The main topic of this thesis are neutron-rich potassium nuclei with mass numbers ranging from 41 to 46. As a part of this work we analysed and interpreted data related to the electromagnetic transitions excited by the nuclear reaction 40Ar + 208Pb measured with the PRISMA magnetic spectrometer coupled with the CLARA γ -ray detector. Using a neutron-rich stable beam of 40Ar we can observe excited isotopes in the exit channel, originating from nucleon pick-up or stripping. Proton pick-up channels are a major research interest as up to now they have rarely been identified in terms of their atomic and mass numbers in measurements near the Coulomb barrier. In our measurement isotopes of potassium are created by pick-up reactions of neutrons and protons. Our main objective was to identify their characteristic electromagnetic transitions throughout the complete potassium isotopic chain. These results were compared to previously published results and theoretical predictions of the nuclear shell model. We observed so far unknown electromagnetic transitions and, by embedding corresponding levels in the energy level scheme and comparing them with shell model calculations, obtained new information on previously known levels of unknown spin and parity. Furthermore, we observed that the cross section in all excited potassium nuclei is equally distributed among states of positive and negative parity. We also observed strong excitations of highest spin states for a given energy (“yrast”). Finally, we discussed the inversion of the first excited state and ground state, 1/2+ and 3/2+ for odd-even nuclei and 3− and 2− for odd-odd nuclei, in which the inversion is caused by strong mixing of proton configurations, as the neutron shell f7/2 is being filled.