Collaboration with Dr. Efrem Sh. Soukhovitsukii: our fortuitous experiences on optical model analysis, his contribution to nuclear data activities of Japan and a posthumous study on light-nuclei

Optical model or coupled-channels calculation serves as an entrance to sophisticated calculation of nuclear data. It gives the optical quantities such as total, shape elastic scattering, absorption cross sections, direct inelastic scattering cross sections, angular distributions of elastic and inelastic scattering, and transmission coefficients for subsequent statistical model calculations. Traditionally, coupling of the elastic scattering channel to excited states of the target nucleus was ignored or treated with a simplified model such as rigid rotor or harmonic oscillator. It was a great contribution of Dr. Efrem Sh. Soukhovitsukii who has developed an excellent computation scheme which takes account of the low-lying collective nuclear structure in terms of the soft-rotator + vibrational model, and integrated it into the coupled-channels calculation. This methodology was realized as 2 computer codes, SHEMMAN and OPTMAN. In Japan, we had a fortuitous experience with him to employ this methodology in nuclear data evaluation, which started as a nuclear physics work to analyze neutron-scattering cross section of ^12 C which were published as a series of 3 papers in Nuclear Physics A journal. After recognizing the usefulness of this methodology, it was applied to evaluation of nuclear data gradually and extensively, which resulted in obtaining awards of Atomic Energy Society of Japan (AESJ) by one of the authors (SK). This paper describes our collaborative works and recent findings on light-nuclei based on what he had developed.