SiO 2: chlorophyll gels under 4He irradiation

SiO ₂ gels doped with chlorophyll extracted from natural leaves were exposed to different fluences of a 3-MeV ⁴He beam from the Instituto de Física Pelletron Accelerator. Optical absorption, emission and excitation spectra were measured as a function of fluence in the interval (0-2.5) × 10 ¹⁴ cm ^-2. Slight increases in both emission and excitation spectra at small fluences were observed. For larger fluences a characteristic exponential-type decay was produced due to degradation of the organic molecules. The data were fitted with a Lorentzian curve. A discussion of possible mechanisms is given in terms of the irradiation parameters.