Micro-Raman Spectroscopy Case Study
Micro-Raman Spectroscopy
Raman spectroscopy is a micro-analytical method that showed many advantages in analysis of cultural heritage materials. It is a form of vibrational spectroscopy that allows the identification of particles in homogeneous materials in the micron order. The identification is employed on the basis of the molecular vibrational spectra of samples, obtained by excitation with visible laser light. In micro-Raman spectroscopy, the laser beam is focused by means of a microscope objective employing a backscattering configuration (Perardi, Zoppi and Castellucci 2000).
Case study
Red pigment samples were collected from Roman over-paintings dated back to the reign of the Emperor Diocletian (the late 3rd century AD). These …show more content…
Furthermore, modern software algorithms help to obtain quantitative analysis. This technique works on the fact that bonds and groups of bonds vibrate at characteristic frequencies. A molecule that is exposed to infrared rays absorbs infrared energy at frequencies which are characteristic to that molecule. Then, the resulting FT–IR spectra are compared and matched with known signatures of identified materials in the FT–IR library (Bruni et al. 1999).
Case study
Pigment samples were collected from the monastery of Saint Anthony in Egypt. The origins of the monastery are due to the 4th century AD. FTIR–ATR spectra were collected on a Perkin Elmer spectrometer 400 equipped with an ATR detector (attenuated total reflectance) in the wavelength range of 4000–650 cm–1, at a spectral resolution of 4 cm–1 over 32 scans. In attenuated total reflectance (ATR) spectroscopy, the sample is placed in contact with a special crystal (e.g., zinc selenide, ZnSe). Figure 6 shows FTIR–ATR spectrum of the green paint sample. Mineralogical species of the green earths can be distinguished in the 3400–3700 cm−1 and 950–1100 cm−1 range. Glauconite was characterized by the broad peaks in the 1100–944 cm−1 region. (see Figure …show more content…
These measurements help in the registration of the characteristic reflectance spectra and the detection of the chromatic alterations. Measuring devices, such as spectrophotometers and tristimulus colorimeters, provide a numeric expression of color that is based on mathematical conversions of tristimulus values. Also, measurement reproducibility is also greatly affected by surface uniformity, which is significant, as surfaces of wall paintings tend to be quite irregular (Schilling et al. 1993). One of the most common numeric systems for expressing color or color difference is CIELAB
Raman spectroscopy is a micro-analytical method that showed many advantages in analysis of cultural heritage materials. It is a form of vibrational spectroscopy that allows the identification of particles in homogeneous materials in the micron order. The identification is employed on the basis of the molecular vibrational spectra of samples, obtained by excitation with visible laser light. In micro-Raman spectroscopy, the laser beam is focused by means of a microscope objective employing a backscattering configuration (Perardi, Zoppi and Castellucci 2000).
Case study
Red pigment samples were collected from Roman over-paintings dated back to the reign of the Emperor Diocletian (the late 3rd century AD). These …show more content…
Furthermore, modern software algorithms help to obtain quantitative analysis. This technique works on the fact that bonds and groups of bonds vibrate at characteristic frequencies. A molecule that is exposed to infrared rays absorbs infrared energy at frequencies which are characteristic to that molecule. Then, the resulting FT–IR spectra are compared and matched with known signatures of identified materials in the FT–IR library (Bruni et al. 1999).
Case study
Pigment samples were collected from the monastery of Saint Anthony in Egypt. The origins of the monastery are due to the 4th century AD. FTIR–ATR spectra were collected on a Perkin Elmer spectrometer 400 equipped with an ATR detector (attenuated total reflectance) in the wavelength range of 4000–650 cm–1, at a spectral resolution of 4 cm–1 over 32 scans. In attenuated total reflectance (ATR) spectroscopy, the sample is placed in contact with a special crystal (e.g., zinc selenide, ZnSe). Figure 6 shows FTIR–ATR spectrum of the green paint sample. Mineralogical species of the green earths can be distinguished in the 3400–3700 cm−1 and 950–1100 cm−1 range. Glauconite was characterized by the broad peaks in the 1100–944 cm−1 region. (see Figure …show more content…
These measurements help in the registration of the characteristic reflectance spectra and the detection of the chromatic alterations. Measuring devices, such as spectrophotometers and tristimulus colorimeters, provide a numeric expression of color that is based on mathematical conversions of tristimulus values. Also, measurement reproducibility is also greatly affected by surface uniformity, which is significant, as surfaces of wall paintings tend to be quite irregular (Schilling et al. 1993). One of the most common numeric systems for expressing color or color difference is CIELAB