Improved Laser Calorimetric Techniques
A number of improvements in laser calorimetric techniques are described for the measurement of very low absorption coefficients in materials. Of these the most important is the method for separating surface and bulk absorption involving a long rod geometry. It is shown that the initial slope of the thermal rise curve for long rods is associated with bulk absorption alone. The method is illustrated with KCl at 10.6 μm and with NaCl at 1.06 μm. In the latter case an absorption coefficient at least as low as 7 × 10−6 cm−1 has been extracted and this is one of the lowest, if not the lowest, absorption coefficient reported for a crystalline material so far.
KeywordsSurface Absorption Initial Slope Bulk Absorption Bulk Effect Differential Thermocouple
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