  Measurements of rubidium lifetime in a dark magneto-optical trap (DMOT) was
performed at various populations of the bright and dark hyperfine states of the
trapped atoms. The rubidium lifetime in the trap appeared to be shorter if the
atom spent more time in the bright state. A simple explanation of this effect
is based on the increase of the cross-section of rubidium collisions with the
surrounding warm atoms upon rubidium electronic excitation.
