There are a large number of substances whose resonance Raman (RR) spectra are of interest but which are prepared in low yields in one laboratory while spectral measurements are performed in another. This generally creates some experimental problems, especially when the samples in question remain stable only below room temperature and/or must be handled under anaerobic conditions. Most of the existing Raman cells require transfer of the sample from a storage vessel into the cell, and this additional manipulation may easily destroy compounds which are temperature- or O2-sensitive before their spectra can be recorded. This paper describes a miniature Raman cell for frozen solutions that once loaded with sample can be shipped between laboratories in dry ice or liquid N2 and then attached without further manipulation to a helium closed-cycle refrigerator (CCR) station for RR measurements. The main features of the cell are: (1) very small quantities of sample are required, i.e., <30 μL; (2) the cell atmosphere is controlled; (3) cryogenic temperatures are obtained; and (4) Raman scattering originates directly from the surface of a frozen solution. These make the CCR minicell particularly advantageous for studying biological compounds which are isolated in small amounts or may be very expensive.
Roman S. Czernuszewicz, "Closed-Cycle Refrigerator Solution and Rotating Solid Sample Cells for Anaerobic Resonance Raman Spectroscopy," Appl. Spectrosc. 40, 571-573 (1986)