MASER EMISSION FROM AN AMMONIA INVERSION TRANSITION THROUGH COLLISIONAL COOLING

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1995

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Ohio State University

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We have observed stimulated emission from the J = 4, K = 3 inversion transition of ammonia $(^{14}NH_{3})$ as it was cooled by collisions with cold He atoms in a low temperature cell. Maser emission was observed for cell temperatures of 10 to $\sim 27 K$. Above $\sim 27 K$ the transition was seen in absorption. Several other ammonia inversion transitions were also observed at low temperature, but only the (4,3) line was seen in emission. The mechanism we postulate for the establishment of the necessary population inversion is similar to one put forward to explain certain types of interstellar ammonia masers and involves a preference for parity changing in collisional energy transfer into K = 0 levels.

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Author Institution: Allegheny College, Meadville, PA 16335.; University of Rochester, Rochester, NY 14627-0171.

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