Multipass capillary cell for enhanced Raman measurements of gases.

A simple Raman multipass capillary cell (MCC) is described that gives 12- to 30-fold signal enhancements for non-absorbing gases. The cell is made by coating the inside of 2-mm inner diameter silica capillary tubes with silver. The device is very small and suitable for remote and in situ Raman measurements with optical fibers.