Spin relaxation: is there anything new under the Sun?

Abstract. Spin relaxation has been at the core of many studies since early days nuclear magnetic resonance (NMR) and underlying theory worked out by its founding fathers. This Bloch–Redfield–Abraham recently reinvestigated (Bengs Levitt, 2020) in perspective Lindblad quantum Markovian master equations order to account for situations where widely used semi-classical breaks down. In this article, we review conventional approach mechanical NMR show that, under usual assumptions, it is equivalent formulation. We also comment on debate versus versions spectral density functions involved relaxation.