New cryogenic apparatus for FT-IR spectroscopic studies

Cryogenic Fourier transform infrared (FT-IR) spectroscopy, being an effective technique in improving the spectral resolution and signal-to-noise ratio, is utilized in our group. However, we have found the traditional cryogenic apparatus inconvenient in the following aspects: (1) The system does not work very well in preventing moisture/frost from condensing on the salt windows or samples. (2) The indirect way of cooling using a metal cold finger limits the efficiency of the system. We have designed a new cryogenic apparatus. The apparatus is composed of a cooling stage and a measuring stage. In the cooling stage, the sample is directly immersed in liquid nitrogen. In the measuring stage, the sample is lifted just above the surface of liquid nitrogen, and the FT-IR spectrum is recorded. The dry cold nitrogen gas evaporated from liquid nitrogen forms a protective layer surrounding the sample and prevents moisture from condensing on the sample. Thus, neither vacuum nor salt windows are needed in cryogenic spectroscopic experiments using this method. The experimental results show that our method is effective in cryogenic FT-IR spectroscopic studies.