الفهرس 
Cover EnglishOnly 14 pages are availabe for public view
 |  | from | 156 |  |  |
| | | from | 156 | | |
Abstract
Laser Induced Breakdown Spectroscopy (LIBS) has emerged in the past two decadesas a very promising technique for the analysis and characterization of a broad variety of objects of cultural heritageespecially bio-archeological samples such as calcified tissues namely teeth and bone. The most important advantages of LIBS from the archeological point of view are its quasi nondestructive nature and ts potential of performing in situmeasurements. In the present work human calcified tissue samples of recent and archeological bone samples have been studied via LIBS technique. The old samples were from four different ancient Egyptian dynasties representing the middle kingdom (1980–1630 B.C.), the 2nd ntermediate period (1630–1539/23 B.C.), Roman-Greek period (30 B.C.-A.D.395) and the late period (664–332 B.C.). from the obtained results it was possible to differentiate between recent and old samples in view of the emission intensities of the CN and C2 molecular bands. In addition, it was possible to classify the samples according to their age by obtaining the ratio of the ionic to atomic line intensity of calcium. Elements used to study dietary habits such as strontium (Srand barium (Ba) were analyzed and the interference of postmortem or diageni effects due to the burial conditions were investigated via LIBS analysis of soil samples taken from the same locations where the archeological bones have been excavated. In most laser-based analytical methods, the reproducibility of quantitative measurements strongly depends on maintaining uniform and stable experimental conditions. LIBS technique hasbeen used for quantitative analysis for biological samples;however accurateestimation of elemental concentration using LIBS needs some precautions. Calibration curves obtained from reference samples, and the plasma parameters have to be kept as constant as possible. Since calcified tissues such as bone are normally less “tough” in their texture than many other solid samples, especially metals,thus, the ablation process could change the sample morphological features rapidly, leading to poor reproducibility statistics. In he present work, three artificial reference sample sets have been fabricated. These samples represent 3 different calcium based matrices, calciumcarbonate matrix, bone ash matrix and calcium hydroxyapatite matrix. A comparative study of UV (266 nm) and IR (1064 nm) LIBS for these 3 sets of samples has been performed under similar experimental conditions for the two systems (laser energy, spot size,repetition rate, irradiance…etc.) to examine the wavelength effect. The analytical results demonstrated that UV-LIBS hasimproved reproducibility, and precisionof the results. Moreover, UV-LIBS provided stableplasma conditions, better linear fitting, and reduction of matrix effects. Bone ash could be used as a suitable standard reference material for calcified tissue calibration using LIBS with 266 nm excitation wavelength.In this thesis,comparative LIBS measurements of archaeological bone samples from four different dynasties have been performed using UV (266nm) and IR (1064nm) laser light to examine the wavelength effect.The analytical results demonstrated that UV-LIBS has morestable plasma conditions for samples from different dynasties. Such results are similar to that obtained using standard reference sample (bone ash) used for calibration. On the other hand, UV-LIBS results gave more reliable statistics for bone elemental composition within the same dynasty since itcould decrease the elemental fluctuation due to the physical changes in the samples from old dynasties subjected to longer postmortem effects.