Analysis of heritage stones and model wall paintings by pulsed laser excitation of Raman, laser-induced fluorescence and laser-induced breakdown spectroscopy signals with a hybrid system

Abstract

Analysis of heritage stone samples, alabaster, gypsum, limestone and marble, and model wall paintings was carried out with a laboratory, hybrid system based on the pulsed laser excitation of Raman, laser-induced fluorescence and laser-induced breakdown spectroscopy signals. The system is based on a nanosecond Q-switched Nd:YAG laser operating at its second (532 nm), third (355 nm) and fourth (266 nm) harmonics and a spectrograph coupled to a time-gated intensified charge coupled device for spectral analysis and detection with temporal resolution. For the stone samples, Raman spectra upon excitation at 355 and 532 nm display the characteristic vibration modes of SO 4 2of calcium sulphate, in alabaster and gypsum, and of free CO 3 2of calcium carbonate, in limestone and marble. Simultaneously acquired laserinduced fluorescence spectra reveal characteristic bands that help to distinguish materials of the same base chemical composition. Elemental composition of stone samples is obtained by laser-induced breakdown spectroscopy upon excitation at 355 nm. Spectra of all stone samples reveal their elemental composition that includes Ca, Na, Mn and Sr and the presence of molecular species such as CN, C 2 and CaO. Additional emission lines ascribed to Mg, Si, Al and K, appear with different intensities according to the nature of the stone material. Model wall paintings, based on a red pigment, prepared as fresco or mixed with two different binders, were also studied. The complementary information provided by the three spectroscopic modes allows the identification of the pigment as red vermillion and of the different preparations based on the pigment alone or in mixtures with linseed oil and egg yolk binders.

Characterization of medieval-like glass alteration layers by laser spectroscopy and nonlinear optical microscopy

“…However, calcite and aragonite show a vibration at the same frequency, V 1 1085 cm −1 , differentiated by the V 4 and lattice vibrations at the wavenumbers around 712 and 280 cm −1 for calcite and around 705 and 205 cm −1 for aragonite [67]. Given the bands observed we can conclude that the spectra reveal the presence of calcite polymorph [68]. These results agree with those retrieved by SEM-EDS and LIBS (Tables 1 and 2).…”

A Review on Laser-Induced Breakdown Spectroscopy in Different Cancers Diagnosis and Classification

“…For excitation and de-excitation purposes, a high-energy pulsed laser (Nd: YAG laser with typical wavelength 1,064 nm) is applied to the sample (usually within nanosecond range) in LIBS [29], because of its durability, ease of use, and high energy peak pulse. Similarly, Nd: YAG laser second and third harmonic wavelengths 532 and 355 nm are also often used as excitation sources [37,38]. The femtosecond (fs) laser is also used in various applications of LIBS [29].…”

Non-Linear Microscopy: A Well-Established Technique for Biological Applications towards Serving as a Diagnostic Tool for in situ Cultural Heritage Studies

“…It permits a large scanning area; it can identify the binding media on frescoes, but also gives information on the pigment distribution and degradation [63]. Due to limitations concerning the low spectral resolution and the modest distinction in spectral signatures, LIF is being combined with other spectroscopy techniques, such as Raman and LIBS, to investigate model wall paintings and heritage stone samples [64].…”