Knowledge Bank

The transition near 310 run free base purine has been observed in the phosphorescence excitation spectra of matrix-isolated samples. The transition exhibits vibrational structure dominated by a progression in a frequency of about $850cm-1$. A vibrational assignment has been made. Extrapolated matrix shifts gives an estimated gas phase transition origin of 31 400 $cm-1$. Comparison of the spectrum with those from related molecules suggests that the transition is associated with the pyrimidine portion of the molecule. Specific matrix effects on the spectrum including an unusual shift in methane and the role of the state in determining the optical properties of purine and its derivatives will be discussed.