Non-thermal $\text{O}\text{(}{}^1\text{D}\text{)}$ produced by dissociative recombination of O₂⁺: A theoretical model and observational results     

G.A. Schmitt  V.J. Abreu  P.B. Hays 《Planetary and Space Science》1981,29(10):1095-1099

Thermal and non-thermal $\text{O}\text{(}{}^1\text{D}\text{)}$ number density profiles are calculated. The two populations are assumed to be coupled by a thermalization cross-section which determines the loss and production in the non-thermal and thermal populations, respectively. The sources, sinks and transport of the two populations are used to model volume emission rate profiles at 6300 Å. The 6300 Å brightness measured by the Visible Airglow Experiment is then used to establish the presence of the non-thermal population and to determine the thermalization cross-section.  相似文献   

Aeronomical determination of the efficiency of O¹D) production by dissociative recombination of O₂⁺     

L.L. Cogger  L.S. Smith  R.M. Harper 《Planetary and Space Science》1977,25(2):155-159

Simultaneous measurements of the 6300 Å airglow intensity, the electron density profile, and F-region ion temperatures and vertical ion velocities taken at the Arecibo Observatory in March 1971 are utilized in the height integrated continuity equation to extract the number of photons'of 6300 Å emitted per recombination. After accounting for quenching of $\text{O}\text{(}{}^1\text{D}\text{)}$ and the electrons lost via NO⁺ recombination, the efficiency of $\text{O}\text{(}{}^1\text{D}\text{)}$ production by the dissociative recombination of O₂⁺ is determined to be 0.6 ± 0.2 including cascading from the $\text{O}\text{(}{}^1\text{S}\text{)}$ state. The uncertainty includes both random measurement errors and estimates of possible systematic errors.  相似文献   

Branching ratios for the photoionization cross section of atomic oxygen     

A.K. Pradhan 《Planetary and Space Science》1980,28(2):165-167

Branching ratios $\text{σ(}\text{O}{}^0{}^3\text{P}\text{→}\text{O}{}^{\mathrm{+}}{}^2\text{D}{}^0\text{)}\text{σ(}\text{O}{}^0{}^3\text{P}\text{→}\text{O}{}^{\mathrm{+}}{}^4\text{S}{}^0\text{)}$ and $\text{σ(}\text{O}{}^0{}^3\text{P}\text{→}\text{O}{}^{\mathrm{+}}{}^2\text{P}{}^0\text{)}\text{σ (}\text{O}{}^0{}^3\text{P}\text{→}{}^4\text{S}{}^0\text{)}$ are calculated at 584 Å and 304 A employing the close-coupling approximation to compute the photoionization cross section values. The coupled channels include the states dominated by the ground configuration 1s²2s²p³ of O⁺and the next excited configuration ls²2s2p⁴. It is found that the partial c section $\text{σ(}{}^2\text{D}{}^0\text{)}$ decreases more rapidly than $\text{σ(}{}^2\text{P}{}^0\text{)}$, and at the lower wavelength 304 Å, the ratio $\text{σ(}{}^2\text{D}{}^0\text{)}\text{σ(}{}^4\text{S}{}^0\text{)}\text{<}\text{σ(}{}^2\text{P}{}^0\text{)}\text{σ(}{}^4\text{S}{}^0\text{)}$. Present results at 304 Å differ considerably from previous work.  相似文献   

Distribution functions for energetic oxygen atoms in the earth's lower atmosphere     

Jennifer A. Logan  Michael B. McElroy 《Planetary and Space Science》1977,25(2):117-122

Direct photolysis of O₃ and quenching of $\text{O}\text{(}{}^1\text{D}\text{)}$ by N₂ provide abundant sources of fast oxygen atoms for the Earth's lower atmosphere. The concentration of atoms with energy above 0.7 eV may exceed the concentration of $\text{O}\text{(}{}^1\text{D}\text{)}$ for all altitudes below 18 km and these atoms may play an important role in lower atmospheric chemistry. Distribution functions for $\text{O}\text{(}{}^3\text{P}\text{)}$ are given for the energy interval 0.1-1.3 eV, for a range of altitudes from 0 to 62 km.  相似文献   

