The authors describe the performance of a compact (41-cm-long) e-beam sustained atmospheric pressure CO/sub 2/ laser using a Gaussian reflectivity mirror in an unstable resonator configuration. The device operated on a single longitudinal and transverse mode (W/sub 1L/=12.9 mm) at an output energy of around 1 J. The frequency characteristics were studied and acoustic effects were observed as a result of the near-threshold operation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>