The spectrum of V v has been observed by using a vacuum sliding spark at 1000-A peak current. Fifty-nine lines in the region 480–8500 Å have been observed and interpreted as transitions among 29 levels, 19 of which are new. The ionization energy is determined as 526 524 ± 5 cm-1. An isoelectronic comparison confirms the inversion of the 3p64ƒ2F5/2, 7/2° levels as being caused by their interaction with those of the 2F° term in the 3p5 3d2 configuration.
Cornelius H. H. Van Deurzen, John G. Conway, and Sumner P. Davis, "Spectrum and energy levels of quadrupole-ionized vanadium (V v)," J. Opt. Soc. Am. 64, 498-502 (1974)