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1.
A scheme of excitation, quenching, and energy transfer processes in the oxygen nightglow on the Earth, Venus, and Mars has been developed based on the observed nightglow intensities and vertical profiles, measured reaction rate coefficients, and photochemical models of the nighttime atmospheres of the Venus and Mars. The scheme involves improved radiative lifetimes of some band systems, calculated yields of the seven electronic states of O2 in termolecular association, and rate coefficients of seven processes of electronic quenching of the Herzberg states of O2, which are evaluated by fitting to the nightglow observations. Electronic quenching of the vibrationally excited Herzberg states by O2 and N2 in the Earth's nightglow is a quarter of total collisional removal of the O2(A, A′) states and a dominant branch for the O2(c) state. The scheme supports the conclusion by Steadman and Thrush (1994) that the green line is excited by energy transfer from the O2(A3Σu+, v≥6) molecules, and the inferred rate coefficient of this transfer is 1.5×10−11 cm3 s−1. The O2 bands at 762 nm and 1.27 μm are excited directly, by quenching of the Herzberg states, and by energy transfer from the O2(5Πg) state. Quenching of the O2 band at 762 nm excites the band at 1.27 μm as well. Effective yield of the O2(a1Δg) state in termolecular association on Venus and Mars is ∼0.7. Quantitative assessments of all these processes have been made. A possible reaction of O2(c1Σu−)+CO is a very minor branch of recombination of CO2 on Venus and Mars. Night airglow on Mars is calculated for typical conditions of the nighttime atmosphere. The calculated vertical intensity of the O2 band at 1.27 μm is 13 kR, far below the recently reported detections.  相似文献   

2.
Numerous fluorescent emissions from the Herzberg bands of molecular oxygen lie in the spectral region 242–300 nm. This coincides with the wavelength range used by orbiting spectrometers which observe the Rayleigh backscattered spectrum of the earth for the purpose of monitoring the vertical distribution of stratospheric ozone. Model calculations indicate that Herzberg band emissions in the dayglow could provide significant contamination of the ozone measurements if the quenching rate of O2(A3Σ) is sufficiently small. This is especially true near 255 nm, where the most intense fluorescent emissions relative to the Rayleigh scattered signal are located and where past satellite measurements show a persistent excess radiance above that expected for a pure ozone absorbing and molecular scattering atmosphere. However, very small quenching rates are adequate to reduce the dayglow emission to negligible levels. Available laboratory data have not definitely established the quenching on the rate of O2(A3Σ) as a function of vibrational level, and such information is required before the Herzberg band contributions can be evaluated with confidence.  相似文献   

3.
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(A3Σu+?X3Σg?) system to infer the total Herzberg I emission profile are assessed.  相似文献   

4.
In 1999, observations of the Venus nightglow with the Keck I telescope showed that the 5577 Å oxygen green line was a significant feature, comparable in intensity to the terrestrial green line. Subsequent measurements have been carried out at the Apache Point Observatory (APO) and again at Keck I, confirming the presence of the line with substantially varying intensity. The Herzberg II emission intensity, from the O2(c-X) transition, was found to have an intensity near 3 kR in one APO run, comparable to the value found on all previous measurements. Thus, of the three oxygen features seen at Venus—the green line, the Herzberg II emission system, and the 1.27-μ 0-0 band of the IR atmospheric system—the first is quite variable, the second is relatively constant, while the third also shows large variations. The reaction between O2(, v=0) and CO is considered as a possible mechanism to explain green line production and its variability, as well as the variability of the 1.27-μ emission and the stability of the CO2 atmosphere. This reaction may catalyze CO2 recombination some five orders of magnitude faster than the slow three-body O + CO reaction.  相似文献   

5.
Measurements of the emission intensities of the 557.7 nm line and Herzberg bands and of O(3P) concentrations carried out on two coordinated rocket flights at South Uist during the night of 8/9 September 1975 are presented. An examination of the 557.7 nm emission and O(3P) data on the basis of recent data on relevant rate coefficients has shown that the results can be interpreted on the basis of the Barth mechanism for the production of O(1S) atoms but not the Chapman mechanism. Evidence is provided that the A3Σ+u state of O2 could be responsible for the O(1S) production in the Barth mechanism. Values of the rate coefficients involved are deduced from a comparison of the 557.7 nm and Herzberg emission rates.  相似文献   

