`ISRN Astronomy and AstrophysicsVolume 2011 (2011), Article ID 905015, 10 pagesdoi:10.5402/2011/905015`
Research Article

## On the Cosmic Ray-Induced Ionization Rate in Molecular Clouds

V. A. Ambartsumian Byurakan Astrophysical Observatory, Byurakan 0213, Armenia

Received 30 January 2011; Accepted 13 March 2011

Academic Editors: C. Meegan and T. Wilson

Copyright © 2011 Ararat G. Yeghikyan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. L. Nagy and L. Végh, “Ionization of molecular hydrogen by proton impact. I. Single ionization,” Physical Review A, vol. 46, no. 1, pp. 284–289, 1992.
2. J. F. Cooper, E. R. Christian, J. D. Richardson, and C. Wang, “Proton irradiation of Centaur, Kuiper Belt, and Oort Cloud objects at plasma to cosmic ray energy,” Earth, Moon and Planets, vol. 92, no. 1-4, pp. 261–277, 2003.
3. W. R. Webber and S. M. Yushak, “A measurement of the energy spectra and relative abundance of the cosmic-ray H and He isotopes over a broad energy,” The Astrophysical Journal, vol. 275, pp. 391–404, 1983.
4. M. A. Dopita and R. S. Sutherland, Astrophysics of the Diffuse Universe, Springer, New York, NY, USA, 2003.
5. C. F. McKee, “Multiphase gas in quasar absorption systems,” in The Physics of the Interstellar Medium and Intergalactic Medium, A. Ferrara, C. McKee, C. Heiles, and P. Shapiro, Eds., vol. 80 of ASP Conference Series, pp. 468–477, ASP Press, San Francisco, Calif, USA, 1995.
6. R. I. Kaiser, “Experimental investigation on the formation of carbon-bearing molecules in the interstellar medium via neutral-neutral reactions,” Chemical Reviews, vol. 102, no. 5, pp. 1309–1358, 2002.
7. A. G. G. M. Tielens, The Physics and Chemistry of the Interstellar Medium, CUP, 2005.
8. L. Blitz and J. P. Williams, “Molecular clouds,” in The Origins of Stars and Planetary Systems, C. Lada and N. D. Kilafis, Eds., pp. 3–28, Kluwer Academic Press, 1998.
9. E. F. van Dishoeck and J. H. Black, “The photodissociation and chemistry of interstellar CO,” The Astrophysical Journal, vol. 334, pp. 771–802, 1988.
10. J. E. Dyson and D. A. Williams, Physics of the Interstellar Medium, IoP, 1997.
11. R. Stark and K. Reif, “Surface brightness measurements of extended galactic nebulae,” Publications Astronomical Society of Australia, vol. 15, no. 1, pp. 86–90, 1998.
12. E. Herbst, “The astrochemistry of ${\text{H}}_{3}{\text{\hspace{0.17em}}}^{+}$,” Philosophical Transactions of the Royal Society A, vol. 358, no. 1774, pp. 2523–2534, 2000.
13. P. Caselli, “Constraining chemical-physical properties of pre-stellar cores,” Astrophysics and Space Science, vol. 285, no. 3-4, pp. 619–631, 2003.
14. P. Ehrenfreund and S. B. Charnley, “Organic molecules in the interstellar medium, comets, and meteorites: a voyage from dark clouds to the early Earth,” Annual Review of Astronomy and Astrophysics, vol. 38, no. 1, pp. 427–488, 2000.
15. T. R. Geballe and T. Oka, “Detection of ${\text{H}}_{3}{\text{\hspace{0.17em}}}^{+}$ interstellar space,” Nature, vol. 384, no. 6607, pp. 334–335, 1996.
16. P. Caselli, C. M. Walmsley, A. Zucconi, M. Tafalla, L. Dore, and P. C. Myers, “Molecular ions in L1544. II. The ionization degree,” The Astrophysical Journal, vol. 565, no. 1, pp. 344–358, 2002.
17. T. R. Geballe, “${\text{H}}_{3}{\text{\hspace{0.17em}}}^{+}$ between the stars,” Philosophical Transactions of the Royal Society A, vol. 358, no. 1774, pp. 2503–2513, 2000.
18. H. H. Lee, R. P. A. Bettens, and E. Herbst, “Fractional abundances of molecules in dense interstellar clouds: a compendium of recent model results,” Astronomy and Astrophysics Supplement Series, vol. 119, no. 1, pp. 111–114, 1996.
19. P. Jenniskens, G. A. Baratta, A. Kouchi, M. S. de Groot, J. M. Greenberg, and G. Strazzulla, “Carbon dust formation on interstellar grains,” Astronomy and Astrophysics, vol. 273, p. 583, 1993.
20. J. P. Williams, E. A. Bergin, P. Caselli, P. C. Myers, and R. Plume, “The ionization fraction in dense molecular gas. I. Low-mass cores,” The Astrophysical Journal, vol. 503, no. 2, pp. 689–699, 1998.
21. J. Skilling and A. W. Strong, “Cosmic ray exclusion from dense molecular clouds,” Astronomy and Astrophysics, vol. 53, no. 2, pp. 253–258, 1976.
22. C. J. Cesarsky and H. J. Volk, “Cosmic ray penetration into molecular clouds,” Astronomy and Astrophysics, vol. 70, p. 367, 2001.
23. L. Spitzer Jr. and M. G. Tomasko, “Heating of H i regions by energetic particles,” The Astrophysical Journal, vol. 152, p. 971, 1968.
24. P. M. Solomon and M. W. Werner, “Low-energy cosmic rays and the abundance of atomic hydrogen in dark clouds,” The Astrophysical Journal, vol. 165, p. 41, 1971.
25. T. Cravens and A. Dalgarno, “Ionization, dissociation, and heating efficiencies of cosmic rays in a gas of molecular hydrogen,” The Astrophysical Journal, vol. 219, no. 15, pp. 750–752, 1978.
26. T. Umebayashi and T. Nakano, “Fluxes of energetic particles and the ionization rate in very dense interstellar clouds,” Publications of the Astronomical Society of Japan, vol. 33, p. 617, 1981.
27. R. L. Curran and A. Chrysostomou, “Magnetic fields in massive star-forming regions,” Monthly Notices of the Royal Astronomical Society, vol. 382, no. 2, pp. 699–716, 2007.
28. E. G. Zweibel and C. Heiles, “Magnetic fields in galaxies and beyond,” Nature, vol. 385, no. 6612, pp. 131–136, 1997.
29. J. P. Meyer, L. O. Drury, and D. C. Ellison, “Galactic cosmic rays from supernova remnants. I. A cosmic-ray composition controlled by volatility and mass-to-charge ratio,” The Astrophysical Journal, vol. 487, no. 1, pp. 182–196, 1997.
30. J. F. Ziegler, J. P. Biersack, and U. Littmark, The Stopping and Range of Ions in Matter, Pergamon, 1985.
31. J. F. Ziegler and J. P. Biersack, 2010, http://www.srim.org/.
32. S. D. Brittain, T. Simon, C. Kulesa, and T. W. Rettig, “Interstellar ${\text{H}}_{3}{\text{\hspace{0.17em}}}^{+}$ line absorption toward LkHα 101,” The Astrophysical Journal, vol. 606, no. 2, pp. 911–916, 2004.
33. C. J. Shen, J. M. Greenberg, W. A. Schutte, and E. F. van Dishoeck, “Cosmic ray induced explosive chemical desorption in dense clouds,” Astronomy and Astrophysics, vol. 415, no. 1, pp. 203–215, 2004.