Induction and memory effects in the UV laser ablation of weakly absorbing van der Waals films

The ablation of thick (2≈ 15 μm) films of CH2Cl2 and C6H12 at 248 nm is studied by means of time-of-flight quadrupole mass spectrometry. For both compounds, desorption intensities are observed to exhibit a pronounced and well-defined dependence on previous irradiation of the films (‘induction’ and ‘memory’ effects). Weak absorption at the irradiation wavelength is shown to be a necessary condition for the observation of these effects. Plausible mechanisms are proposed.