Single beam spectrum, infrared spectroscopy

The Michelson interferometer does not measure the infrared spectrum directly. Rather, an interfero-gram is measured, and converted to a single-beam spectrum via Fourier transformation. Because of the critical role of this transformation, the method is generally referred to as Fourier-transform infrared spectroscopy, or FT-IR . Instruments using this... 

However, the first experimental achievement of a narrow Doppler width in fast-beam spectroscopy had already been reported independently by Wing et They performed the first precision measurements in the infrared vibrational-rotational spectrum of the simplest molecule by crossing the ion beam with the beam from a single-mode CO laser at a very small intersection angle. 

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