6.
Some results following from two contemporary photographical programs (Slovakia and Japan) for persistent meteor train spectra are compared. It shows that even though both programs are not too different according to their lenses and films used, the spectral interval detected is very different. In this respect prism as a dispersion element is more favourable than the grating with blaze wavelength near 610 nm. However, some results previously assumed as typicai for presented persistent trains-e.g. the forbidden Herzberg O2 emission, the NO2 continuum and OH red emissions-seem to be substanciated especially due to higher and linear dispersion of those grating spectra.  相似文献   

7.
A general analysis of the absorption of the Schumann-Runge bands of molecular oxygen has been made in order to compare the various experimental and theoretical results which have been obtained for an application to the O2 atmospheric absorption and its photodissociation in the mesosphere and stratosphere. The different values of the oscillator strengths deduced from the laboratory absorption spectra and of the predissociation linewidths used for the calculation of the absorption have been compared.Calculations based on a Voight profile of the O2 rotational lines have led to simple formulas for atmospheric applications taking into account that the total photodissociation rate in the stratosphere depends strongly on the absorption of solar radiation in the spectral range of the O2 Herzberg continuum. Specific examples are given.  相似文献   

8.
The nitrogen isotope ratio of middle atmosphere nitrogen oxide is predicted as a function of altitude. Nitrogen oxides originate photochemically either from stratospheric nitrous oxide reacting with O(1D) or in the mesosphere and thermosphere from direct dissociation of N2 and ionization-initiated reactions involving O2 and N2. During its formation process, N2O acquires a nitrogen isotopic composition of N isotopes different than N2. Photodissociation within the stratosphere also modifies the proportion of isotopes. Reaction of stratospheric NO with O3 produces NO2, which when photodissociated yields NO depleted in 15N relative to NO2 in laboratory air. The value of δ15NO in the stratosphere is −100‰. In the altitude region between 50 and 65 km, NO is transformed into NO2 and then returned to NO by reaction of NO2 with O and by NO2 photodissociation. These reactions determine the isotopic makeup of NO. Above 65 km, nitric oxide is produced by local ionization processes and gas phase photochemical reactions involving N2 and excited O2. These processes determine the isotopic composition of NO in the upper mesosphere and thermosphere. Here δ15NO is 0‰. Air transported into the mesosphere above 65 km will reflect the NO isotopic values of the region below, while mesospheric NO transported below 65 km will not be distinguishable from NO originating in the stratosphere.  相似文献   

9.
A critical analysis has been made of solar irradiance in the spectral region covering wavelengths from 100 nm upwards; the absorption characteristics of molecules of oxygen and ozone have been taken into account with a view to the direct application of the results to atmospheric photochemistry. The absorption of radiation by these molecules results in the photodissociation of both of them in the homosphere, and it also makes possible the penetration of solar radiation from the thermosphere, through the mesosphere and the stratosphere, down to the troposphere.Special attention has been given to each of the following spectral regions: Lyman-alpha radiation at 121.6 nm, the O2 Schumann-Runge continuum at wavelengths less than 175 nm, the O2 Schumann-Runge band system from 200 to 175 nm, and the O2 Herzberg continuum at 242.4 nm. For absorption by ozone, the solar spectrum has been analysed in the following regions: the Hartley band at wavelengths less than 310 nm, the Huggins bands at wavelengths above 310 nm and the visible Chappuis bands. Finally, for the photodissociation of O3, particular attention has been given to the transition region (300–320 nm) in which there is a change-over from the production of the excited atom O(1D) to that of the atom in its ground state O(3p).  相似文献   

10.
The evolution and variability of atmospheric ozone over geological time   总被引：1，自引：0，他引：1  
The rise of atmospheric O3 as a function of the evolution of O2 has been investigated using a one-dimensional steady-state photochemical model based on the chemistry and photochemistry of Ox(O3, O, O(1D)), N2O, NOx(NO, NO2, HNO3), H2O, and HOx(H, OH, HO2, H2O2) including the effect of vertical eddy transport on the species distribution. The total O3 column density was found to maximize for an O2 level of 10?1 present atmospheric level (PAL) and exceeded the present total O3 column by about 40%. For that level of O2, surface and tropospheric O3 densities exceeded those of the present atmosphere by about an order of magnitude. Surface and tropospheric OH densities of the paleoatmosphere exceeded those of the present atmosphere by orders of magnitude. We also found that in the O2-deficient paleoatmosphere, N2O (even at present atmospheric levels) produces much less NOx than it does in the present atmosphere.  相似文献   

