Inefficient Vibrational Cooling of C₆₀ in a Supersonic Expansion

Table 1

Summary of attempted absorption spectroscopy of C₆₀. The measured mass loss rate for each attempt was used to calculate 𝑆/𝑁. 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	𝑇0 (K)	𝑃0 (torr)	NEA (ppm)^a	Estimated 𝑆/𝑁^b
1	955	150	1.0	130
2	955	500	0.9	140
3	965	1900	0.6	74

aNEA: noise equivalent absorption.
^bThese values represent the largest 𝑆/𝑁 value for a single rovibrational transition at 𝑇_rot = 20 K and 𝑇_vib = 0 K following the analysis presented in Section 2.3.