Collective modes in free plasmas subjected to a radiation field

In this study we report the effects of an electromagnetic field on the physical properties of free plasmas3.The calculations are carried out in the semi-classical approximation, i.e., the electromagnetic field is treated classically and the electrons from a quantum mechanical viewpoint. The results show that the collective modes are damped away more smoothly and in a smaller frequency range than those reported by previous studies. An exponential-like decay of the frequencies is readily observable from the plot of the plasmon frequency as a function of the external field amplitude. We successfully recreate the results of previous studies. We also obtain that the single photon processes has a pronounced effect on the decrease of the frequency range of modulation.