We present a novel chemical database for gas-phase astrochemistry. Named the KInetic Database for Astrochemistry (KIDA), this database consists of gas-phase reactions with rate coefficients and uncertainties that will be vetted to the greatest extent possible. Submissions of measured and calculated rate coefficients are welcome, and will be studied by experts before inclusion into the database. Besides providing kinetic information for the interstellar medium, KIDA is planned to contain such data for planetary atmospheres and for circumstellar envelopes. Each year, a subset of the reactions in the database (kida.uva) will be provided as a network for the simulation of the chemistry of dense interstellar clouds with temperatures between 10 K and 300 K. We also provide a code, named Nahoon, to study the time-dependent gas-phase chemistry of zero-dimensional and one-dimensional interstellar sources.

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A KInetic Database for Astrochemistry (KIDA)

John D. Mill* Environmental Research Institute of Michigan, Arlington, Virginia 22209 Robert R. O'Neil* and Stephan Price* U.S. Air Force Phillips Laboratory, HanscomAFB, Massachusetts 01731 Gerald J. Romick and O. Manuel Uy Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723 E. M. Gaposchkin** Massachusetts Institute of Technology, Lexington, Massachusetts 02173 Glenn C. Light The Aerospace Corporation, Los Angeles, California 90009-2970 W. Walding Moore Jr.** U.S. Army Space and Strategic Defense Command, Huntsville, Alabama 35807-3801 Thomas L. Murdock General Research Corporation, Danvers, Massachusetts 01923 and A. T. Stair Jr. Visidyne, Burlington, Massachusetts 01803

Midcourse Space Experiment: Introduction to the Spacecraft, Instruments, and Scientific Objectives

We present models of the low and high solar activity thermospheres and ionospheres of Venus for a background atmosphere based largely on the VTS3 model of Hedin et al. [1983]. Our background model consists of 12 neutral species, and we compute the density profiles of 13 ions and 7 minor neutrals. We find that the peak production rates of some ions, such as CO2+ and N2+, vary approximately as the solar flux and that some, whose parent neutrals are photochemically produced, such as O+, N+, and C+, show variations that are amplified over that of the solar flux. The solar cycle variation of the O2+ density at its peak is about a factor of 1.6, in good agreement with the radio occultation measurements and previous models. The peak density of N2+ varies by a factor of ∼ 2, but that of CO+ varies by a larger factor because the mixing ratio of CO is also correlated with solar activity. The atomic ions O+, N+, and C+, which peak at high altitudes, exhibit larger density enhancements at high solar activity of factors of 5–18. Thus there is a solar cycle variation in the overall composition of the ionosphere, with a relatively larger proportion of atomic ions at high solar activity. In both measurements and models the solar activity variation of the electron density profile is altitude-dependent, with variations of only ∼60% near the peak but up to an order of magnitude near 300 km. The high solar activity electron density profile exhibits an F2 “shoulder,” which is rarely seen in the radio occultation data and may indicate that the VTS3 atomic O mixing ratios are too large at high solar activity. We also discuss the solar activity variations of N, NO, C, O(1D), and O(1S).

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Solar activity variations of the Venus thermosphere/ionosphere

[1] The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiment on the Thermosphere-Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite observed the infrared radiative response of the thermosphere to the solar storm events of April 2002. Large radiance enhancements were observed at 5.3 μm, which are due to emission from the vibration-rotation bands of nitric oxide (NO). The emission by NO is indicative of the conversion of solar energy to infrared radiation within the atmosphere and represents a “natural thermostat” by which heat and energy are efficiently lost from the thermosphere to space and to the lower atmosphere. We describe the SABER observations at 5.3 μm and their interpretation in terms of energy loss. The infrared enhancements remain only for a few days, indicating that such perturbations to the thermospheric state, while dramatic, are short-lived.

/pdf/the-natural-thermostat-of-nitric-oxide-emission-at-5-3-mm-in-2568dd4zit.pdf

The natural thermostat of nitric oxide emission at 5.3 μm in the thermosphere observed during the solar storms of April 2002

: An improved kinetic model for the Meinel bands of OH has been constructed from rate constants and Einstein A coefficients derived in recent laboratory experiments. Using a semiempirical parameterization of the state-to-state rate constants for OH(v) quenching by O2, the absolute OH(v) nightglow radiances are modeled to within the accuracies of the atmospheric constituent concentrations and the radiometric calibrations. Collisional quenching is found to be predominantly multiquantum at high v but single-quantum at low v.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/97JA01622

Kinetic parameters for OH nightglow modeling consistent with recent laboratory measurements

Classical trajectory calculations have been performed to determine the reaction rate constants and NO final vibrational-rotational distributions of the N(4S) + O2 reaction at hyperthermal translational energies. The reaction occurs on two electronic potential energy surfaces, both of which must be considered for a realistic description of the N(4S) + O2 dynamics. The calculations, which are in good agreement with the available experimental data, show that the reaction has a very strong translational energy dependence and produces NO with extensive vibrational and rotational excitation. The present study provides the N(4S) + O2 reaction attributes necessary to predict NO formation and emission from translationally hot N(4S) in the thermosphere.

