PICOSECOND IR STUDY OF THE UV PHOTOINDUCED DECOMPOSITION OF BIS(NAPHTHOYL)PEROXIDE AND OF A NAPHTHYL PEROXYCARBONATE

Picosecond UV pump/IR probe experiments were carried out on bis(1-naph thoyl)peroxide (1) and on tert-butylperoxy-2-naphthylcarbonate (2) dis solved in CCl4. After excitation by a 308 nm pulse the formation of CO 2 is measured with a time resolution of 1.8 ps via the IR-absorption o f the nu(3)-mode at around 2340 cm(-1) for delay times up to 550 ps. A pronounced temporal and spectral evolution of the nu(3)-absorption ba nd of CO2 is found which is assigned to the initial formation of vibra tionally excited CO2 and subsequent vibrational cooling by energy tran sfer to the surrounding solvent. CO2 concentration versus time profile s are obtained from the time dependence of the integrated nu(3)-band a bsorbance. The data suggest that 2 decomposes in a consecutive stepwis e process whereas 1 undergoes concerted bond scission leading to CO2 f ormation within the time resolution of the experiment.