Definition of ammonia maser

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Photonics Dictionary

ammonia maser: An ammonia maser is a device that amplifies microwave radiation using ammonia gas molecules in a process analogous to how lasers amplify visible light through stimulated emission of radiation. The term maser stands for "microwave amplification by stimulated emission of radiation."

Operating principle: Ammonia masers operate on the principle of stimulated emission, similar to how lasers work but at microwave frequencies (typically around 23.87 GHz for the rotational transition of ammonia molecules).

Molecular transition: In an ammonia maser, ammonia (NH3) molecules are excited to a higher energy state by an external energy source, such as a pump microwave field. These excited molecules then emit microwave photons as they return to a lower energy state. This emission process is amplified by placing the ammonia gas within a resonant cavity that reflects and re-amplifies the emitted microwaves.

Cavity design: The maser cavity is designed to enhance the stimulated emission process by ensuring that the microwaves produced by the excited ammonia molecules undergo multiple reflections and interactions, leading to coherent emission and amplification.

Applications: Ammonia masers have been historically used in radio astronomy for sensitive receivers due to their ability to amplify weak microwave signals with high gain and low noise. They have also found applications in atomic clocks, precision spectroscopy, and microwave communication systems.

Ammonia masers represent an important development in microwave technology, providing a means to amplify and detect weak microwave signals with high sensitivity and precision. They have contributed significantly to advancements in both fundamental research and practical applications in areas requiring precise microwave amplification and detection.