Proceedings e report - Firenze University Press

NIR ARCHAEOMETRY FOR ARCHAEOLOGICAL WOOD - OBSERVATION USING DEUTERIUM EXCHANGE
where A t (OH) and A t=0 (OH) are the integrated absorbances of the OH-related band measured at
saturated diffusion condition and before the start of the deuteration, respectively. The isolated left
wing -7000 cm -1 , and the integrated absorbance of ±20 cm -1 at 6718, 6600, 6450, and 6287 cm -1 were
employed for the calculation of the accessibilities of the Am, Sc, CI, CII and CIII regions, respectively.
Absorbance
1.5
1.0
0.5
0
-0.5
10000
Before deuteration,
thermal treatment time 0hour
After deuteration,
thermal treatment time 0hour
8000 6000
Wavenumber (cm
4000
-1 )
Wavenumber (cm-1 0
7000
6500
)
(a) (b)
198
Absorbance
0.3
0.2
0.1
A m Sc
C I
A m: >6950 cm -1
S c : 6718±20 cm -1
C I : 6600±20 cm -1
C II: 6450±20 cm -1
C III:6287±20 cm -1
Fig. 2; The variation of (a) NIR original spectra and (b) baseline corredted NIR spectra (7200-6000cm -1 ) with
deuterium exchange.
3.3. Variation of accessibility at OH-related absorption with thermal treatment time
Thermal changes of the saturation accessibilities in thermally-treated wood samples were observed.
During the initial stage of hydrothermal treatment up to tht = 10 hr, the saturation accessibilities of Am
(i.e. the amorphous region) rapidly increased with increment of tht. The increases of the saturation
accessibility suggest that the inter-microfibril space has expanded causing disintegration in wood cell
wall, and that, consequently, the region itself disappears locally. In the case of Sc originating from the
semi-crystalline regions, the saturation accessibility for D2O also increased. Also in the cases of CI, CII
and CIII, the saturation accessibilities for D2O increased. From the observation of variation of
accessibility with the thermal treatment time, respectively, we could find the supermolecular
difference of the fine structure in the microfibrils in the cell walls.
Accessibility
100
80
60
40
20
0
Am Sc CI CII CII I
0 20 40 60 80 100 120 140 160
Thermal treatment time (hour)
C II
C III
6000
Fig. 3- The variation of accessibility of amorphous
(Am), semi-crystalline (Sc), crystalline regions (CI, CII,
CIII) in cellulose with thermal treatment time.
Acknowledgement
This study was partly supported by Research Fellowship for Young Scientist from the Japan Society
for the Promotion of Science (grant numbers 20007231).
References
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Spectrosc. Rev. 42: 43-71.
2. S. Tsuchikawa, H. Yonenobu and H. W. Siesler (2005): Near-infrared spectroscopic observation
of the ageing process in archaeological wood using a deuterium exchange method The Analyst,
130: 379-384.