11.
Auroral ultraviolet spectra in the range 1200–3200 A have been obtained by the spectrometer onboard the OGO-4 satellite. Emissions of N2, H, O and N are readily identified. Atomic and molecular intensities are deduced from the comparison with a synthetic spectrum and compare reasonably well with some previous measurements and calculations. A feature at 2150 A is assigned to the (1-0) NO γ band. Taking into consideration the various excitation mechanisms of NO(A2σ) we propose that the energy transfer from N2 metastable molecules to oxygen accounts for the excitation of the NO γ bands. In particular, we suggest that the resonant reaction between O2 and highly metastable N2(W3Δ) molecules may be a major source of NO(A2σ).  相似文献   

12.
The purpose of this paper is to study the nature of variation of O3 concentration of Antarctic Survey Stations and its correlation with solar ultraviolet radiation. Solar UV data for the period November 1978 to October 1984 are taken from Solar Geophysical Data Book. In absence of solar UV data for long period, a calibration curve between solar UV radiation and solar flare number (S.F.NO.) is drawn. (A straight line is obtained and correlation coefficient between two variables is 80%). The equation of straight line from least square principle becomes, UV flux = 0.2672 + 2.7578 × 10?5 × S.F.NO. From this equation UV flux values for long period are calculated from known values of solar flare numbers. O3 concentration of two Antarctic Survey Stations, Halley Bay (76? S, 27? W) and McMurdo (78? S, 166? E) are considered for analysis and following important results are obtained:
  1. Yearly variations of O3 concentrations and UV radiations are mainly controlled by their October concentrations.
  2. Correlation coefficient between O3 concentration and UV radiation is 62% for the month of October. For the other months it is poor.
  3. It is concluded that dramatic decrease of O3 concentration at Antarctica is independent of solar UV radiation and chemical processes are responsible for special depletion of O3.
  相似文献   

13.
The absolute reaction cross sections and reaction rate coefficients as a function of photoionisation energy for 25 ion-molecule reactions (charge transfer reactions except for one) have been measured between the most abundant species present as ions or neutral in the Mars, Venus and Earth ionospheres: O2, N2, NO, CO, Ar and CO2.This study shows the strong influence of electronic as well as vibrational internal energy on most ion-molecule reactions. In particular endothermic charge transfer reactions are driven by electronic excitation of O2+ and NO+ ions in their a4Πu and a3Σ+ metastable states, respectively. Moreover, it is shown that lifetimes of these metastable states are sufficient to survive the mean free path in the lowest part of ionospheres and therefore express their enhanced reactivity. The reactions of O2+ with NO as well as the reactions of CO2+ with NO, O2, CO and to a less extent N2 are driven by vibrational excitation. N2+ and CO+ reactions vary much less with photon energy than the other ones, except for the case of reactions with Ar. The effects of the molecular ion internal energy content on their reactivity must be included in the ionospheric models for most of the reactions investigated in the present work. It is also the case for the effect of collision energy on the CO++M reactions as we expect that a significant proportion of these CO+ could be produced with translational energy by dissociation of doubly charged CO22+, in particular in the Mars ionosphere. Recommended effective rate constant values are given as a function of VUV photon energy.  相似文献   

14.
Absorption of solar radiation of wavelengths between 175 to 205 nm plays a fundamental role in the photochemistry of the middle atmosphere. Nitric oxide photodissociates in the δ(0-0) and δ(1-0) bands near 191 and 183 nm, respectively, initiating the primary mechanisms for NOx removal in the middle atmosphere. The spectrally rich Schumann-Runge (S-R) bands of O2 are the main source of atmospheric opacity at these wavelengths. A re-evaluation of O2 absorption has been made based on recent advances in understanding of S-R line shapes, leading to differences with conventional approaches assuming Voigt line profiles in line-by-line calculations of the O2 cross section. The new results are used to examine the impact of O2 transmission on the photodissociation of NO in the δ(0,0) and δ(1,0) bands.  相似文献   

