COHERENT RAMAN SPECTROSCOPY IN GASES

The instrumental resolution in nonlinear coherent Raman spectroscopy is determined by the convoluted linewidths of the lasers used for excitation. This is of special importance for the investigation of high resolution rotation-vibrational spectra of gases. It is now possible not only to determine line positions with accuracies better than 10-3 cm-1, but also to study linewidths as a function of pressure. Methods and results of coherent anti-Stokes Raman scattering are treated here

Intensity distribution in the 2v4 Raman band of acetylene

9 pags., 2 figs., 1 tab.Peer reviewe

Inverse Raman-Spectrum of Cyclopropane in the Region 3000-3050 cm-1

International audienc

Continuous-wave cavity-ringdown detection of stimulated Raman gain spectra

Cavity ringdown (CRD) spectroscopy, with its high sensitivity, provides a novel way to perform continuouswave (cw) stimulated Raman gain (SRG) spectroscopy, rather than by conventional optically detected coherent Raman techniques. Tunable cw laser light at ∼1544 nm is used to probe ringdown decay from a rapidly-swept, high-finesse optical cavity containing a gas-phase sample of interest and itself located inside the cavity of a cw single-longitudinal-mode Nd:YAG ring laser operating at ∼1064.4 nm. This approach is used to measure cw SRG spectra of the ν1 fundamental rovibrational Raman band of methane gas at ∼ 2916.5 cm−1. The resulting SRG-CRD resonances have ringdown times longer than in the off-resonance case, in contrast to the usual shorter ringdown times arising from absorption and other loss processes. Previously reported noise-equivalent sensitivities have been substantially improved, by using a second ringdown cavity to facilitate subtraction of infrared-absorption background signals. Moreover, by employing a ringdown cavity in the form of a ring, the SRG-pump and CRD-detected Stokes beams can co-propagate uni-directionally, which significantly reduces Doppler broadening.F.V. Englich, Y. He and B.J. Or