We use a pump-probe technique to measure the change in optical transmission through a 1 cm C₆₀/benzene (0.58 g/l) solution caused by a 532 nm 25 ps `pump' pulse having fluence up to approximately 10 mJ/cm². Temporal dependence indicates that transmission drops within the pump pulse width and stays at the reduced level up to our maximum delay time (approximately 10 ns). If we use the standard three-level model for the C₆₀ molecule we deduce that either the excited-singlet-to-triplet crossing happens faster than our pulse width or the two states have indistinguishable absorption cross-sections ((sigma) _S approximately equals (sigma) _T) at our laser wavelength. We believe that the latter assumption is more probable, and interpret our data by a simple two-cross-section ((sigma) _O, (sigma) _T) model. We find that the difference (sigma) _T - (sigma) _O is (3.5 +/- 0.2) X 10^-17 cm². We measure the ground state absorption cross-section (sigma) _O to be (3.5 +/- 0.3) X 10^-18 cm² in an independent experiment.

Date Published: 15 May 1994
PDF: 9 pages
Proc. SPIE 2143, Organic, Metallo-Organic, and Polymeric Materials for Nonlinear Optical Applications, (15 May 1994); doi: 10.1117/12.173827

Published in SPIE Proceedings Vol. 2143:
Organic, Metallo-Organic, and Polymeric Materials for Nonlinear Optical Applications
Seth R. Marder; Joseph W. Perry, Editor(s)