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Photoelectric Emission Measurements on the Analogs of Individual Cosmic Dust GrainsThe photoelectric emission process is considered to be the dominant mechanism for charging of cosmic dust grains in many astrophysical environments. The grain charge and equilibrium potentials play an important role in the dynamical and physical processes that include heating of the neutral gas in the interstellar medium, coagulation processes in the dust clouds, and levitation and dynamical processes in the interplanetary medium and planetary surfaces and rings. An accurate evaluation of photoelectric emission processes requires knowledge of the photoelectric yields of individual dust grains of astrophysical composition as opposed to the values obtained from measurements on flat surfaces of bulk materials, as it is generally assumed on theoretical considerations that the yields for the small grains are much different from the bulk values. We present laboratory measurements of the photoelectric yields of individual dust grains of silica, olivine, and graphite of approx. 0.09-5 micrometer radii levitated in an electrodynamic balance and illuminated with ultraviolet radiation at 120-160 nm wavelengths. The measured yields are found to be substantially higher than the bulk values given in the literature and indicate a size dependence with larger particles having order-of-magnitude higher values than for submicron-size grains.
Document ID
20060050248
Document Type
Reprint (Version printed in journal)
Authors
Abbas, M. M. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Tankosic, D. (Alabama Univ. Huntsville, AL, United States)
Craven, P. D. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Spann, J. F. (NASA Marshall Space Flight Center Huntsville, AL, United States)
LeClair, A. (Alabama Univ. Huntsville, AL, United States)
West, E. A. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Weingartner, J. C. (George Mason Univ. Fairfax, VA, United States)
Tielens, A. G. G. M. (Kapteyn Astronomical Lab. Groningen, Netherlands)
Nuth, J. a. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Camata, R. P. (Alabama Univ. Birmingham, AL, United States)
Date Acquired
August 23, 2013
Publication Date
July 1, 2006
Publication Information
Publication: The Astrophysical Journal
Volume: 645
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: NNC8-580
Distribution Limits
Public
Copyright
Other