Date of Award

Spring 2000

Document Type

Restricted Thesis

Terms of Use

© 2000 Beth A. Biller. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Physics & Astronomy Department

First Advisor

Vladimir Strelnitski

Second Advisor

Eric L.N. Jensen

Third Advisor

Frank Moscatelli


The λ = 1.35-cm H₂O masers in sites of star formation typically display very narrow linewidths, narrower than the separation of the three strongest hyperfine components of the transition, as well as unexpectedly steep variation in linewidth as a function of intensity. We critically analyze various mechanisms proposed to explain these observations. These include narrowing due to unsaturated amplification in various geometries and blending of two features. The linewidths of a number of maser features remain unexplained by any of these or other proposed mechanisms. In particular, unsaturated amplification can produce the observed narrow line widths but it is insufficient to produce the observed steepness of line narrowing with increasing intensity. Blending can provide the necessary rate of line narrowing but it produces characteristic shifts in the central velocity of the line that are not observed in a number of features. We suggest that frequency mode competition due to positive feedback may be responsible for both the narrowness and the high rate of narrowing of these lines.