Figure 3.

(A) The AFS light-induced action spectrum of a bR film obtained using (tunable) dye laser excitation. The solid line represents the measured absorption spectrum, while the points represent alterations in the position sensitive detector voltage (PSDV) as a function of the excitation wavelength (normalized to the variation in pulse intensity). (B) Action spectrum of the AFS back-photoreaction monitored in a two-pulse experiment. The first laser (532 nm) drives the bR photocycle, while the second (tunable dye) laser pulse is fired with a delay of 100 μsec. The points represent the net effect of the second laser after correcting the effects due to its absorption by bR molecules, which have not been photocycled by the first pulse. The net effect of the second pulse, denoted as Δ (ΔPSDV), is to reverse the AFS signal. The points represent this signal reversal as a function of the dye laser wavelength. The solid line, representing the best fit curve, closely coincides with the absorption spectrum of the M intermediate.