A transition in the spectral statistics of quantum optical model by   different electromagnetic fields
  The effects of the quantized electromagnetic fields on the spectral statistics of two-level atoms are considered. We have used the Berry- Robnik distribution and Maximum Likelihood estimation technique to analyze the effect of mean photon and two level atoms numbers and also the quantum number of considered states. Results suggest the intensity of electromagnetic fields as control parameter which the spectral statistics change due to its variation in the 0-1200 region. Also, we observed the universality in the spectral statistics of considered systems when the number of two level atoms is approached to unrealistic limits and there are some suggestions about the effect of the quantum number of selected levels and the atom-field coupling constant on level statistics. 
H. Sabri
quant-ph