The experimental setup has been described in detail elsewhere , and only a short description follows. 2,6-dAP (Aldrich, 98% purity) was placed on a translating graphite bar and desorbed by a focused Nd:YAG laser pulse (1064 nm, ~1 mJ/pulse at 10 Hz). A pulsed argon molecular beam (8 atm backing pressure, 30 μs pulse width) entrained the gaseous molecules in a supersonic jet expansion, quickly cooling them. Downstream, resonance enhanced multiphoton ionization (REMPI) ionized the cold, gaseous molecules and the ions entered into a reflectron time-of-flight mass spectrometer for detection.