FOURIER-TRANSFORM INSTRUMENT FOR HIGH-RESOLUTION RAMAN-SPECTROSCOPY OF GASES

An instrument is described for recording vibrational-rotational Raman spectra of gases with a resolution of 0.02-0.03 cm(-1). The Raman scat tered light is collected by near forward scattering within the cavity of a single-mode, long-term, stabilized Ar-ion laser. The Raman light is analysed in an ordinary step-scanned Michelson interferometer. To c ompensate for the low intensity of vibrational-rotational Raman spectr a, the interferometer has a beam diameter of 160 mm. The movable mirro r, weighing 2.7 kg, is mounted on a smoothly moving sledge, the stepwi se motion being performed by three piezotranslators and controlled by three independent He-Ne laser beams. It is shown experimentally that i t is possible for one to move the mirror with sufficient precision, us ing only 13% of the scan time in a typical experiment. In a preliminar y spectrum of the fundamental vibration of N-14(2), the width of the t he lines has been measured to 0.015 cm(-1). (C) 1997 Optical Society o f America