Towards a Solution of the Polycyclic Aromatic Hydrocarbon - Diffuse   Interstellar Band Hypothesis
  A novel theoretical method is developed to study the polycyclic aromatic hydrocarbon - diffuse interstellar band (PAH-DIB) hypothesis. In this method, a computer program is used to enumerate all PAH molecules with up to a specific number of fused benzene rings. Fast quantum chemical calculations are then employed to calculate the electronic transition energies, oscillator strengths, and rotational constants of these molecules. An electronic database of all PAHs with up to any specific number of benzene rings can be constructed this way. Comparison of the electronic transition energies, oscillator strengths, and rotational band contours of all PAHs in the database with astronomical spectra allows one to identify possible individual PAH carriers of some of the intense narrow DIBs. Using the current database containing up to 10 benzene rings we have selected 8 closed-shell PAHs as possible carriers of the intense lambda6614 DIB. 
Xiaofeng Tan