A photoabsorption, photodissociation and photoelectron spectroscopy study of C6H6 and C6D6

The absolute photoabsorption, photoionisation and photodissociation cross-sections and the photoionisation quantum efficiency of benzene and hexadeuterobenzene have been measured from the ionisation threshold to 350 Angstrom using a double ion chamber and monochromated synchrotron radiation. The HeI excited photoelectron spectrum of C6D6 has been recorded and the vibrational structure exhibited in the (XE1g)-E-2, A(2)E(2g), (EB1u)-B-2 and F(2)A(1g) bands has been analysed with the aid of theoretical predictions and by analogy with the recently reported high-resolution photoelectron spectrum of C6H6. The photoabsorption spectrum displays extensive vibrational structure extending from the ionisation threshold to similar to 730 Angstrom, and many of these absorption features have been arranged into Rydberg series. A detailed assignment of the vibrational progressions associated with some Rydberg states has been accomplished by making use of the corresponding photoelectron spectrum. A sum rule analysis has been carried out by combining the present absolute photoabsorption measurements with similar data covering the remaining wavelength regions. (C) 1998 Elsevier Science B.V.