Investigation of ultraviolet spectrum and energy level assignments of Gd I in the 305–325nm region

• The ultraviolet spectrum of Gd I in the 305–325 nm range was investigated through resonance ionization spectroscopy. • 196 transition lines were determined with their normalized intensities and transition patterns, 172 of which are reported for the first time. • The pump-probe technique was ued to confirm the lower energy level assignments for 76 lines. • The lower energy levels were revealed for 32 unassigned lines, leading to the discovery of 17 new even-parity excited states. • 66 strong lines reported in this work will contribute to future studies of Gd I Rydberg and autoionization states. The ultraviolet spectrum of Gd I in the 305–325 nm range was studied using resonance ionization spectroscopy, revealing 196 transition lines, including 66 strong ones. The lower and upper energy levels were assigned to 190 lines by combining available reference data with pump–probe verification, 172 of which are reported for the first time. Seventeen new even-parity high-lying excited states were also identified. The strong lines reported here will contribute to future studies of Gd I Rydberg and autoionization states and enable two-color, two-step photoionization pathways for isotope separation and resonance ionization mass spectrometry analysis.