A Physical Hypothesis on the Origin of the Body Image Embedded into the Turin Shroud by Paolo Di Lazzaro (dilazzar@frascati.enea.it). Friday, August 15, 2:00 p.m.�2:30 p.m.

 The body image of the Turin Shroud has not yet been explained by traditional science so a great interest in a possible mechanism of image formation still exists. Here we present preliminary results of irradiation of a raw linen fabric and of a linen cloth, both uncovered and covered by a thin polysaccharides layer, using distinct Excimer Lasers having different emission wavelengths (namely, 308 nm and 193 nm) and different pulse-widths (120 ns, 30 ns, and 12 ns). We obtained a permanent coloration of linens (both sugared and unsugared) as a threshold effect on the laser beam intensity (energy per unit area per unit time). The coloration can be achieved only in a narrow range of irradiation parameters, which are strongly dependent on the laser pulse-width and on the sequence of laser shots, including time interval between consecutive shots and number of bursts. These results suggest that the coloration may be due to the addition, with different weights, of the ultraviolet induced photochemical effect and of the thermal effect, both acting to dehydrate the linen fibers.

 We also obtained the first direct evidence of latent images impressed on linen that appear in a relatively long period (one year) after a laser irradiation that at the moment did not generate a visible image.

 The main results (depth of coloration, color distribution, fibers morphology, appearance in cross polarized light, and ultraviolet induced fragility of single yarns) are compared to the characteristics of the Turin Shroud, comment�ing the possibility that a burst of directional ultraviolet radiation may have played a role in the formation of the Shroud image.