High-fluence laser photoluminescence in C60 solutions

摘要

The nonlinear absorptive properties of C$-60$/ are of significant interest. In this paper we describe spectral emission measurements on C$-60$//toluene solutions and neat toluene in the fluence regime of 3 to 1500 J/cm$+2$/ excited by nanosecond and picosecond pulses. Ten emission lines between 547 nm and 635 nm are observed in both toluene and C$-60$/ solutions. These lines are found to correlate well with published Raman spectra of toluene. In C$-60$/ solutions an additional broad double feature is observed with peaks at 692 nm and 732 nm matching the published fluorescence spectra of C$-60$/. At the highest fluences a broad new feature appears at 655 nm, grows nonlinearly, and saturates in the C$-60$/ solution. In the blue spectral region, at wavelengths shorter than the pump wavelength, a plethora of lines are observed in neat toluene between 340 and 520 nm and found to correlate with molecular disassociation products. No evidence for breakdown, however, is apparent in the C$-60$/ solutions. Both neat toluene and C$-60$/ solutions show evidence of photochemical reaction.