ToF-SIMS and other surface spectroscopies applied to the study of ancient artifacts: Preliminary investigation of a tetradrachm of Claudius
Notice bibliographique
Résumé
A group of ancient coins is among the Diniacopoulos collection of Central and Eastern Mediterranean antiquities housed at Queen's University. At first glance, nine coins in the collection appear to be billon tetradrachms minted in Alexandria, Egypt, dating to the period of the Emperor Claudius (41–54 AD). On the obverse, there is a portrait of the Emperor Claudius, on the reverse his wife Messalina is holding their two children. A closer examination reveals, however, that each of these coins weighs substantially less than the majority of specimens belonging to the same issues. All of the coins appear to have silver-rich plated surfaces with copper-rich cores. Questions are raised, therefore, about their authenticity and methods of manufacture. The surfaces display a variety of corrosion products, some of which may also indicate past restoration treatments. A single coin was selected for time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and energy dispersive x-ray analysis (EDX) analyses to investigate the viability of utilizing these combined techniques in the study of ancient coins. In order to gain information on the composition and distribution of the various chemical components present at the surface and into the bulk, it is necessary to profile into the sample, which by definition is destructive. Thus, it is important to identify areas of interest for further analysis so that the amount of damage can be minimized while maximizing the information obtained. To accomplish this, large area imaging ToF-SIMS has been performed using the stage-raster option in an IonTOF ToF-SIMS V. Bi3++ primary ions were used to map the surface and the positive secondary ion distribution images were obtained. Because of the varying topography of the sample, delayed onset of the generated secondary ion had to be used. Four areas were identified for further analysis, namely: (1) a Ag rich (minimal Cu content) area; (2) an area showing the presence of both Cu and Ag; (3) an area displaying visibly different surface characteristics, and finally, (4) a Cu rich (minimal Ag content) area. Chemical composition was obtained from these areas using XPS. To obtain further (nondestructive) depth information, EDX images were obtained, which would arise from a deeper sampling depth. In this case Ag was seen to be more dominant except for region (4). This implies a Cu enrichment at the surface as observed by the ToF-SIMS except for region (1). In this paper, the results of depth profiles in the bulk of the chosen areas are presented in order to ascertain the distribution of the various chemical components. This will allow future investigation on how the coins were manufactured.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,002 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».