow beam distributions was empirically established by the CAPS measurements. (E) Slowing down of the ambient plasma due to pickup ion mass loading was observed by both instruments on the anti-Saturn side of Titan. (F) Strong mass loading just outside the ionotail by a heavy ion such as N₂⁺ is apparent in PLS and CAPS measurements. (G) Except for the expected differences due to the differing trajectories, the magnitudes and structures of the electron densities and temperatures observed by both instruments are similar. The high-energy electron bite-out observed by PLS in the magnetotail is consistent with that observed by CAPS.  相似文献   

Representative abundances of a few positive ions in the innermost coma of comet Halley     

P. P. Saxena  Alka Misra 《Earth, Moon, and Planets》1993,60(1):59-68

The production rate of H₂O molecules at a heliocentric distance of 1 AU for comet Halley and the abundance ratio with respect to water (H₂O) of parent molecules at the cometary nucleus from the paper of Yamamoto (1987) have been used to compute the number densities of positive ions viz. H₃O⁺, H₃S⁺, H₂CN⁺, H₃CO⁺, CH₃OH ₂ ⁺ and NH ₄ ⁺ at various cometocentric distances within 600 kms from the nucleus.The role of proton transfer reactions in producing major ionic species is discussed. A major finding of the present investigation is that NH ₄ ⁺ ion which may be produced through proton transfer reactions is the most abundant ion near the nucleus of a comet unless the abundance of NH₃ as a parent is abnormally low. Using the quoted value of Q(NH₃)/Q(H₂O) for comet Halley and the life times of NH₃ and H₂O molecules, the abundance ratio N(NH₃)/N(H₂O) is found to be one-third of that used in the present paper. The consequent proportionate decrease in the NH ₄ ⁺ ions does not, however, affect its superiority in number density over other ions near the nucleus.The number density of the next most abundant ion viz. H₃O⁺ is found to be 4 × 10⁴ cm^-3 at the nucleus of comet Halley and decreases by a factor of two only upto a distance of 600 K ms from the nucleus. The ionic mass peak recorded by VEGA and GIOTTO spacecrafts atm/q = 18 is most probably composite of the minor ionic species H₂O⁺, as its number density = 10² cm^-3 remains virtually constant in the inner coma and of NH ₄ ⁺ , the number density of which at large cometocentric distances may add to the recorded peak atmlq = 18. The number densities of other major ions produced through proton transfer from H₃O⁺ are also discussed in the region within 600 K ms from the nucleus of comet Halley.  相似文献   

The upper ionosphere of Titan     

R.C. Whitten  L.A. Capone  L. McCulley  P.F. Michelson 《Icarus》1977,31(1):89-96

Photoionization of the upper atmosphere of Titan by sunlight is expected to produce a substantial ionospheric layer. We have solved one-dimensional forms of the mass, momentum, and energy conservation equations for ions and electrons and have obtained electron number densities of about 10³ cm^?3, using various model atmospheres. The significant ions in a CH₄H₂ atmosphere are H⁺, H₃⁺, CH₅⁺, CH₅⁺, CH₃⁺, and C₂H₅⁺. Electron temperatures may be as high as 1000°K, depending on the abundance of hydrogen in the high atmosphere. Interaction of the solar wind with the ionosphere is also discussed.  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   

Deuterium on Venus: Model comparisons with pioneer Venus observations of the predawn bulge ionosphere     

Shailendra Kumar  Harry A. Taylor 《Icarus》1985,62(3):494-504

A model of the predawn bulge ionosphere composition and structure is constructed and compared with the ion mass spectrometer measurements from the Pioneer Venus Orbiter during orbits 117 and 120. Particular emphasis is given to the identification of the mass-2 ion which we find unequivocally due to D⁺ (and not H₂⁺). The atmospheric D/H ratio of 1.4% and 2.5% is obtained at the homopause (～ 130 km) for the two orbits. The H₂⁺ contribution to the mass-2 ion density is less than 10%, and the H₂ mixing ratio must be <0.1 ppm at 130 km altitude. The He⁺ data require a downward He⁺ flux of ～2 × 10⁷ cm^?2 sec^?1 in the predawn region which suggest that the light ions also flow across the terminator from day to night along with the observed O⁺ ion flow.  相似文献   

