Superficial and Shroud-like coloration of linen by short laser pulses in the vacuum ultraviolet.

We present a survey on five years of experiments of excimer laser irradiation of linen fabrics, seeking a coloration mechanism able to reproduce the microscopic complexity of the body image embedded onto the Shroud of Turin. We achieved a superficial, Shroud-like coloration in a narrow range of irradiation parameters. We also obtained latent coloration that appears after artificial or natural aging of linen following laser irradiations that, at first, did not generate any visible effect. Most importantly, we have recognized photochemical processes that account for both coloration and latent coloration.