Classical dynamics of the N(4S) + O2 (X³ Σg−) → NO(X²II) + O(³P) reaction

Room-temperature and temperature-dependent thermal rate constants are calculated for the state-to-state vibrational relaxation of NO(v ⩽ 9) by atomic oxygen using the quasiclassical trajectory method and limited ab initio information on the two lowest O + NO potential-energy surfaces which are responsible for efficient vibrational relaxation Comparisons of the theoretical results with the available experimental measurements indicate reasonable agreement for the deactivation of NO(v = 2, 3) at 300 K and NO(v = 1) at 2700 K, although the calculated relaxation rate constant for NO(v = 1) at 300 K is approximately a factor of two below the measured value The state-to-state relaxation rate coefficients involve the formation of long-lived collision complexes and indicate the importance of multiquantum vibrational relaxation consistent with statistical behaviour in O + NO collisions The present results, combined with recent measurements of vibrational relaxation for NO(v = 2, 3), suggest that the current atmospheric models of NO cooling rates require higher atmospheric temperatures and/or an increase in the NO/O number densities

Quasiclassical trajectory study of NO vibrational relaxation by collisions with atomic oxygen

This paper models the fundamental vibration-rotation band emission from NO around 5.3 μm observed by the interferometer aboard the cryogenic infrared radiance instrumentation for shuttle (CIRRIS 1A) during the sunlit terrestrial thermosphere. The four dominant contributions to the 5.3 μm emission are solar pumping, the inelastic collisions with O of NO(v=0), the reactions of N(2D) with O2, and the reactions of N(4S) with O2. The contribution to the chemiluminescence due to the reaction of N(4S) with O2 is calculated using the energy distribution function (EDF) of these atoms obtained by solving the time dependent Boltzmann equation. The calculated radiance is derived using two model atmospheres: (1) the model atmosphere obtained from the atmospheric ultraviolet radiance integrated code (AURIC) [Strickland et al., 1998] and (2) the model atmosphere obtained from the thermosphere-ionosphere-mesosphere electrodynamics general circulation model (TIME-GCM) [Roble and Ridley, 1994]. The calculated results reproduce gross features of the CIRRIS 1A observations, and disagreement by a factor of ∼2 in the total band radiance calls for a fine tuning of the model atmospheres and/or the underlying phenomenology. The cooling of the atmosphere at high altitudes due to chemiluminescence from the reaction of N(4S) with O2 is found to be comparable to that due to collisions of NO with O.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/98JA00896

Model of the 5.3 μm radiance from NO during the sunlit terrestrial thermosphere

[1] The temperature dependence of the rate coefficient of the N(2D)+O2→NO+O reaction has been determined using ab initio potential energy surfaces (PES) and classical dynamics. The calculation agrees with the recommended rate coefficient at 300 K (∼110 km altitude). The rate coefficient is given by the expression k(T) = 6.2 × 10−12(T/300) cm3/s/molec. In contrast to the nearly temperature-independent value of this rate coefficient previously recommended, the value given here increases by almost a factor of about four as the altitude increases from 110 to 200 km. It is also shown that even though N(2D) atoms in the thermosphere are produced with large translational energies, using the value of the rate coefficient at the local temperature introduces negligible error in the amount of NO produced. The new value of this rate coefficient will significantly increase the amount of NO computed in the aeronomic models causing a re-evaluation of the heat budget and temperature and density structure of the thermosphere. In particular, implications of the larger rate coefficient for the recent observations of dramatically enhanced 5.3 μm emission from NO in the thermosphere due to solar storms are discussed.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2002GL016720

On the rate coefficient of the N(2D)+O2→NO+O reaction in the terrestrial thermosphere

Rate coefficients for the N+NO→N 2 +O reaction are calculated over the temperature range 100 - 1000 K by a quasiclassical trajectory calculation on the 3 A″ potential energy surface (PES) based on the serniempirical London-Eyring-Polanyi-Sato (LEPS) formalism, neglecting spin-orbit coupling The calculated results are only slightly temperature dependent and are in excellent agreement with available experimental data and the JPL recommended rate coefficient [DeMore et al, 1994] at room temperature The present results do not support either the rate coefficient arrived at by Siskind and Rusch [1992] from modeling of the terrestrial thermosphere or the one arrived at by Fox [1994] from modeling of the Martian thermosphere Possible causes of the discrepancies between the calculated rate coefficients and those arrived at from modeling studies may be additional NO production (loss or loss and production) mechanisms in the Martian (terrestrial) thermosphere

J. W. Duff

Papers

Classical dynamics of the N(4S) + O2 (X³ Σg−) → NO(X²II) + O(³P) reaction

Quasiclassical trajectory study of NO vibrational relaxation by collisions with atomic oxygen

Model of the 5.3 μm radiance from NO during the sunlit terrestrial thermosphere

On the rate coefficient of the N(2D)+O2→NO+O reaction in the terrestrial thermosphere

Quasiclassical trajectory study of the N(4S)+NO(X2Π)→N2(X1Σ+g)+O(3P) reaction rate coefficient