Recombination of electrons with H₃⁺ and H₅⁺ ions     

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 T_e using a microwave afterglow-mass spectrometer apparatus. At ion and neutral temperatures T_u+ = T_n = 240 K, the coefficient α (H₃⁺) is found to vary slowly with T_e at first, decreasing from 1.6 × 10^?7 cm³/s at T_e = 240 K to 1.2 × 10^?7 cm³/s at T_e = 500 K, thereafter falling as T_e^?1 over the range 500 K ? T_e, ? 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₊ = T_n = 128 K, the coefficient α(H₅⁺) is found to be (1.8 ± 0.3) × 10^?6 [T_e(K)/300]^?0.69 cm³/s over the range 128 K ? T_e ? 3000 K, with a more rapid decrease, as T_e^?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   

Models of the cometary coma in which abundances are calculated for various heliocentric distances     

Michael B. Swift  George F. Mitchell 《Icarus》1981,47(3):412-430

One-dimensional radial models of the chemistry in cometary comae have been constructed for heliocentric distances ranging from 2 to 0.125 AU. The coma's opacity to solar radiation is included and photolytic reaction rates are calculated. A parent volatile mixture similar to that found in interstellar molecular clouds is assumed. Profiles through the coma of number density and column density are presented for H₂O, OH, O, CN, C₂, C₃, CH, and NH₂. Whole-coma abundances are presented for NH₂, CH, C₂, C₃, CN, OH, CO⁺, H₂O⁺, CH⁺, N₂⁺, and CO₂⁺.  相似文献   

Radioastronomical observations of comets IRAS-Araki-Alcock (1983d) and Sugano-Saigusa-Fujikawa (1983e)     

W.M. Irvine  Z. Abraham  M. A&#x;Hearn  W. Altenhoff  Ch. Andersson  J. Bally  W. Batrla  A. Baudry  D. Bockelée-Morvan  G. Chin  J. Crovisier  I. de Pater  D. Despois  L. Ekelund  E. Gerard  T. Hasegawa  C. Heiles  J.M. Hollis  A. Wootten 《Icarus》1984,60(1):215-220

Detections and upper limits to the continuum emission (1 ≤ λ ≤6 cm) and spectral line emission (OH, CO, CS, HCN, HCO⁺, CN, CH₃CN, CH₃C₂H, NH₃, H₂O, HC₃N, CH₃CH₂CN) are reported from radio observations of Comets 1983d and 1983e. Comparison is made with observations of CN at optical wavelengths. These results may be useful in planning future cometary observations.  相似文献   

Synthesis of hydrogen peroxide in water ice by ion irradiation     

M.J. Loeffler  U. Raut  R.A. Baragiola 《Icarus》2006,180(1):265-273

We present infrared absorption studies on the effects of 50-100 keV Ar⁺ and 100 keV H⁺ ion irradiation of water ice films at 20-120 K. The results support the view that energetic ions can produce hydrogen peroxide on the surface of icy satellites and rings in the outer Solar System, and on ice mantles on interstellar grains. The ion energies are characteristic of magnetospheric ions at Jupiter, and therefore the results support the idea that radiolysis by ion impact is the source of the H₂O₂ detected on Europa by the Galileo infrared spectrometer. We found that Ar⁺ ions, used to mimic S⁺ impacts, are roughly as efficient as H⁺ ions in producing H₂O₂, and that 100 keV H⁺ ions can produce hydrogen peroxide at 120 K. The synthesized hydrogen peroxide remained stable while warming the ice film after irradiation; the column density of the formed H₂O₂ is constant until the ice film begins to desorb, but the concentration of H₂O₂ increases with time during desorption because the water sublimes at a faster rate. Comparing the shape of the 3.5-μm absorption feature of H₂O₂ to the one measured on Europa shows excellent agreement in both shape and position, further indicating that the H₂O₂ detected on Europa is likely caused by radiolysis of water ice.  相似文献   

Mass spectrometric measurements of fractional ion abundances in the stratosphere—Negative ions     

F. Arnold  R. Fabian  E.E. Ferguson  W. Joos 《Planetary and Space Science》1981,29(2):195-203

Fractional abundances of stratospheric negative ions are for the first time explicitly reported. The measurements made by balloon-borne ion mass spectrometers also rely on recent studies of electric field induced collisional dissociation of negative cluster ions conducted at our laboratory. These indicate that the negative ion composition measurements around 36 km conducted by our group do not suffer from any significant dissociation. The new composition data support ion identifications NO₃^?(HNO₃)_b and HSO₄^?(H₂SO₄)_c(HNO₃)_d and the underlying ion reactions propo previously. Moreover, it is found that HSO₄^?(H₂SO₄)_g-ions appear to be particularly stable and that H₂SO₄-association is very fast. Implications of the ion composition data for ion processes are discussed.  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