Figure 3: Representative absorption spectrum of the Ar/C60 expansion from 1184 to 1186 cm−1. This plot is from attempt 3 listed in Table 1. Baseline drifts have been corrected by use of polynomial fitting and subtraction. Periodic fringing was removed by Fourier transforming the spectrum, eliminating the most intense frequency components, and then inverse Fourier transforming the result to retrieve the spectrum. Similar data processing was used for all attempts where periodic fringing was observed. The spikes near 1185.6 cm−1 are due to noise and were not reproducible. The line at 1184.1 cm−1 is due to absorption by water vapor in the vacuum chamber. The standard deviation of the spectrum is 0.6 ppm.