Resonant collisions of K Rydberg atoms

We have observed resonant-energy-transfer collisions between K Rydberg atoms. We have tuned the ns1/2+(n-2)dj→npj'+(n-1)pj'' collisional process into resonance with a static electric field. The measured resonance field positions from n=24 to 29 agree well with the calculated positions. We show that the dipole-dipole selection rule, Δmj=0,±1, is valid for these resonances but that ΔJ=0,±1 is not, due to the presence of the electric field. In addition, the polarization of the lasers used to excite the Rydberg states can suppress many of the resonances