Control of singlet excited state kinetics by stimulated emission

Abstract EN

For testing mechanisms, stimulated emission of an excited reaction partner is a clean and powerful alternative to quenching.

This is shown in the case of the Forster cycle: ROH *hv-+ ROH*-> RO* + H3CT ——> RO' + H30+-> ROH.

A small percentage of a ruby laser pulse serves for excitation of ROH at 347 nm; the main portion is used for generating pulses for stimulated emission of RCT* at 520 nm, using a dye laser together with a laser amplifier.

The stimulation power of 0.2 MW/cm2 giving half the value of RO"* fluorescence quantum yield was found to be in accordance with a theoretical estimate.

Stimulated emission, namely deactivation of RO'*, increases the amount of fast geminate recombination of RO' ...H30+ at the expense of detectable free ions in the ground state.

Various features which are not explained in the present state of knowledge are reported.