State-to-State Time-of-Flight Measurements of NO Scattering from Au(111): Direct Observation of Translation-to-Vibration Coupling in Electronically Nonadiabatic Energy Transfer
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- 作者：Kai Golibrzuch ; Pranav R. Shirhatti ; Jan Altsch盲ffel ; Igor Rahinov ; Daniel J. Auerbach ; Alec M. Wodtke ; Christof Bartels
- 刊名：Journal of Physical Chemistry A
- 出版年：2013
- 出版时间：September 12, 2013
- 年：2013
- 卷：117
- 期：36
- 页码：8750-8760
- 全文大小：469K
- 年卷期：v.117,no.36(September 12, 2013)
- ISSN：1520-5215
文摘
Translational motion is believed to be a spectator degree of freedom in electronically nonadiabatic vibrational energy transfer between molecules and metal surfaces, but the experimental evidence available to support this view is limited. In this work, we have experimentally determined the translational inelasticity in collisions of NO molecules with a single-crystal Au(111) surface鈥攁 system with strong electronic nonadiabaticity. State-to-state molecular beam surface scattering was combined with an IR-UV double resonance scheme to obtain high-resolution time-of-flight data. The measurements include vibrationally elastic collisions (v = 3鈫?, 2鈫?) as well as collisions where one or two quanta of molecular vibration are excited (2鈫?, 2鈫?) or de-excited (2鈫?, 3鈫?, 3鈫?). In addition, we have carried out comprehensive measurements of the effects of rotational excitation on the translational energy of the scattered molecules. We find that under all conditions of this work, the NO molecules lose a large fraction (0.45) of their incidence translational energy to the surface. Those molecules that undergo vibrational excitation (relaxation) during the collision recoil slightly slower (faster) than vibrationally elastically scattered molecules. The amount of translational energy change depends on the surface temperature. The translation-to-rotation coupling, which is well-known for v = 0鈫? collisions, is found to be significantly weaker for vibrationally inelastic than elastic channels. Our results clearly show that the spectator view of the translational motion in electronically nonadiabatic vibrational energy transfer between NO and Au(111) is only approximately correct.