Basic studies on the identification of excavated archaeological textile fibers using polarized FT-IR micro-spectroscopy [II] - The investigation of the infrared dichroism of ramie

Abstract

The precise identification of bast fibers such as ramie and hemp found at several archaeological sites is a very difficult problem because organic materials are usually heavily degraded during the long term preservation at underground or mound. Both excavated ramie and hemp usually show very similar degraded FT-IR spectra (glober light source). The authors are continuing to study the identification of several kinds of archaeological silk and vast fibers using BL43IR beam line (FT-IR micro-spectroscopy) at SPring-8. It has already known that excavated ramie and hemp show the possibility of distinguish ramie from hemp under polarized light source. In this report, various modern ramie fibers are analyzed by detailed IR polarization measurement. As a result of the measurement, the absorption band of 1160 cm-1 disappeared at 45° (angle of polarizer) irrespective of sample history. In the next measurement, the disappearance angle of specific peak of modern hemp (several origins) will be confirmed. The determination of specific disappearance of certain peak for ramie or hemp will be effective for the identification of each fiber.