Debating Christianity and Religion

SHROUD-LIKE COLORATION OF LINEN BY NANOSECOND LASER PULSES IN THE VACUUM ULTRAVIOLET

P. DI LAZZARO, D. MURRA, A. SANTONI
ENEA Unit Tecnica Sviluppo di Applicazioni delle Radiazioni
Laboratorio Sorgenti di Radiazione
Centro Ricerche Frascati, Roma

E. NICHELATTI
ENEA Unit Tecnica Tecnologie dei Materiali
Laboratorio Sviluppo e Realizzazione di Componenti Ottici
Centro Ricerche Casaccia, Roma

G. BALDACCHINI
ENEA Guest

Abstract
We present a survey on five-years experiments of excimer laser irradiation of linen fabrics, seeking for 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 distinct photo-chemical processes that account for
both coloration and latent coloration. These processes may have played a role in the generation of the body image on
the Shroud of Turin.

Keywords: Excimer laser, Latent image, Coloration depth, Photo-chemistry, Shroud of Turin

After years of exhaustive study and data evaluation, STURP team achieved the following results:
a) The body image is not painted, nor printed. X-ray, fluorescence and microchemistry on the
fibers preclude the possibility of paint being used as a method for creating the image [7, 8, 11, 12].
Ultraviolet and infrared evaluation confirm these studies [3, 5, 6, 10].
b) Both kinetics studies and fluorescence measurements support the image was formed by a low-
temperature process. In fact, the temperature was not high enough to change cellulose within the
time available for image formation, and no char was produced [12, 14].
c) The Shroud's image is superficial as the color resides on the outer surface of the fibers that
make up the threads of the cloth [8, 11]. Recent measurements on image-fibers of the Shroud [19]
confirmed that the coloration depth is extremely thin, approximately 200 nm, which corresponds to
the thickness of the primary cell wall of the linen fiber [22]. In a single linen thread there are some
200 fibers.
d) The colored (image) fibers are brittle, show "corroded" surfaces and are more fragile than
uncolored fibers [8, 11].
e) The shallow coloration of the Shroud image was formed by an unknown process that caused
oxidation, dehydration and conjugation of polysaccharide structure of fibers, to produce a
conjugated carbonyl group as the chromophore [8, 11, 12]. In other words, the color is a result of
an accelerated aging process of the flax.
f) The image seen at the macroscopic level is an areal density image. This means shading is not
accomplished by varying the color, but by varying the number of colored fibers per unit area at the
microscopic level [5, 9, 11, 12].

We first irradiated linen fabrics with two XeCl excimer lasers
(wavelength emission = 0.308 m) emitting pulses lasting, respectively, 120 ns and 33 ns [32 -
34]. The analysis of the results, summarized in 3, suggested that a radiation with shorter than UV
wavelength would have allowed a coloration more similar to that of the Shroud. Our choice was the
ArF excimer laser that emits in the vacuum ultraviolet (VUV) at = 0.193 m, and the results [35 -
38] are summarized in 4.

Let us summarize in the following the main results we achieved.

I. We obtained a linen coloration only in a narrow range of laser parameters. In particular, the
temporal duration of the single laser pulse must be shorter than 50 ns [32, 33].

II. The most interesting results were obtained with VUV light. The permanent linen coloration is a
threshold effect, i.e. the color is obtained only when F T > 22 J/cm 2 , see Table. When F T > 60
J/cm 2 the linen is ablated and/or vaporized, while when F T < 13 J/cm 2 the linen does not change
color. Even when F T is in the coloration range, not all the irradiated fibers are colored (Figs. 5
and 16) due to the spatial fluctuations of energy density of the laser pulses shown in Fig. 15.

III. We triggered a photochemical coloration process. In fact, the thermal heating associated with
UV and VUV radiation is within a few degrees centigrade and therefore irrelevant for the
purpose of coloring by scorching linens, see Fig. 13. This result fits with the "cold" coloration
process of the Shroud estimated in [8, 11, 12].

IV. The hue of color mainly depends on the wavelength of the radiation and on the number of
pulses incident on linen, which is proportional to F T . Irradiations at 0.308 m generate a
brownish coloration, while the 0.193 m photons produce a yellow color, see Fig. 4, similar to
the color of the Shroud image. In both cases, the contrast slowly increases with the number of
laser pulses, allowing an accurate control of the RGB value by varying F T .

V. The different hue of color obtained by UV and VUV radiation is due to different chains of
photochemical reactions respectively triggered. In particular, the VUV radiation at 0,193 m is
absorbed by alkene groups in degraded cellulose, whose number increases with F T , thus
inducing a photolysis of the cellulose which promotes the formation of chromophores, see Fig.
14. These chromophores determine the yellow coloration of the fibers [8, 12, 41, 42].

