Excitation, relaxation, and quantum diffusion of CO on copper
Abstract
We investigate the effect of intermode coupling and anharmonicity on the excitation and relaxation dynamics of CO on Cu(100). The nonadiabatic coupling of the adsorbate to the surface is treated perturbatively using a position-dependent state-resolved transition rate model. Using the potential energy surface of Marquardt [J. Chem. Phys.JCPSA60021-960610.1063/1.3308481 132, 074108 (2010)], which provides an accurate description of intermode interactions, we propose a four-dimensional model that represents simultaneously the diffusion and the desorption of the adsorbate. The system is driven by both rational and optimized infrared laser pulses to favor either selective mode and state excitations or lateral displacement along the diffusion coordinate. The dissipative dynamics is simulated using the reduced density matrix in its Lindblad form. We show that coupling between the degrees of freedom, mediated by the creation and annihilation of electron-hole pairs in the metal substrate, significantly affects the system excitation and relaxation dynamics. In particular, the angular degrees of freedom appear to play an important role in the energy redistribution among the molecule-surface vibrations. We also show that coherent excitation using simple IR pulses can achieve population transfer to a specific target to some extent but does not allow enforcement of the directionality to the diffusion motion.
- Publication:
-
Physical Review B
- Pub Date:
- July 2012
- DOI:
- 10.1103/PhysRevB.86.045438
- Bibcode:
- 2012PhRvB..86d5438T
- Keywords:
-
- 68.43.Pq;
- 82.50.Bc;
- 32.80.Qk;
- 68.43.Jk;
- Adsorbate vibrations;
- Processes caused by infrared radiation;
- Coherent control of atomic interactions with photons;
- Diffusion of adsorbates kinetics of coarsening and aggregation