Assignment of the VUV electronic spectrum of allene

Early assignments of the vacuum UV photoabsorption spectrum of allene (1951–1972) gave a number of Rydberg series, but these series had limiting values for the ionization potential, which are incompatible (by up to 0.4 eV) with more recent adiabatic IPs from molecular beam and high resolution photoelectron spectra (UV-PES). We have performed a re-analysis of the VUV spectrum of allene by a combination of overlay of the VUV and UV-PES spectra which leads to new experimental assignments. Major differences in assignment to the early studies are reported, and these include the lowlying Rydberg states, which are now assigned as follows: 6.55 (3s), 7.2 (3p), 8.15 (3d), and 8.25 eV (4s), respectively, with further assignments up to 6s, 6p, and 6d.