Direct evidence of inefficient vibrational energy transfer in gas-surface collisions

Abstract

Vibrational energy equilibration between n-octane and hot seasoned silica surfaces at T, has been studied at low pressures (≤10^-4) torr) by modulated beam mass spectrometry in the range 350 ≤ T_S ≤ 800 K. The sensitive temperature dependence of the dissociative ionization of n-octane at 15 eV was used to monitor the temperatures attained by the gas after undergoing a few nonreactive collisions with the surface. In this system, the low-lying vibrational levels of n-octane, whose relative populations account for the mass spectral changes, never reach T_S in a single collision: the vibrational energy accommodation coefficient has a value of 0.66 at 350 K and decreases with temperature.

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