Doppler shift effect in storage of terahertz frequency signals in Rydberg atoms

Motivated from a recent theoretical work [1] on efficient storage of terahertz frequency signals in ultracold Rydberg atoms, I have studied the above mentioned storage process in the case when Doppler effect is present. It is present when the atoms are moving with a velocity which is coming from the thermal effect. Here, I have shown that this effect has made a prominent change in susceptibility and relative difference of the slope of dispersion which is the key factor of group index and group velocity [2].