Linewidth studies on the NI(⁴S−⁴P) resonance multiplet     

P.W. Erdman  E.C. Zipf 《Planetary and Space Science》1983,31(11):1291-1298

We have measured the linewidths of the NI multiplets $\text{[2p}{}^2\text{3p}{}^4\text{D}{}^0\text{?2p}{}^2\text{3s}{}^4\text{P, λ8691}\text{A}\text{?}\text{; 2p}{}^2\text{3p}{}^4\text{P}{}^0\text{?2p}{}^2\text{3s}{}^4\text{P, λ8212}\text{A}\text{?}\text{; 2p}{}^2\text{3s}{}^4\text{P?2p}{}^3{}^4\text{S}{}^0\text{, λ1200}\text{A}\text{?}\text{]}$ produced in the dissociative excitation of N₂ by energy electrons. The infrared transitions excite the N(⁴P) resonance state by cascade and they account for > 50% of the total N(⁴P) cross section at 100 eV. Both the i.r. and v.u.v. lines are found to be highly Doppler broadened ( ～ 25 times the thermal Doppler line width). These results indicate that dissociative excitation of N₂ produces N (⁴P) atoms with sufficient kinetic energy so that the $\text{λ1200}\text{A}\text{?}$ resonance radiation $\text{[2p}{}^2\text{3s}{}^4\text{P ?2p}{}^3{}^4\text{S}{}^0\text{]}$ emitted by these excited atoms would be optically thin in the Earth's upper atmosphere. We also found that the line strength ratios for the resolved components of the $\text{λ1200}\text{A}\text{?}$ triplet excited by dissociative excitation differ from those predicted by the multiplicities of the states involved and used in current entrapment models; the intensity ratios also vary with the energy of the incident electron. These developments introduce new complications into the analysis of the terrestrial ultraviolet dayglow.  相似文献   

Resonant electron scattering by metastable nitrogen     

Iztok Čadež 《Planetary and Space Science》1983,31(8):843-848

The resonant electron impact quenching of metastable molecules might be important for understanding the phenomena in the upper atmosphere. In order to obtain information about the relative importance of this scattering event the resonant cross sections for electron scattering by metastable nitrogen in the $\text{A}{}^3\text{∑}\text{u}\text{+}$ state were calculated using the “boomerang” model and quenching rates for this state were evaluated for the altitudes of 130,170 and 210km. The obtained quenching rates are small (?5 × 10^?3 s^?1), even with respect to the radiative transition rate showing that under the considered conditions this process is unimportant for population of nitrogen $\text{A}{}^3\text{∑}\text{u}\text{+}$ state in the Earth's thermosphere.  相似文献   

The chemistry of metastable species in the Venusian ionosphere     

J.L. Fox 《Icarus》1982,51(2):248-260

Reactions of metastable species are important in determining the densities of minor ions in the Venusian ionosphere. Calculations are carried out in which the coupled continuity and momentum equations are solved for twelve ions and four neutral species in the dayside ionosphere, including $\text{O}{}^{\mathrm{+}}\text{(}{}^2\text{D),}\text{O}{}^{\mathrm{+}}\text{(}{}^2\text{P),}\text{N}\text{(}{}^2\text{D),}\text{and N}\text{(}{}^2\text{P)}$. Altitude profiles of these metastable species are presented. Their reactions are shown to be a significant source of several minor ions, especially N₂⁺, CO⁺, and N⁺. The discrepancies which existed between model and measured densities of these ions are resolved.  相似文献   

Cross-section for the dissociative photoionization of hydrogen by 584 Å radiation: The formation of protons in the Jovian ionosphere     

K.M. Monahan  W.T. Huntress  A.L. Lane  J.M. Ajello  T.E. Burke  P. Le Breton  A. Williamson 《Planetary and Space Science》1974,22(1):143-149

The cross-section for dissociative photoionization of hydrogen by 584 Å radiation has been measured, yielding a value of 5 × 10^?20 cm². The process can be explained as a transition from the $\text{X}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ ground state to a continuum level of the $\text{X}{}^2\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ ionized state of H₂ The branching ratio for proton (H⁺) vs molecular ion (H₂⁺) production at this energy is 8 × 10^?3. This process is quite likely an important source of protons in the Jovian ionosphere near altitudes where peak ionization rates are found.  相似文献   

A discussion of the energy transfer from N₂(A³Σ_u⁺) to $\text{O}\text{(}{}^1\text{S}$) in pulsating aurora     

Asgeir Brekke 《Planetary and Space Science》1973,21(4):698-702

In a recent paper, Brekke and Pettersen (1972) have introduced a method for estimating any indirect process in the production of the $\text{O}\text{(}{}^1\text{S}$) atoms in pulsating aurora; for 38 per cent of their data they found that the decay time for the indirect mechanism was shorter than the effective lifetime of the ${}^1\text{S}$ state. These data are related to the energy transfer from the N₂(A³Σ) molecules to the $\text{O}\text{(}{}^1\text{S)}$ state, and evidence is found for this process to contribute in the altitude range below 125 km.  相似文献   

