INSTITUTO DE INVESTIGACIONES FISICAS DE MAR DEL PLATA
Unidad Ejecutora - UE
A Jost function description of zero-energy resonance and transparency effects in elastic collisions
P. A. MACRI; R. O. BARRACHINA
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
IOP PUBLISHING LTD
Lugar: Londres; Año: 2013 vol. 46 p. 65202 - 65202
Under certain circumstances, an elastic cross section at very low energies could differ by orders of magnitude above or below any reasonable estimate. The first case occurs near a zero-energy resonance, while the second one is akin to the well-known RamsauerTownsend effect. In spite of their intrinsic similarity, both effects are usually explained in very different ways, either in terms of poles of the scattering matrix or by means of a partial-wave analysis, respectively. In this paper we show that a unified description is actually possible. We demonstrate that in a zero-energy resonance or transparency, the standard 2 threshold law of the -wave cross section is changed into 2(−1) (−1 for = 0) or 2(+1), respectively. Finally, we show that while the zero-energy resonance occurs whenever the scattering length associated to an individual zero of the Jost function diverges, the transparent scattering is a collective effect, where the sum of all the individual scattering lengths plays a relevant role.