Conclusions The calculated excitation energies of three low-lying states in bicyclobutane are nearly degenerate at 6.9 eV and have essentially 3P Rydberg character. The calculated 3P Rydberg states correspond to a broad ab- sorption band which peaks at 6.6 eV. The sum of the calculated oscillator strengths for these states agrees well with the measured oscillator strength. The predicted 4P Rydberg states correspond to a broad absorption band with a peak at 7.8 eV. The sum ...
