 In his early years, he contributed to X-ray spectroscopy, but then broadened out to make contributions to quantum mechanics, quantum electrodynamics, and meson theory.Gregor Wentzel was born in Düsseldorf, Germany, as the first of four children of Joseph and Anna Wentzel.He married Anna "Anny" Pohlmann in 1929 and his only child, Donat Wentzel, was born in 1934.