Abstract
The marked efficiency of certain hydrocarbons in promoting the interconversion of translational and vibrational energy during collisions with ethylene has been further studied by ultrasonic methods. In order to elucidate the detailed influence of molecular structure, molecules with approximately the same mass have been compared. Including other published results, the average number of collisionsZeftrequired for each act of interconversion at 298°K is as follows: added gasZeπ.n-hexane 30iso-hexane 40cyclo-hexane 100 sulphur hexafluoride 120 added gasZeff.n-hexane 45iso-hexane 55neo-pentane 120 ethylene self collisions 2500cyclo-pentane 3300 A gradation of efficiency is apparent in going from then-hexane tocyclo-pentane. This scale of efficiencies in the colliding molecules might be attributed to possible overlaps of vibration frequencies, or to molecular flexibility smearing quantum restrictions and thus favouring transfer during a collision. At present, the balance of evidence strongly support the importance of molecular flexibility in promoting the interconversion of translational and vibrational energy. The effect of dipoles in facilitating transfer in the case of vibrations active in the infra-red is also discussed. Further extension of experimental results on the dispersion of sound in pure ethylene at different temperatures supportsT-⅓ the relation developed by Landau & Teller and by Schwartz, Slawsky & Herzfeld.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call