Time-Resolved Laser-Induced Optoacoustic Spectroscopy

Abstract

The use of broad band piezoelectric detectors in optoacoustics permits the determination of yields of production and lifetimes (τ_T) of photoproduced transient states. After the absorption of the 15 ns laser pulse, the fast dissipated heat is related to the amplitude of the first pressure pulse h according to (1):

$$H = K \cdot \alpha \cdot {E_0} \cdot (1 - {10^{ - A}}),$$

(1)

where k is an apparative constant, e ₀ the pulse energy and a the absorbance of the sample. α is the fraction of absorbed energy dissipated as ‘prompt heat’, i.e. faster than the instrumental time resolution. This is determined by the transit time τ_a [1], the time that the pressure pulse needs to travel through the illuminated regiona. For a ’reference sample’ (τ_T ≪ τ_a) α = 1.0.