The use of an unintensified charged-coupled device detector for low light level Raman Spectroscopy.

Spontaneous Raman scattering from adsorbates on surfaces is a powerful vibrational spectroscopy technique due to the very large frequency range and high resolution currently possible with visible lasers and spectrometers. Because of the extremely low Raman cross sections of nonresonant molecules, one must use either some sort of signal enhancement technique or long integrations using multichannel detection in order to have monolayer sensitivity. We have used a backthinned, unintensified, liquid nitrogen cooled charged-coupled device (CCD) detector to obtain high quality multichannel unenhanced Raman scattering spectra from organic monolayers on surfaces. This system has roughly a factor of ten greater sensitivity than intensified multichannel detectors currently on the market. A description of our detection system is given along with a comparison with other commercially available multichannel detectors suitable for low light level Raman spectroscopy.