PROBING QUANTAL DYNAMICS OF MIXED-PHASE SPACE SYSTEMS WITH NOISE

We study how weak broadband noise affects 30.36 GHz 10%-''ionization'' thresholds F(10%) (that produce ''ionization'' probability P(ion) = 1 0%) of no = 54, ..., 72 H atoms. Calculations confirm that increased n oise lowers F(10%) for most n0's, raises some, but affects others litt le. We show noise to be a useful spectroscopic tool for uncovering nov el quantal phenomena such as scarred states, which we link semiclassic ally to approximately adiabatic evolution near the separatrix of a non linear resonance island. Our results apply generally to the quantal be havior of classical mixed phase space systems.