Classical calculations of NH3 and H2O rotational excitation in energetic collisions with atomic oxygen

Kolb, C. E.; Elgin, James B.

doi:10.1063/1.433658

Cited by 14 publications

(4 citation statements)

References 17 publications

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“…Furthermore, since spectral observations are only sensitive to internally excited products, the magnitude and energy dependence of these observations minimize contributions from products formed with little internal excitation, products which may in fact carry most of the total reaction cross section and dynamical information. In addition, theoretical examination of the reactions (1) and (2) has been problematic because they involve computation of high-spin open shell wave functions which presents special difficulties for theory. There have been theoretical studies which used nonreactive O( 3 P) + H 2 O(X, 1 A 1 ) potential surfaces to examine the collisional excitation channel (Eq.…”

Section: π)mentioning

confidence: 99%

“…10 The electronically excited OH is apparently formed through high-lying conical intersections in the potential energy surfaces of the four-atom complex. 12 The surfaces involved in Reactions (1)(2) are part of a large manifold of electronic states which give rise to the products of Reaction (4). …”

Section: π)mentioning

confidence: 99%

“…Other studies 6 have attributed all such radiation from 1-5 µ to Reaction (2). It is particularly difficult to distinguish between (1) and (2) in the 1-5 µ spectral region because spectral observations remain the main source of data and OH(X, 2 …”

Section: Introductionmentioning

confidence: 99%

“…Collisions of O( 3 P) with H 2 O(X, 1 A 1 ) give rise to spectral radiation observed from the long wave infrared (~20-10 µ) [1][2][3] , through the infrared (10-1 µ) [1][2][3][4][5][6][7][8][9] and up to the vacuum ultraviolet (~0.25 µ), [10][11][12] depending on the relative collision energy. These emissions are important to characterize because they can be a significant background noise source for telescopes mounted on spacecraft in low-Earth-orbit or LEO.…”

Section: Introductionmentioning

confidence: 99%

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Potential Surfaces and Dynamics of the O(3P) + H2O(X1A1) yields OH(X2Pi) + OH(X2Pi) Reaction

Braunstein¹,

Panfili²,

Shroll³

et al. 2004

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We present global potential energy surfaces for the three lowest triplet states in O( 3 P Π) reaction using these surfaces. The surfaces are spline-based fits of ~20,000 fixed geometry ab-initio calculations at the CASSCF+MP2 level with a O(4s3p2d1f)/H(3s2p) one electron basis set. Computed rate constants compare well to measurements in the 1,000-2,500 K range using these surfaces. We also compute the total, rovibrationally resolved, and differential angular cross sections at fixed collision velocities from near threshold at ~4 km s -1 (16.9 kcal mol -1 collision energy) to 11 km s -1 (122.5 kcal mol -1 collision energy), and we compare these computed cross sections to available space-based and laboratory data. A major finding of the present work is that above ~40 kcal mol -1 collision energy ro-vibrationally excited OH(X 2 Π) products are a significant and perhaps dominant contributor to the observed 1-5 µ spectral emission from O( 3 P) + H 2 O(X 1 A 1 ) collisions. Another important result is that OH(X 2 Π) products are formed in two distinct ro-vibrational distributions.)The 'active' OH products are formed with the reagent O-atom, and their ro-vibrational distributions are extremely hot. The remaining 'spectator' OH is relatively ro-vibrationally cold.For the active OH, rotational energy is dominant at all collision velocities, but the opposite holds for the spectator OH. Summed over both OH products, below ~50 kcal mol -1 collision energy, vibration dominates the OH internal energy, and above ~50 kcal mol -1 rotation is greater than vibrational energy. As the collision energy increases, energy is diverted from vibration to mostly translational energy. We note that the present fitted surfaces can also be used to investigate direct We present global potential energy surfaces for the three lowest triplet states in O(3P) + H2O(X1A1) collisions and present results of classical dynamics calculations on the O(3P) + H2O(X1A1) OH(X2) + OH(X2) reaction using these surfaces. The surfaces are spline-based fits of 20,000 fixed geometry ab-initio calculations at the CASSCF+MP2 level with a O(4s3p2d1f)/H(3s2p) one electron basis set. Computed rate constants compare well to measurements in the 1,000-2,500 K range using these surfaces. We also compute the total, ro-vibrationally resolved, and differential angular cross sections at fixed collision velocities from near threshold at ~4 km s-1 (16.9 kcal mol-1 collision energy) to 11 km s-1 (122.5 kcal mol-1 collision energy), and we compare these computed cross sections to available space-based and laboratory data. A major finding of the present work is that above ~40 kcal mol-1 collision energy ro-vibrationally excited OH(X2) products are a significant and perhaps dominant contributor to the observed 1-5  spectral emission from O(3P) + H2O(X1A1) collisions. Another important result is that OH(X2) products are formed in two distinct ro-vibrational distributions. The 'active' OH products are formed with the reagent O-ato...

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Section: π)mentioning

confidence: 99%