Picosecond time-resolved S2→S0 fluorescence of xanthione in different fluid solvents

Effects of Solute-Solvent Interactions on Radiationless Decay of Thioketones Excited to Their S2- and T1-States

“…Deuteration of benzene practically affects neither the S2-state lifetime nor the quantum yield of xanthione fluorescence. In C 6 H 6 , τF is 11 ps [15,17] or 12 ps [18], whereas in C 6D6 , τF = 12 ps [15,17]. In both solvents φF was determined to be 2 x 10 -3 [15].…”

“…In this way, the use of benzene permits investigation of physical and π-electron (quantum mechanical type) interactions with thione molecules. This should lead to highly efficient deactivation of the S2-states [7,10,17,18] and to formation of excited complexes (exciplexes) which are untypical in the sense that they are formed in the S2-state, which provides a possibility of their deactivation to lower, bonding exciplex states. Moreover, the results obtained with benzene used as solvent can be compared with the data from earlier studies of transient absorption in thiones performed in the picosecond [18,20], nanosecond and microsecond [14,31,32] scale in benzene.…”

“…5 recorded in the long-wave part of the spectum. This peak has been ascribed to the S2 → Sn absorption realizing that as it appears in the first picoseconds after excitation it must be due to the directly excited individuum (singlet XT), and the time width of this peak corresponds to the lifetime of XT in the S2 state (11 ps [17]) convoluted with the width of the exciting pulse. Moreover, the spectrum of this absorption corresponds to the S2 → Sn absorption recorded by Hochstrasser et al [18].…”

“…3, the transient absorption spectum of XT in C6H6 includes two main components: the S2 -Sn absorption of short duration and the slowly increasing Τ1 -Tn absorption of long duration which disappears in the scale of microseconds. The former band disappears in about 20 picoseconds as a direct consequence of a very short lifetime of xanthione in the S2-state which in C6H6 is only 11 ps [17]. After this state has decayed, all other singlet states of XT are also empty as they live shorter than the S2-state.…”

“…alkanes) the transient individua are radicals. Despite many attempts, emission studies have so far failed to provide either direct evidence of existence of such individua or indirectly determine their properties [7,10,17]. Moreover, a few attempts have been made to use transient absorption spectroscopy with picosecond resolution to study the S2-thione decay and to search for the transient individua.…”