Table 3: Estimated number of two body hard sphere collisions experienced by large molecules seeded in an argon supersonic expansion. The first three entries in the table are from the attempted C60 spectroscopy reported in this work. The pyrene entry is from our previous work observing pyrene in the same experimental setup which we used to attempt C60 spectroscopy [13]. The remaining entries are from laser induced fluorescence spectroscopy of the listed PAHs performed by Amirav et al. [14]. The listed pressures for the PAHs were sufficient to produce vibrationally cold molecules (  K). The C60 and pyrene expansions used a 12.7 mm × 150 μm slit. For the work of Amirav et al. [14] all expansions used a 150  m diameter pinhole. Further details on how the number of collisions was calculated can be found in the article text.

Molecule (K) (torr) Nozzle typeNumber of collisions

C60 (att. 1) 955 150 Slit 320
C60 (att. 2) 955 500 Slit 1100
C60 (att. 3) 965 1900 Slit 4000
Pyrene 430 150 Slit 560
Anthracene 410 270 Pinhole 600
Tetracene 485 175 Pinhole 360
Pentacene 550 250 Pinhole 500
Ovalene 630 300 Pinhole 620