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Published January 15, 1975 | Published
Journal Article Open

Radiative Trapping and Hyperfine Structure: HCN

Abstract

The anomalous weakness of the F = 1 → 1 hyperfine component in the J = 1 → 0 emission of interstellar HCN can be caused by radiative trapping in the J = 2 → 1 lines. The anomaly is readily produced if the J = 1 levels are populated largely by collisional excitation from J = 0 to J = 2 followed by radiative decay to J = 1 with the J = 2 → 1 lines optically thick. Regions where the anomaly is found probably have H_2 densities less than 10s^5 cm^(-3) and optical depths in the J =1 → 0 lines greater than 50.

Additional Information

© 1975. The American Astronomical Society. Received 1974 September 12; revised 1974 October 29. This research is sponsored by the National Science Foundation grants GP-40768X (JK) and GP-30400-X5 (NS) and by the Office of Naval Research under contract N0014-67-A-0094-0019 (NS).

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August 19, 2023
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