Emission line shapes produced by dissociative excitation of atmospheric gases     

E.C. Zipf  W.C. Wells 《Planetary and Space Science》1980,28(8):859-866

Special line shapes are derived fro the λ 1356 Å (${}^5\text{S}{}^0\text{-}{}^3\text{P}$) transition of atomic oxygen from metastable (${}^5\text{S}{}^0\text{-}{}^3\text{P}$) time-of-flight spectra produced by electron impact dissociative excitation of O₂, CO₂, CO, and NO, and they are compared with the broadened λ 1304 A resonance line shapes deduced by Poland and Lawrence (1973) from atomic oxygen absorption studies. The non-thermal line shapes for both airglow emission features are shown to have an effective width comparable to a 60,000 K thermal doppler line shape for an electron impact energy of 100eV. The variation of the effective line width with electron-impact energy from threshold to 300 eV is given. Since the effective line width of the resonance radiation produced by dissociative excitation is very large compared with the doppler absorption widths of the ambient O atoms at normal exospheric temperatures, the anomalously broadened resonance lines will propagate through a planetary atmosphere as though they were optically thin. Thus, electron-impact dissociation of CO and CO₂ will contribute to the observed optically thin component of the λ 1304 Å emission in the upper atmospheres of Venus and Mars. However, the process cannot account for more than 10% of the observed optically thin emission because of the small magnitude of the excitation cross-section and the comparatively high-energy threshold for the process. The possibility that the source of the kinetically energetic $\text{O}\text{(}{}^3\text{S}$) atoms is the dissociative recombination of vibrationally excited CO₂⁺ ions is discussed.  相似文献   

Contamination of ground-based measurements of OI (6300 Å) and NI (5200 Å) airglow by OH emissions     

R.G. Burnside  J.W. Meriwether  M.R. Torr 《Planetary and Space Science》1977,25(10):985-988

High resolution spectra of the 6300 Å and 5200 Å regions of the night sky have been obtained using a 1 m spectrometer. Typical errors in measurements of $\text{O}\text{(}{}^1\text{D}\text{)}$ 6300 Å and $\text{N}\text{(}{}^2\text{D}\text{)}$ 5200 Å intensities due to contanimation by overlapping OH emissions have been calculated for a fixed-filter photometer, a tilting-filter photometer and a spectrophotometer. The importance of careful selection of certain instrumental parameters in order to minimize measurement errors is emphasized.  相似文献   

The O(1S) quantum yield from O2+ dissociative recombination     

D.R. Bates  E.C. Zipf 《Planetary and Space Science》1980,28(11):1081-1086

Recent laboratory studies show that the $\text{O}\text{(}{}^1\text{S}\text{)}$ quantum yield, $\text{f}\text{(}{}^1\text{S}\text{)}$, from O₂⁺ dissociative recombination varies considerably with the degree r of vibrational excitation. However, the suggestion that the high values for $\text{f}\text{(}{}^1\text{S}\text{)}$ deduced from airglow and auroral observations can be explained by invoking vibrational excitation, creates a number of problems. Firstly, the rapid vibrational deactivation of O₂⁺ ions by collisions with O atoms will keep r too low to account for the magnitude of $\text{f}\text{(}{}^1\text{S}\text{)}$; secondly, r varies considerably from one atmospheric source to another but its relative values (which should be reliable) do not co-vary with those of $\text{f}\text{(}{}^1\text{S}\text{)}$; thirdly, because r increases markedly above the peak of the $\text{X5577}\text{A}\text{?}$ dissociative recombination layer, the fits which theorists have obtained to the observed volume emission rate profiles would have to be regarded as fortuitious. It is tentatively suggested that $\text{f}\text{(}{}^1\text{S}\text{)}$ is higher in the airglow and aurora than in the laboratory plasma studied by Zipf (1980) because of the electron temperature dependence of the $\text{O}\text{(}{}^1\text{S}\text{)}$ specific recombination coefficient for O₂⁺(v^' ? 3) ions.The repulsive ${}^1\text{Σ}{}_{\mathrm{<mtext>u</mtext>}}\text{[}{}^1\text{D}\text{+}{}^1\text{s}\text{]}$ state of O₂ does not provide a suitable channel for the dissociative recombination. A possible alternative is the bound ${}^3\text{Π}{}_{\mathrm{<mtext>u</mtext>}}\text{[}{}^5\text{S}\text{+}{}^3\text{s}\text{]}$ state with predissociation to the repulsive ${}^3\text{Π}{}_{\mathrm{<mtext>u</mtext>}}\text{[}{}^3\text{P}\text{+}{}^1\text{s}\text{]}$ state.  相似文献   

