Infrared absorption spectrum of liquid cryogen R-134a

Abstract

Cryogen spray cooling (CSC) is an effective method to minimize epidermal damage during laser treatment of various cutaneous anomalies such as port wine stains, excess hair, and facial rhytides. Radiometric temperature measurements provide a noninvasive method to estimate the skin surface temperature. Since the infrared absorption spectrum of the cryogen film has remained unknown, assumptions for those values may lead to inaccurate temperature estimations. We have constructed several high-pressure infrared transparent cuvettes to determine the absorption coefficient of room temperature R-134a in liquid phase using Fourier Transform Infrared Spectroscopy (FTIR) in the 2.5 - 14 μm spectral bandwidth. Results demonstrate that liquid R-134a has several absorption bands in the infrared, with those between 7 - 10.5 and 11.5 - 12.5 μm being the most prominent. Additionally, the absorption coefficient at two common radiometric bands, 3 - 5 and 7 - 11 μm differ by four orders of magnitude. Results of this study will lead to further improvements in interpreting radiometric temperature measurements when using CSC.