APPLICATION OF CONTINUOUS EXTENDED SCANNING TECHNIQUES TO THE SIMULTANEOUS DETECTION OF RAMAN-SCATTERING AND PHOTOLUMINESCENCE FROM CALCIUM DISILICATES USING VISIBLE AND NEAR-INFRARED EXCITATION

A novel method of data acquisition is described for spectrographs employing charge-coupled device (CCD) detection. The technique, called continuous extended (CE) scanning, allows data collection over the full spectral range of the spectrograph, rather than a limited window determined by the wavelength, spectral dispersion, spectrograph focal length and detector dimensions. The CE method removes the need to sacrifice resolution for spectral range or the need to record and splice many spectral segments to reproduce a full-range spectrum. The advantages of this method are discussed and the capability is demonstrated with respect to several calcium disilicate minerals, recently shown to exhibit intriguing behaviour under near-infrared (NIR) excitation, including intense photoluminescence. Data obtained using both visible (514.5 nm) and MR (779.1 nm) excitation are presented and the results are briefly discussed in the light of recent Fourier transform Raman studies using 1064.1 nm excitation.