Maser effects in the interstellar hydrogen clouds of the galactic halo
1967 ◽
Vol 31
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pp. 291-293
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It is suggested that the neutral hydrogen atoms in clouds with high negative velocities observed at high galactic latitudes may, when moving towards a galactic H 11 region, be excited by radiation in the red wing of the Lyman-α profile. The steepness of this wing may cause a population inversion of the hyperfine-structure levels. Consequently, estimates of the hydrogen density in the high-velocity clouds, and of the flow of matter towards the galactic plane (or into the Galaxy), when based on the assumption of collisional excitation, may be too high by two orders of magnitude.
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1989 ◽
Vol 120
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pp. 416-423
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1974 ◽
Vol 60
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pp. 599-616
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1991 ◽
Vol 144
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pp. 27-40
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2004 ◽
Vol 217
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pp. 130-135
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1967 ◽
Vol 31
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pp. 239-251
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1995 ◽
Vol 164
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pp. 369-369
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