The DOI matches its Crossref record; 6 of the 6 references it cites were found in a registry or an index.
Excitation of the Hydrogen 21-CM Line
Abstract
The importance of spin temperature for 21-cm line studies is reviewed, and four mechanisms which affect it are studied. Two of the mechanisms, collisions with free electrons and interactions with light, are studied here in detail for the first time. The results are summarized in Table II of Section VI, in the form of certain efficiencies which can be used with (15) to calculate the spin temperature. In Section VI the results are applied to a variety of astronomical situations, and it is shown that in the usual situation collisions with H atoms are very effective in establishing the spin temperature equal to the kinetic temperature. Under conditions of low-density and/or high-radiation intensity, however, important deviations from the usual are noted. The significance of such deviations for absorption studies of radio sources and the galactic halo is discussed. In Section VII the deuterium line at 91.6 cm is considered in like fashion. It is shown that for deuterium also, the spin temperature probably is close to the kinetic temperature.
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Ewen, H. I., & Purcell, E. M. (1951) · Nature · doi:10.1038/168356a0 · Cited by 406
(1926) · Nature · doi:10.1038/117299d0 · Cited by 252
Influence of Collisions upon Population of Hyperfine States in Hydrogen.
Purcell, E. M., & Field, G. B. (1956) · The Astrophysical Journal · doi:10.1086/146259 · Cited by 217
Self-citationSchmidt, M. (1954) · Bulletin of the Astronomical Institutes of the Netherlands · Cited by 36
An Investigation of Monochromatic Radio Emission of Deuterium from the Galaxy
Stanley, G. J., & Price, R. M. (1956) · Nature · doi:10.1038/1771221a0 · Cited by 20
Intensity of the Radio Line of Galactic Deuterium
Adgie, R. L., & Hey, J. S. (1957) · Nature · doi:10.1038/179370a0 · Cited by 11
Cited by
LOFAR: The LOw-Frequency ARray
van Haarlem, M. P., Wise, M. W., Gunst, A. W., Heald, G., McKean, J. P., Hessels, J. W. T., de Bruyn, A. G., Nijboer, R., Swinbank, J., Fallows, R., et al. (2013) · Astronomy & Astrophysics · doi:10.1051/0004-6361/201220873 · Cited by 2,662
Fundamental physics with the Square Kilometre Array
Weltman, A., Bull, P., Camera, S., Kelley, K., Padmanabhan, H., Pritchard, J., Raccanelli, A., Riemer-Sørensen, S., Shao, L., Andrianomena, S., et al. (2020) · Publications of the Astronomical Society of Australia · doi:10.1017/pasa.2019.42 · Cited by 384
Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries
Madau, P., & Fragos, T. (2017) · The Astrophysical Journal · doi:10.3847/1538-4357/aa6af9 · Cited by 334
Detecting the Earliest Galaxies through Two New Sources of 21 Centimeter Fluctuations
Barkana, R., & Loeb, A. (2005) · The Astrophysical Journal · doi:10.1086/429954 · Cited by 278
The Karl G. Jansky Very Large Array Local Group L -Band Survey (LGLBS)
Koch, E. W., Leroy, A. K., Rosolowsky, E. W., Chomiuk, L., Dalcanton, J. J., Pingel, N. M., Sarbadhicary, S. K., Stanimirović, S., Walter, F., Archer, H. N., et al. (2025) · The Astrophysical Journal Supplement Series · doi:10.3847/1538-4365/ade0ad · Cited by 13
Metadata
- Authors
- Field, G.
- Venue
- Proceedings of the IRE
- Published
- 1958-01
- Volume
- 46
- Issue
- 1
- Pages
- 240-250
- ISSN
- 0096-8390 (ISSN-L)
- OpenAlex
- W2157427356
- Cited by
- 586
- References
- 6
- FWCI
- 2.48
- Type
- journal article
- Language
- en
- Open access
- closed
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