Excited states of rubidium populated by stepwise excitation using a rubidium lamp andor a tunable dye laser : importance of redistribution collisions

Abstract

Excited states of rubidium have been populated by using a stepwise excitation scheme. The fir s t step is either a transition to an atomic intermediate state using a rubidium resonance lamp, or a transition to a molecular intermediate state using a laser as the excitation source. The second step in both cases is accomplished using a laser to populate high 2[subscript S1/ 2] or 2[subscript D5/2,3/2] states in the rubidium atom. Two different commercial lasers were used and the results compared. One laser is a single mode laser whereas the other is a multimode laser, therefore different parameters are important. Once the excited states are populated, the importance of collisions with ground state rubidium atoms is investigated. I t is seen that over the temperature range of 85??C to 200??C the fine structure states of the 6 ??D level are completely mixed, and that other transfer cross sections out of these states are of comparable magnitude as the fine structure changing collision cross sections. The ground state density change in this region is from about 1.5 x 10???? atoms/cm?? to 1.5 x 10???ü?atoms/cm??. A minimum value for the fine structure changing collision cross section of the 6 ??D state is estimated to be: ?â[subscript fs](min)=19 x 10?ü?????cm??. ...