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%'e show how a collection of noninverted two-level systems, under the action of a quasiresonant pump field, can produce an exponential amplification of a probe signal through the mechanism of a dynamical instability with spatial self-bunching in a way very similar to that experienced by a high-gain freeelectron laser. We offer a detailed description of this phenomenon, specify the conditions under which it takes place, and sketch possible experimental parameters for its observation in a gaseous medium. PACS number(s): 42.55. -f, 42.50. -p, 32.80.Pj

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This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the D!SfR:G' ; ' ; J : i United States Government or any agency thereof.

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