PRACTICAL AND CONVENIENT 355-NM AND 337-NM SHARP-CUT FILTERS FOR MULTICHANNEL RAMAN-SPECTROSCOPY

The interference from Rayleigh and other elastic scattering is a serious problem for multichannel Raman spectroscopy. This problem becomes more serious if the surface subjected to the excitation reflects stray light, particularly in front-face excitation and in systems using rotating samples or applying the flow technique to avoid local heating and accumulation of the protoproduct. In order to have an optimum TRR (Time-Resolved Raman Spectroscopy) signal, the ideal method is to apply a single spectrograph equipped with a sharp line elimination filter tuned to the wavelength of the exciting line. Several commercially available sharp-cut long-wavelength bandpass filters and a recently developed J-aggregate filter applying organic dye molecules are also useful for the elimination of exciting lines in the visible region. The authors have applied these filters in their TRR studies, and a significant improvement of the signal quality is obtained. Further development of sharp line eliminating filters for use at 266 nm (fourth harmonic of Nd:YAG laser) and several exciting lines of the excimer laser is currently in progress.