Expected Microwave Absorption Coefficients of Water and Related Molecules

King, G.W.; Hainer, R. M.; Cross, Paul C.

doi:10.1103/physrev.71.433

Cited by 73 publications

(14 citation statements)

References 15 publications

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“…The H 2 O-electron collision coefficients are calculated following Xie & Mumma (1992), using the approximation for the electron-H 2 O collision cross section derived by Itikawa (1972) and the line strength of the transitions listed in King et al (1947). Typical collision rates for the transitions considered in our model are in the range (4 30) ; 10 À7 s À1 cm 3 for T e % 100 K and (1 5) ; 10 À7 s À1 cm 3 for T e % 10 4 K.…”

Section: Line Excitation By H 2 O-electron Collisionsmentioning

confidence: 99%

The Pure Rotational Line Emission of Ortho‐Water Vapor in Comets. I. Radiative Transfer Model

Bensch

Bergin

2004

ApJ

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We present a numerical model for the simulation of water line emission in cometary coma. The model is based on a spherically symmetric density distribution with a constant expansion velocity (Haser model) and the Monte Carlo radiative transfer code published by Hogerheijde & van der Tak. It includes the seven lowest rotational levels of ortho-water, which are the primarily populated levels in the rotationally cold gas of the coma. We discuss the main excitation mechanisms for ortho-water in the coma and study their relative contribution as a function of distance from the comet nucleus. The model is used to derive the water production rate from observations made with the Submillimeter Wave Astronomy Satellite toward comet C/1999 T1 (McNaught-Hartley). They differ from the water production rates derived with an independent model by less than 20% and thus agree within the larger uncertainty due to the limited signal-to-noise ratio of the observations. We give predictions for spectral line observations of H 2 O and H 2 18 O in comets with present and future airborne and space observatories, including ESA's Herschel Space Observatory and the Stratospheric Observatory for Infrared Astronomy (SOFIA). These models cover a range of water vapor production rates (10 27 -10 29 s À1 ) and heliocentric distances (1-3 AU) and demonstrate that water line emission can be easily detected with Herschel.

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Section: Line Excitation By H 2 O-electron Collisionsmentioning

confidence: 99%

The Pure Rotational Line Emission of Ortho‐Water Vapor in Comets. I. Radiative Transfer Model

Bensch

Bergin

2004

ApJ

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“…[16,17,19,20], as the nonperturbed starting point became the way to analyze the experimental data on rotational molecular spectroscopy [20][21][22][23][24][25][26][27][28][29][30][31]. However, its numerical application for higher excited states was not efficiently implemented.…”

Section: On the Quantization Of Asymmetric Topsmentioning

confidence: 99%

Rotations of Asymmetric Molecules and the Hydrogen Atom in Free and Confined Configurations

Méndez-Fragoso

Ley‐Koo

2011

Advances in Quantum Chemistry

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“…where J and J 0 are the quantum numbers for the initial and final state of the transition, k and k 0 are the initial and final wavenumbers of the electron, and D is the permanent dipole moment of HCN (D ¼ 3:34 debye ¼ 1:176 amu), which gives the cross section in cm 2 . The matrix element hJ 0 jJ i 2 is related to the line strength (S ) via ( King et al 1947;Schwendeman & Laurie 1958)…”

Section: Collisional Excitation Ratesmentioning

confidence: 99%

“…The line strength for rotational transitions of HCN, a linear molecule, is simply J 0 , the quantum number for the final state ( King et al 1947). The collisional cross sections for electron-HCN collisions can thus be calculated as a function of wavenumber and related to electron energy.…”

Section: Collisional Excitation Ratesmentioning

confidence: 99%

On the Effect of Electron Collisions in the Excitation of Cometary HCN

Lovell¹,

Kallivayalil²,

Schloerb³

et al. 2004

ApJ

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The electron-HCN collision rate for the excitation of rotational transitions of the HCN molecule is evaluated in comets C/1995 O1 (Hale-Bopp) and C/1996 B2 (Hyakutake). Based on theoretical models of the cometary atmosphere, we show that collisions with electrons can provide a significant excitation mechanism for rotational transitions in the HCN molecule. Computed values of the cross section e-HCN can be as high as 1:3 ; 10 À12 cm 2 , more than 2 orders of magnitude greater than the commonly assumed HCN-H 2 O cross section. For the ground rotational transitions of HCN, the electron-HCN collision rate is found to exceed the HCN-H 2 O collision rate at distances greater than 3000 km from the cometary nucleus of Hale-Bopp and 1000 km from that of Hyakutake. Collisional excitation processes dominate over radiative excitation processes up to a distance of 160,000 km from the cometary nucleus of Hale-Bopp and 50,000 km from that of Hyakutake. Excitation models that neglect electron collisions can underestimate the HCN gas production rates by as much as a factor of 2.

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Expected Microwave Absorption Coefficients of Water and Related Molecules

Cited by 73 publications

References 15 publications

The Pure Rotational Line Emission of Ortho‐Water Vapor in Comets. I. Radiative Transfer Model

The Pure Rotational Line Emission of Ortho‐Water Vapor in Comets. I. Radiative Transfer Model

Rotations of Asymmetric Molecules and the Hydrogen Atom in Free and Confined Configurations

On the Effect of Electron Collisions in the Excitation of Cometary HCN

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