Teaching product operators using the Vega diagram.

We all will remember Shimon Vega (1942-2021) as wonderful human and scientist. Paramount examples of his scientific work are quoted in this special issue dedicated to his memory. This article is dedicated to remember Shimon Vega as a fantastic teacher. To introduce to the world of product operators, Shimon created a simple scheme that we now call the Vega diagram. It allows for fast analysis of pulse sequences for AX spin systems. Here, we want to document this scheme for future generations.