Applications of a new 206.5-nm continuous-wave laser source: UV Raman determination of protein secondary structure and CVD diamond material properties

We demonstrate the utility of a new 206.5-nm continuous-wave UV laser excitation source for spectroscopic studies of proteins and CVD diamond, Excitation at 206.5 nm is obtained by intracavity frequency doubling the 413-nm line of a krypton-ion laser, We use this excitation to excite resonance Raman spectra within the pi-pi* amide transition of the protein peptide backbone. The 206.5-nm excitation resonance enhances the protein amide vibrational modes. We use these high signal-to-noise spectral data to determine protein secondary structure, We also demonstrate the utility of this source to excite CVD and gem-quality diamond within its electronic band-gap. The diamond Raman spectra have very high signal-to-noise ratios and show no interfering broad-band luminescence. Excitation within the diamond bandgap also gives rise to narrow photoluminescence peaks from diamond defects. These features have previously been observed only by cathodoluminescence measurements, This new continuous-wave UV source is superior to the previous pulsed sources, because it avoids nonlinear optical phenomena and thermal sample damage; Photoluminescence.