Ion beam analysis of light elements in cultural heritage materials

1. Centre de recherche et de restauration des musées de France, C2RMF, Palais du Louvre - Porte des Lions, 14 Quai François Mitterrand, 75001 Paris, France
2. PSL Research University, Chimie ParisTech-CNRS, Institut de Recherche Chimie Paris, UMR8247, 75005 Paris, France

IBA application to Art and Archeology is a vibrant and innovating field. While PIXE remains the predominant technique owing to an easy implementation in air, alternate ones such as BS, ERDA and NRA exhibit attractive features, notably an unrivaled ability to non-destructively quantify light elements. Elements from hydrogen to fluorine are often present in cultural heritage materials where they play a key role; their direct determination is thus highly relevant. While external beam implementation of NRA, EBS and ERDA is challenging, progress made over years permits to carry them out at ambient pressure with a quality reaching that obtained in vacuum. After a quick review of the IBA techniques suitable for the measurement of light elements in heritage materials, this contribution focus on specific developments and results obtained with a small accelerator (less than 2 MV) and classical ion beams (excluding deuterons and heavy ions), in the present case with the AGLAE facility of the C2RMF.

Hydrogen is the first and most important light element. It is implied in hydration and weathering processes affecting, for instance, the surface of ancient glass. Concentration in hydrogen can be determined using ERDA with He beams to provide insights on the preservation state of historical objects and hydrogen depth profile can be used as an authentication criterion to detect fakes. Boron, a fluxing agent used in modern glassmaking was found to be also an important tracer in Renaissance glazed ceramic; its measurement by PIGE allowed discriminating between historical ceramic productions. Identification of organic matter usually requires sampling for identification by GC-MS or IRTF, but quantification of organic compounds is particularly difficult. EBS permits to determine non-destructively the absolute carbon content which is very useful, for example, in the estimation of the binder/pigment ratio in paintworks. The dating of ancient bones by C-14 AMS requires the presence of sufficient preserved quantities of ancient collagen. Quantitative concentrations of nitrogen can be obtained using the reaction ¹⁴N(α,pγ)¹⁷O to quantify the presence of this amino acid, providing a quick and non-destructive test before undertaking the dating of prehistoric bones.