SPECTROSCOPY 35
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n recent years, planetary spectroscopy has emerged as a useful tool to help scientists in the search for signs of
extraterrestrial life. So, what types of technologies are being used? And what innovations can we expect in the coming years?
Remote Raman One interesting recent example is a technology used by NASA and the University of Hawaii at Mānoa (UHM), which have jointly developed a remote Raman spectroscopy instrument to aid the search for extraterrestrial life. As Anupam Misra, researcher at UHM, explains, the system chiefl y consists of two components – a nano-second pulsed laser for excitation and a time gated detector, such as intensifi ed CCD. Since Raman signals are spontaneous, he points out that the laser excitation produces Raman photons, which ‘have a short lifetime and last for the same duration as the laser pulse width.’ A gated detector is also able to detect the Raman
spectra in daylight by synchronising the timing of the arrival of photons with the opening and closing of the detector. “Raman photons are diff erent in
energy from the laser photons. T e Raman systems are designed to block all the laser photons and measure only the photons that are diff erent from the laser wavelengths. Short gating of the system also eff ectively reduces the contribution from daylight and mineral phosphorescence background. T e remote Raman system can record high quality Raman spectra of various targets in daylight,” says Misra. In Misra’s view, Raman spectroscopy
provides a very high level of confi dence in identifying molecules because the Raman spectrum of a molecule is ‘unique to the molecule and is normally used as a fi ngerprint method for chemical identifi cation.’ “Raman spectroscopy has a number
of advantages over passive spectroscopy, chief among them being the sharpness of
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