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    Physical Interpretation of Anomalous Absorption of Partial Waves by Nuclear Optical Potential,
    (University of Kelaniya, 2008) Piyadasa, R.A.D.; Munasinghe, J.; Karunatileke, N.G.J.
    Anomalous absorption of light ion partial waves by the nuclear optical potential is an interesting phenomenon showing striking systematic in various parameter planes. However, the theoretical description of this phenomenon is extremely difficult. In this contribution, we address the problem of its physical interpretation. It is shown that the zero of the S-matrix element associated with the anomalous absorption of a partial wave is due to the destructive interference of the reflected waves, from the innermost turning point and the outermost turning point, in the asymptotic region when WKB approximation is feasible.
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    Exact Formula for the Sum of the Squares of the Bessel Function and the Neumann Function of the Same Order of Half-Odd Integer
    (University of Kelaniya, 2008) Piyadasa, R.A.D.; Mallawa Arachchi, D.K.
    Sum of the squares of the Bessel function and the Neumann function of the same order of half-odd integer has been found to be very useful in addressing a puzzle in nuclear physics. One approximate formula available in the literature is valid for the complex argument whose real part is greater than zero, and the absolute value of error term is undefined for half-odd integers. Another approximate formula which is valid for all complex arguments has been obtained using sophisticated mathematical method called Barnes' method. However, the error in the formula is very difficult to calculate. We have obtained exact formula for the sum of the squares of Bessel and Neumann functions of the same order of half-odd integers which is valid for all complex arguments, and its proof is also given.