The excitation of atomic oxygen to the $\text{O(}{}^1\text{S)}$ level by energy transfer from N₂(A³∑_u⁺) molecules in aurora     

Kjell Henriksen 《Planetary and Space Science》1973,21(5):863-871

The part that the energy transfer reaction $\text{N}{}_2\text{(A}{}^3\text{∑}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{) + O(}{}^3\text{P) → N}{}_2\text{(X}{}^1\text{∑}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{) + O(}{}^1\text{S)}$ plays in the excitation of the auroral green line has been investigated. The contribution is estimated to be 40 per cent in this case, containing pulsating aurora in class IBC 1. Due to greater quenching of the A³∑_u⁺ state, the centroid of the VK emission is displaced 10 km upwards of the green line height, which is centred at 110 km.  相似文献   

Quantal calculation of the lifetime of N+(5S) and the λ2145Å auroral mystery feature     

A. Hibbert  D.R. Bates 《Planetary and Space Science》1981,29(2):263-268

The calculated radiative lifetime of the metastable ion is 6.4 × 10^?3s. Used in conjunction with the results of measurements by Erdman, Espy and Zipf this sets 1.3 × 10^?18 cm² as the upper limit to the cross section for the formation of $\text{N}{}^{\mathrm{+}}\text{(}{}^5\text{S}\text{)}$ in e - N₂ collisions at 100eV which leaves the possibility that the process is responsible for the $\text{λ2145}\text{A}\text{?}$ feature in auroras only just open. The cross section for the formation of $\text{N}{}^{\mathrm{+}}\text{(}{}^5\text{S}\text{)}$ in e — N collisions is large. However for this process to lead to the observed intensity of $\text{λ2145}\text{A}\text{?}$ relative to $\text{λ3914}\text{A}\text{?}$ the N:N₂ abundance ratio would have to be as high as 1.6 × 10^?2.  相似文献   

The possible effects of translationally excited nitrogen atoms on lower thermospheric odd nitrogen     

Susan Solomon 《Planetary and Space Science》1983,31(1):135-139

In the quiet lower thermosphere, photolysis of N₂ produces translationally excited $\text{N}\text{(}{}^4\text{S}\text{)}$ and $\text{N}\text{(}{}^2\text{D}\text{)}$ atoms. A fraction of these $\text{N}\text{(}{}^4\text{S}\text{)}$ atoms may react rapidly with O₂ while still translationally hot. This results in substantially larger calculated NO densities than those obtained if translational excitation is not considered. The sensitivity of the calculated NO density in the lower thermosphere to this process is examined.  相似文献   

A self-consistent evaluation of the rate constants for the production of the OI 6300 Å airglow     

R. Link  J.C. McConnell  G.G. Shepherd 《Planetary and Space Science》1981,29(6):589-594

The quenching rate k_N2 of $\text{O(}{}^1\text{D)}$ by N₂ and the specific recombination rate α_1D of O₂⁺ leading to $\text{O(}{}^1\text{D)}$ are re-examined in light of available laboratory and satellite data. Use of recent experimental values for the $\text{O(}{}^1\text{D)}$ transition probabilities in a re-analysis of AE-C satellite 6300 Å airglow data results in a value for k_N2 of 2.3 × 10^?11 cm³s^?1 at thermospheric temperatures, in excellent agreement with the laboratory measurements. This implies a value of J_O2 = 1.5 × 10^?6s^?1 for the O₂ photodissociation rate in the Schumann-Runge continuum. The specific recombination coefficient α_1D = 2.1 × 10^?7cm³s^?1 is also in agreement with the laboratory value. Implications for the suggested $\text{N}\text{(}{}^2\text{D) + O}{}_2\text{→ O(}{}^1\text{D) + NO}$ reaction are discussed.  相似文献   

On the $\text{D}\text{C}$ ratio in the atmosphere of Uranus     

Th. Encrenaz  M. Combes 《Icarus》1982,49(1):27-34

A method for deriving mixing ratios in the outer planets, mostly independent of scattering processes, is applied to Uranus. It is shown that scattering processes play a major role in the line formation in the atmospheres of Uranus and Neptune; consequently, abundance ratios derived from a reflecting-layer model can be questionable. Using our method, we derive for Uranus $\text{D}\text{C}\text{< 6 × 10}{}^{\mathrm{?3}}$, which is significantly smaller than our result on Jupiter. The simplest explanation implies a C/H enrichment by at least a factor of 6 relative to the solar value.  相似文献   

