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The 15th International Conference on

Vibrations at Surfaces

June 22-26, 2015 ▪ Donostia-San Sebastián, Spain

Donostia Igeldotik

Program

OverviewMondayTuesdayWednesdayThursdayFriday

Monday June 22

09:00-14:30 Registration
14:30-14:40 Conference opening, T. Frederiksen
14:40-16:20 Mo1: Surface scattering and chemistry
16:20-17:00 Coffee break
17:00-18:40 Mo2: Solid-liquid interfaces
19:00-21:00 Welcome reception, Sala de Musica, Palacio Miramar

Mo1: Surface scattering and chemistry

Chair: U. Höfer, Marburg, Germany

14:40-15:10 R. D. Beck, Lausanne, Switzerland
Probing the role of vibrations in dissociative chemisorption by state resolved molecular beam/surface experiments
15:10-15:40 A. Wodtke, Göttingen, Germany
Toward a dynamical understanding of chemistry at metal surfaces
15:40-16:00 O. Galparsoro, San Sebastián, Spain & Talence, France
Role of the vibrational energy to enhance the dissociative adsorption of N2 on metal surfaces
16:00-16:20 J. R. Manson, Clemson, USA
Hyperthermal atom scattering from surfaces

Contributed talk

Role of the vibrational energy to enhance the dissociative adsorption of N2 on metal surfaces

O. Galparsoro1,2, I. Goikoetxea3,5, J. I. Juaristi1,4, and M. Alducin1,3

1Donostia International Physics Center, 20018 San Sebastián, Spain

2Univ. Bordeaux and CNRS, ISM, UMR5255, F-33400, Talence, France

3Centro de Física de Materiales (CSIC-UPV/EHU), 20018 San Sebastián, Spain

4Dep. Física de Materiales, Apartado 1072, 20080 San Sebastián, Spain

5Humboldt Universität zu Berlin, Institut für Chemie, Unter den Linden 6, D-10009 Berlin, Germany

The dissociation of N2 on metal surfaces is usually the rate limiting step in the synthesis of many important compounds (ammonia, nitric acid, organic nitrates...) that are produced in chemical industry. In this theoretical study we investigate the efficiency of the vibrational energy to increase the dissociative adsorption of N2 on the Fe(110) and the W(110) surfaces. As shown in Refs. [1] and [2] for the non-vibrationally excited N2, dissociation, which is activated in both cases, is dominated by the energy barriers that appear when the molecule is close to the surface in the former [Fe(110)] and far from it in the latter [W(110)].

Here, we perform multidimensional molecular dynamics simulations on precalculated ab-initio potential energy surfaces to calculate the dissociative sticking probability as a function of the initial translational and vibrational energy of the molecule. Based on low dimensional schemes (see Fig.1), it has been thought that the vibrational energy would be efficient to promote dissociation in late barrier systems such as N2/Fe(110), but inefficient in early barrier systems such as N2/W(110). Our results show that though the vibrational energy is more efficient in the former, it is still efficient in the early barrier N2/W(110) system. The reason is that the vibrational energy not only allows to overcoming late barriers, but also can open new dissociation paths with lower early barriers than those found for N2 in the vibrational ground state. In particular, we observe that the new dissociation paths on the N2/W(110) system are actually dominated by late barriers. Therefore, there is no contradiction between our results and the original Polanyi's rules developed for gas-phase collisions [3].

Galparsoro.jpg

Figure 1: Examples of 2D cuts of early barrier and late barrier systems. The brown (green) line corresponds to the dissociating process of a molecule with (without) vibrational energy in the 2D simplified model.

[1] G. A. Bocan, R. Díez Muiño, M. Alducin, H. F. Busnengo, and A. Salin, J. Chem. Phys. 128, 154704 (2008)

[2] I. Goikoetxea, M. Alducin, R. Díez Muiño, and J. I. Juaristi, Phys. Chem. Chem. Phys. 14, 7471 (2012)

[3] J. C. Polanyi and W. H. Wong, J. Chem. Phys. 51, 1439 (1969)