"Paramagnetic relaxation of liquid solutions for perpendicular fields": Zavoisky's foundational papers of Electron Paramagnetic Resonance

In July 1944, Evgeny Konstantinovich Zavoisky (Евгений Константинович Завойский) submitted his observations on the paramagnetic relaxation of solutions of manganese(II) salts, under magnetic fields using microwave radiation (actually, he used 12 and 5.3 MHz frequencies, which can also be considered radiowaves).

This work, which is considered to have initiated Electron Paramagnetic Resonance (EPR) spectroscopy, was published in 1945 in Russian (Zhur. Eksperiment. i Theoret. Fiz. [Журнал экспериментальной и теоретической физики], 1945, 15:7, 344–350), and in English (Journal of Physics, 1945, IX:3, 211-216). Several more papers were published shortly thereafter.*

The English version of this very hard to find foundational paper is presented here.

I would like to particularly thank Mr. Igor I. Silkin from the Evgeni Zavoisky Museum for providing this copy, as well as copies some of the other early EPR papers of E. Zavoiksy.

*Previous to that, the article "The paramagnetic absorption of a solution in parallel fields" appeared in English (Journal of Physics, 1944, XIII:6, 377-380) and in Russian ("Парамагнитная абсорбция в растворах при параллельных полях", Журнал эксперимент. и теоретич. физики., 1945, 15:6, 253-257).