TUNABLE NEAR-INFRARED RAMAN-SPECTROSCOPY

Approaches to generating fluorescence-free Raman spectra using excitation in the near-infrared (near-IR) region of the spectrum are not limited to the use of Fourier transform (FT) Raman spectroscopy. Although FT-Raman does introduce the well-established advantages of Fourier transform methods to the field of Raman spectroscopy, it is clearly not the only alternative to obtaining a Raman spectrum with near-IR excitation. The coupling of laser excitation at wavelengths longer than 700 nm with low noise multichannel detection can also produce fluorescence-free Raman spectra. In this paper we describe the capabilities and use of a slow scan camera system employing a silicon charge-coupled device (CCD) specifically fabricated with enhanced performance in the near-IR region of the spectrum as a detector for near-IR Raman spectroscopy. This highly sensitive detection method provides a convenient means to rapidly generate high-quality and nearly fluorescence-free spectra using a variety of excitation sources including diode lasers tuned beyond 800 nm. Examples of spectra generated with CCD detection and the FT-Raman technique are compared. A discussion of the appropriate conditions for application of the two approaches is also included.