Fig. Experimental MS of FLU obtained with only the IR laser pulse for different intensities. The spectra were background-subtracted and normalized to the maximum intensity peak of the FLU monocation (C 13 H + 10 , m/z = 166) observed with the unattenuated data corresponding to a laser peak intensity of 6.8 × 10 13 W/cm 2 . Gray-shaded areas highlight the four peaks of interest: C + (m/z = 12), FLU 3+ (m/z = 55.3), FLU 2+ (m/z = 83), and FLU + (m/z = 166). The full-range spectrum in the logarithmic scale and signal dependencies of the intensities of these peaks as a function of laser intensities are given in the ESI.