Threshold photoelectron spectroscopy of ozone

Threshold photoelectron spectrum of ozone is presented for the first time at a resolution of 21 - 38 meV using synchrotron radiation in the energy region of 12 - 21 eV . The ionization energies of the first ionized states were determined and an interpretation of the O 3 spectrum with respect to its first three ionic states, 1 A 1 2 , 1 B 2 2 , and 1 A 2 2 , is presented. Above 16 eV the enhancement of the intensities of the 2 B 1 2 , 3 A 1 2 , and 4 B 2 2 band systems due to the contribution of indirect processes was observed, not accessible by conventional photoelectron spectroscopy. It was also resolved and assigned the extensive vibrational structures of ozone. Between 15.5 and 18.5 eV the main band contours are similar to those found in conventional photoelectron spectroscopy, except that our threshold photoelectron spectrum reveals extensive additional vibrational structures. The band 2 B 1 2 was found to present an irregular vibrational spacing Δ E , with a minimum value of 80 meV at ∼ 16.47 eV .