Development of a compact high-resolution spectrometer for multi-line UV Raman spectroscopy

Abstract

We report on the development of a compact and robust instrument for multi-line ultraviolet resonant Raman spectroscopy. This instrument will be able to collect simultaneous full-range (800-4000 cm 1 ) high-resolution Raman spectra resulting from resonance-enhanced excitation at multiple UV laser wavelengths. The resulting matrix of spectra will allow the identification and analysis of several organic chemical compounds of interest for the detection of extraterrestrial life, including amino acids and nucleosides. This instrument is being developed under NASA's Planetary Instrument Definition and Development Program, and we will also discuss its potential contributions to future planetary exploration missions.

Selection of Portable Spectrometers for Planetary Exploration: A Comparison of 532 nm and 785 nm Raman Spectroscopy of Reduced Carbon in Archean Cherts

“…When using a visible source such as the 532 nm laser to be used by the RLS, fluorescence will be a problem; however, the resonance effect that occurs in organic molecules at this wavelength means they are readily detected. Upon shifting to a UV excitation source (e.g., 248 nm), the fluorescence becomes spectrally separated from the Raman signal since it occurs at a fixed wavelength, whereas Raman shifts are relative to the excitation wavelength (Kohel et al, 2010). This produces spectra with an almost flat baseline.…”

Raman spectroscopy on Mars: identification of geological and bio-geological signatures in Martian analogues using miniaturized Raman spectrometers

“…In 2004, MMRS was ranked Category One in the MSL payload selection [35], but further development to improve its science capability and Technology Readiness Level has given rise to a Compact Integral Raman system (CIRS). CIRS shares a similar architecture to MMRS (minus the use of an optical fibre [36]) and will be capable of satisfying the current 2020 mission goals related to context and fine-scale mineralogy [32].…”

“…This fluorescence emission can overwhelm the Raman signal, especially the weaker bands generated by organic molecules which have lowenergy electronic states [66]. By contrast, the use of a UV excitation source can discriminate the Raman bands in the UV from the fluorescence that occurs at visible wavelengths [67]. However, a shorter excitation wavelength increases the irradiance of the incident laser beam at the sample, increasing the chances of thermal degradation [68].…”

“…In addition, ultraviolet excitation wavelengths can promote the observation of biological compounds such as proteins and DNA compounds. These compounds often exhibit strong fluorescence in the visible wavelength region, but their strong absorption of UV wavelengths means the resonance Raman effect can aid their detection, even in dilute solutions [67].…”