- Article
- Published:
Infrared excitation processes of C2H6 in comets
Earth, Planets and Space volume 55, pages 139–151 (2003)
Abstract
A time-dependent and line-by-line fluorescence model of the v7 band of C2H6 has been constructed. Collisional (neutrals and electrons) and radiative excitation effects have been considered in the calculations of fluorescence efficiency factors (g-factors) of the C2H6 v7 band. Since the lifetime of C2H6 is ∼91,000 seconds at a heliocentric distance of 1 AU, C2H6 molecules far from the nucleus approach fluorescence equilibrium, while molecules within the contact surface should have a much colder rotational distribution due to collisional equilibration with the low temperature gases in that region. We would recommend using “single-cycle” fluorescence models for the analysis of v7 band spectra taken with small apertures centered on the nucleus. We analyzed a v7 band spectrum of comet Hale-Bopp (C/1995 O1) obtained at the IRTF with the CSHELL on 2 March, 1997 (R = 1.1 AU, Δ = 1.5 AU) using a square aperture of 1,000 × 2,000 km, and constructed synthetic spectra to compare with the observation. We analyzed spatial brightness profiles of the R Q0 sub-branch and found that the eastward profile is very well matched by the models, but the observed westward profile is clearly broader than the eastward profile suggesting asymmetric outflow and/or extended sources. We derived a C2H6 production rate of ∼1.7±0.9 × 1028 molec s−1 from the inner coma region of the comet at the time of the observation.
References
Arvesen, J. C., R. N. Griffin, Jr., B. D. Pearson, Jr., Determination of extraterrestrial solar spectral irradiance from a research aircraft, Applied Optics, 8, 2215–2232, 1969.
Balsiger, H., K. Altwegg, F. Bühler, J. Geiss, A. G. Ghielmetti, B. E. Goldstein, R. Goldstein, W. T. Huntress, W.-H. Ip, A. J. Lazarus, A. Meier, M. Neugebauer, U. Rettenmund, H. Rosenbauer, R. Schwenn, R. D. Sharp, E. G. Shelley, E. Ungstrup, and D. T. Young, Ion composition and dynamics at comet Halley, Nature, 321, 330–334, 1986.
Cole, A. R. H., K. J. Cross, J. A. Cugley, and H. M. Heise, Infrared rotation-vibration spectra of ethane, The perpendicular band, v7, of C2H6, J. Mol. Spect., 83, 233–244, 1980.
Cravens, T. E., A magnetohydrodynamical model of the inner coma of comet Halley, J. Geophys. Res., 94, 15025–15040, 1989.
Dang-Nhu, M., A. S. Pine, and W. J. Lafferty, Les intensités dans les bandes v5, v7, et v6+ v11 de l’éthane 12C2H6, Can. J. Phys., 62, 512–519, 1984.
Dello-Russo, N., M. J. Mumma, M. A. DiSanti, K. Magee-Sauer, and R. Novak, Ethane production and release in Comet C/1995 O1 Hale-Bopp, Icarus, 153, 162–179, 2001.
Dickinson, A. S., T. G. Phillips, P. F. Goldsmith, I. C. Percival, and D. Richards, Rotational excitation of molecules by electrons in interstellar clouds, Astron. Astrophys., 54, 645–647, 1977.
Farmer, C. B. and R. H. Norton, A High-Resolution Atlas of the Infrared Spectrum of the Sun and the Earth Atmosphere from Space, A Compilation of ATMOS Spectra of the Region from 650 to 4800 cm (2.3 to 16 μm), Vol. I. The Sun, NASA Reference Pub. 1224, 1989.
Gear, C. W., Numerical Initial Value Problems in Ordinary Differential Equations, Prentice Hall, Englewood Cliffs, New Jersey, 1971.
Green, S., Collisional excitation of CO by H2O—An astrophysicist’s guide to obtaining rate constants from coherent anti-Stokes Raman line shape data, Astrophys. J., 412, 436–440, 1993.
Hairer, E. and G. Wanner, Solving ordinary differential equations II. Stiff and differential-algebraic problems, Springer Series in Computational Mathematics 14, Springer-Verlag 1991, 2nd Edition, 1996.
Holmes, R., G. R. Jones, and N. Pusat, Vibrational relaxation in propane, propylene, and ethane, J. Chem. Phys., 41, 2512–2516, 1964.
Huebner, W., Solar Photo Rates for Planetary Atmospheres and Atmospheric Pollutants, Kluwer Academic Publishers, Dordrecht, 1992.
Kim, S. J., M. F. A’Hearn, and S. Larson, Multi-cycle fluorescence: Application to S2 in comet IRAS-Araki-Alcock 1983VII, Icarus, 87, 440–451, 1990.
