Hyperfine anomalies of HCN in cold dark clouds
We report observations of the J = 1..-->..0 line of HCN measured toward six positions in nearby low-temperature dark clouds. The measured relative intensities of the hyperfine components of the J = 1..-->..0 line are anomalous in that the F = 0..-->..1 transition is stronger than would be expected if all three components (F = 2..-->..1, F = 1..-->..1, F = 0..-->..1) had equal excitation temperatures. Differences of approximately 20% in the populations per sublevel of J = 1 could account for the observations. The results are in contrast to the situation observed in warmer molecular clouds associated with H II regions where the F = 1..-->..1 line is anomalously weak. The apparent overpopulation of J = 1, F = 0 in dark clouds may be related to the phenomenon observed in the J = 1..-->..0 transitions of HCO/sup +/ and HNC in the same objects where /sup 13/C substituted version of these species is found to be stronger than the /sup 12/C species.
- Research Organization:
- Max-Planck-Institut fuer Radioastronomie; and Physics Department, University of Illinois at Urbana-Champaign
- OSTI ID:
- 6806174
- Journal Information:
- Astrophys. J., Lett. Ed.; (United States), Vol. 258:2
- Country of Publication:
- United States
- Language:
- English
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