VI. We observed an irradiated fiber whose coloration was confined in the primary cell wall [36, 37],
which is comparable with the thinnest coloration depth observed in the fibers image of the
Shroud of Turin [8, 11, 19].

VII. After laser irradiations that do not produce a visible coloration of linen, a latent coloration
appears either by artificial (Fig. 8) or natural ageing of linen [33, 36]. Latent coloration is
interesting on the one hand for the synergy between UV, oxidation and the dehydrating effect of
heat (or of aging) which triggers the coloration process, and on the other hand for historians,
attracted by the possibility that the Shroud image may have developed over time (years) from
the moment the process of latent coloration acted.

VIII. The partial inhibition of fluorescence induced by VUV laser radiation (Fig. 9) is an additional
feature of our coloration similar to the Shroud image. The induced fluorescence is also capable
to selectively recognize the uniformity of F T incident on linen, cf. Figs. 9a and 9b.

IX. Both UV and VUV light coloring linen is compatible with the absence of image under the
bloodstains on the Shroud, because in this spectral region light is absorbed by very thin layers of
blood hemoglobin. According to [46] the UV light may be responsible for another very special
feature of the Shroud, the red color of blood stains after so much time since their deposition.23

X. Using a petrographic microscope, we have observed some defects induced by UV radiation in
the structure of irradiated linen fibers, see Fig. 12, similarly to very old linen fabrics, including
the image fibers of the Shroud [11, 47].

XI. A highly unconventional hypothesis about the origin of the Shroud image was proposed in [15],
which assumes a corpse emitting electromagnetic radiation. Although this hypothesis is out the
realm of Science, we note VUV light is compatible with both the shading correlation with cloth-
body distance and the absence of side images expected from it. This is because VUV photons
are strongly absorbed by air, so the greater the distance in air the VUV light must travel, the
lower the percentage of light impinging on linen, and less likely the intensity of the residual
light is above threshold to color the linen (see item II above). Since the sides of the body are
more distant from the cloth than frontal and dorsal area, it is obvious that the alleged light
emitted from the bodys sides would have had a low probability to color the linen.

XII. Absolute reflectance measurements show that when irradiated in the UV and VUV, our linen
behaves like the linen of the Shroud.

In summary, our results demonstrate that a short and intense burst of directional VUV radiation can
color a linen cloth so as to reproduce many of the peculiar characteristics of the image on the
Shroud of Turin, including the hue of color, the shallow penetration depth of the color, the
inhibition of fluorescence. The work summarized in this paper shows that the excimer laser is a
tool suitable to study in detail the physical and chemical processes that might have played a role in
the generation of the Shroud body image, regardless of the source of radiation (or energy) that may
have caused this image.

The Shroud image has characteristics that we have been able to reproduce only in part, for example
the gross shading structure that is determined by the ratio of yellow to uncolored fibers in a given
area, see point f) in 1 and Fig. 16. As discussed in 8.1, there are sophisticated diffractive optics
that allow replicating these features, but this effort is far beyond our goal. In fact, our purpose was
not to demonstrate that a battery of ten thousand lasers can accurately reproduce the image on the
Shroud. Our main purpose was to perform accurate, controlled and reproducible experiments, apt to
understand the details of the physical and chemical mechanisms that have produced the Shroud
image, thanks to a powerful and versatile tool such as the laser. In this frame, our experimental data
can be helpful to scholars seeking a linen coloration with experiments such as corona discharge
[18] or electrostatic discharge and radon emitted during seismic events [48] which involve UV and
VUV light but are difficult to control and characterize.

We are not the conclusion, we are composing pieces of a fascinating and complex scientific puzzle.
The enigma of the body image of the Shroud of Turin is still "a challenge to our intelligence" [49].

"However, Enea scientists warn, "it should be noted that the total power of VUV radiations required to instantly color the surface of linen that corresponds to a human of average height, body surface area equal to = 2000 MW/cm2 17000 cm2 = 34 thousand billion watts makes it impractical today to reproduce the entire Shroud image using a single laser excimer, since this power cannot be produced by any VUV light source built to date (the most powerful available on the market come to several billion watts )".

The Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile (ENEA) (Italian National Agency for New Technologies, Energy and Sustainable Economic Development) is an Italian Government-sponsored research and development agency. The agency undertakes research in areas which will help to develop and enhance Italian competitiveness and employment, while protecting the environment. ENEA is an acronym that stands for Energia Nucleare ed Energie Alternative ("Atomic Energy and Alternative Energy").