15.
The behavior of mesospheric odd nitrogen species during and following relativistic and diffuse auroral precipitation events is simulated Below 75 km nitric oxide is enhanced in proportion to the ion pair production function associated with the electron precipitation and the length of the event. Nitrogen dioxide and nitric acid are also enhanced. At 65 Ian the percentage of odd nitrogen for N is 0.1%, HNO3 is 1.6%, NO2 is 15%, and NO is 83.3%. Between 75 and 85 km, NO is depleted during particle events due to the faster destruction of NO by N relative to the production of NO by N reacting with O2 Recovery of NO depends on transport from the lower thermosphere, where NO is produced in abundant amounts during particle events.  相似文献   

16.
Laboratory measurements of the reaction of O2+ with NO from thermal energy to 0.6 eV in an Ar buffered flow drift tube agree with similar measurements made earlier in the same drift tube with He buffer. Since the O2+ ions are substantially vibrationally excited in Ar and not in He it follows that the reaction is not enhanced by vibrational excitation of the O2+.  相似文献   

17.
Analysis of observed spectrograms is based on comparison with synthetic spectra. The O2(b1Σ+g?X3Σ?g Atm. (1,1) band in high latitude auroras observed from the ground is found to be the strongest in the Δv = 0 sequence. It is enhanced with altitude relative to the N2 1P(2, 0)and N+2 M(2,0) bands, but the O2 Atm. (2, 2) band has an unexpected low intensity. The range of rotational temperatures of the O2 Atm. bands varies from approx. 200 to above 500 K which indicates that the altitude of the centroid of the emission region varies from about 100 km to the F-region. The highest temperature is found in the midday aurora associated with the magnetospheric cusp. Conspicuous relative variations between the intensities of N2 and O2 spectra are documented, but a satisfactory explanation of the variety is not given. Deviations of the observed O2 Atm. band intensities from the vibrational intensity distribution predicted by Franck-Condor factors indicate that the excitation of the O2 Atm. bands in aurora is not mainly due to particle impact on O2, and the contribution due to energy transfer from hot O(1D) atoms has to be found in future research.  相似文献   

18.
The development of the theory of the 5577 Å emission from the upper atmosphere is reviewed. Evidence from both aeronomy and chemical kinetics shows that the Barth mechanism is a much more important source of O(1S) than in the Chapman process. The molecular oxygen state involved is probably c1Σ?u (the upper state of the Herzberg II band system).  相似文献   

19.
Venus nightglow was observed at NASA IRTF using a high-resolution long-slit spectrograph CSHELL at LT = 21:30 and 4:00 on Venus. Variations of the O2 airglow at 1.27 μm and its rotational temperature are extracted from the observed spectra. The mean O2 nightglow is 0.57 MR at 21:30 at 35°S-35°N, and the temperature increases from 171 K near the equator to ∼200 K at ±35°. We have found a narrow window that covers the OH (1-0) P1(4.5) and (2-1) Q1(1.5) airglow lines. The detected line intensities are converted into the (1-0) and (2-1) band intensities of 7.2 ± 1.8 kR and <1.4 kR at 21:30 and 15.5 ± 2 kR and 4.7 ± 1 kR at 4:00. The f-component of the (1-0) P1(4.5) line has not been detected in either observation, possibly because of resonance quenching in CO2. The observed Earth’s OH (1-0) and (2-1) bands were 400 and 90 kR at 19:30 and 250 and 65 kR at 9:40, respectively. A photochemical model for the nighttime atmosphere at 80-130 km has been made. The model involves 61 reactions of 24 species, including odd hydrogen and chlorine chemistries, with fluxes of O, N, and H at 130 km as input parameters. To fit the OH vibrational distribution observed by VEX, quenching of OH (v > 3) in CO2 only to v ? 2 is assumed. According to the model, the nightside-mean O2 emission of 0.52 MR from the VEX and our observations requires an O flux of 2.9 × 1012 cm−2 s−1 which is 45% of the dayside production above 80 km. This makes questionable the nightside-mean O2 intensities of ∼1 MR from some observations. Bright nightglow patches are not ruled out; however, the mean nightglow is ∼0.5 MR as observed by VEX and supported by the model. The NO nightglow of 425 R needs an N flux of 1.2 × 109 cm−2 s−1, which is close to that from VTGCM at solar minimum. However, the dayside supply of N at solar maximum is half that required to explain the NO nightglow in the PV observations. The limited data on the OH nightglow variations from the VEX and our observations are in reasonable agreement with the model. The calculated intensities and peak altitudes of the O2, NO, and OH nightglow agree with the observations. Relationships for the nightglow intensities as functions of the O, N, and H fluxes are derived.  相似文献   

20.
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   

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