A PHOTOABSORPTION, PHOTODISSOCIATION AND PHOTOELECTRON-SPECTROSCOPY STUDY OF C6H6 AND C6D6

The absolute photoabsorption, photoionisation and photodissociation cr oss-sections and the photoionisation quantum efficiency of benzene and hexadeuterobenzene have been measured from the ionisation threshold t o 350 Angstrom using a double ion chamber and monochromated synchrotro n radiation. The HeI excited photoelectron spectrum of C6D6 has been r ecorded 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 h igh-resolution photoelectron spectrum of C6H6. The photoabsorption spe ctrum displays extensive vibrational structure extending from the ioni sation threshold to similar to 730 Angstrom, and many of these absorpt ion features have been arranged into Rydberg series. A detailed assign ment of the vibrational progressions associated with some Rydberg stat es has been accomplished by making use of the corresponding photoelect ron spectrum. A sum rule analysis has been carried out by combining th e present absolute photoabsorption measurements with similar data cove ring the remaining wavelength regions. (C) 1998 Elsevier Science B.V.