For the acquisition of high-quality ultraviolet resonance Raman spectra of strongly scattering samples such as membrane protein suspensions, an f /3.5 Littrow prism prefilter has been designed, built, and characterized. This prefilter has a Czerny-Turner configuration, and its focal length is 25 cm. The apex angle of the dispersive prism (20 ) was chosen to provide maximum performance in the 220 to 240 nm range. The prism prefilter significantly reduced stray background due to Rayleigh scattering and visible fluorescence, while maintaining a low dispersion of 1300 cm-1/mm at 253 nm as well as a large fl /3.5 aperture. The sharpness of the transmission edge (at 242 nm, the T = 0% to 95% transition occurs in 1.3 nm) quantitates its effectiveness as a sharp-cut Rayleigh scattering filter. The total throughput of the prefilter is ~60% at 235 nm and 50% at 632.8 nm. The utility of this prefilter is demonstrated by obtaining high signal-to-noise resonance Raman spectra of bacteriorhodopsin in a purple membrane suspension with 239.5 nm excitation.
Shoji Kaminaka and Richard A. Mathies, "High-Throughput Large-Aperture Prism Prefilter for Ultraviolet Resonance Raman Spectroscopy," Appl. Spectrosc. 52, 469-473 (1998)