Charge exchange of metastable D oxygen ions with N₂ in the thermosphere     

D. G. Torr  N. Orsini 《Planetary and Space Science》1977,25(12):1171-1176

Measurements of N₂⁺ and supporting data made on the Atmosphere Explorer-C satellite in the ionosphere are used to study the charge exchange process The equality k = (5 ± 1.7) × 10^?10cm³s^?1. This value lies close to the lower limit of experimental uncertainty of the rate coefficient determined in the laboratory. We have also investigated atomic oxygen quenching of O⁺(²D) and find that the rate coefficient is 2 × 10^?11 cm³s^?1 to within approximately a factor of two.  相似文献   

A dynamical effect in the ionospheric f₁ layer     

C. Taieb  G. Scialom  G. Kockarts 《Planetary and Space Science》1978,26(11):1007-1016

Incoherent scatter observations of the ionospheric F₁ layer above Saint-Santin (44.6°N) are analyzed after correction of a systematic error at 165 and 180 km altitude. The daytime valley observed around 200 km during summer for low solar activity conditions is explained in terms of a downward ionization drift which reaches ?30 m s^?1 around 180 km. Experimental determinations of the ion drift confirm the theoretical characteristics required for the summer daytime valley as well as for the winter behaviour without a valley. The computations require an effective dissociative recombination rate of $\text{2.3 × 10}{}^{\mathrm{?7}}\text{(}\text{300/}\text{T}{}_{\mathrm{e}}\text{)}{}^{0.7}\text{(}\text{cm}{}^3\text{s}{}^{\mathrm{?1}}\text{)}$ and ionizing fluxes compatible with solar activity conditions at the time when the valley is observed.  相似文献   

The locating of hydromagnetic whistler sources and determination of their generating proton spectra     

Ja.L. Al&#x;pert  D.S. Fligel 《Planetary and Space Science》1977,25(5):487-497

Results are given of the calculations of the group delay time propagating τ(ω, φ₀) of hydromagnetic whistlers, using outer ionospheric models closely resembling actual conditions. The τ(ω, φ₀) dependencies were compared with the experimental data of τ_exp(ω, φ₀) obtained from sonagrams. The sonagrams were recorded in the frequency range $\text{? ? (0.5?2.5) Hz}$ at observation points located at geomagnetic latitudes φ₀ = (53?66)° and in the vicinity of the geomagnetic poles. This investigation has led us to new and important conclusions.The wave packets (W.P.) forming hydromagnetic whistlers (H.W.) are mainly generated in the plasma regions at L = 3.5?4.0. This is not consistent with ideas already expressed in the literature that their generation region is $\text{L ? 3?10}$. The overwhelming majority of the τ_exp values differ considerably from the times at which wave packets would, in theory, propagate along the magnetic field lines corresponding to those of the geomagnetic latitudes φ₀ of the observation points. The second important fact is that the W.P. frequency ω is less than $\text{Ω}{}_{\mathrm{H}}$ everywhere along its propagation trajectory, including the apogee of the magnetic force line ($\text{Ω}{}_{\mathrm{H}}$ is the proton gyrofrequency). Proton flux spectra $\text{E ? (30?120)}$ keV, responsible for H.W. generation, were determined. Comparison of the Explorer-45 and OGO-3 measurements published in the literature, with our data, showed that the proton flux density energy responsible for the H.W. excitation $\text{N}{}_{\mathrm{p}}\text{(}\text{MV}{}_6{}^2\text{2}\text{) ? (5 × 10}{}^{\mathrm{?3}}\text{?10}{}^{\mathrm{?1}}\text{)}\text{H}{}_{\mathrm{a}}{}^2\text{8π}$ where H_a is the magnetic field force in the generation region of these W.P. The electron concentration is $\text{N}{}_{\mathrm{a}}\text{? (10}{}^2\text{?10}{}^3\text{) cm}{}^{\mathrm{?3}}$. The values given in the literature are $\text{N}{}_{\mathrm{a}}\text{? (10}{}^{\mathrm{?10}}\text{?10}{}^3\text{) cm}{}^{\mathrm{?3}}$. The e data considered also leads to the conclusion that the generating mechanism of the W.P. studied probably always co-exists with the mechanism of their amplification.  相似文献