Kim, S. J., Y. C. Minh, S. Hyung, and Y. H. Kim, High-resolution optical and infrared observations of molecules in comets, Astrochemistry: From Molecular Clouds to Planetary Systems, IAU Symposium, edited by Y. C. Minh and E. F. Van Dishoeck, Sheridan Books, Inc., Chelsea, Michigan, 197, 471–480, 2000.
Kostiuk, T., F. Espenak, M. J. Mumma, D. Deming, and D. Zipoy, Variability of ethane on Jupiter, Icarus, 72, 394–410, 1987.
Kostiuk, T., F. Espenak, P. Romani, D. Zipoy, and J. Goldstein, Ethane abundance on Neptune, Icarus, 88, 87–96, 1990.
Krankowsky, D., P. Lämmerzahl, I. Herrwerth, J. Woweries, P. Eberhardt, U. Dolder, U. Herrmann, W. Schulte, J. J. Berthelier, J. M. Illiano, R. R. Hodges, and J. H. Hoffman, In Situ gas and ion measurements at comet Halley, Nature, 321, 326–329, 1986.
Lii, J. H. and N. L. Allinger, Intensities of infrared bands in molecular mechanics (MM3), J. Comput. Chem., 13, 1138–1141, 1992.
Livengood, T. A., T. Kostiuk, F. Espenak, and J. J. Goldstein, Temperature and abundances in the Jovian auroral stratosphere 1. Ethane as a probe of the millimeter region, J. Geophys. Res., 98, 18812–18822, 1993.
Mumma, M. J., M. A. DiSanti, N. D. Russo, M. Fomenkova, K. Magee-Sauer, C. D. Kaminski, and D. X. Xie, Detection of abundant ethane and methane, along with carbon monoxide and water, in comet C/1996 B2 Hyakutake: Evidence for interstellar origin, Science, 272, 1310–1314, 1996.
Neubauer, F. M., K. H. Glassmeier, M. Pohl, J. Raeder, M. H. Acuna, L. F. Burlaga, N. F. Ness, G. Musmann, F. Mariani, M. K. Wallis, E. Ungstrup, and H. U. Schmidt, First results from the Giotto magnetometer experiment at comet Halley, Nature, 321, 352–355, 1986.
Nishimura, T. and Y. Itikawa, Electron-impact vibrational excitation of water molecules, J. Phys. B: At. Mol. Opt. Phys., 28, 1995–2005, 1995.
Nishimura, T. and Y. Itikawa, Vibrationally elastic and inelastic scattering of electrons by hydrogen sulphide molecules, J. Phys. B: At. Mol. Opt. Phys., 29, 4213–4226, 1996.
Nyquist, I. M., I. M. Mills, W. B. Person, and B. Crawford, Jr., Vibrational intensities. VII. Ethane and Ethane-d6, J. Chem. Phys., 26, 552–558, 1957.
Pedersen, A., R. Grard, J. G. Trotignon, C. Beghin, Y. Mikhailov, and M. Mogilevsky, Measurements of low energy electrons and spacecraft potentials near comet P/Halley, Astron. Astrophys., 187, 297–303, 1987.
Penner, S. S., Quantitative molecular spectroscopy and gas emissivities, Addison-Wesley Pub. Com., Inc. London, England, 1959.
Pierson, R. H., A. N. Fletcher, and E. S. C. Gantz, Catalog of infrared spectra for qualitative analysis of gases, Analytical Chemistry, 28, 1218–1239, 1956.
Pine, A. S. and W. J. Lafferty, Torsional splittings and assignments of the Doppler-limited spectrum of ethane in the C-H stretching region, J. of Res. National Bureau of Standards, 87, 237–256, 1982.
Press, W. H., S. A. Teukolsky, W. T. Vetterling, and B. P. Flannery, Numerical Recipes in Fortran, The Art of Scientific Computing, 2nd edition, Cambridge University Press, 1992.
Schwartz, R. N., Z. I. Slawsky, and K. F. Herzfeld, Calculation of vibrational relaxation times in gases, J. Chem. Phys., 20, 1591–1599, 1952.
Takekawa, M. and Y. Itikawa, Vibrational excitation of carbon dioxide by electron impact: symmetric and antisymmetric stretching modes, J. Phys. B: At.Mol. Opt. Phys., 31, 3245–3261, 1998.
Tokunaga, A. T. and P. Varanasi, Intensity of the rQ0 branch in the v9 fundamental of ethane, J. Quant. Spectrosc. Radiat. Transfer, 16, 1057–1059, 1976.
Weaver, H. A., T. Y. Brooke, G. Chin, S. J. Kim, D. Bockelée-Morvan, and J. K. Davies, Infrared spectroscopy of comet Hale-Bopp, Earth, Moon, Planets, 78, 71–80, 1999.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Kim, S.J. Infrared excitation processes of C2H6 in comets. Earth Planet Sp 55, 139–151 (2003). https://doi.org/10.1186/BF03351741
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1186/BF03351741