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We consider a quantum system dynamics caused by successive selective and nonselective measurements of the probe coupled to the system. For the finite measurement rate τ-1 and the system-probe interaction strength γ we derive analytical evolution equations in the stroboscopic limit τ→0 and γ2τ=const, which can be considered as a deviation from the Zeno subspace dynamics on a longer time scale T∼(γ2τ)-1≫γ-1. Nonlinear quantum dynamics is analyzed for selective stroboscopic projective measurements of an arbitrary rank. Nonselective measurements are shown to induce the semigroup dynamics of the system-probe aggregate. Both nonlinear and decoherent effects become significant at the time scale T∼(γ2τ)-1, which is illustrated by a number of examples. [ABSTRACT FROM AUTHOR]

We studied light-assisted collisions of Tm atoms in a magneto-optical trap (MOT), working on a weak cooling transition at 530.7 nm [4f13(²Fo)6s²,J=7/2,F=4 to 4f12(³H6)5d5/26s²,J=9/2,F=5]. We observed a strong influence from radiation trapping and light-assisted collisions on the dynamics of this trap. We carefully separated these two contributions and measured the binary loss rate constant at different laser powers and detuning frequencies near the cooling transition. Analyzing losses from the MOT, we found the light-assisted inelastic binary loss rate constant to reach values of up to β=10-9cm³/s and gave the upper bound on a branching ratio k<0.8×10-6 for the 530.7 nm transition. [ABSTRACT FROM AUTHOR]