I am reading the book "Super-radiance Multiatomic Coherent Emission" by Benedict et al. and on pg. 32, they discuss the initial conditions for a particular case covered by Burnham and Chiao (1969). It mentions that the system was "excited to a state with angle ##\theta_0## by a short coherent pulse of area ##\pi - \theta_0##." I have looked elsewhere in the text, but have not come across any particular definition/expression for a coherent pulse of a specified area. Would you happen to know what is meant by a "coherent pulse" of specified area and what the analytic form for such a pulse would be? Also, when discussing an incident pulse of a particular area, is this considered to be a function of time or a function of space (i.e. area defined as spatial width or integration over time domain)?