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Licensed Unlicensed Requires Authentication Published by De Gruyter (O) July 3, 2015

Observation of Translation-to-Vibration Excitation in Acetylene Scattering from Au(111): A REMPI Based Approach

Kai Golibrzuch , Joshua H. Baraban , Pranav R. Shirhatti , Jörn Werdecker , Christof Bartels EMAIL logo and Alec M. Wodtke

Abstract

We present quantum-state and velocity resolved experiments for molecular beam scattering of acetylene (C2H2) from a single-crystal Au(111) surface, observations that reveal translational, rotational and vibrational inelasticity. The experiments are made possible by a novel (1 + 2) REMPI scheme for acetylene. The scattered molecules' velocity distributions as well as their ro-vibrational quantum-state distributions depend on the translational energy of incidence, EI, providing unambiguous evidence that the scattered molecules were not trapped and equilibrated on the surface. We report the EI-dependence of the collisional excitation of one and two quanta of the trans-bending vibrational mode, ν4 = 0 → 1, 2, which is consistent with a mechanism involving conversion of incidence translational energy to acetylene vibration. Rotationally resolved velocity measurements on scattered acetylene in its ground vibrational state are interpreted in terms of orientation-dependent rotational and vibrational excitation probabilities.

Acknowledgement

We are very grateful to Professor Robert W. Field for his advice on spectroscopy of acetylene. We thank Professor Daniel J. Auerbach for his careful reading of the manuscript and for useful discussions. JHB thanks Dr. C. Western for his assistance with PGOPHER, including the gracious addition of new features for use in this work. AMW and CB acknowledge support from the Alexander von Humboldt foundation.

Received: 2015-3-30
Accepted: 2015-6-7
Published Online: 2015-7-3
Published in Print: 2015-10-28

©2015 Walter de Gruyter Berlin/Boston

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