Table 1: Summary of attempted absorption spectroscopy of C60. The measured mass loss rate for each attempt was used to calculate . The mass loss rates were 2.0 g/hr for attempts 1 and 2 and 0.7 g/hr for attempt 3. For all attempts, the supersonic expansion was probed 6 mm downstream from the exit of the slit.

Attempt (K) (torr)NEA (ppm)aEstimated

19551501.0130
29555000.9140
396519000.674

NEA: noise equivalent absorption.
bThese values represent the largest value for a single rovibrational transition at = 20 K and = 0 K following the analysis presented in Section 2.3.