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Resonance Raman spectra are obtained when the wave number of the exciting radiation is close to, or coincident with, that of an electronic transition of the scattering species. Such spectra are usually characterized by a very large enhancement of the intensities of particular Raman bands, sometimes with the appearance of intense overtone and combination tone progressions. The technique provides detailed information about excited electronic states because it is only the vibrational modes associated with the chromophore that are resonance‐Raman active. Additionally, the high sensitivity is such that compounds at concentrations as low as 10−6 mol/L may be detected, enabling resonance Raman spectroscopy to be used as an analytical tool and for the study of chromophores in molecules of biological interest.

Atmospheric pressure chemical vapor deposition of SnS 2 , Sn 2 S 3 , and SnS has been achieved onto glass substrates from the reaction of SnCl 4 with H 2 S at 300-545 °C. The films show good uniformity and surface coverage, adherence, and a variety of colors (black, yellow, brown, and gray) dependent on deposition temperature and film thickness. Growth rates were on the order of 1-2 µm min -1 . All the films were crystalline. For substrate temperatures of up to 500 °C single phase films with the hexagonal SnS 2 structure (a ) 3.65(1) Å, c ) 5.88(1) Å) were formed. At 525 °C a film of mixed composition containing predominantly orthorhombic Sn 2 S 3 (a ) 8.83(1) Å, b ) 3.76(1) Å, c ) 14.03(1) Å) was formed together with some SnS 2 . At 545 °C films with orthorhombic SnS structure (a ) 4.30(1) Å, b ) 11.20(1) Å, c ) 3.99(1) Å) were formed. Scanning electron microscopy (SEM) revealed a variety of different film thicknesses and morphologies, including needles, plates, and ovoids, dependent on the deposition temperature and time. Energy-dispersive X-ray analysis (EDX) and electron probe measurements on the films indicated elemental ratios close to those for tin disulfide (SnS 1.98 ), ditin trisulfide (SnS 1.60 ), and tin monosulfide (SnS 1.10 ) and revealed no incorporation of chlorine. X-ray photoelectron spectroscopy (XPS) gave results in agreement with those from EDX and revealed binding energies of Sn 3d 5/2 ) 486.5(1) eV and S 2p ) 161.6(2) eV for films grown at less than 500 °C (SnS 2 ), and Sn 3d 5/2 ) 485.7 (1) eV and S 2p 3/2 ) 161.0 eV for the film grown at 545 °C (SnS). Raman microscopy showed that the films of SnS 2 had bands at 315 and 215 cm -1 , those of Sn 2 S 3 had bands at 307, 251, 234, 183, 71, 60, and 52 cm -1 , and those of SnS had bands at 288, 220, 189, 163, and 96 cm -1 . The band gap of SnS 2 was 2.14 eV. Sheet resistance measurements showed that all of the films were essentially insulating.

The Raman spectra of plattnerite [lead(IV) oxide, PbO2] and of the lead pigments red lead (Pb3O4), lead monoxide [PbO, litharge (tetragonal) and massicot (orthorhombic)], lead white [basic lead carbonate, 2PbCO3.Pb(OH)2] and of their laser-induced degradation products were recorded using a range of different excitation lines, spectrometer systems and experimental conditions. The degradation of PbO2 is more extensive along the pathway PbO2-->Pb3O4-->PbO (litharge)-->PbO (massicot) the shorter the wavelength of the excitation line and the higher its power. The Raman spectrum of PbO2, which is black and of the rutile structure, is particularly difficult to obtain but three bands, at 653, 515 and 424 cm-1, were identified as arising from the b2g, a1g and e(g) modes respectively, by analogy with the corresponding modes of isostructural SnO2 (776, 634 and 475 cm-1). A further oxide was identified, PbO1.55, the Raman spectrum of which does not correspond to that of any of the laser-induced degradation products of PbO2 at any of the wavelengths used. The Raman results are critical to the future use of Raman microscopy for the identification of lead pigments on artworks.