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Quantum threshold reflection is a well known quantum phenomenon whichprescribes that at threshold, except for special circumstances, a quantumparticle scattering from any potential, even if attractive at long range, willbe reflected with unit probability. In the past, this property has beenassociated with the so-called badlands region of the potential, where thesemiclassical description of the scattering fails due to a rapid spatialvariation of the deBroglie wavelength. This badlands region occurs far from thestrong interaction region of the potential and has therefore been used to"explain" the quantum reflection phenomenon. In this paper, we show that thebadlands region of the interaction potential is immaterial. The extremely longwavelength of the scattered particle at threshold is much longer than thespatial extension of the badlands region which therefore does not affect thescattering. For this purpose, we review the general proof for the existence ofquantum threshold reflection to stress that it is only a consequence ofcontinuity and boundary conditions. The nonlocal character of the scatteringimplies that the whole interaction potential is involved in the phenomenon. Wethen provide a detailed numerical study of the threshold scattering of aparticle by a Morse potential especially in the time domain. We compare exactquantum computations with incoherent results obtained from a classical Wignerapproximation. This study shows that close to threshold the time dependentamplitude of the scattered particle is negligible in the badlands region andthat the mean flight time of the particle is not shortened due to a localreflection from the badlands region. This study should serve to definitely ruleout the badlands region as a qualitative guide to the properties of quantumthreshold reflection.

Quantum threshold reflection is not a consequence of the badlands region of the potential