“…Precise quantum chemical calculations (Hirao & Yamabe, 1984;de M. Carneiro et al, 1994;East et al, 1998)Ðincluding dynamical calculationsÐhave veri®ed the picture which emerged from an early temperature variable high pressure mass spectrometry study (Hiraoka & Kebarle, 1976), and more recent studies of infrared photodissociation of C 2 H 7 (Yeh, Price, & Lee, 1989), and of observation of fast protium/ deuterium exchange between the seven hydrogen atoms (Heck, de Koning, & Nibbering, 1992). There are three isomers of C 2 H 7 (including the weakly bonded complex C 2 H 5 Á Á Á H 2 ), of which the two covalent forms are separated by a very low barrier.…”