Coulomb blockade in a cold Rydberg gas measured by Ramsey Fringes

Dipole blockade, the suppression of the excitation of neighboring atoms, at higher principle quantum number n has been studied in a cold Rydberg gas. Free ions, often ignored, exist in a cold Rydberg gas, which can shift the energy levels and contribute the blockade effect. Accurately measuring this field is challenging. In this paper, Ramsey fringes driving the d to f transition, a transition between two electric field sensitive states, are used to estimate this field and the excitation suppression will be presented.